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Collection, Preservation and Display of Old Lawn Mowers

Punch died suddenly - cannot revive

Hi

I’m a newbie here, but I’m the owner of three Suffolk Punches, one of which I bought about 30 years ago, and which has been my “Number 1” machine, in regular use until it very suddenly stopped in the middle of the lawn a couple of weeks ago. Since then all my attempts to get it going again have come to nought.

When I bought the machine (1994), it was a second hand “re-build” supplied by a local dealer and he had removed the usual ID plate, and so even now, I’m not 100% what the machine is, but the Operating Instructions (L24130) that came with it says it’s a Qualcast Suffolk Punch 43D-L (17”) with an A98 engine and I have no reason to dispute that. Until now, it has never given me any problems; it gets fresh oil every year, I installed a new cutting cylinder a couple of years ago and the Zenith 13 was taken off last winter, cleaned, and worked well on replacement.   After it stopped, it has been quite dead; no coughs or splutters.

There is a spark, and two alternate plugs have been tried and the points look good.

There is compression, and the engine turns over with little resistance with the plug out. Removal of the magneto confirms the Woodruff key is present and correct. Removal of the valve chest cover (breather plate) shows both valves moving appropriately.

I’ve just bought a replacement carb and I’ve cleaned that up and my next action may be to try the second carb. 

If anyone has any suggestions as to what else I could do, I’d be really pleased to hear them.

Thanks

Bazz

 

Forums

wristpin Fri, 10/06/2022

You seem to have covered most bases but you don’t mention compression with the plug in place. Sudden death but with a spark that you describe could be a loose valve seat. 

Bazz B Fri, 10/06/2022

With the plug in place, the compression is high, which is to say the pull starter is taking the same effort as before. Could it be that, in my imagination at least, the pull starter seems to need a little bit more effort than previously???

Although I re-built the machine when I replaced the cutting cylinder, I've never had to do any work on the engine, so apart from looking at the drawings, I've never seen one dismantled.

Bazz B Fri, 10/06/2022

Oh dear; one step forward and three back. I put the alternative carb on, but then found that the pull starter is slipping; the two centrifugal fingers are just not locking on properly (which they were last night) and it's even slipping when I remove the spark plug. There seems to be quite few worms in this can!

wristpin Fri, 10/06/2022

A high proportion of recoil starter problems are the result of rough use in an attempt to overcome a less obvious mechanical issue.  The starter is what’s known as an inertia starter; that is the compression spring acting on the engagement or activator bar causes it to resist turning , forcing the pawls to expand and grip the inside of the cup. Wear or over lubrication results in the activating bar turning without expanding the pawls. Easier to demonstrate or explain!

In simple terms, if  as you say you  have compression and a spark** it suggests the fuel is not reaching the combustion area of the cylinder. That said, you description of a sudden failure doesn’t match a typical fuel issue which will normally give  some erratic running before stopping the engine. Arm yourself with an aerosol of carburettor cleaner ( most are inflammable) and squirt some directly into the carburettor air intake or even after removing the spark plug , directly into the combustion chamber .

**  Before you go any further, try a new plug.

 

Bazz B Sat, 11/06/2022

OK, fixed the recoil mechanism - one of the centrifugal fingers had forced its way off its pivot. I put it back in place and then added another packing washer on the central spindle to help keep in place.

So, with that done, and the back-up carb on place, I tried to start and.... it ran for about two seconds, but that is the best it's done for a few weeks, and then it was time for bed.

Bazz B Sat, 11/06/2022

What I'm finding is that it is hard to start and when it does start, it's only good for a few seconds.

What bothers me is that there seems to be loud clattering noise when it's running; cannot be very specific on that.

Any suggestions appreciated, but looks like it might be an engine off job?

wristpin Sun, 12/06/2022

Going back to my earlier post, possibly a loose valve seat. You don’t need to remove the engine to investigate but it will make things easier; particularly if it becomes a repair job. If caught and repaired in time a loose seat is not terminal but the repair does need to be done properly. Readily available instructions can be found in the Briggs and Stratton L head ( side valve) repair manual. Doesn’t matter that your engine is not a Briggs, the principle is the same.

Bazz B Wed, 15/06/2022

Thanks for those comments wristpin.  It's been a good machine and so I would like to repair it, so I think I need to check out the valve seats rather that do anything which may just make it worse.

I'll report back when I have news.

Bazz B Sun, 19/06/2022

I’ve now got the head off the engine; everything came apart nicely as did the gasket.

The cylinder shows no score marks of any kind and I cannot detect any slap on the piston. Both valves open and close just as I would expect them to. When they are open, both valve heads can be spun on their axis, so neither is sticking in the guide. I cannot see, feel or hear any mechanical aspect which seems unhappy.  However, I was surprised by the amount of carbon there was inside the head, particular in the region of the inlet valve. This is not such much hard carbon as carbon mixed with oil.  It was clear that although the inlet valve was opening, it head was reaching the carbon, leaving a flat impression on it.

This is the first time in 30 years the head has been off, and judging my the most minimal oil consumption over a grass-cutting season, I am not too worried about that.

Having thoroughly cleaned the head, I think I will re-assemble things without further investigation, in the hope that it will run well (or well-enough) now to serve in to autumn. At that time, a full engine rebuild might be worth while. But I’d be grateful to hear any comments on this plan.

wristpin Sun, 19/06/2022

Before you put the head back on, with each valve fully open have a good look at the valve seats where the hard steel inserts are set into the recesses in the alloy block. Look for any signs of movement between insert and block, try a bit of a probe with a scriber or pick to make sure they are tight - think a dental check up! Can’t remember whether you have mentioned that you have actually checked for the correct the valve clearances . Even if the valves have some clearance when cold they may loose it all when hot. Just enough cold could be no good at all when hot.

Bazz B Thu, 28/07/2022

I've got this engine stripped down now. The was a lot of soot in the head and on the ex valve stem, but generally, everything seems to be pretty good. The piston and the cylinder are fine, as are all the bearing surfaces, the cam lobes and the cam followers. The valve seats took just a few minutes of grinding with fine paste to get good seating surfaces.  The guide for the ex valve seems well worn at the top but not too bad at the bottom. I've looked after the machine and changed the oil religiously every autumn, so it's not bad, aged 40 or 50 years old

I fiddled around trying to put the valves back in using just screwdrivers, and did not get very far, so I made a very quick and dirty spring compressor tool based on the one sold by Briggs and Stratton and will try that tomorrow.

Watching a YouTube video on rebuilding this engine, the presenter said that he had rebuilt a number and that it was often the case that the spring which pushes down on the breather valve was often missing.  I wonder if people have done this deliberately thinking that more oil mist will get in to the valve chest and help stop wear on the guides?

However, the issue as to why this engine stopped so abruptly and would not re-start continues to be a mystery.

wristpin Fri, 29/07/2022

Watching a YouTube video on rebuilding this engine, the presenter said that he had rebuilt a number and that it was often the case that the spring which pushes down on the breather valve was often missing. 

How strange, I’ve been working on old Suffolk’s for 40+ years and never found one missing! However, if I understand your original post correctly you have an A98 engine ( aluminium alloy cylinder block) and that doesn’t have that type of breather.

So, just for clarity , the A98 valve chest cover is held on with two screws / bolts. The older Cast iron engines with the breather that you describe have a valve chest cover  held in place with a central stud and nut. - which do you have?

At one point you commented  on the amount of carbon . It could be that a lump broke loose and held a valve open, but disappeared during your investigation . 

Bazz B Fri, 29/07/2022

Sorry to have confused you. I did start off believing it to be the aluminium engine (I'm getting on these days) but it is in fact the iron block.  All details are as per the "Suffolk Super Punch" maintenance manual on this site. The cover for the valve chest is held with just one nut. The soot on the head and valve stem seemed fairly soft and most came off quite easily with a wire brush.

Re the breather and its spring, certainly this engine has both. Presumably, if that valve was to stick in the closed position, no oil mist could find its way to the valve chest? I guess there was a time when having the exhaust valve guide changed could be done but I expect that part is very hard to find and the labour rather expensive.

I'm hoping to get the valves back in to night and try the engine quite soon.

I do have two more Suffolk punches in the shed, both needing work on them. One is the 17" with aluminium engine, Dellorto carb and electronic ignition. I bought it cheaply in a local junk sale, found the ignition module needed replacing, but even after doing that (and getting visible sparks), and ultrasonically cleaning the carb, I've never managed to start it. The other machine is from the "Bosch Punch" era and has the cassette cutter/raker system, and that too needs attention.

wristpin Fri, 29/07/2022

I'm hoping to get the valves back in to night and try the engine quite soon.

Presumably you will lap them in or have even had them refaced. Then you need to set the gaps / clearances.  7 thou for the inlet and 15 for the exhaust on the cast iron block engines. The clearances should be measured / set with the piston just past Top Dead Centre on the power stroke.

Bazz B Sun, 31/07/2022

That's something I'd overlooked.  It needed only a short time to grind the valves to restore uniform matt grey seats on both valves and valve seats.

So, before the tricky task of getting the springs and cotter pins back in, is it the case that I should re-install the valves, the followers and cam shaft and check the clearance looking for the values you mentioned? Moreover, how do you adjust the clearance?

I've seen reference to this engine design (valve seats above the stems) as an "L Type" configuration; do you know where that comes from (USA ?).

Thanks

 

wristpin Sun, 31/07/2022

Your engine is of side valve/ L head design. Pop the valves in , position the piston as per my last post and use feeler gauges to check the clearances between the end of the valve stem and the top of the tappets. Unless the engine has been messed with before, the clearances are likely to be either ok or too tight. The only adjustment is by careful filing or  grinding  the end of the valve stem .  

If you are not confident about doing this , I would suggest that so long as you have 5 and ten thou , you could leave them as is for now. Otherwise seek help locally.

 

wristpin Sun, 31/07/2022

Re my last post. No need to completely reinstall the valve springs etc until you are sure about the clearances . Position the piston and drop the valves in, then put finger pressure on each in turn while using feeler gauges to check the clearances. Only when you have achieved satisfactory clearances is it necessary to fit the spring.

Refitting and compressing  the springs can be done with a couple of old screw drivers but having a suitable spring compressor makes things a lot easier. I’ve never don this,  but I’ve seen images of someone compressing the springs and tying them compressed with small cable ties , then inserting them and cutting the ties ones the retaining pins are in place.

Bazz B Mon, 01/08/2022

Many thanks for your continued help with this task!

Ok, now without the piston in, but with just the camshaft, followers and valves, I'm measuring clearance as follows;

exhaust  2 thou

inlet        5 thou.

I think I have to admit to not taking as much care of this engine as a I should have.

So, how do open up the clearances? Looking at one of the cam followers, it has slightly bevelled edges on the end of the stem, making me wonder if someone has reduced its length at some stage in the past? I cannot find any reference to achieving the proper clearance in any of the manuals.

wristpin Mon, 01/08/2022

It’s my view that the safe way to get the clearances correct without the risk of the cam moving, the engine should be reassembled with the piston , crank and camshaft assembled and timed. The figure that you quote, assuming that you measured it with the tappet on the back of the cam lobe is far too low for the exhaust and if you are going to correct it, you may as well correct the inlet as well. 

Once you have assembled the cam, crank and piston and re- checked the clearances it will be the time to look at your options .

Bazz B Tue, 02/08/2022

OK, with the piston and crankshaft in and positioned as you recommend, I'm measuring the exhaust at 2.5  and the inlet at 7 thou.

I had a look at the rest of the machine this afternoon. There's a little wear on the sintered bronze bearing behind the clutch, but I don't think it's too bad. I guess it would be hard to find a new one, but I'll make a couple of calls. Everything else seemed very fair for a machine of this age.

wristpin Tue, 02/08/2022

That bush used to be a top hat one but was replaced with a plain cylindrical one and a plain steel thrust washer . The oilite bushes are a standard size available from most bearing suppliers such as Simply Bearings. Soak the bush in oil and wipe off the surplus oil before fitting.

Valve clearances are achieved by grinding or filing the end of the valve stems. It’s important that they are filed or ground square . There are tools for doing that but for a one off job, a hard wood block drilled and slit then clamped in the vice will suffice. Drill the block to the diameter of the valve stem, push the stem through with just a few thou protruding , clamp it tight in the vice and use a new flat fine file to remove a few thou at a time, checking as you go.

Bazz B Wed, 03/08/2022

OK, I'll measure the bush and see if I can replace it. Failing that, I do have a vacuum oven, so I could immerse it in oil, pump it down to vacuum for a while and then let the air back in, which should at least force some oil in to it.

The inlet valve is now close on 15thou, so I'll see if I can re-fit the springs and collets tonight. I tried using the cable ties, expecting the small (2mm) ones to break, but they worked OK, and should be easy to get out.

Hopefully, back in action quite soon. Thanks.

wristpin Thu, 04/08/2022

The inlet valve is now close on 15thou,

Hope that you mean exhaust!!  Inlet 7.

There’s a far simpler way of loading a bush with oil, no special kit required!

 

 

Bazz B Sat, 06/08/2022

I managed to find the bronze bearing from JAPG mowers. The engine is at the point where I need to re-install it on the chassis.  I made a “timing indicator” from a welding rod and it’s as near to 23° as I think I can get. Yes, the exhaust is 15 and the inlet 7 thou.

 

I needed to take a day off the project to do other things today, to do other things, but I’ll get back to you shortly, hopefully to report a happy outcome!

 

Bazz B Mon, 08/08/2022

OK, we having a running engine!  It's starting quite easily, sounds good, but runs a little erratically (a little hunting?), more so as it gets hot, and I suspect the carb needs some attention.

The carb it is presently running on is actually my spare. I think I will get the one that was on the machine originally, strip it down and throw it all in my ultrasonic cleaner, and re-fit that, with the adjusting screws set up as per the standard numbers. Any thoughts?

wristpin Mon, 08/08/2022

As useful as U/S tanks are, they are not the be all answer . Time spent with an aerosol of good carb cleaner and an extended nozzle can be just as productive . The standard Zenith carb is a fairly crude instrument and usually responds to that treatment and a bit of poking with nozzle cleaners. ( yes, I know what the books say,  but if they are good enough to be a Honda service tool ....... ) . As for setting the jets by numbers; fine for a base setting to get it started and warmed up but a finely tuned ear and fractional jet adjustments is all that’s needed to get the best result.

Bazz B Tue, 09/08/2022

Yes, US cleaners work exceeding well on open surfaces (I used then all the time when I was working - mainly corrosion testing) but they are less good with galleries and fine-bore tubes. Of course, US cleaners do deteriorate with time, so need testing. Have you seen the test in which an area of kitchen foil is tightly spread over small frame and you have to time how long it takes for the cleaner to "punch" holes through it?

I've just realised that there is no condenser visible on my Punch; didn't think about it until now.

I've just started to look at the "youngest" of my Punches; a Qualcast (Bosch) which takes either a cutting cylinder or a raking cassette. It has Tecumseh engine and a Dellorto carb. I took it out of use as there was so much rust on it. It has not been painted but powder coated at manufacture.  But having dealt with the rust (over a period of time), it did not want to start. It was very useful for raking up leaves, and it may well be that they will be falling early this year with things being so dry.

wristpin Tue, 09/08/2022

Points but no condenser; it will be embedded into the coil. No points and no condenser, a solid state system.

I did the foil test on my tank a year or two ago and it seemed quite satisfactory but I suspect that the cheaper end of the market for casual use may not be that durable.  When it comes to cleaning carbs  etc the effectiveness should be increased by altering the orientation of the components being cleaned at intervals during the session so that the loosened dirt can fall out of the nooks and crannies. 

Your Dellorto carb has a little gallery supplying the idling and progression jets , which is covered by a welch plug . Just about only way to deal with a badly contaminated  carb is to remove that plug to get the crud out of the system.