But I don't want to...

[subxero]

Last night I finally got a chance to open up the top end of my 2stroke dirtbike as I thought it was making an odd sound that I did not care for.

The good news... top end looks pretty good, no abnormal wear or tear, piston was pretty clean, looked like rings had been sealed well. Cylinder looks to be in good shape. Will probably send it out to get expert opinion and to get honed at least.

The bad, I think my bottom end needs replaced. The rod and bearings feel tight up and down with no play which is super important but I have a good feeling my side to side play is definitely out of spec (need to check manual). There is a little bluing on part of the crank so it must have been a little toasty in there at some point, and there seems to be a little corrosion/rust spots on one part of the crank as well, most likely from sitting around for long period without riding.

I am all for fixing things that need replaced and I would love to replace my bottom end so I guess title of topic is misleading, the problem is more along the lines of I don't feel like paying for a bottom end rebuild. BAH!! I need to do some research, price out parts and talk to a few different shops and get some quotes or just consider doing it myself. I would need to buy case separator along with a few other tools. Might be the route to go to save some cash as I don't have much disposable income right now + I need to get a top end kit to, that is ~$115 or so. Bottom end kits can run from $200-$400 bucks from what I see, then add labor to that. I would probably tear the bottom end apart as far as I could before I would give it to shop so maybe it would not be that bad for labor IDK?

/end my sob story

[ninjamunky85]

I say go for the full rebuild. Once you learn to do it you'll never have to send it out for a rebuild again. Plus you'll know exactly what's going on with your engine.

I'm rebuilding the top end of my buddies ttr-125 right now. I've never rebuilt an engine before, but I'm doing it for experience. The experience will definitely help out when I go to rebuild my kx. I could afford to have it professionally done, but I take pride in doing all the work on my motorcycles.

[subxero]

after you do the top end in that ttr 125 4stroke, doing the top end in the kx 2 stroke will be borderline boring. I had my top end torn down in ~ 30 min lastnight ( I might have cut a corner and left the radiators on, made a mess with the coolant because of it, but it was worth it IMO )
The bottom end is a different monster all together though, so many parts, so much to lose or ef up. I am definitely going to get a quote on the rebuild, if it is not that much I will just have a shop do it.

[subxero]

talked with a small local shop and they seemed very reasonable with everything from hourly rate to pricing on parts so I think I am going to drop off the motor next week and have them do the bottom end. Which will be nice cuz they will also notice anything else that looks like it needs replaced while they are in there.

Can't wait to get this thing running again BRAAAAAP!!!

[Motofool]

Originally Posted by subxero

...........The bad, I think my bottom end needs replaced. The rod and bearings feel tight up and down with no play which is super important but I have a good feeling my side to side play is definitely out of spec (need to check manual). There is a little bluing on part of the crank so it must have been a little toasty in there at some point, and there seems to be a little corrosion/rust spots on one part of the crank as well, most likely from sitting around for long period without riding........

Lateral play is not critical there and much less is any rust.

Before jumping into a repair, I would verify everything against specs, if you have the instruments to measure all.

Normally, the top bearing goes first, causing some noise when the throttle is closed.

Failure or wear of the bottom bearing produces a sound more under load.

Play in the base of the piston is more constant at any load and rpms'.

What I am trying to say is: measure twice, cut once ........... or let a shop determine the source of the noise before changing parts that are in good condition just to leave bad parts in, wasting cost of labor.

Be generous with lubrication, ....yes, it affects performance, but extends engine's life.

[subxero]

Exciting news!... well for me.

Picked up my yz250 motor last night from the shop.

I feel like they treated me pretty well and the works looks good.

When all was said and done, They split the case, replaced, all bearings, gaskets, seals, and crank. Threw it back together, check spec on my cylinder (it was still in spec and looked reasonable) they honed it for me and slapped in the new piston, rings, ect... and threw it all back together. They checked other odds and ends (power valve)
Sure I could have handled the work myself but I just don't have the time and energy right now to tackle that kind of work so I was happy to pay the shop for their time and have peace of mind that It was done right.

In the end for pretty much a complete engine rebuild (given, case and cylinder, gears, clutch are in good shape) $600 including labor. Gotta love simplicity of a 2stroke!! Figure only thing left for me to do is put the bike back together and I want to get a light weight flywheel weight to help tame the hit just ever so slightly as I do a decent amount of single track woodsy stuff.

Ill post some pics this weekend as I get things back together.