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Collection, Preservation and Display of Old Lawn Mowers

Just bought an AtCo Commodore B20 - A few teething problems!


Thanks for letting me join the forum. My first post - so please be gentle!

Just bought myself an old AtCo B20 secondhand for £30 as I got fed up with the modern stuff breaking by the second season! It didn't come with any accessories or a manual but I found a link to the manual on this forum - so downloaded that - thanks! (I found I don't have the rake attachment, nor the long grass replacement wheels for the rollers.)

Its recoil starter was in bits when I bought it but I got all that fixed in short order. Apparently, it hadn't been run for a couple of seasons, but it fired up on about the 10th pull of the starter - So far, so good. (If a little loud!)

However, it just wouldn't cut, the rollers would drive over my tarmac drive (with the machine tilted back so the cutting cylinder didn't get hit), but as soon as I tried cutting grass, the resistance stopped the mower moving forward and overloaded the clutches and engine.

Adjusted the front rollers for the longest cut (although grass was only about 2" long and ground firm.) The mower still seemed to have problems moving forward. I then located the cutting cylinder adjustment screws and adjusted the cylinder up off the bottom blade. Now the mower would move forward but didn't cut very much. Most of the grass was rolled flat by front rollers before it got to the cutting cylinder (I guess I'm going to need the "long grass wheels", at least initially!)  However, I don't think the cutting cylinder and bottom blade were engaged at all, so I didn't expect much cutting action!

Disconnected spark plug and tried manually turning cutting cylinder at various adjustments. The cylinder turned reasonably freely initially but became stiffer as I adjusted it to approach the bottom blade. It didn't feel like the resistance was coming from between the cutting cylinder and bottom blade however, so I undid the chain cover and here, I think, I have located the problem. The primary drive chain was as tight as a drum. The chain tensioner was not engaged at all; it appears there are just too few links in that chain. Either somebody's remove a link or two, or the cylinder has worn to more than the slack that the original chain would allow. I think I counted 25 links in the chain. Is this the correct number? Also, I am not sure how to judge how much wear I have got left in my cutting cylinder - is there any way of measuring this?

Looked for a genuine replacement chain online, but the only one I can find, they want £45 for, plus delivery - more than I bought the mower for! Had a look at the original chain; it looks like old motorcycle simplex roller 1/2" x 3/8" [EDIT: 1/2" x 3/16"] (415) to me - is that the case? If so, I can get a metre of it for a tenner. 

WRT the other two drive chains to the rear driven rollers, the first is quite loose (1.5" of slack) and the second is drum tight again. So I guess I am going to have to get to that big nut behind the roller clutch and try adjusting the centre clutch cog position to balance the slack out?

Once I've got all that sorted out, I've got a couple of other jobs I'd like to do:

1. Back-Lapping the blades to condition them. I think this can be done by disconnecting the cutting cylinder from the chain and running the cylinder in reverse with a low speed drill after coating the blades in lapping paste? Is that the idea?

2. I looked for the long-grass wheels for the B20 but they all seem out of stock and horrendously expensive if they ever come back into stock. Have read the manual and it seems that the roller axle is re-used (after the rollers have been removed) and the wheels units screw onto the threaded ends? I have dismantled the front roller axle and, by my calculations, those end threads are 1/2" UNF Fine (20tpi) - is that correct? If so, my plan is to buy a couple of stud connectors and 1/2" bolts, plus a couple of heavy duty trolley wheels - Has any one done this mod before? (Or is "modding" a sacrilege on this forum :( ) 

Well that's my initial findings and questions - if anybody would be kind enough to reply, comment and advise, it would be much appreciated.




[EDIT : I thought i would share a few pics to support the above - see this link]




wristpin Tue, 14/06/2016


First off, I don't think that you have a Commodore but its predecessor the lightweight  De Luxe. However the Commodore was an upgraded De Luxe and shared many components .Certainly the engine in your link is not from a Commodore which had an enveloping plastic cowl incorporating the recoil starter  - and you are better off with the the starter that you have! I 

As you have observed its possible that both the cutting cylinder and the bottom blade have lost metal over the years and have run out of adjustment.

Chains. Not sure how you've arrived at 25 "links" for the primary chain as the book says 50 pitches, ie "gaps" + a connecting link .

Primary F016L10721  50P, Intermediate F016L03734 40P, Final F016L09704 35P. Buy chain by the metre from your local bearing and belt supplier or on line from Simply Bearings or Bearingboys etc .

High cut wheels. Once you've got the grass down to cylinder mower length you possibly wont need high cut wheels but the set up for your machine was completely different from that on the Commodore so you will definitely will have to make your own.

hortimech Wed, 15/06/2016

No, it is definitely a Commodore, but an early one. It has the grassbox support tube and even the decal says its a Commodore.

The chains look like 1/2inch X 3/16inch and, as Wristpin has pointed out, should easily be available from your local bearing supplier.

The cylinder seems to have plenty of life left in it, but the bottom blade looks like it could do with replacing, hard to really tell from the pictures.

horatiog Wed, 15/06/2016

Hi Wristpin,

Thanks for your reply and observations.

Sorry for the confusion over the models. I just took the model to be a Commodore B20 as that's the name that is splashed across the drive cowling. (And on the silver label if you squint hard - terrible pic!) The guy who sold it to me said he had bought it as a refurbished item from a Garden Machinery company, so maybe they mated a Deluxe Engine with a Commodore Chassis? I've had a look at a few web photos and I see what you mean about the engine & starter cowling. However, these images are all of much newer examples of the model than mine. I'll try and get better pics of my mower - but will have to wait for better weather - currently coming down Cats-N-Dogs in northern Scotland!

I concur with you about the recoil starters - my findings are, the more modern the starter, the more shonky the build quality and the less amount of time it will last and the more impossible to DIY repair. Its on that principle that I have bought this mower.

Re Adjustment: Looking at the pics of the cutting cylinder, do you think it still has some life left in it?

Re Chain Links. Apologies, I was only counting outside links. I guess 50 / 2 = 25 but I included the connector link in my count, so my chain would appear to be one link shorter the specified length. Since writing my first message, I have found a pic from an old EBay auction with a close up photo of a L10721 chain, and there appear to be 26 outside links in that one, which supports the above deduction? Guess I'll just buy a metre length of new chain and make it a couple of links longer than my current one. EDIT: Chain now ordered and on the way :)

Any thoughts or advice on the back-lapping plan?

Also ordered the parts for the "high cut wheels". Total cost just under £20. The first parts arrived today and the thread was indeed 1/2" UNF Fine - Yay!

Also, I meant to ask; my exhaust seems somewhat loud; it doesn't seem to have any leaks, but has anyone else had experience of the baffles having corroded away or blown out. (I seem to remember from my younger days, these type of mowers having a lot more sedate "phut-phut-phut" that was drowned out by blackbirds and bumble-bees!)

Again, many thanks for your input and advice. Will let you know how the project progresses.


horatiog Wed, 15/06/2016

Hi Hortimech,

Thanks for your reply that crossed over my latest post. That all seems to fit in with my deductions from Wristpin's post and answers a few of my further questions. I'll try and get a better pic of the bottom blade when the weather improves! Will the back-lapping help recondition the bottom blade if I can get that done?


hillsider Wed, 15/06/2016

The subject of back lapping cylinders is one that arises here periodically and has been known to raise the emotions a bit among some folk who think it is the cure all for all things related to cutting grass.

The facts as I see them are that yes back lapping will help to maintain the condition of a cylinder that is in good condition - if used correctly.  In truth if you have a worn bottom blade and a cylinder that is worn and rounded on the cutters then a regrind of both is the only effective cure. You should then be able to set the cut to contact very lightly and still achieve a good cutting action, this will also help lighten the load on the clutches etc.

Hope this helps

wristpin Wed, 15/06/2016

Apologies, Yes, it is a Commodore chassis but I don't think that the engine is correct , as even the early ones had the enclosing cowling and the horrible starter. Specsavers moment.

Forget back lapping as a means of restoring the cut on a blunted cylinder and bottom blade. As Hillsider say, back lapping is a maintenance operation for cylinders that are in good condition and have been correctly ground in the first place.

The downside of it being a Commodore is that it's more difficult to take apart and was prone to various setting up issues resulting with a cutter unit that had set up perfectly on the bench going off cut when installed back into the chassis. There was one service bulletin ( which I can't find) specifying the order for tightening all the chassis bolts and another giving instructions for shimming the bottom blade to correct the resulting distortion - a practice which went out with the ark or was the reserve of those without access to bottom blade skimming equipment.

The final solution  offered to combat ( allegedly)  this issue was a design change to the sole plate ( bottom blade carrier)  stiffener .

horatiog Thu, 16/06/2016

Hi Wristpin,

Thanks for your further input. Yes, I hear you regarding back-lapping and I have also now read the Toro manual that hillsider provided a link to - I never knew there was so much to sharpening your lawnmower blades!

Looks like grinding requires a professional set-up, even for the bottom blade. And that info on cylinder/chassis set-up requiring bottom blade shimming and precise (but unknown) order of bolt tightening is just scary! So I am hoping that, when my new chain arrives, and I sort all the tensions out on the drive chains, that I will be able to just adjust the cylinder down onto the bottom blade and it will cut well enough for my purposes. (I am not looking for the bowling green finish.) I've seen the info on how the blades should just pinch a piece of paper across the whole blade width, so with the dual adjusters I should be able to get it just so unless the cylinder has barreled or coned. (Or is that being naively optimistic!)

Again, I will get out and get a few more & better photos of the bottom blade when it deigns to stop raining up here. (I'm starting to feel like Noah here up in Strathspey.) 

Also I note that I referred to my suspected chain size, in my first post, as 3/8 when I meant 3/16 - Doh! (I am only (just) slightly too young to have been indoctrinated in the old imperial measurement system!)

Again, thanks for everybody's ongoing help here.


wristpin Thu, 16/06/2016

Finally got my brain into gear. The engine on your machine is totally wrong for a Commodore. What you should have is the A114-2a alloy block engine derived from a Tecumseh design. What you have is an old cast iron block lump that  way back owes its existence to an early Briggs  and Stratton  design. 

​It may be of 75cc capacity or 98. If you post an image taken from the opposite side to that of the starter the cylinder head bolt / stud layout will determine which you have. With the 75cc lump a 20" machine is going to struggle a bit especially in long grass. The 98cc was used on the heavy cast iron chassis Super Punch so should cope.

horatiog Fri, 17/06/2016

Hi Wristpin

Thanks for the further advice. The rain eased off in the late afternoon so I've been outside doing a bit more footering with the Atco. When I got back in this evening, I was in the middle of writing a lengthy report of my findings whilst also busy uploading several pics & vids to dropbox. Unfortunately, I got distracted and somehow managed to delete all my text. Too late at night to start the big report again now. However, on reading your latest post tonight, I went out and took some more pics of the engine, which should help you determine what "iron lump" I have been palmed off with ;)

Hope these help & thanks for the ongoing help. Will have another shot at posting the report on my other findings tomorrow (Friday) or at the weekend.


wristpin Fri, 17/06/2016

It's a 98cc engine and so possibly man enough for the job as it's quite "torquey" with a heavy flywheel.

horatiog Sat, 18/06/2016

Hi All,

A update on where I've got to with the Atco Commodore B20 "Hybrid" :)

First off, thanks Wristpin for the update re: the fact that I have a 98cc engine - Yay! I think the stalling issues were down to the fact that there was a LOT of friction and tension in the drivetrain (see more below), plus the fact that I was trying to cut long grass with a front roller rather than wheels.

OK - first item - the primary drive chain. Well, I removed it from the lawnmower a couple of days ago and counted the links again on the workbench:

Definitely 50 links (or 25 "link pairs" depending on how you want to consider it) INCLUDING the connecting link. The new chain length arrived yesterday - Chunkier chain than the original but with the same dimensions where it matters. I immediately set to work breaking the new 1m length down to a size which was 1 link pair longer than the original chain:

And guess what, when I tried the new chain it was too long. Argh - thought I had cocked up with my link counting but when I considered taking another link pair out, it was obvious I was going to be back in my original situation with the new chain being too short as well. I just didn't appreciate how much affect the removal or addition of  a single link pair would have on  the chain tension when mounted "on the sprocket". (I think this is because it is such a short chain run compared to motorcycles/bikes, etc.) Anyhoo, after a bit of research, I've ordered a "half" or "crank" link which should give me the correct chain length (please!) Meanwhile, I have mounted the new, long chain which has JUST about been brought to a tolerable adjustment with the tensioner at full deflection. (If I adjusted the tensioner any further, the two sides of the chain would be touching!)

I also managed to get at the big nut behind the roller drive clutch, slackened it off and managed to balance the slackness in the secondary & tertiary chains so that they are both now about right. I've got a vid showing the the outcome of this operation but won't upload it to DropBox unless anybody is particularly interested?

When I took the primary chain off the lower sprocket on Thursday afternoon, it looked as if  that side of the cutting cylinder just fell back into the cylinder void. My initial, dismal thought was that the bearing on that side had collapsed, but further inspection revealed that it was the whole bearing housing that was moving against the chassis. My next thought that one or more bolts had fallen out, but further inspection revealed that the carrier was designed to slide freely up and down a track and its position was controlled by the adjuster screw on one-side and a spring on the other. (I worked this out by reference to the other end of the cylinder where there was actually a spring!) The problem was that the spring was missing from the chain end. Here's a vid of me discovering all of this and the horrendous friction & grating that resulted from this problem:

I thought I was going have to order a new spring but, during the filming of the above vid, I noticed a circular item lodged further back in the cylinder void. (Its possible to see this in the vid.) It turns out that this was the missing spring (end on) - result! After a few minutes of swearing and skinned knuckles, I managed to fish it out - it had obviously been in there some time! Reference to the manual suggests that this spring just sits between two indents, one on the carrier and the other on chassis but is then held in place by the spring's own tension alone? So I relocated the aberrant spring, wound the adjuster back down and - wow - the difference that made to smoothness of the cylinder rotation - here's a vid demonstrating that:

You'll notice, in the above video, that I continued on to adjust the cylinder down onto the bottom blade. By the way, here are a few pics of the bottom blade: 

As I adjusted the cylinder down onto the bottom blade whilst test spinning it, the cylinder appeared to catch on a few burrs on the bottom blade. I thought "what the hell", if I am going to have to get the blade re-ground or replaced anyway, there's no harm in gently manually filing the burrs off just now. Which seemed to work fine. In the above vid you'll then see I'm carrying out the test where it is attempted to pinch a piece of paper, presented parallel to blade, right across the cylinder's width. It seemed that the paper was pinched uniformly all the way across. So I guess that means that my cylinder has not been worn into a "barrel" or "cone"? However, you can also see that the blades failed to cut the piece of paper when the paper was presented perpendicularly, which I guess means the blade and/cylinder are dull/rounded and will need re-grinding for an optimal cut?

I've also been progressing my DIY "long grass" wheels mod. The stud connectors arrived the other day and - Yay! - the roller axle thread was indeed 1/2" UNF Fine. The connectors screwed on without a problem:

 Also to have arrived this morning were the wheels as well as additional bolts, nuts & washers I needed. The wheels looked of good quality (steel & heavy rubber) BUT the wheel bearing internal diameter was not the advertised 13mm but more like 12.5mm, hence the axle bolts would not initially fit through.

Having examined the wheels' bearing hole, it looked like there were metal ribs mounted longitudinally sunk into the plastic/rubber of the bearing. I took a chance and prised these out. I think these were strengtheners or friction bars and I've probably just reduced the life of that central bearing but the wheels were only £9 the pair. So, my "long grass wheels" mod then took shape quite quickly after that!

The wheels keep the rollers about 2cm off the ground, so there is no need to remove them from the axle (and possibly forget where I had put them.) 

Once I had got as far as I could go with the chain and cylinder, on Friday, I decided to video the engine being fired up to give you an idea of what I mean when I say its noisy::

As I said in the video - its loud. I also said its smoky but, on further thought, this could be due to the fact that I had had the mower on its back all afternoon and some oil could have crept up the bore.

Today's Update: Good weather returned to the Strath, so I carried out the final part of the wheel mod build and put the new "long chain" on, both as described above. So I thought I would have a bash at trying to cut grass! I re-fitted the chain guard and fired the engine up again. Initially the engine ran rough again (similar to yesterday's vid) but then, slowly, it seemed to be smoothing out. (Sorry no vid of that - the following events overtook me!) I started trying to cut grass for a a minute or so, but was still trying to sort out the cutting height when the engine suddenly cut out and wouldn't restart. I suspect a carb blockage. I can see that my carb is marked on its side as a Zenith Type 13 TCA-2:

Any useful advice as to what the problem might be? (I think I saw some crap in the fuel line when I first got the mower but then I got distracted and forgot to flush it.)

At this point in proceedings the midgies came out to play and so I called it a day! I also discovered, when I had man-handled the beast back into shed, that the bearing carrier spring had come out again - Argh! Maybe it needs a new spring - any ideas where I can get one for not too much dosh?

Well - that's the tale so far - any further info gratefully received.


wristpin Sun, 19/06/2016


All things being equal you should not need a cranked link in the primary chain. 49 pitches (ie two "narrow" ends) plus a connector making 50 pitches. As has been said, your cylinder and bottom blade look to be in reasonable condition wear-wise and with the correct chain should be compressing the spring enough to keep it in place - what's happening at the other end? Try comparing the length of the two springs.  May be your cylinder and bottom blade are not as good as they appear. If that is the case it would account for your chain trouble.

Just a thought, I have seen springs cut down and even the shaft hole in the chassis side plates enlarged to get a worn cylinder down onto a worn bottom blade and as we know that some one has "bodged " the engine  there is a possibility .......!

The Zenith carb is a simple affair and a good clean out should sort it.


horatiog Mon, 20/06/2016

Quick update - didn't have long to muck about with mower this evening. So just got both cutter adjustment springs off the mower and started on the carb clean-up,

Springs: Well, as can be seen in the photo below, Wristpin, you were right. The chain end one was broken - its lost a coil!  However, that looks like a shear fracture to me, rather than somebody deliberately cutting down the size of the spring?

Tried to find a replacement spring by reference to the part code (L100124 - Cutter Adjustment Spring) on the web. Nothing! Then tried taking its measurements to see if I could find a pattern match - see below:

Still no joy! To me it looks like a smallish valve spring; also tried googling with the term "Compression Spring" and the approx measurements - but again nothing that's close enough. Has anyone got any pointers for me? (Or a couple of springs spare ?!?)

I tried to take a couple of shots of the mounting points for the springs as I still cannot believe how small the shoulders are - see the following:

Also managed to get the carb and air filter off the engine and drained the fuel pipe from the tank. (a few pieces of crud came out!) Carb now soaking in petrol as the outside of it was really gunked up. (see Saturday's pic) Will probably have a go at a strip-down and clean tomorrow.

I also suspect you might be right, Wristpin re the "bodge-factor" extending from an incorrect engine, to also encompass an overly lowered cylinder. However, there's no obvious evidence of the lower sprocket slot having been "manually" elongated. I am also slightly puzzled by your suggestion that "the chain should be compressing the spring". Actually, I think it is the adjustment screw that pushes down on the bearing carrier & sprocket and this is what tensions the chain. As the screw pushes down on the bearing carrier, the carrier also pushes down on the spring. Therefore, I think, the chain is, theoretically, reducing tension on the spring?  Anyway, the longer chain, plus the correctly fitted springs seemed to have resulted in a smoothly spinning cylinder (for a short period over the weekend), so, hopefully, a couple of new springs should bring sweetness & light on a longer lasting timeframe!

Cheers For Noo,

wristpin Tue, 21/06/2016

Misunderstanding there, what I was trying to say was that with an apparently  ok cylinder and bottom blade and a chain of the correct length the spring should be under compression but now we know that the spring is too short it explains why it isn't ! 

One of the problems with having dismantled and reassembled so many machines that one can do it in the proverbial sleep is that one tends to assume things that someone new to the job fails to grasp.

If you cant find a suitable spring locally, two possible sources of the correct spring

The Gateshead Mower Centre

Jon Cruse at the Hailsham Mower Centre


horatiog Tue, 21/06/2016

Just finished cleaning out the carb, so I remounted it and tried to fire the beast up. Took a while to get going, fiddling with the two jet settings. Eventually managed to get it to start OK, but its still hunting at idle. Revs a good bit better than before. Still noisy! Here's a vid of me running it up.

Can't start trying to cut grass yet as I am still trying to source replacement Cutter Adjustment Springs. My latest thought is clutch springs. Anybody got an idea where I can get these? Many thanks.


wristpin Tue, 21/06/2016

Vid wouldn't work for me but did you draw a blank with my two suggestions for the springs?

 Otherwise  a breaker from the bay of evil . You might even get a correct engine.

horatiog Tue, 21/06/2016

That's the link on the video fixed - thanks for letting me know.

Gateshead don't seem to have an online browseable shop and there's not much in the Hailsham Mower Centre's one. I guess I'll have to phone them if I cannot find what I want online. (I'm crap at making myself understood on the phone!) But thanks for the leads. Also, (coz I'm a tight Scot on a budget), I'm trying to find a couple of pattern springs! Been scanning the "Bay of Evil" all evening but cannot yet come up with a close enough match.

At least the engine's running (a bit) better. Might splash out on a replacement exhaust, if I can get the thing running & cutting well!


wristpin Tue, 21/06/2016

Talking to parts departments and storesmen  used to be a hazard of doing business: Then came the Fax which printed on thermal paper that faded after a couple of months - you haven't lived!

You've got the part number which is more than half the battle. 

horatiog Wed, 22/06/2016

Have ordered a couple of pattern springs for £5, off that "South American River" site. I'll update the discussion when they arrive and I get them fitted. I fmy blades & cylinder still don't seem good at cutting, what do you think of a bottom blade at £25 and a replacement cylinder at £55? (Are they good prices or can I do better?) [EDIT: Belay that price on the cylinder - it was actually £59 and it was for a B20, not a Commodore B20 - not the same part apparently!]


wristpin Wed, 22/06/2016

If you buy a new bottom blade it should really be skimmed once screwed to the sole plate, so why not get yours skimmed.  Also unless you can buy a re-ground cylinder really cheap why not have yours sharpened - or are they both in worse condition than they appear?

Atco's naming system doesn't help. There was the Heavy Duty 20, aka B20. The lightweight/De Luxe 20 that preceded the Commodore and then the Commodore B12 which was really a Suffolk 12"/30cm and then the proper Commodores , including the B20. And that list is by no means complete and exhaustive!

horatiog Wed, 22/06/2016

Hi Wristpin,

I am not really sure how to judge whether the blade and/or cylinder have reached the end of their life. The only thing making me think they might have (well, the cylinder anyway), was that the cylinder has had to be adjusted so far down, to be in contact with the bottom blade, that it is over-tensioning a primary chain that we have now established is the correct length.

Is there any empirical way to measure some aspect of the cylinder to determine this categorically.

Also, any idea of what a fair price for sharpening the two items would be? Sometimes up here, prices can be better than the UK average, many times a whole lot worse; mainly, I suspect, due to the lack of local competition!


wristpin Wed, 22/06/2016

I take your point re the chain and spring compression etc : its just that looking at the pix of the cylinder and bottom blade that you posted earlier they just don't look that bad. However the fact that you cant get correct adjustment with the correct chain length must suggest that something is worn: maybe start with a new bottom blade.  Ive never seen any reject measurements stated for cylinder blade wear. The first indication is usually a complaint that the machine is not throwing the grass into the back of the box, followed by the inability to obtain correct blade adjustment.

Cylinder grinding etc. If you go to a main dealer, particularly one that does commercial and golf course equipment etc the price of grinding is likely to be high as they are having to pay off the eye watering price of modern grinding equipment  - around 30-40k .  To get a more acceptable price you need to find "a man in a shed" who has an old but serviceable grinder and does it for the cost of new grinding wheels etc plus a bit of beer money - Around here, £2 per cylinder inch for the cylinder and bottom blade.

horatiog Fri, 24/06/2016

Just got the two new springs today. A lot of swearing and skinned knuckles later, I had them fitted! They eventually clicked in OK. Adjusted cylinder down onto lower blade as before and test fired it up in the shed (Cue the CO poisoning!). However, couldn't head for the lawn as, by that time, it was hissing down again. Here's a couple of pics with the funky new blue springs!

horatiog Tue, 28/06/2016

Hi Wristpin et al,

Sorry for going "dark" on you. Just managed to get a few day's driving work - but hours are fun - 06:00 to 17:00, so no real chance to play with the mower or report. Still think I have carb probs - engine keeps cutting out on me when I tried it last on Monday. Could tickle carb, start engine, rev it a couple of times, start carb adjusting or mowing and engine would die. Think this is more of an engine/carb problem than drive chain related. (Cylinder now lovely and loosey-goosey!) Going to have another go cleaning it out when I get a chance. Got several different views on what adjustments should be made on the two needles. And also what people refer to as a complete turn. I think this is a 360 degree rotation but several YouTube vids, they are saying a complete turn and only doing 180 degrees?

Normal service will be resumed soon (! hope!)

Cheers, Harry.

wristpin Tue, 28/06/2016

Sounds as though you may have a blockage in the idle circuit of the carb. Assuming that you've cleaned the obvious areas including the slow running tube 21 there may still be a blockage where the fuel passes from that tube into the upper part of the carb and then via the Air Regulator Screw 1 and into the inlet manifold.

If you remove the carb from the manifold and in a good light look into the carb, slightly down and to the right you should see a very small drilling connecting in to where the fuel and air are mixed for controlling the slow running. With the idle screw removed, use an aerosol of carb cleaner with a thin tube to squirt cleaner into that drilling and see if it comes out from where the screw was and where the carb top connects to the slow running tube in the carb bowl. If none appears you can poke through that drilling with the bristle from a wire brush held in tweezers. Hopefully that will solve your problem.

A base setting for the idle adj screw is around 3/4 of a turn from fully closed and two turns out on the main jet should allow the engine to start and warm up for fine tuning.

A turn is 360 degrees!

horatiog Wed, 29/06/2016

Many thanks Wristpin - that gives me some things to try, once I finish this contract and catch up on my sleep debt!

Will report back when I have had a further futter!.


rayjack Sun, 10/07/2016

Hi Horatio I am in much the same position as you, but with a B14. Can you give some details of the trolley wheels which you obtained. Were they from a dealer or "scavenged"? What size did you use?

horatiog Mon, 11/07/2016

Hi Rayjack,

They were off EBay:

I went for the 100mm wheels as the centre bore should have been correct for the 1/2" diameter roller axle. However, as stated, I had to "pop-out" the centre bore strengthening pins in each wheel, to get then to fit. However only £10 for the pair. If you want links to the other components I used, let me know.

To Wristpin et al: After further work on the carb, the problem has got worse, not better. I think my float maybe u/s or I've destroyed the tiny washer into which the float needle locates. The carb is now flooding out of the float chamber overflow hole all the time fuel is switched on. Also, the engine is still very difficult to start and will not keep running. This despite me clearing out the idle port and all other orifices within the carb. I think I may need a new carb! 

However, at the moment, other things in my life are reducing the time I have to spend on the project. Will report back when I can.



hillsider Tue, 12/07/2016

Re the flooding problem on the carburettor drop the float bowl and double check that the needle valve has actually engaged with the fuel inlet valve seating, it is possible for the needle to completely miss the valve resulting in an uncontrolled flow of fuel.