Post by numbski on May 18, 2011 11:02:17 GMT -5
Sorry to have fallen off for a year, but I'm back. I had a bad, bad year last year. The local Harley dealer had my Buell Blast for 8 months. Long story. :\ Meanwhile, my 150cc Longbo (now a 170cc) was blowing oil by badly, and finally the piston that was in there cracked. Took it to a local motorcycle mechanic that replaced the piston and rings, honed the cylinder....but by the time it got put back together and I did a gentle, slow break in on that engine, I basically didn't have a riding season at all last year.
This year has not gotten off to an auspicious start. I got 2 days of riding on the 170cc in, was in the process of riding home from work, and all of a sudden I lose power. Hoof it home from work the rest of the way, get my pickup truck, go get it. Let it sit for a week.
Last night I tore into it. Pulled the spark plug out - it was all chewed up. Top tab, gone. Center pin jammed into the side threads, and pieces of it appear to be sheered off. For grins, I tested to make sure I had spark using another plug. There's spark. Also checked whether fuels getting into the carb. It is.
I have fuel. I have spark. I have a chewed up spark plug. I haven't pulled the head off yet, but I am pretty sure my lack of compression would be another failed piston. I can't see how it could be anything else that would do this kind of damage. Of course, I'm not mechanic. I've merely been Kliff's whipping boy since I popped up on here. I'll only be certain once I pull the head back off.
Question is - now what? I mean of course I could go, get another piston and ring set, get the cylinder honed again, put it back together *AGAIN* - but I'm thinking this is one of those "definition of insanity" moments - doing the same thing over and over again expecting different results. Putting my non-mechanic's hat on and behaving like an engineer, I'm thinking what I'm seeing is EXCESSIVE compression. The first piston that failed was an aftermarket high-compression piston. When that failed I wasn't that surprised, figuring that it was probably too much compression. This one is the one that came with the big-bore, which was more-or-less a flat bottom. That surprises me. In both cases I had a whole lot of oil blow-by, which we on this board and myself/mechanic kept presuming was a ring-seating issue could have been excessive combustion chamber compression. That would have made oil seep past the rings, yes?
Aside from going back to the smaller cylinder/piston set, which I suppose at this point has to be an option, what options do I have? I'm going to have a bit of time off work coming up, so I might be able to sink a day or two into futzing with this. Just hate to repair the symptom without dealing with the cause.
I know at one point there was a suggestion that I "mail the engine to Kliff". Heh. I feel like I'd be crating up the back half of the bike, but given the circumstances I'd almost be tempted now. One thing's for certain - I have learned faaaaar too much about engines from this bike.
This year has not gotten off to an auspicious start. I got 2 days of riding on the 170cc in, was in the process of riding home from work, and all of a sudden I lose power. Hoof it home from work the rest of the way, get my pickup truck, go get it. Let it sit for a week.
Last night I tore into it. Pulled the spark plug out - it was all chewed up. Top tab, gone. Center pin jammed into the side threads, and pieces of it appear to be sheered off. For grins, I tested to make sure I had spark using another plug. There's spark. Also checked whether fuels getting into the carb. It is.
I have fuel. I have spark. I have a chewed up spark plug. I haven't pulled the head off yet, but I am pretty sure my lack of compression would be another failed piston. I can't see how it could be anything else that would do this kind of damage. Of course, I'm not mechanic. I've merely been Kliff's whipping boy since I popped up on here. I'll only be certain once I pull the head back off.
Question is - now what? I mean of course I could go, get another piston and ring set, get the cylinder honed again, put it back together *AGAIN* - but I'm thinking this is one of those "definition of insanity" moments - doing the same thing over and over again expecting different results. Putting my non-mechanic's hat on and behaving like an engineer, I'm thinking what I'm seeing is EXCESSIVE compression. The first piston that failed was an aftermarket high-compression piston. When that failed I wasn't that surprised, figuring that it was probably too much compression. This one is the one that came with the big-bore, which was more-or-less a flat bottom. That surprises me. In both cases I had a whole lot of oil blow-by, which we on this board and myself/mechanic kept presuming was a ring-seating issue could have been excessive combustion chamber compression. That would have made oil seep past the rings, yes?
Aside from going back to the smaller cylinder/piston set, which I suppose at this point has to be an option, what options do I have? I'm going to have a bit of time off work coming up, so I might be able to sink a day or two into futzing with this. Just hate to repair the symptom without dealing with the cause.
I know at one point there was a suggestion that I "mail the engine to Kliff". Heh. I feel like I'd be crating up the back half of the bike, but given the circumstances I'd almost be tempted now. One thing's for certain - I have learned faaaaar too much about engines from this bike.