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Post by jessy03 on Dec 22, 2009 12:51:19 GMT 1
Hi Guys, just rebuilt the top end on an engine which i recently bought. Fitted PWK 28mm carbs modified (bodged) the cables to suit, trouble is when the engine is warm it cuts out and runs poor.
The top end has been ported and running abbey pipes can't see that being the problem though. any ideas would be much appreciated.
Jessy.
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Post by jessy03 on Dec 22, 2009 18:58:29 GMT 1
main jet is 150, slow jet unsure need to check, air screw 1.5 turns out and needle middle notch.
Do you think it could be the slow jet? a sit seems to run ok on choke???
thanks, Jessy
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Post by jessy03 on Dec 22, 2009 19:49:45 GMT 1
just took a carb off and the slow jet is 48.
thanks Jessy
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Post by dredge3 on Dec 23, 2009 0:47:15 GMT 1
Runs better on choke when warm...hmmm. If it likes it rich when warm, then is should run like crap from cold
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Post by dredge3 on Dec 23, 2009 0:48:59 GMT 1
Have u stripped and blown out the carbs. Sounds like a blokage and the choke is bypassing somewhere. Is this on idle and full throttle?
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Post by nikfubar on Dec 23, 2009 1:59:33 GMT 1
Mmmmmm sounds a bit like mine  Just put the engine back together, ported with new rings etc, fitted the PWK 28s with 150 mains, 42 pilots air screw 1&1/4 turns out, JJH needle on middle clip. Start on choke fine, revs no problem, as soon as its warm completely flat from tick over to 4k then ok. Took it out for a run and after fiddling with throttle stop screws got a good even tick over but if you wack open the throttle I get the booowang sound and the motor is flat and sometimes stalls. I havn't sorted mine yet ( too dam cold to go outside) but this is caused ( so I read ) by incorrect settings of the needle, pilot screw & pilot jet. Apparently you turn the pilot screws in a 1/4 turn at a time untill the motor revs crisply, then you listen to it revving back down if the revs drop quickly and it bogs or dies you are too rich, back the screws out 1/4 turn at a time. If after you let the throttle off the motor tends to run on and on you are too lean and need to turn the air screw in 1/4 turn at a time. You need the revs to go up and come down at the same speed. If you turn the air screws all the way in and need to go further you need a larger pilot jet. If you have to turn the air screws out so far they almost fall out you need a smaller pilot jet. Before you change jets try clip 1 (top) to richen the needle or clip 5 (bottom) to lean the needle. Wheather this works or not, may try on mine tomorrow. |
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Post by jessy03 on Dec 23, 2009 7:17:25 GMT 1
Thanks for the help chaps, I'll try some smaller pilot jets may be 42 and let yoy know, Don't think the carbs are blocked as they are new carbs. I'm also running std air box and premix I've not modified the airbox at present. I was going to get it running right first then remove the snorkol and go from there.
Thanks again, Jessy
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Post by dredge3 on Dec 23, 2009 19:45:38 GMT 1
Mine revs and ticks over spot on. As soon as I take it for a run its chocked up to 4K then it goes. Had 2 sets of carbs now
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