hewson Posted March 13, 2013 Report Share Posted March 13, 2013 Hi all Anybody know a good starting point with jetting on a Mk 1 Amal carb , its to fit a Villiers 250cc 32A motor Cheers Quote Link to comment Share on other sites More sharing options...
hewson Posted March 14, 2013 Author Report Share Posted March 14, 2013 Come on Guy's someone must have a rough idea , or should i ask my mate Bondy ?????? Quote Link to comment Share on other sites More sharing options...
b40rt Posted March 14, 2013 Report Share Posted March 14, 2013 Ask Amal ? Quote Link to comment Share on other sites More sharing options...
hewson Posted March 14, 2013 Author Report Share Posted March 14, 2013 Ok , but what's the point of this forum ? I did ask one certain rider at poacher's club ( a top rider ) only to get a reply i don't know . Ill ring round tomorrow ...... Quote Link to comment Share on other sites More sharing options...
b40rt Posted March 14, 2013 Report Share Posted March 14, 2013 Amal told me exactly which jets slide etc for a b40, they were very helpful. Quote Link to comment Share on other sites More sharing options...
hewson Posted March 14, 2013 Author Report Share Posted March 14, 2013 Ok Ross , but its a bit secret on here sometimes , and at trials , ill never win anything major lads ...Honest Quote Link to comment Share on other sites More sharing options...
old trials fanatic Posted March 15, 2013 Report Share Posted March 15, 2013 Thing is jetting all depends on so many things for example my James runs a 120 main jet and pulls and runs fine however a mate of mines James with the same ignition etc runs a 140 main jet. The sort of exhaust and port timings compression ignition advance etc you are running all have a massive effect on the jetting as does inlet length and exhaust pipe length and diameter oh yes and the type of fuel and oil mix you run too. Then we get to altitude, we are in the Derbyshire Peak District which is a fair bit higher than Lincolnshire and everything all gets a bit grey on jetting. All I can say is if it's any help main somewhere between 120 and 140 probably a 2 1/2 or 3 slide cutaway and take it from there. You'll just have to get a few jets and try it. Sorry I cant be of any more help but I've always found what works on my bike quite often doesn't match exactly what works on someone elses and applies equally to the James and the Ossa and Bult and don't get me started on the TY LOL. Quote Link to comment Share on other sites More sharing options...
hewson Posted March 15, 2013 Author Report Share Posted March 15, 2013 Thanks OTF , the bike was fitted with a near new amal when i bought it . It had a 160 main jet fitted but wouldn't rev out cleanly , iv'e tried a 130 and now i'm on a 120 , its still the same , it as a 25 pilot and a 31/2 slide . I did the Captain's cup last weekend , and it was worse than ever .... Quote Link to comment Share on other sites More sharing options...
woody Posted March 15, 2013 Report Share Posted March 15, 2013 Ignition fault? Quote Link to comment Share on other sites More sharing options...
tayld Posted March 15, 2013 Report Share Posted March 15, 2013 Hi there, As Woody noted are you certain the ignition including spark plug is working and correctly timed? A leaking crankshaft seal or blocked exhaust can also have an effect. When no known settings are available the tuning guide published by Amal is very useful. http://amalcarb.co.uk/downloadfiles/amal/Mk1_Hints_and_Tips.pdf The five step tuning sequence does work providing the engine is actually working against a steady load and you know where the slide is at each stage. If in doubt start with a large main jet and work down from there in stages. The main jet does need to be done first. When adjusting the pilot air screw (and pilot jet size, when fitted) make sure the slide is not set too high. Hope this helps. Quote Link to comment Share on other sites More sharing options...
hewson Posted March 15, 2013 Author Report Share Posted March 15, 2013 Bike was still on points when i got it , always started 2nd kick . I fitted electronic ignition and new oil seal just before last Sundays trial , first time starter now , but still as the problem . I'll ask around and see if i can try another carb out on it ...... Quote Link to comment Share on other sites More sharing options...
twinshockdude Posted March 15, 2013 Report Share Posted March 15, 2013 sounds like the ignition is too retarded Quote Link to comment Share on other sites More sharing options...
woody Posted March 16, 2013 Report Share Posted March 16, 2013 It doesn't appear your jetting is too far away from the jetting for the 250cc Ossa Montesa and Bultacos that ran 27mm Amals where it's generally around 25 pilot, 106 needle jet, 150 main and 3.5 slide. The needle is one standard size only on the Amal MK1. I'm assuming it's a 26mm carb you have. Coming down from a 160 to a 120 main jet is a huge change and the fact that it doesn't change anything suggests the carb isn't the problem. If I put a 120 in the Ossa instead of the 160 it would definitely make a difference. However, you don't mention the needle jet and needle position, if they are too rich it could maybe give the symptoms you have. 105 or 106 needle jet and middle clip on the needle is a good start point. Some new Amals can be less than 'satisfactory' but usually the symptoms are poor slow running because of poor pilot circuits. So it doesn't suggest the carb itself is an issue if it runs at low revs ok. The problem with Villiers engines is you never really know what you've got. I had what should have been a 250 37a once with square barrel. It turned out to be a 200cc with a karting barrell or suchlike as it rev'd it's nuts off but had no bottom end whatsoever. In the end I got fed up of trying to sort it, it was swallowing money and pretty soon it went out the door - the end of me and Villiers engines. I entered a whole new world of pain with BSA 4-strokes instead... It could be the porting that's at fault, wrong head, restrictive exhaust - anything. You don't say what ignition you've bought but sounds as though you can probably rule out the ignition due to the problem being there before it was fitted If it was me, given the lack of change in performance following the main jet range and assuming the oother jets are in the right range, I'd be looking elsewhere now. Double check the timing as mentioned elsewhere as there is no guarantee it was correct when the points were fitted. If your ignition is Electrex it could be timed incorrectly. It would be worth trying a carb from another bike that you know works correctly, just as a comparison, but as OTF said, you'll find what works on one Villiers may not work so well on another. Then look at the intake, does it have a restrictive filter (how does it run with no filter / airbox. What kind of exhaust is on it etc. I don't think there is a definitive answer to this one. Quote Link to comment Share on other sites More sharing options...
hewson Posted March 16, 2013 Author Report Share Posted March 16, 2013 Hi Woody , Its a iron barrel 32a , the electronic ignition was fitted to a spare engine i have , this spare engine is fitted with the square Marcelle top end , 250cc short rod , it run spot on in the sprite i had .The ignition came from a chap who suppliers bully uk and trail and trial , cant really fault his system's . I'm going to try another carb in the week and see how it goes . Thanks for the reply's lads Quote Link to comment Share on other sites More sharing options...
old trials fanatic Posted March 17, 2013 Report Share Posted March 17, 2013 Keep us posted as I would love to find out what the problem was and what the fix was. Agree with Woody about you never know what you've got but port timing is easy to check once you know what port timing you like but so many Villiers barrels etc have been "modified" and not always for the good. Also so many parts are interchangeable you really have to know what you've got and what you should have. Saying all that they probably have the very best spares availability of any P65 or twinshock bar none with everything available even remanufactured using better materials and tolerances than original. Cliffs ignitions are normally very robust and reliable I agree but a few did have problems which Cliff has always sorted immediately he's a nice bloke and very helpful. Anyway as I said keep us posted. Quote Link to comment Share on other sites More sharing options...
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