ok,i installed my gx200 today with the following mods and it wont rev past 3900rpms :billet flywheel,.010 rod,ss valves.molly pushrods,26lb springs,mikuni 22mmcarb,140 main,17.5 piolt, mikuni fuel pump,super x dyno cam,15cc clone head mild porting,8 deg timing key, (all valve train stock size) i cannot get this to rev up,checked cam timing=ok rechecked valve lash,was a little tight on ex.side adjusted it to .003,what the heck is wrong with this motor?to much timing?too much what???? please,please,help me:censure::shrug:
not enough rpms
- Thread starter collinsdad
- Start date
- Tags rpms
Eliminate a variable one at a time, and only ONE variable. If you eliminate 2, you may not know which one caused the problem.
It is probably something simple, like a cam tooth, bent pushrod, valve lash loosening up, bad compression.
Check compression if you can. If your compression is low it hurts the engine's performance dearly...
Did you hone/install new rings?
Your problem could be cause by lots of things. Like I said, eliminate one thing at a time.
It is probably something simple, like a cam tooth, bent pushrod, valve lash loosening up, bad compression.
Check compression if you can. If your compression is low it hurts the engine's performance dearly...
Did you hone/install new rings?
Your problem could be cause by lots of things. Like I said, eliminate one thing at a time.
You might be too rich. Way too rich.
Small single cylinder motors can do this once they really start breathing. They'll pull hard on the low end, but once the RPM's start to rise, they pull so much fuel in, it can't ignite it all, and they start to crap out.
Reading the plug will usually show super lean, because it's washed from the excess fuel. 140 is an awfully big jet for a 22 mm Mikuni.
Small single cylinder motors can do this once they really start breathing. They'll pull hard on the low end, but once the RPM's start to rise, they pull so much fuel in, it can't ignite it all, and they start to crap out.
Reading the plug will usually show super lean, because it's washed from the excess fuel. 140 is an awfully big jet for a 22 mm Mikuni.
well the posibility of being to rich still exists,however charles (minidragbike)gave me his opion on the phone which totally never crossed my mind,my stupid coil was bad.wasnot getting enough to get the rpms up where they should be,which hopefully fixes the problem,so i ordered a new one and am having charles build me one of his heads for the sled.amazing what stupid crap can make you insane,if anyone has other ideas please feel free to share im open for all sugg. thank you all who are helping me with this mini collinsdad:thumbsup:
the 140 main jet was a trial and error thing as for ignition it makes sense,the spark isnt hot enough with the coil being weak,at low rpms it will fire but once it starts to rev it is not hot enough to burn that amount of feul and if a 95 main still does the same thing id rule out any jetting at this point,not that in theroy it couldnt be the problem but it does not work no matter what jet i put in it.
the point in trying to make here is that i went from 140 down to 130 down to 120 down to 110 down to 100 down to 95 and guess what they all had in common? they all did the same thing,nothing,the motor would not turn past 4000rpms with each jet the result was the same,so im going out on a linb and say its not the jetting.:censure::shrug::hammer: