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mowersman
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Quote mowersman Replybullet Topic: Solve this one then...
    Posted: 28 May 2012 at 10:56am
Been having fun and games with the villiers Mk12 on my Barford atom yet again today. Every time I take it out of gear and shut the throttle down, it tries to rev itself to bits, if I let it (I get the cut out switch first)
The carb had been stripped and rebuilt with a new gasket set and it spotless internally. The mounting faces have been flattened and new gaskets made for the inlet manifold. There is very little play in the throttle butterfly and the butterfly is closing completely in the carb. It has the correct air filter on. The mixture is set perfectly for when the engine is working, and when started up it idles fine, it only runs away when it comes off load.
All the throttle linkages are completely free and I can see the throttle shuts down as soon as it comes off load, yet it still over revs.
The engine has excellent compression and the bore is in good condition. The mag has a brilliant spark. The exhaust is present. The petrol in the tank is only about a week old. Correct spark plug fitted and gapped.
Anybody got an idea as I'm getting fed up of this engine, every time I try and use it, there is another problem. It is in great danger of being removed with a sledge hammer and a 5hp Briggs being fitted in its place.
Any ideas?
Andrew
The more I work with petrols, the more I like diesels...
Yeovil, Somerset
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rogers6183
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Quote rogers6183 Replybullet Posted: 28 May 2012 at 11:30am
Hi Andrew
 
I have had similar issues in the past and done very much the same as you with regards the carb. I ended up sending the Carb to George at Villiers spare and have him acid dip it then replace all th consumables inside. Then hey presto all working again. I recon it will be an issue inside the carb the, is the float in the bowl fillign with fuel? some with the brass ball float type can get the smallest hole in and fill with fuel. Anyway there are my thoughts for you, mine got sent away and came back perfect had 5 years of trouble free running...
Serious about Drama... Serious about Sport...
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mowersman
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Quote mowersman Replybullet Posted: 28 May 2012 at 11:44am
Hi, the float is perfectly fuel tight, it is one of my spares, I had it sitting immersed in a bucket of diesel for a month and there was no liquid inside it afterwards. I'd love to send the carb off and have it properly done, but I just can't afford to at the moment. I suspect I'll end up changing the engine and then possibly selling it as I need the money at the moment.
Andrew
The more I work with petrols, the more I like diesels...
Yeovil, Somerset
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Charlie
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Quote Charlie Replybullet Posted: 28 May 2012 at 11:45am
Try disconnecting governor and throttle linkages from carb to rule them out. Engine should not be able to rev with throttle shut as not enough air can get in.
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mowersman
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Quote mowersman Replybullet Posted: 28 May 2012 at 11:58am
Still does it, suggesting an air leak some where, but I can't fathom out where, new manifold gaskets all round? I'm going to have that carb to bits yet again, see if that solves anything.
Andrew
The more I work with petrols, the more I like diesels...
Yeovil, Somerset
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mowersman
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Quote mowersman Replybullet Posted: 28 May 2012 at 2:51pm
I give up, So I've bought a NOS carb for 30 plus the usual. Will fit and see if that helps.
Andrew
The more I work with petrols, the more I like diesels...
Yeovil, Somerset
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simar kid
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Quote simar kid Replybullet Posted: 28 May 2012 at 7:21pm
just a thought here. even if you have disconected the governers lever and spring,is it possible that inside the engine there is something amiss with the goveners original setting ???????????????
Not sure whats wrong. i think we will let it develop
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Dieselhead
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Quote Dieselhead Replybullet Posted: 28 May 2012 at 8:44pm
Just what I was thinking. Worth a look.
 
Just lift the block from the sump & see
Chris. I aint getting on no plane. Fool!
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enginear
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Quote enginear Replybullet Posted: 28 May 2012 at 9:09pm
If you shut the throttle by hand on the carb and it is shutting the butterfly but the engine is still reving then its an air leak, but if it shuts down hand then it's the govenor,if you suspect carb can you move the butterfly shaft up and down ,if that's ok check with a straight edge across the carb flanges if it's bowed use emery paper on a known flat surface and reface the flanges, don't overtighten when reffiting.,  
simple
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