francisjohn
Active Member
I have been diagnosing what I couldn't determine to be a misfire or backfire. I took ohm readings from the magneto & cdi and everything checked out. I replaced both to see if it helped, and it didn't. I was leaning more towards a backfire as opposed to a misfire. Time for process of elimination.
I replaced my crank/clutch bearings. My theory was the magnet was running into the magneto due to a bad bearing possibly causing a misfire. Due to the bad bearing it destroyed my ZL-40mm crank as it removed 0.2mm of material. I swapped cranks, pressed new bearings/seals in. Following advice from strangers on the internet, it was encouraged to remove the outer seals on the crank bearings to lube the seals. I was concerned w/ compression blowing out out the seals.
I pedal, let engage the clutch, I move about fifteen feet and the "issue" happened immediately. At this point, I still wasn't sure if it was a backfire or misfire as it didn't feel like a backfire that I've experienced with outboard engines. I ride it for a couple more minutes, and I couldn't move fifteen feet without the bike backfiring. I get it home, and see the main seal blew from the ID out. I began putting two and two together. If the problem got worse with blown out seals, then maybe I'm looking at a backfire. I richened my carb to #5 (richest) and it happened less, but still happened. This is when I was certain it's backfiring and not misfiring if richening the tune made the issue "better" but still present.
I send the info to my buddy, and he tells me "it's funny you bring this up, this video from Don Butler came in my feed the other day, it sounds identical to what you're going through" and everything ol' boy talked about in the video was exactly what happened. Removed the outer seals, compression blew the seals out. I was starting to put together the picture.
I split the case, I put new bearings in with the outer seals in, but I notice something, and my flex exhaust has a crack. It is cracked towards the flange, but at the end of the "stinger" it's cracked too. I then realized this is in fact a backfire I've been experiencing. This was causing my tune to run super lean.
I swapped my flex exhaust for the stock pipe. Now she rides in glory.
In conclusion, leave the outer seals or shields to your bearings.
I replaced my crank/clutch bearings. My theory was the magnet was running into the magneto due to a bad bearing possibly causing a misfire. Due to the bad bearing it destroyed my ZL-40mm crank as it removed 0.2mm of material. I swapped cranks, pressed new bearings/seals in. Following advice from strangers on the internet, it was encouraged to remove the outer seals on the crank bearings to lube the seals. I was concerned w/ compression blowing out out the seals.
I pedal, let engage the clutch, I move about fifteen feet and the "issue" happened immediately. At this point, I still wasn't sure if it was a backfire or misfire as it didn't feel like a backfire that I've experienced with outboard engines. I ride it for a couple more minutes, and I couldn't move fifteen feet without the bike backfiring. I get it home, and see the main seal blew from the ID out. I began putting two and two together. If the problem got worse with blown out seals, then maybe I'm looking at a backfire. I richened my carb to #5 (richest) and it happened less, but still happened. This is when I was certain it's backfiring and not misfiring if richening the tune made the issue "better" but still present.
I send the info to my buddy, and he tells me "it's funny you bring this up, this video from Don Butler came in my feed the other day, it sounds identical to what you're going through" and everything ol' boy talked about in the video was exactly what happened. Removed the outer seals, compression blew the seals out. I was starting to put together the picture.
I split the case, I put new bearings in with the outer seals in, but I notice something, and my flex exhaust has a crack. It is cracked towards the flange, but at the end of the "stinger" it's cracked too. I then realized this is in fact a backfire I've been experiencing. This was causing my tune to run super lean.
I swapped my flex exhaust for the stock pipe. Now she rides in glory.
In conclusion, leave the outer seals or shields to your bearings.
