Posts
6613
Joined
9/8/2006
Location
Spring Lake, MI, USA
Edited Date/Time
1/27/2012 4:05am
07 RM250. I thought I threw a reed, so I started there. That was fine. When I pulled the reed block out and looked in there, I could see the cracks in the piston. There was even a chunk lying on the edge of the intake port.
Quick question. The only other time I'ive done this is on a few CR's that I rode and the cylinders were trashed on those. (ring on exhaust side let go, have a pile of cylinders to prove it)
The bottom back half of the piston is cracked/shattered, so it doesnt' look like it did any damage to the cylinder wall. I haven't taken the piston out though, I only took the head off to see what the damage looked like. Any chance I'll be able to save the cylinder? They aren't as cheap as CR's.
And, what do you guys think? Split the cases and top end, depending on what else I find when I finish taking it a part..
Man, I'm really bummed. I just got my suspension figured out and it was actually running super crisp. Now some shit like this happens, and its always going to feel like I'm riding a time bomb.
Quick question. The only other time I'ive done this is on a few CR's that I rode and the cylinders were trashed on those. (ring on exhaust side let go, have a pile of cylinders to prove it)
The bottom back half of the piston is cracked/shattered, so it doesnt' look like it did any damage to the cylinder wall. I haven't taken the piston out though, I only took the head off to see what the damage looked like. Any chance I'll be able to save the cylinder? They aren't as cheap as CR's.
And, what do you guys think? Split the cases and top end, depending on what else I find when I finish taking it a part..
Man, I'm really bummed. I just got my suspension figured out and it was actually running super crisp. Now some shit like this happens, and its always going to feel like I'm riding a time bomb.
Yes, split the cases. Do it right.
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Recently my RM250 piston fragged and took a nice slice out of the wall, right near a port. My buddy at Heavy Duty Racing honed it very slightly and sandblasted the whole cylinder for a couple hundred $$$. Now it barks.
He's in Virginia, and you're in Michigan, but give him a shout if you want. You can mail it to him.
Heavy Duty Racing Stafford, VA. Contact: Pete Payne Phone: 540-659-6994
If there is no visible damage I would just throw in a new piston. RMs run hot on pump gas btw. I mix race gas 50/50 with pump.
I can remember tearing down our motors each week to inspect/replace parts not to mention we would go through a clutch at least every other week on those things. Our race bikes were our practice bikes also so they were getting tons of time on them. BUT so are our 4 stks that we ride today!
On our 450's we tear down once a year to inspect and only more frequently if something actually goes wrong like hard starting or the very rare clutch. Pros of course tear down each race but most amateurs go a year or more on a motor now. Sure, you can get a lemon or have problems with a poorly maintained motor but again its rare. The good old days really were not that good unless you enjoy late nights fixing the smoker!
I was probably due for a top end by manufacturs standards, but the bike was still tight and crisp as ever. It was relativly low hour. (I'm still on my stock brake pads) I didn't ride it much last season at all, and only about 4 times this season. I'm not even at the point to being in riding shape yet. I usually due a top end middle of season..
Pit Row
If you did not use the shite out of your clutch on your small bore 2 stk then you were not getting all you could out of it. If you did well lugging that 125 around then you are a hero and a great rider! But most of us use the clutch constantly to explode out of each and every corner on a 2 stk under 500cc. Now days on a modern 4 stk most non-pros use the clutch to get off the line and maybe once or twice a lap and that's about it.
Ya you are right about the power, i deal with a guy each week that rides one of those things and he takes me 75% of the time to the first corner and up big hills but after that it becomes rider no matter what you ride. But i can tell you this, he is more shot than i am at the end of a moto hanging on to that rocket!
My RM, if I run pump gas, will start doing this late in motos, especially on hilly and/or sandy tracks where it runs hot.
Dude, you have apparently blown a lot of motors... I was a fast local intermediate and have only blown one motor (and that was a bit of sabotage by a competitor, loosened my plug a bit).
As for tearing down 2 strokes, yes, you do tear them down more but it takes less than an hour to completely rebuild a top end and you don't have to mortgage the house if you blow an engine.
www.powersealusa.com
If the cylinder is scarred up, buy yourself a Wiseco 2mm bigger piston and send it to Powerseal and they can bore it and re-coat it with nikasil for just over $200
Just keep in mind that Wiseco is forged and not cast like OEM. The expansion rate of forged pistons varies and its imperative to let the cylinder/piston heat up to operating temp before you hammer it, otherwise you may gall a cylinder or skirt.
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