Was out on the highway and it was running strong, then out of nowhere comes the backfiring and hesitation under throttle. It seemed like it wasn't getting gas so i hopped off the highway and hit the gas station. It still had about 2 gallons but i topped it off anyway. I got back on the highway and after about 30 seconds it starts backfiring and losing power again. I pull to the side of the road and it dies and won't start back up. Starter stopped engaging and I got it trailered home. Checked battery and it was good, fuel was flowing & carb wasn't clogged + no debris in the bowl.

I did notice when i took off the air cleaner/carb bracket bolt off of the front head some oil leaked out + the passage was filled with oil. I def have never seen that before; It is a bottom breather. (Although supposedly 1992 heads were set up for top breathing but they use a solid bolt).

After I put everything back together it fired up and it idled but super rough; it wanted to die but If i give it any throttle it backfires, pops, and spits out a puff of black smoke from the exhaust. Do you think think my problem is related to the excessive amount of oil i saw in the front cylinder head? I just swapped in 10:1 dome top pistons + jugs maybe 300 miles ago.

 

Did you have the heads decked to match? I hate to suggest it, but something may have collided with something else in there! (piston and valve) Evos have a notoriously small oil return in the heads and that may explain the oil. I'd pull the plugs and rotate the motor to see if there's any interference heard or felt.

 

If you are running a CV carb, it has likely slid out of the boot that holds it to the manifold and is sucking air. Has happen to a couple times

 

Long story short I had to use the stock heads; the heads I was going to use were milled too much. Gonna grab my jack on Tues and try rotating the motor.

 

Unfortunately that's not the issue

 

Confused over the part where you say you started it and it runs fine until you give it any throttle. Serious engine problem would present itself even idling. Can you slowly increase throttle/rpms?

 

After I trailered it home & checked battery, fuel, + carb I was able to get it to start (it wouldn't start when I was stuck on the side of the road). It started but wanted to die shortly after; idle didn't sound right at all. When giving it throttle so it didn't die it was just backfiring, popping, and gave a couple puffs of black smoke.

 

Check your iggy module for brown goo?

 

Yup....... Iggy Moo.....

 

Thanks, I'll check it tonight. I probably should've mentioned I put in an s&s hi 4n kit (module, coil, +wires) maybe 350-400 miles ago. I have heard some horror stories about the crane hi 4n's failing but thought s&s stepped up the quality.