motor won't turn up

[jeff baham]

i have a cmb evo 1 with the fat 60-80 pipe, motor ran great before. now i have rebuilt it , new p-l, and new bearing, front and back. except for rod needles. it won't turn up the rpm's. on top end. it would come on and then sag.come on and then sag. i have to pinch the fuel line to get it started. so i dont think it is too lean. pipe is set at 11'' from plug to center of flat spot on pipe. plus add on muffler rumracing.

 

[Russell Bear]

It's mad at you. You have the smell of gasoline on your hands. Traitor..

 

[Cleatus Cooper]

May sound dumb but does it have a drum or disk in it? if so check that it's in correctly as it will run either way but if wrong it's h-ll to start and don't run worth a crap.

 

[John Knight]

Jeff,

Try pulling the pipe out to 11.5". You may be missing the power band by a little and can cause the symptoms you describe. Rebuilding it may have restored the power to it and might need the longer pipe length. I have a CMB 90 and run 11.5" unless it is the heat of the summer and I go in about 1/4".

 

[jeff baham]

russell, you maybe right, it could be jealous. he he he

cleatus, the rotor is a disk and it's in the same as always. i know what you are talking about , because i tried different timeing on rotor.

john, i pulled the pipe out to 13'' and started back in all the way to 10'', with making two to three runs on one setting, was leaning or richening it on each set. i know i put a different crank in it, im wondering if the needles are bad in the rod.

one guy told me that the motor is too rich on top end i personally dont think that being sloopy rich will do that .

 

[Don Ferrette]

i have a cmb evo 1 with the fat 60-80 pipe, motor ran great before. now i have rebuilt it , new p-l, and new bearing, front and back. except for rod needles. it won't turn up the rpm's. on top end. it would come on and then sag.come on and then sag. i have to pinch the fuel line to get it started. so i dont think it is too lean. pipe is set at 11'' from plug to center of flat spot on pipe. plus add on muffler rumracing.

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Put everything where you had it originally, put a smaller prop on it & run at least a gallon thru it nice & rich. I ran CMB90's for a number of years & it sounds like you just need to properly break it in, the P/L fit is typically quite tight when you rebuild them. This of course is assuming all the parts are in correct working order. Why did you replace the crank/rod assembly & was the replacement piece new?

 

[jeff baham]

i had to replace the crank and rod essembly because on the old crank at bdtc the crank was chipped off due to bad needle bearing. the replaced crank was purchased fron bob finn he said that the crank was new. i had a machinist check the crank to see if it was running true.

 

[Joe Warren]

Jeff Drain the gassssss out of the tank & install Nitro....... You Know Gas is for washing parts.... Nitro for racing..... :lol:

 

[Russell Bear]

Jeff  Drain the gassssss out of the tank & install Nitro....... You Know Gas is for washing parts.... Nitro for racing..... :lol:

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I think Joe has solved the problem....

 

[jeff baham]

joe, were you watching me, one about six months ago at a practice run i caught myself starting to put gas in instead of nitro ha ha ha ha h.

 

[Pennywizz6]

If it is not fixed already :lol: :lol: :lol: check that you put the right amount of shims for head clearance. That may be whats up.

Phil B)