Can someone explain to me how I can have equal compression front and rear cyls, and have hot exhaust from the front cyl, and cold exhaust from the rear? have changed plugs, wires, checked timing, anyone? 1982 flh
snoeman

 

How long you run the engine before doing that little test & what kind of pipes she have ? Stock duals or aftermarket ? need a bit more info & what are you trying to diagnose .

 

I ran the engine (82 shovel)for about 15 minutes. I had just reset the valve lash, i was trying to find the source of the engine stumbling under a load. I have done a rebuild on the carb, (S&S shorty E) replaced intake bands, adjusted valves, changed coil, wires, plugs. there is still a stumble, miss,under a load. While the scoot was idling I walked behind the shotgun exhaust and noticed the front exhaust was hot but the rear exhaust was cold, Any ideas? Snoeman

 

Timing maybe , plugs sooted black or oily when pulled ? A test for air leaks is the old WD-40 or Brake Cleaner trick , warm the bike and using the red tube spray short bursts at the intake clamps and the carb mounting flange see if it stumbles . I've had issues with " E " carbs having a flat spot out of the box with some shovels they like to be a bit on the fat side with mixture adjustment . What jets you running ?

 

Did you confirm you have spark on the rear cylinder? Just because you replaced it don't necessarily mean it is working. If I had a cylinder that was completely cold, first thing I would do is pull the plug, place it in the wire, ground it and turn the bike over to see if there was spark.

 

Yeah, I did the wd test, also switched wires and plugs. the plugs are grey/black, not sooty or oily. Sorry about the delayed answer. I drive a big truck, only home on weekends.

 

Thats about normal for plugs could be a little lighter in color but a number of things like age & wear would account for it . Rear exhaust is always " cooler " than front it's the nature of the beast and the way they are timed . Still would like to know what your trying to do here ? Just curious or is there a problem ?

 

The scoot has a miss under a load. It developed suddenly one night, I figgured it was trash in the carb. So i got a rebuild kit for the shorty e carb. I rebuilt the carb, but it still has the miss. I noticed the exhaust at that time. I did a compression test, front and rear are equal. I reset the timing, changed out the bands on the intake, new plugs, wires, coil, the scoot has points also new ( 3rd set new) i'm out of ideas.
Any suggestions?

 

look very carefuly at the intake seals make sure no leaks, timming could be off, lose wire on bottom of coil. thats what i would look see first

 

Have a lot of oil showing inside the ports on the intake side valve stems ? Starts and runs fine until it gets hot then starts missing ? If so do a leak down test or have it done . Basically getting each cylinder up to tdc on the compression stroke and putting LOW air pressure to the spark plug hole and listen to where you hear & feel it coming it coming out . Like the in. & exh. ports or the crankcase vent tube .

Like another post said check your intakes , new doesn't mean sealed do the brake cleaner spray test when at an idle . Short shots of cleaner at the intake clamps at an idle if it stumbles your leaking .