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Rebuilding a 2 stroke?
- Thread starter unL33T
- Start date
I don't think that pic is my bike.
What causes that?
boyoboy
Well-known member
any pics of rs125 damage?
did you say motor was rebuilt by previous owner?
on the upside, i find $500 for cylinder and piston a reasonable cost. are these good quality from a reputable source?
hung ring on exhaust port...excessive wear maybe, and or combined with poor chamfering during last rebuild. whats your take on it bittz?
running the rs125 at or above redline, in top gear, for SUSTAINED PERIODS OF TIME is not good to engine life. running up to redline while working up through the gears is acceptable. if your riding for sustained periods of time try to keep the bike at least a few hundred rpm below redline. EDIT: looking back in the thread the engine was rebuilt previously due to a seizure. and others have mentioned to you that engine seizures during cool weather often happen. I would really try running the bike with a one step richer main jet - you can always change it back if not happy. and change the rubber intake - before it really does cause you problems.
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The working theory is the rings were worn past spec and that allowed them to enter the exhaust port (the biggest port).
The port chamfer was OK, at least it wasn't a problem for several thousand kilometers, so I don't think it all of a sudden BECAME a problem.
It was jetted nice and fat, maybe even TOO fat (the stinger is full of oil) and the intake boot is fine.
Other than the ring embedded in the side, the piston looks neigh on perfect. Lubrication was not an issue, what ever oil he was using seems to work.
I think Aprillia's maintenance schedule, at least in regards to the rings, is a little optimistic... maybe even A LOT optimistic.
The port chamfer was OK, at least it wasn't a problem for several thousand kilometers, so I don't think it all of a sudden BECAME a problem.
It was jetted nice and fat, maybe even TOO fat (the stinger is full of oil) and the intake boot is fine.
Other than the ring embedded in the side, the piston looks neigh on perfect. Lubrication was not an issue, what ever oil he was using seems to work.
I think Aprillia's maintenance schedule, at least in regards to the rings, is a little optimistic... maybe even A LOT optimistic.
Bitzz would have to supply them as he's got the bike right now.
He said it seized solid on him on the 403 at about 130 kph at about 5000 km. Whoever he took it to told him it was too lean and made it much richer. As of the last fillup, about 1 hr before failure, it had 12211km on it.
That's a Mitaka kit from AF1 Racing in the US. They claim it is the same quality as Aprilia parts, at 1/3 the price, and they run it in their endurance race bike without any problems.
http://www.af1racing.com/store/Scripts/prodView.asp?idproduct=38844
Only comment I have here is that it seized during hot weather (well it was supposed to be like 30+ that day but it was only 25ish so I was happy it wasn't as hot as I was used to) and like Bitzz said, it's running so rich I have oil pouring out all the mating points in the exhaust (which I was told by the importer is a good thing but Bitzz let me know I was heading for a fire soon).
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I'm going to have to look into that. Maybe the service manual I found online isn't correct or I'm misunderstanding it.
Here's what I have from a 2006 service manual. Everything I can find online says they are the same from 2006-2009 but I believe the 2009 model (mine) has newer styled bodywork.
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Ooops
View attachment 37365
View attachment 37365
Before failure:
After:
(They look the same. lol)
Last year:
Year or two ago:
Same pic, different angle, seems to be one of few from this side:
Shortly after I got it, with my 650R before I sold it to someone that destroyed it:
There's one on Kijiji right now, almost new:
http://www.kijiji.ca/v-sport-bikes/...al/1076026744?enableSearchNavigationFlag=true
That's a shame, if it wasn't for the gouge it's otherwise in pretty good shape
We were looking at it yesterday and the piston still has those hash lines AF1 said should be missing.
theraymondguy
Well-known member
Perhaps the ring that failed wasn't gapped properly.
boyoboy
Well-known member
new piston, rings, and cylinder: doing it right. better that you replaced all as a set - putting used parts back in would have been false economy. waiting to hear an update from bitzz soon. love that eighth litre firecracker. from what i read, your one of the few who got the rs125 road legal.
There are actually quite a few on the road. I've seen about 5 road legal on Kijiji.
We had to do it all unless I got the cylinder repaired which probably would've cost quite a bit, anyway.
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