Posts
3945
Joined
4/1/2008
Location
Visalia, CA
US
Fantasy
Edited Date/Time
10/10/2014 5:35pm
My son and I decided to start the new year out right with a ride at the local Mx park in Tulare.
He got about 30 minutes of riding in on his RM85 when the bike suddenly quit. I didn't want to end the day, so we alternated using my bike. I was both proud and a bit embarrassed, as my 105 pound 13 year old piloted my CR250R around the track better than I did, and he'd only ridden it a couple of times before in a big field.
While at the track I had pulled the pipe to see if the piston had any telltale scarring marks, I didn't expect any since we'd only burned through 2 tanks of fuel since it was last replaced, and we were running on fresh fuel. It seemed low on compression, so once home I pulled the top end off, and this is what I found:
Note that one circlip looks more spread out than the other- it's not. The missing part of it is embedded in the piston
That item sticking up was the source of the low compression.
Here are some other pictures of the piston.
Had the damage been limited to the piston, I would really not care too much. Of course, that was not to be.
I can't decide if I should buy another RM85 and part his out, find a cylinder on FeeBay, or just move him to a 125. The last one will eventually happen, but he's wanting to have a go at Loretta's this year- and it won't be on a 125.
He got about 30 minutes of riding in on his RM85 when the bike suddenly quit. I didn't want to end the day, so we alternated using my bike. I was both proud and a bit embarrassed, as my 105 pound 13 year old piloted my CR250R around the track better than I did, and he'd only ridden it a couple of times before in a big field.
While at the track I had pulled the pipe to see if the piston had any telltale scarring marks, I didn't expect any since we'd only burned through 2 tanks of fuel since it was last replaced, and we were running on fresh fuel. It seemed low on compression, so once home I pulled the top end off, and this is what I found:
Note that one circlip looks more spread out than the other- it's not. The missing part of it is embedded in the piston
That item sticking up was the source of the low compression.
Here are some other pictures of the piston.
Had the damage been limited to the piston, I would really not care too much. Of course, that was not to be.
I can't decide if I should buy another RM85 and part his out, find a cylinder on FeeBay, or just move him to a 125. The last one will eventually happen, but he's wanting to have a go at Loretta's this year- and it won't be on a 125.
I'm going to contact Namura and see if they have any helpful suggestions; the dealership I bought the piston from has since gone out of business. The whole thing is just a bit baffling, from the blowby with low hours, to the circlip being the issue and not the piston itself.
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BTW, it looks like the piston is wearing at 4 corners. This is usually caused by too quick warm-up.
Heartebreak I agree, based on the blowby it does look like there are a lot more than 2 tanks of gas through it. My son thinks it might be 3 tanks worth, but unless the RM85 was equipped with 15 gallon tanks I don't see that being an issue. Also, the machining marks are still visible all over the piston, they haven't worn off. I've guessing Jakes dad may have hit the nail on the head, but that's just a guess right now.
CamP I've run just about every type of piston in my pingers over the years with nary an issue until now. Maybe this is the sign I needed. You're correct, there does seem to be a bit more wear on the 4 corners. When I first pull the bikes out of the truck, they sit there and idle until the cylinder is too warm to keep my hand on. After that, I don't worry about it for the rest of the day. Looks like I need to add just a bit more time to the warmup before each moto or practice session.
Madmaxperformance The circlip was installed with the ends pointing down.
Thanks for the ideas. Now I just have to figure out how to reach Namura, there's no phone number listed on their website (never a good sign when it comes to customer service).
or for a few more bucks make it a big bore. I went the big bore route (265cc) and don't regret it one bit, plus he's cheaper then Eric Gorr
Also, it looks like you have a fairly serious detonation problem by the way the carbon is scrubbed off the crown.
The lesson I took away from it was to never re-use a circlip on a piston. And I haven't. Never realized there was a proper position to install a circlip???
Fresh cylinders I have found are key to "good consistent performance" and better wear on parts.
There's better deals if you can get in with a local dealer by sending a bulk deal on the cylinders. Send me an email for more specifics on this. This has allowed me to keep things fresher and performance is always there and it ends up costing me less in the long run.
I'm also quite certain when I bought the bike it was on the original piston (this one was the 3rd I had installed, making it a total of 4 pistons). When I bought the bike, the only non-original items were bars, grips, throttle tube, and stickers. All replaced because the kid crashed after a couple of rides, then lost interest in riding.
Terry, you're the lone person that thought detonation was occurring. I could be wrong, but I don't think any carbon was being scrubbed from the crown. If anything the black color makes me think it might have been jetted on the rich side (?).
I was able to make email contact with Namura today, and was given their phone number by a helpful member of another board I posted on (thanks for the interweb, Al Gore
Pit Row
The best investment one can make is a circlip installation tool. Even the slightest divot or gouge in the clip could result in a stress fracture of the clip. Saves from scratching / gouging the piston as well.
The area of the broken clip pictured looks about where one would grab it with a pair of needle nose pliers to tweak it in place. Clips are stiff, and with the pressure needed to grasp / install with NN pliers, it is very east to mar the clip, possibly creating a stress riser.
I'd make sure next time to not bend the clip too much while installing. Rather than compressing the clip, I insert half in the groove, and gently push the other half side in with a screwdriver or similar. Pops right in a check all the way around it's seated.
Plus use Wiseco.
Millenium Technologies----they'll weld, hone and replate that cylinder better than new for a couple hunnies no problem.
Change my avatar, huh? That was, like, the SICKEST whip ever! Made JS look like a rookie. It was even better than a DDavis SCRUB! Now I have to go dig that fuckin' thing up and reload it into the computer. For your insolence, you shall PAY!.
I'll be in town tomorrow night. We'll see who's laughing, when I'm watching A-1 on YOUR brand new big screen. While sitting on your chest on your livingroom floor. After giving you a wedgie so bad, your wife will ask if your new friend gave you a new HOODIE as a late Christmas present!
You can laugh now, my friend. But be afraid. VERY.........................afraid. I know..............where you live.
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