30 HP Big Twin No High End RPM

[Griffschoony]

We've got a 1956 30 HP Big Twin. When running the motor straight away on full throttle it doesn't seem to be able to get up on high rpm's. When turning, in neutral, or in reverse it revs just fine, but under load on straight aways it will not wind up all the way. We've taken carb apart, cleaned, replaced jet, replaced fuel filter, replaced gas lines, etc. It will not even plane out a 16 ft semi V john (bare bones). Any ideas would be appreciated?? We were possibly thinking wrong prop pitch?? Thanks,

 

[lindy46]

Re: 35 HP Big Twin No High End RPM

Re: 35 HP Big Twin No High End RPM

Check spark. Sounds like it's running on one cylinder. Probably a bad coil. It'll run fine at idle on one cylinder, but not when you put the pedal to it. BTW if it's a 1956 it's 30hp.

 

[Chinewalker]

Re: 35 HP Big Twin No High End RPM

Re: 35 HP Big Twin No High End RPM

Also, check compression. May have a blown head gasket...

 

[Griffschoony]

Re: 30 HP Big Twin No High End RPM

Oops meant 30HP. Thanks for the replys