Hard start low power 56 bigtwin

[twobills76]

My 56 rude Bigtwin is hard to start with low power when started. I have checked compression...it is low, but still should run to get me through this tournament this weekend. 60 on top cyl 55 on bottom cylinder. I pulled the carb it is really clean. Reeds?? and could that also be part of compression issue?

 

[Chinewalker]

Re: Hard start low power 56 bigtwin

If your gauge is accurate, not only are your numbers low, they are very low. Big Twins seem to pop over 100 in good tune. Reeds have nothing to do with cylinder compression readings. I'd borrow another gauge and try again.

Operating under the assumption that your gauge is NOT accurate, here is what I'd check - spark, spark and more spark! The most common issue associated with "low power" is the motor running on one cylinder. Being that your compression readings are at least close, then we can also assume your head gasket is intact, which leads once again to checking for spark. Should jump a 3/8" to 1/2" gap. Check plug wires for condition, coils for cracks, and points for pitting.

 

[kfa4303]

Re: Hard start low power 56 bigtwin

+1. These link may help.

http://www.outboard-boat-motor-repa...on 3 HP 1952-1967 Ignition System Tune-up.htm

http://www.duckworksmagazine.com/04/s/columns/max/24/index.cfm

 

[twobills76]

Re: Hard start low power 56 bigtwin

WOW! I have no idea how this thing actually ran the other day. The advance was off BAD! So at half throttle I had Idle. Someone had Jerry Rigged the throttle gear outside the motor so at half throttle the mark on the advance cam was lined up were it is supposed to be at idle. Gonna refire her today and get everything tuned in then hit the water again wednesday....thanks again for the help guys! this forum has helped tremendously with this project!

 

[1946Zephyr]

Re: Hard start low power 56 bigtwin

Somebody could have "de-tuned" it for an undersized boat, or an inexperienced operator. It's easy enough to jerry rig them, to where they won't rev up to their maximum RPM's. As far as your compression goes, I'm totally with Chinewalker. Anything over 100 psi is more favorable. And +1 on trying a different guage. Did you pull start it for the test, or use the starter? These are a little hard to get an accurate compression reading with the hand starter, unless you're built like Hercules

 

[twobills76]

Re: Hard start low power 56 bigtwin

I used the starter. the pull rope was removed from this thing years ago. I never remember on being on it. I have now ran into another issue too...the highspeed needle will not go back in all the way...the threads seem off a bit so I am going to find a die and rethread them. I haven't had any luck finding a new one around here.