need help with valve timing 1989 yfm 250 moto-4
#11
#14
well, you may have been bored last night but i'll tell ya what, you sure helped me! i'm heading out to the garage to start tearing covers off. i'll fill ya in later today. again, thanks for all the help!
update, i just pulled the covers off and it appears to me the marks line up perfectly and there is very little slack in the timing chain. now im abit lost. from past experience, a backfire through the carb is almost always a valve timing issue. could it possibly be a burned valve? (although it doesnt backfire constantly everytime the valve opens or closes). maybe just worn valve seats?
update, i just pulled the covers off and it appears to me the marks line up perfectly and there is very little slack in the timing chain. now im abit lost. from past experience, a backfire through the carb is almost always a valve timing issue. could it possibly be a burned valve? (although it doesnt backfire constantly everytime the valve opens or closes). maybe just worn valve seats?
#15
update, ok, i stand corrected. lol the timing marks were dead on, no slack in the chain so i took the carb off AGAIN and cleaned the crap out of it. looks like it was just starving for fuel at a very slow rate. that explains why it would idle for 20 or 30 seconds just fine and then outa no where it would "skip a beat" so to speak. at times it would be so bad it would die. im guessing i had some small obstruction in the carb that was just enough to cause this. a little carb tuning and it seems to have cleared up. i sure want to thank you for all your help. without it i believe id still be searching for the fix. thanks man!
#16
hey no problem, i figured it was most likely a carb problem, even when people tell me they cleaned the carb that still doesnt eliminate the possibility of it being the carb,all it takes is a little spec of dirt and thats it...thats why its so critical to clean the carb best you can and take your time when you do it, those old moto-4s are tanks i figured it would be something a little more simple then valve train being worn out, one thing you can do to help prevent that from happening again is by cleaning the airfilter and installing an inline filter, you just cut the line that goes from the fuel pet **** to the carb in half then slip the filter in between that line, and it helps filter out any little specs that may be flowing out from your tank, nice cheap addition that costs like 3 dollars.
#19
update, ok, i stand corrected. lol the timing marks were dead on, no slack in the chain so i took the carb off AGAIN and cleaned the crap out of it. looks like it was just starving for fuel at a very slow rate. that explains why it would idle for 20 or 30 seconds just fine and then outa no where it would "skip a beat" so to speak. at times it would be so bad it would die. im guessing i had some small obstruction in the carb that was just enough to cause this. a little carb tuning and it seems to have cleared up. i sure want to thank you for all your help. without it i believe id still be searching for the fix. thanks man!
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Mojave250A
Performance Mods and Project Quads
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07-11-2015 10:38 AM
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