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Villers MK10 Carb

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Trantm Mon, 05/06/2023

Hello,

I have had to put a new carb on my Villiers mk10 (it was cheaper buying a new one over getting the old one serviced).  The engine starts on first pull and all is good.  On a cold start I leave the choke closed for a while.  After about 60 seconds the exhaust smoke gets a little heavier and the engine does not rev up when I apply the throttle.  It generally gets slower and slower, when moving, and after 2 to 3 mins it will stop.  It won't start again until after an hour or so.  The carb is from a trusted parts supplier.

I am assuming that too much unburnt fuel is getting up to the spark plug.  I am told the needle valve was supplied open by 2.5 turns.  should I close it further?  any ideas if something else is going wrong?

Many thanks,

Mark

 

Forums

wristpin Mon, 05/06/2023

“  I am told the needle valve was supplied open by 2.5 turns.  should I close it further?  any ideas if something else is going wrong? “

So have you actually checked that or tried adjusting it ? 
Trusted supplier of new carburettors that are cheaper than a service kit ? ?  Have the Chinese got in on the act with Villiers repro carbs?

How about an image of said carb?

Trantm Tue, 06/06/2023

Please see pictures below.  

I tried by closing 1 turn.  Started fine but same issue IE slows down and stops.

wristpin Tue, 06/06/2023

Hmm, never seen that adjustable jet on an original one but it should make fine adjustment easier. Does it actually need choke to keep it running after a cold start ? Try taking it off choke as soon as it’s fired. If it falters try opening the jet an 1/8 of a turn a bit at a time. 

Trantm Wed, 07/06/2023

Yes I can open the air filter as soon as it starts from cold.  So I should just open the valve screw a little at a time and not close it?  

Thanks,

Mark

UTC Wed, 07/06/2023

Your symptoms certainly indicate the engine is running far too rich although it’s a little strange it takes 60 seconds before this richness starts to take effect.

You might take a look at the spark plug to confirm that it is a mixture problem, if so it will be very black and sooty.

I’d also remove the float bowl and float just to ensure everything looks OK here because the symptoms could result from a fuel level which is too high due to a sticky float or needle or dirt.

It’s very unlikely and Wristpin might like to comment as he is far more knowledgeable than me but a symptom of a failing condenser is that it starts to fail as the engine gets hotter and will then work again when it’s cooled down. I do notice this engine has a flywheel magneto similar to those typically fitted to Villiers two strokes.

UTC

 

wristpin Wed, 07/06/2023

Quite literally you need to play it by ear. First gently screw that jet right in , counting the turns so that you have a reference point. Then unscrew it back to the original setting . Then with the choke open play with the adjustable jet  - a little in and a little out while listening and deciding on the smoothest setting . Just open and close it an 1/8 of a turn at a time, giving the engine time to settle at each adjustment.

Out of interest, what is the source of that pattern or modified  S10 look alike  carb with the adjustable jet ?  If going public is an issue, I’d appreciate a private message.

UTC Wed, 07/06/2023

You could also try removing the aircleaner in case this is causing some obstruction to the incoming air supply.

Trantm Thu, 08/06/2023

Thanks for the comments thus far.

I will try the suggestions over the weekend and let you know.  

I bought the carb from Villiers parts.  I still have the original one but was worried if I tried cleaning the needle I could end up doing more damage.  

wristpin Thu, 08/06/2023

Have you spoken to George at Villiers Parts ;He’s usually very helpful. I’m guessing that the adjustable jet  may be their  mod to a new old stock S10. 

Trantm Wed, 14/06/2023

I started with closing the valve screw fully and gradually opening.  Currently I have it open about 1 1/4 turns and it seems to be going okay ISH.  I start on full choke and remove once engine fires up.  Last night it was running for 7 or 8 minutes then suddenly cut out.  I may try opening the needle a fraction more.  I also imagine the plug needs a clean as was sooty before.  Hoping that helps it become more consistent.

Re The flow jet thing that was mentioned above.  I am assuming this is not on the original carbs?  At the moment the screw is largely out.  Should I worry about this?  I assume it adds resistance to the flow jet.  What should I look for if I adjust this.

Thanks again for the help this far.

Changing the subject.  Changing engine oil.  Any trusted suppliers where I can buy it?

 

wristpin Wed, 14/06/2023

Seven or eight minutes sounds like progress. Check the fuel flow from the tank where it connects to the carb. Pull the pipe off or undo the banjo and let it run into a jam jar or some such . Look for an uninterrupted flow for half a minute. If it falters look for a small breather hole in the tank cap. Should be clear to let air in. 
Oil. From a garden centre or even Halfords  , in a bottle labeled Mower Oil!  Possibly SAE 30.  Some oil is always better than no oil - trusted supplier or otherwise!