ericfreeman
20th May 2008, 05:59
Posted this in the Ironhead section but thought it might be interesting to see what advice I'd get from this group, perhaps some good points to prevent it from happening again.
Only 1500 miles on my new topend: worked over heads, new Wiseco 10:1 pistons, R5 cams, etc. Bike has been running fantastic, until last Thursday. Went for my usual 80 mile run on some backroads and wound up on a stretch of highway where I had to keep up with traffic at about 65 mph. No big deal right? Well, after coming back down to slower speed I noticed some pinging and other signs of not running perfectly. Made it home OK but noticed a definite knock/slap sound from the front cylinder. Did a compression test the next day and found the front cylinder down about 50 psi from the rear. Also wanted to check the timing but I'm not getting a consistent flash from the front coil (rear coil is firing fine). Not sure if this is related to the piston problem or not.
Pulled the front head (looks fine) and jug and found this.
http://xlforum.net/photopost/data/500/medium/L1010240.JPG
http://xlforum.net/photopost/data/500/medium/L1010241.JPG
http://xlforum.net/photopost/data/500/medium/L1010244.JPG
The galling is on the intake side of the front piston. Scoring on the barrel is not deep but you can feel it, so a rebore is likely. Will have to pull the rear head and barrel as well to have them both done together.
Biggest disappointment is I've been taking great pains to ensure I never ran lean while breaking in the new top end. My big Weber carb is jetted pretty much as recommended by several other fellows running them and by the Weber jetting expert back east. Bike just never felt like it was running lean (needs a little enrichener when cold, never any carb farts) and judging by the exhaust pipe it appears to be a little too rich.
Anyway, will be sending the barrels off later in the week for inspection and I'll change jets on the carb to richen up the mixture. Pisses me off to have screwed up bad enough to wreck my new top end. Still need to look in to why the front cylinder spark seems erratic since it's a single fire setup with independent coils. Don't know if a bad coil (it's nearly new as well) could have contributed to overheating condition.
Guess I'll be riding my Honda Trail 90 for the time being!!
Eric
Sportsterless North of Seattle
Only 1500 miles on my new topend: worked over heads, new Wiseco 10:1 pistons, R5 cams, etc. Bike has been running fantastic, until last Thursday. Went for my usual 80 mile run on some backroads and wound up on a stretch of highway where I had to keep up with traffic at about 65 mph. No big deal right? Well, after coming back down to slower speed I noticed some pinging and other signs of not running perfectly. Made it home OK but noticed a definite knock/slap sound from the front cylinder. Did a compression test the next day and found the front cylinder down about 50 psi from the rear. Also wanted to check the timing but I'm not getting a consistent flash from the front coil (rear coil is firing fine). Not sure if this is related to the piston problem or not.
Pulled the front head (looks fine) and jug and found this.
http://xlforum.net/photopost/data/500/medium/L1010240.JPG
http://xlforum.net/photopost/data/500/medium/L1010241.JPG
http://xlforum.net/photopost/data/500/medium/L1010244.JPG
The galling is on the intake side of the front piston. Scoring on the barrel is not deep but you can feel it, so a rebore is likely. Will have to pull the rear head and barrel as well to have them both done together.
Biggest disappointment is I've been taking great pains to ensure I never ran lean while breaking in the new top end. My big Weber carb is jetted pretty much as recommended by several other fellows running them and by the Weber jetting expert back east. Bike just never felt like it was running lean (needs a little enrichener when cold, never any carb farts) and judging by the exhaust pipe it appears to be a little too rich.
Anyway, will be sending the barrels off later in the week for inspection and I'll change jets on the carb to richen up the mixture. Pisses me off to have screwed up bad enough to wreck my new top end. Still need to look in to why the front cylinder spark seems erratic since it's a single fire setup with independent coils. Don't know if a bad coil (it's nearly new as well) could have contributed to overheating condition.
Guess I'll be riding my Honda Trail 90 for the time being!!
Eric
Sportsterless North of Seattle