Two stroke bike question

[SNEAKY]

to me, piston and rings is almost a maintenance item. if you change them before they have to be changed because of damage, then you can save yourself problem with having to get the jug worked on.

the thing is, i am not a "fix it" before it breaks kinda person. but this seems like a cheap once a year PM thing on a two stroke. like adjusting the valves on a high rev MX bike.

[davbrucas]

Depending on how much you ride and what size bike it is, you will need to change the top end on a smoker more often. When I was on 125s I would change the top end every 30hrs...on the 250, it would be around 40-50hrs. Never seized a bike and I rode very hard.

[FastFord19]

Yup, one thing I hated about my old 92 Kx125. I had to change that damn top end so many times. I did it so often I was able to change it out in about an hour. I was about 15 years old then.

[biljames01]

Change that piston and rings often! When you thrash a piston and it cuts the jug so bad that its a paper weight it sux! I had a kx 250 I used for trail riding and pickup mxin with friends, I changed them 2 times a year. Hope this helped

[76 Maverick]

Going by that i'm due for a topend just in the last couple months i've owned it. Blaster seems to run fine though.

[SNEAKY]

Going by that i'm due for a topend just in the last couple months i've owned it. Blaster seems to run fine though.

and it could last a good while. but you schedule a time to do it, say Feb. or Mar. when it is the coldest. or mid summer. just do it at your convenience, and not the bikes.

we do not ride that hard, you have a couple of top end runs on the sand bar, and then it is back to the trails.


BTW, i am picking up those wheels from Lee tomorrow night.

[76 Maverick]

and it could last a good while. But you schedule a time to do it, say feb. Or mar. When it is the coldest. Or mid summer. Just do it at your convenience, and not the bikes.

We do not ride that hard, you have a couple of top end runs on the sand bar, and then it is back to the trails.


Btw, i am picking up those wheels from lee tomorrow night.

sweet!

[93coupett]

Depending on how much you ride and what size bike it is, you will need to change the top end on a smoker more often. When I was on 125s I would change the top end every 30hrs...on the 250, it would be around 40-50hrs. Never seized a bike and I rode very hard.

Yeah 125's need a top end quite often. I found that out the hard way on my old YZ 125. Rode that sucker until it wouldn't go any longer. After that I changed mine every 30-40 hrs. I had a KX 80 from age 5 to 13 and only remember my dad doing a top end a couple times.

[76 Maverick]

Now when we say "top end" are we talking piston ring and cylinder, or is it common practice to just change the piston and ring as long as the cylinder doesn't have any scratches?

[SNEAKY]

Now when we say "top end" are we talking piston ring and cylinder, or is it common practice to just change the piston and ring as long as the cylinder doesn't have any scratches?

:wall:

[onjacks]

Well, with that said...

I have a 1999 CR250r that still "looks" fairly new. It has Never had a new top end, though it still runs strong.

I was looking into buying the Wisco piston kit.

Where do I take the "jug" to have bored over. Or should I?

Do I just remove the jug and put the piston on the rod? I read somewhere that you need a special tool for proper torque.

I plan to throw a little :feedback: into this bike cause it's in great shape.

Gonna get it ready for next Spring.

[davbrucas]

I would just change the piston...never even touched the jug and never had a problem. If there is obvious gouging in the jug then it will need a nikasil plating.

[greenbullitt]

Well, with that said...

I have a 1999 CR250r that still "looks" fairly new. It has Never had a new top end, though it still runs strong.

I was looking into buying the Wisco piston kit.

Where do I take the "jug" to have bored over. Or should I?

Do I just remove the jug and put the piston on the rod? I read somewhere that you need a special tool for proper torque.

I plan to throw a little :feedback: into this bike cause it's in great shape.

Gonna get it ready for next Spring.

later model bikes are usually lined cylinders i.e. nikasil,electrofusion etc. and cannot be bored. when they need to be bored, you have to opt for a new cylinder or a sleeve

[Buick355]

later model bikes are usually lined cylinders i.e. nikasil,electrofusion etc. and cannot be bored. when they need to be bored, you have to opt for a new cylinder or a sleeve

That's not entirely true, depending on the cylinder some can be bored and replated with Nikasil. There's a few places out there that do it if it can be done, I had it done on a YZ250F I had


KTM 2 stroke 250/300/380 pistons last a long time, well over the typical 50 hour mark. The KTM oem pistons are much better quality than what's oem in the jap bikes. Of course riding style greatly depends on this.

[onjacks]

so should I just buy the standard size piston kit & wipe down the inside with some emery cloth.

[TX21]

I had about 200 hours on my 01' YZ125 (134cc) Piston looked great when I changed it. I still have it in fact. It was matched to a new cylinder though (don't know if that matters). If you don't race then you don't need to change it that often. To be safe I'd go 50 hours then change it if you are not running it at MX speeds all the time like on a outdoor track. Sometimes just a ring will do as well.

[TX21]

Here are the pics of that Wiseco piston.

[mikeb]

The more that the rings and piston wear, the greater chance the engine will seize. Blowby heats the piston, and there is nowhere for the heat to go.

Back in the day I just don't remember changing the top end that often on 2 strokes. But then again we ran a 20:1 mix too, and I think today the oil mix is a lot leaner. The boys that ran a castor based oil had to change out top ends due to gum and carbon buildup.

I had a yz400 that I bought used. The thing knocked and banged something terrible, but it sure ran like a scalded dog. I finally did a top end job on it.

[davbrucas]

The more that the rings and piston wear, the greater chance the engine will seize. Blowby heats the piston, and there is nowhere for the heat to go.

Back in the day I just don't remember changing the top end that often on 2 strokes. But then again we ran a 20:1 mix too, and I think today the oil mix is a lot leaner. The boys that ran a castor based oil had to change out top ends due to gum and carbon buildup.

I had a yz400 that I bought used. The thing knocked and banged something terrible, but it sure ran like a scalded dog. I finally did a top end job on it.


People running 32:1 are actually richer, by definition...ie, more fuel with a constant amount of air. But I understood your point.

[davbrucas]

I had about 200 hours on my 01' YZ125 (134cc) Piston looked great when I changed it. I still have it in fact. It was matched to a new cylinder though (don't know if that matters). If you don't race then you don't need to change it that often. To be safe I'd go 50 hours then change it if you are not running it at MX speeds all the time like on a outdoor track. Sometimes just a ring will do as well.

200hrs on a 125? Wow...that things was way down on power.