Black smoking Villiers MK 25

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mikehpw1
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Black smoking Villiers MK 25

Morning All

Firstly a thanks for all the help along the way with the resto of my Atco 28/34. It’s now complete (ish)

im at the running stage! It starts quite easily runs nicely at a very slow idle and full revs, however I’ve used all my limited knowledge but can’t stop it puffing out black smoke. Checked all the jets, air filters clean, new fuel. Engine had a full rebuild including rings and valve regrind. Adjusting the pilot  needle screw doesn’t seem to have any effect however if I remove the screw all together the smoking stops but engine increases speed dramatically. Checked all jets several times. I know there’ll be an answer or several so if anybody has it could they please assist. Cheers

 

 

 

wristpin
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Despite all your efforts, it

Despite all your efforts, it’s running too rich; confirmed by the reduction of the black smoke and coincidental increase in speed.

The possibilities are that the float level is too high or that someone has previously messed with the jet sizes either by using an incorrect jet or enlarging  jet during a heavy handed cleaning session.

I seem to remember that earlier in your restoration you were looking for a carburettor ?  If that is so, it can’t be ruled out that you now have an incorrectly jetted carb for your spec of engine.

 

mikehpw1
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Hi Wristpin

Hi Wristpin

yes I was looking for a carb. I bought a complete engine with a carb and used that on my existing engine. Same model engine. I think the float is correct because it was flooding at first because the float wasn’t cutting off the fuel so I adjusted it but I’ll check again. Do you have any info on main jet size. The pilot jet I can’t change as it’s a drilled hole in the body. I’ll try filling and redrilling main jet a smaller size. Float might be the cause as it smokes on both the pilot jet on idle and main jet on full revs, would be strange for both jets to be wrong???

cheers for now

 

mikehpw1
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Morning 

Morning 

lowering the float level seems to have improved the full speed mixture but still very smokey on idle speed. I’m going to try restricting  the flow through the pilot jet pick up tube when I get some small drills. Any other remedies out there ??? Cheers

wristpin
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Unlikely, as the removal of

Unlikely, as the removal of the air screw gives an improvement, it but may be worth checking that the ignition system is up to scratch . The mixture could be too rich or could be ok but not being properly burnt. 

mikehpw1
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True, but I did fit a new

True, but I did fit a new coil and points and I’m thinking that as it starts fairly easily and idles very slowly there can’t be much wrong there. I’ll recheck, maybe I’ll treat myself to a strobe gun, do you know if can you buy them with there own battery or do they all require to have an external power source ?

wristpin
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Never seen a self contained

Never seen a self contained strobe for automotive use, a 12v battery is usually required .  I think a strobe is of limited use on a single pot engine with fixed timing; un like an engine with a conventional distributor that can be moved with a running engine. First adjust the contact breaker points to the recommended gap , then set the static timing by moving the stator; a multi meter or just a battery and bulb is all that’s needed to determine the exact opening point of the contact breaker points. 

Something to note is that the timing marks , on a lot of Villiers engines with taper fit flywheels,  are applied after the factory has done the before top dead centre measurements and relate to exact top dead centre. This means that having  set the points gap it is only necessary to put the engine to TDC and line up the marks.  On engines with keyed flywheels , static timing using stator position is all that’s needed.

mikehpw1
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Ah, I watched this video

Ah, I watched this video below, same engine as mine. He set the points to open 3/16 plus 1/8 BTDC ignoring the marks on the stator and engine. So to be sure, once the points are gapped I align the two marks and that’s the correct firing position BTDC?? 

https://m.youtube.com/watch?feature=youtu.be&v=S1b_PHs7MOw

wristpin
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Hmm, interesting and a bit

Hmm, interesting and a bit confusing at times but it does confirm that with the points correctly gapped , the piston at TDC and the factory marks lined up the BTDC should be correct.

Just as well that he kept clear of that spinning starter pulley !

mikehpw1
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I’ll check it out today and

I’ll check it out today and report back. Thanks

mikehpw1
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Hi

Hi

well sadly don’t have a preset type engine the marks appear only to indicate TDC as in this position the points are wide open. However back to the smoking I think I may have found something, when I assembled the carb after tumbling the parts I didn’t remove the main needle from the body, I have now done that and found minute traces of walnut media jaming it. So assembled again and now the engine has lost its spark, didn’t touch the ignition!!! I’ve fitted a new Villiers coil, new plug and cleaned points so how can this happen ???

 

wristpin
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The joys of old engines!

The joys of old engines!

So let's back track a bit. Regardless of timing you have the points set at say 14thou" when on the top of the cam, and they are spotlessly clean.  You have an arrow on the flywheel and an arrow on the mag backplate and you have found that with the piston at top dead centre and the flywheel replaced with the arrows in line, the points are wide open and not just starting to open? 

In that case go back to basics. Put the piston to TDC , rotate the crank anticlockwise to lower it by what ever the book says,    3/16" ? Position the flywheel so that the points just start to open (just releasing the proverbial fag paper ) then tighten the flywheel nut. 

If that restores normal operation, what then is the relationship of the two arrows either to TDC or to points just starting to open.

It is of interest that while many Villiers manuals say to align the two arrows with the piston at TDC to avoid the faff of "basics timing", my one and only manual for Mk20 and 25s does not. However there appears to be little point of the arrows if that is not the case.

 

mikehpw1
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Morning 

Morning 

ive now reset timing the basic way and now get a good spark. Re checked the carb and one thing I noticed my info on the S19 with a choke says the protrusion of the main needle should be 2 1/2 inches. Unfortunately it doesn’t show me where that is measured from exactly however I cannot get that length protrusion from any place on the carb. The engine starts easily and runs but it’s all over the place, revs alter without touching throttle and still smoking on idle and also some  hunting. I will crack this but sadly not by my own skills alone. 

wristpin
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Don’t give up!  In your first

Don’t give up!  In your first post of this thread, it was running well,  other than the black smoke. In the meantime you’ve been into the ignition and are now satisfied with the result, so that leaves your recent work on the carburettor; while doing that work is there any possibility that you have upset the governor? Uncontrolled speed suggests a governor issue while your mention of hunting suggests either a governor or a weak fuel mixture one. What has been changed from running ok with a bit of smoke to running like the proverbial bag of nails ?

mikehpw1
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Well, nothing other than

Well, nothing other than finding that I hadn’t cleaned the carb probably and freeing up the spring loaded needle which I thought was the problem. The 2.5 inches protrusion can’t be achieved. I set the governor as it was before the strip down and rebuild but that could be slightly out so I’m researching how to adjust it. This carb came off an engine that I was assured was a good runner when I bought it, in hindsight I should have checked it before fitting it to my engine. I don’t want to quit but trial and error can only get you so far before you need a train ear. Cheers

wristpin
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I can’t be of much help when

I can’t be of much help when it comes to the carburettor set up as my one MK25 manual makes no mention of an S19 . The only on line mentions for S19s appear to be for motorcycle applications . For obvious reasons, in those applications they are not working witha manifold governor butterfly ; could that be the crux of your issues?

As far as setting the governor itself goes, there is one basic setup position, no adjustment other than a choice of spring position .  The basic setting is to replace the arm on the shaft with the clamp bolt slightly loose. Then turn the shaft fully clockwise and hold it there, then move the arm to the right to fully open the manifold butterfly  and do up the clamp. 

The manual suggests that as well as a weak mixture, hunting may be caused by “stiffness in the joints of the carburettor linkage”.

mikehpw1
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Morning 

Morning 

Well, as Wristpin told me don’t give up, I didn’t. My MK 25 is now running like a top. I’m pleased and quite proud of my achievement but at the same time annoyed at my gross stupidity. It was in a very bad state so on strip down I took everything back to metal, bead blasted and tumbled for hours!! Threw everything in including the S19 carb. Rebuilt with care checked everything. Long one short the very fine dust created by the walnuts from the tumbler got to places I didn’t or couldn’t even see were there. Wasn’t until I studied detailed drawings in an old Villiers Book a friend gave me that I could see drilled holes and airways completely invisible on building. To get to them I had drill out the manufacturer’s access blanking plugs that they insert after drilling. Even had to remove the central main jet tube that the book said never to do!! This dust had set like concrete everywhere, it’s testament to the engine that it ever started in the first place. My lesson learned be gentle with these old boys, and pay attention to the details and get to know exactly how the things work, without that old drawing I would never have solved the problem!! 

wristpin
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Great news, perseverance pays

Great news, perseverance pays !  Don’t suppose that you took images along the way ?  Moral of the story is that walnuts are best left to a certain creamy confection.

mikehpw1
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Hi

Hi

no I didn't take pics, I must remember next time I screw up !!! Thanks for all the suggestions  along the way. I'll post some pics when I cut some grass with it.