Newb with a coupla engine questions

[turtle]

I just bought my first dirt bike yesterday, and introduced myself here today. I lurked here a little before buying my bike, and found a lot of references to replacing the stock piston with a forged unit. My bike is a 2004 but it has been ridden a lot so I suspect at some point the top end has been rebuilt, but I do not know for sure.

Is there any way to tell what kind of piston is in the bike without tearing it all the way down to the point where I'd just go ahead and replace the piston anyway?

Also, when I eventually do go through the top end, what is the best way to tell if my crank bearings are OK?

Is there anything else I should be looking for in there?

In 6 years and 35k miles of owning my street bike, it has never been to a dealer so I am OK with a wrench, but I will say the idea of getting this far into an engine - even a "simple" one - is a little intimidating. Once I have done it once I'll be OK, but I'm a little concerned up front. Time to spend a little time with the search function

TIA!

[Julien D]

Lucky for you it's a two stroke, so you're only dealing with a few parts total. Order yourself a service manual, and open her up! It's the first thing anyone should do when they bring home a used 2 stroke. You can check crank and rod bearings while you have the cylinder off, via play in the rod.

[johnyblaze]

You can't tell exactly which piston you have, but you can tell if it's a Wiseco by simply pulling the head off - only takes a few minutes. The Wiseco has a serial number stamped into the top of the piston and the last 3/4 numbers tell you the piston size.

But, hey -while you're there... might as well pull the cylinder, etc and give them a good check.

[nearma12]

It's probably a good idea to pull the top end apart and check it out anyway. A service manual makes that very easy.

But, you can pull the exhaust pipe off and look in the port to see the piston. With a good eye, you can probably tell if it is cast or forged by looking at the grain of the metal.

Where are you at in Central IL? I live in the Mattoon area.

[Julien D]

I don't believe you can tell the difference between OEM and Wiseco through the exhaust port. Not unless you could see the underside of the piston, which you can't. The machined surface on the outside is too similar between the two. We've gone over this a time or two. The only sure way is the W on the bottom of the Wiseco, or the part number stamped in the top.

[turtle]

Where are you at in Central IL? I live in the Mattoon area.

I'm near Peoria in the rural area near Washington and Morton.

I think I will probably tear it down ... my service manual is for a 200, but I assume they are very similar.

[performancecycle]

If you have any problems check out cyclepedia.com Its like $25.00 for a years pass and seems to be better than the manual in my opinion.