Two Stroke Motocross

Two Stroke Motocross Forum => General Two Stroke Talk => Topic started by: cnrcpla on August 22, 2012, 01:13:44 AM

Title: Dodged a bullet (I hope)
Post by: cnrcpla on August 22, 2012, 01:13:44 AM
I was riding today on my track and heard the oddest rattling sound. I stopped my bike and couldn't find anything wrong so I put it in the garage. I looked over it and found my whole left side power valve cover (the one the stops the vavle inside the engine from swinging RIGHT into my piston) was GONE. I looked for it for an hour or so and finally found it. I opened up my top end to make sure nothing had been messed up and found that the top of the piston was ever so slightly chipped at. I can bearly tell it was even touched, but regardless I cleaned and re oiled the bore, the ports, and top of the piston. My question is, should I replace the piston? The rings look untouched and the bore is still perfectly smooth. Like I said, I can bearly tell the piston was chipped from the valve hitting it slightly. But I did dodge a bullet  ;D

On a side note... The O ring closest to the cylinder looks over stretched  :- It wont fit into the groove anymore, I have only taken it out once since it was installed new... It may have been a little warm from the engine, so I put it in the freezer to cool it off. I hope it was just warm...
Title: Dodged a bullet (I hope)
Post by: Logan Dewey on August 22, 2012, 03:31:01 AM
You are a lucky son of a b!tch, you would have lost sooooo much money :D
Title: Dodged a bullet (I hope)
Post by: cnrcpla on August 22, 2012, 04:21:40 AM
Yeah, I would have been out about $800 - $1,000 or so for bottom and top end engine failure.
Title: Dodged a bullet (I hope)
Post by: twosmoke595 on August 22, 2012, 04:39:29 AM
Quote from: cnrcpla on August 22, 2012, 11:21:40 AM
Yeah, I would have been out about $800 - $1,000 or so for bottom and top end engine failure.

if that would've happened, i honestly would've just parted teh thing out and bought a new bike lol you got LUCKY
Title: Dodged a bullet (I hope)
Post by: cnrcpla on August 22, 2012, 05:03:17 AM
Yeah. So should I put a new piston in it? I mean I can bearly tell the piston had been touched. I cant see any chips on the top so maybe Im looking for something wrong hahaha. And I probably wouldn't have parted it out, but maybe parted out the motor and put a good modern yz250 engine in it. I have a lot put in this motor, so I might have even fixed it. Hopefully I will never have to make that decission, but I do see an 06 or so yz250 in my garage in the future.
Title: Dodged a bullet (I hope)
Post by: Coop on August 22, 2012, 08:54:22 PM
In the past when I was young and broke I would re-use piston's if they had marks on the crown (never the sides). Now days I am older and still broke, but I feel safer replacing them if they are at all in question. But post pictures if you can, it will be easier for us to offer opinions if we see it.
Title: Dodged a bullet (I hope)
Post by: cnrcpla on August 22, 2012, 09:17:03 PM
I get my lap top back tomorrow, so I should be able to. But there is nothing that will be visible by picture. I had to put the piston at TDC and look really close to even see anything. I'm honestly beginning to doubt it was even touched the more I look at it... My camera doesn't take good pictures, so you guys wouldnt be able to see anything really. I'm gunna take a magnifying glass to it and see what I can see.
Title: Dodged a bullet (I hope)
Post by: Coop on August 22, 2012, 09:57:23 PM
If it is that small then you will be fine I am sure.

I had a 250 two stroke race quad about 15 years ago that a piece of ring got between the piston and head. Somehow there was no cylinder or piston sidewall damage just deep marks in the head and piston crown both. I used a stone on my drill to smooth them out because nobody had either a head or piston in stock and I was going riding that weekend. I found rings and gaskets luckily. It ran for months. It was still running fine when I finally replaced them just for piece of mind.
Title: Dodged a bullet (I hope)
Post by: cnrcpla on August 23, 2012, 03:55:44 AM
Yeah, I looked really carefully at it and don't see anything that would cause alarm. The top of my piston has some grooves in it, but those are old from when my warped cylinder head (Fixed) was leaking coolant into the engine. I think if anything was going to happen from that tiny chip that is almost invisible, it would have happened. I rode the bike back home and it is fine (thank God  ;D ) This piston only has like 15-20 hours on it max. I am re building this winter before I start ice racing anyways, just hopefully not another replate. My wallet hurts when I have to do that  :(
Title: Dodged a bullet (I hope)
Post by: Stusmoke on August 23, 2012, 10:28:09 AM
You sir, a one lucky SOB. That would've been positively disastrous. Bottom end, top end, maybe even a cylinder and head. That bikes hauled your ass home on an overheated piston if I remember correctly. Man these nineties bikes are unreliable :P
Title: Dodged a bullet (I hope)
Post by: cnrcpla on August 23, 2012, 11:21:00 PM
Yeah, this bike has hauled my ass home about 3 miles home with a stripped water pump gear, blown base gasket, over heated engine (all the coolant was gone), and gouged and scratched piston. I couldn't even notice anything wrong until I stopped the bike at home and was sitting in a cloud of water vapor from the coolant hitting the pipe. It wasn't the bikes or my own fault for that incedant, it was that damn plastic gear. I check up on it now everytime I open the bottom end. To me, having the bike not sieze or stall or even studder, says to me that its reliable  ::)  ;D THIS incedent was probably more or less my fault. I should have stopped the bike as soon as I started hearing the odd rattling and not have assumed it was my pipe or something minor. But I do thank my lucky stars that the valve didn't cause a major mess...
Title: Dodged a bullet (I hope)
Post by: TotalNZ on August 24, 2012, 12:17:00 AM
Quote from: cnrcpla on August 22, 2012, 12:03:17 PM
Yeah. So should I put a new piston in it? I mean I can bearly tell the piston had been touched. I cant see any chips on the top so maybe Im looking for something wrong hahaha. And I probably wouldn't have parted it out, but maybe parted out the motor and put a good modern yz250 engine in it. I have a lot put in this motor, so I might have even fixed it. Hopefully I will never have to make that decission, but I do see an 06 or so yz250 in my garage in the future.
Who ported your motor? and what mods have you done? Just curious
Title: Dodged a bullet (I hope)
Post by: Stusmoke on August 24, 2012, 05:10:06 AM
It would've been almost as bad as a four stroke dropped a valve... but oh yeah, probably $800 bucks cheaper if you're unlucky.
Title: Dodged a bullet (I hope)
Post by: cnrcpla on August 24, 2012, 06:23:53 PM
Quote
Who ported your motor? and what mods have you done? Just curiou
A friend of mine owns a machine shop and was kind enough to do it for me. Ported it, bored it over to a C bore, and he planed (plained?? if that's the right word) the cylinder head for a smaller squish area and more compression. I love the motor, has enough power to rip my arms off, but also has enough low end to bounce through any trail. Great woods and track set up for me.
Title: Dodged a bullet (I hope)
Post by: Stusmoke on August 25, 2012, 12:36:02 AM
Quote from: cnrcpla on August 25, 2012, 01:23:53 AM
Quote
Who ported your motor? and what mods have you done? Just curiou
A friend of mine owns a machine shop and was kind enough to do it for me. Ported it, bored it over to a C bore, and he planed (plained?? if that's the right word) the cylinder head for a smaller squish area and more compression. I love the motor, has enough power to rip my arms off, but also has enough low end to bounce through any trail. Great woods and track set up for me.

If I'm ever riding in America, I'll look you up. I'd love to have a crack at that beast.
Title: Dodged a bullet (I hope)
Post by: cnrcpla on August 25, 2012, 12:37:56 AM
Sounds good man, let me know when you row over to the other side of the pond  ;D