I have some pre-rebuild questions for my 250es.

[bigboy_toy85]

Ok, well I finally got a job! I start this up coming Monday. Well this means I can now rebuild my baby!

Well first off, I'm going to rebuild the engine. It smokes alot. Well I know it needs new rings. But I got to thinking, why not just bore it out while I have it torn apart? My question is, what is a safe size to bore it over to? I don't want to go too big! I was thinking like 15 or 20 over. What's the max you can go over.

And if I do bore it, where is the best place to get a new piston? How will this affect my timing? And would I need to get a bigger carb?

Thanks for the future help.

[Thorpe]

Affect your timing, no. Bigger carb, no... What size to bore, your machinist will tell you when you have it apart... Are you sure your rings are shot, and not just your valve seals leaking?

[MudBug]

glad to hear your gonna fix her up! :beer

[bigboy_toy85]

Well I was thinking about that. I really don't know what's causing it to smoke, but. I figured if I'm going to have it torn apart, why not just replace everything that could cause it.

And I can't wait to get her running good. I won't make enough to fix her exterior right away. But atleast she will run like a champ.

[Thorpe]

Well I was thinking about that. I really don't know what's causing it to smoke, but. I figured if I'm going to have it torn apart, why not just replace everything that could cause it.

And I can't wait to get her running good. I won't make enough to fix her exterior right away. But atleast she will run like a champ.

Thats the most important part! Exterior gets spendy... I have mine almost done, get my tank back this weekend from paint, gotta order my decals, and then mine should look like new again...

[bigboy_toy85]

I'd love to rebuild the exterior. But Im going to wait untill I stop riding the bigred. Because I like to jump into the mud. I rather have it lookng bad and be comfortable running it through the woods and jump into a mud hole, rather than having a beauty queen

[Thorpe]

Mines no stranger to the mudholes... Had my ITPs disappear in the swamp more than once!

[lndy650]

9 times out of ten new valves and valve seals is all you need. as far as boring it you should only need 10 or 20 thousanths and its not even a difference really its like 2 or 3 cc's

[bigboy_toy85]

Yea, mines a stranger to nowhere. If it's possible for it to go somewhere. It's probly been there. Most quads are jeleous too. I've had some guy offer me $500 for it once.

I wouldn't trade my three wheeler for anything.

And Thanks Indy I'm just going to replace most everything. I got to thinking and decided it wasn't the rings. Because usually when you lose the rings, it loses compression and power, and it still has all the power. And I don't want to bore it out too far, just a little to add possibly a little power

[Thorpe]

Just a stock overbore, you wont notice any real power gains...

[Dirtcrasher]

Honestly, it's when guys go 1.5MM or 2MM over stock that the cylinder liner gets very thin and is prone to cracking and can't absorb the heat as well as a thicker liner. But thats .120 or .160 thousandths over and not .020 which is typical and as much as .060 or so.

Allot of 2 strokes back when I was a squirt were pretty much cooked at about .060 - .080 over and you needed a jug. Back them we had no EBAY which made it very expensive to get rolling again.

I put a 2MM oversize and high comp piston in my 87 250SX and along with a cam, exhaust, carb and other changes; It gets up and goes pretty good :D The piston was 25$, how could I turn it down :lol: but if I ever need rings, I'll bet I'm done with the "Rocky" piston and 2MM is the absolute end of that cylinder............

BUT, the ES and SX are so limited with there suspension and gearing that can't be changed that a fresh STOCK motor is probably just as fine rather than dumping 600$ into a limited machine.