1980 115hp surging and sputtering

[Mr.Lang]

My engine ran great. Now it doesnt. It has it's happy spot to run smooth. But below and above that it runs terrible. Replaced the fuel system, except the tank. No help. Even replaced the plugs and coils. Somebody help me please. It sounds almost like a miss mixed with a backfire and some surging... Lots of violent shaking.

 

[emdsapmgr]

You may find a complete overhaul of both carbs may cure your problem. When you have it apart, make sure you remove the brass jets and visually check them to be sure the are clear. Also, blow out all the passages with an aerosol carb cleaner, similar to GUMOUT. Also, violent shaking and backfiring is usually a result of being out of time. That could be a sheared flywheel key, or: when you reassembled it, you may have crossed two of the spark plug wires from the power packs.

 

[Mr.Lang]

I have cleaned the carbs already. And the new coils were the result of the shaking. All are hooked up the same and firing in proper order. I will have to check the flywheel key. What would make it shear?

 

[racerone]

Recommend a compression test on any of these motors as the first step in trouble shooting.------If flywheel is not properly torqued down the key will shear.-----NOTE---The key is there to position the flywheel for proper timing.---The flywheel is driven by the locking tapers when properly torqued.---Torque is 100 ft-lbs on the nut.---If tapers are damaged key will shear.---Tapers can be repaired with valve grinding compound.

 

[NAT1VE]

Agree with Racerone, sounds like timing.

 

[Mr.Lang]

She runs alot smoother now after some further fuel tank cleaning. But my top speed has dropped from over 40mph to struggling for 10... Lower carb is seaping from gaskets. Replacing those. Would that be enough to take all that power?

 

[emdsapmgr]

It is probably not firing on all four cylinders.

 

[Mr.Lang]

Put on a new fuel pump instead of reman, replaced the primer switch with a maintenance switch, rebuilt both carbs with new jets and adjusted the floats... Runs beautiful at full throttle... Still a little crapy in the low rpm range( close to idle) all cylenders are firing... Whats next?