oldmxer

Hi naichuff, thanks for that, this is the same condition as mentioned in the photo from feetupfun, its good to get the correct understanding

scot taco, I confirm the filler cap hole is clear, again this was one of my first checks but failed to mention this in my forum. pschrauber, thank you for your advise but I have sprayed WD40 around the head, cylinder base and induction while engine is running to see if anything is either sucked in or pushed out. feetupfun, thank you for the choke position clarification. stevem75, thank you for the above in-depth information, I will work my way through this forum and hopefully source this problem. Can I say a big thank you to Trials Central for allowing everyone to pass on this constructive information in this Forum, well done, Graham

Thanks Model80, I think this is the next step, just a silly question, is there an arrow on the top of the piston ?

Yes, thanks for that but had the petrol cock apart and cleaned it as well as cleaning the filter in the tank and the filter in the carb inlet banjo, as I said just don't know where to go next

feetupfun, thank you for your info, sorry but can you please confirm AMAL Mk 2 choke lever operation: You stated choke Lever up = ON, this places the plunger down "IN" which you also say is OFF, I really appreciate your help but now I am now very confused !

Thanks again feetupfun & trialsrfun, I have never ridden the bike as it has never ran properly since I bought it. First I thought it was either a blocked fuel filter from the tank or in the carb fuel inlet, or a blocked jet, just like fuel starvation. Then replaced all the parts mentioned at the start of my post. When I am running the engine with choke on it seems to run for a few minuets its not to bad to start with, but then becomes sluggish, when I turn off the choke the engine revs increase and then appears to run out of fuel, as soon as I turn the choke lever back on and the engine picks up again, its very difficult to explain properly, but very frustrating. The electronic ignition was on the bike when I purchased it.

Thanks feetupfun, compression seems fine but I have not removed the head or barrel, is it possible the piston fitted back to front would cause this ?

I purchased the crankcase seals from Bultaco UK and as the original wide seals are no longer available they supply 2 seals per side. They supplied instructions to fit them back to back, one with the wire spring side to the crank shaft and the other wire side to the opposite side. I am not sure of the exhaust or silencer but does not appear to be blocked.

Hi, thank you for your reply. Yes the ignition timing is correct and all the jetting and the carburettor slide and needle has been replaced, carb body seems good, did try another carb, just cant understand why it needs the air screw almost screwed right in and will not run without choke.

Hi, I have just joined this site and looking for some help sorting out my recently acquired Bultaco198A, 250 Sherpa as the bike is running weak. I have tried another Amal type 2 carburettor, I replaced the following: all the jets to original spec, throttle slide, crank case seals, intake rubber, air filter, spark plug and the engine will not run unless the choke is on. It has electronic ignition and starts fine. I appreciate any ideas or experiences that you may have. Thanking you in advance Graham