98 YZ250 Took in some sand

[Nickkle]

I have been browsing various different forums including this forum and would like to get some advice. I recently just purchased a 98 YZ250 for 400$ that took in some sand.

First off is the crank is seized. Should I plan on replacing the entire crank assembly (including the two halfs) or would I be fine replacing the bearings, rod etc but not the two halfs?

Second, the piston looks pretty good with one little score line thats hardly noticable. Looking at the cylinder, it looks good with nothing of real concern. Would polishing up the cylinder with a quick honing, and replacing the piston be alright?

Thanks,
Nick

 

[2-Strokes 4-ever]

Sand is not good.
The crank and rod needs to be checked to see if it's within specs. These motors are truly high performance and I'd be very careful to make sure things inside are ok enough for the bike to withstand running again. I'd bet the piston (and maybe cylinder plating) are toast. Sometimes just a visual will give you a good idea of repairs needed, but you're flirting with a potential grenade if not taking all the technical steps.

I recently almost grenaded my RM. Waited too long to have a look (and measuring) of the lower end. I heard a whining coming from the motor and fortunately shut it off in time. A main bearing cage was coming apart and it sent metal through the motor. New mains, seals, rod kit, top end and cylinder replate... aprox $600 in parts. Oops

 

[whenfoxforks-ruled]

The sand has already honed your cylinder, and bearings. A visual check would be worthy with a magnifier on the bearings and cages, and a bore gauge in the cylinder. If you want to keep it, rebuild it. 600 is kind of high, shop around. Sometimes an entire crank assembly is cheaper than the parts and labor. Some bikes, a complete engine rebuild kit can be had for under 400.

 

[m4i2k2e2]

like fox said, you can get some good deals. i rebuilt my 99 cr250 for 430 bucks. it came with a hot rods crank, bearings, seals, wiseco piston and rings. it came with an athena gasket kit but people where having issues with not getting all the proper gaskets. it all came as a kit so when i got mine i had to many gaskets. so i ordered an oem honda gasket kit. i read reviews and i was unsure of the quality of athena and i didnt want to take a chance. get a good manual and pay close attention. read the chapter first then go ahead and do it. i know for my bike i found a good instructional video for rebuilding my bike, i found it on youtube. you still need a manual though. get the proper tools for splitting the cases. dont hack them with a screwdriver. bag every screw and lable them. put all the bags and parts in a box so you dont loose them. take picture of anything complex. also, make sure you clean out the reeds and assembly. make sure theres no sand hidding in there or anywhere else. go slow.

-mike.

-mike.

 

[2-Strokes 4-ever]

Correction on the $600 figure... figured was for shipping, honeing and replating of my cylinder too.

 

[whenfoxforks-ruled]

Call Eric at Forward Motion. He can probably get the parts to rebuild the crank, and fix the cylinder, with wiseco parts, cheaper than you can get them. If he determines the cylinder and crank are fine, money in the bank, and solid!

 

[DirTasteGood]

In the long run, you should redo the whole motor, it might save you another rebuild. If anything, it will give you asurance that you know that the motor is done right.

 

[Nickkle]

Thanks for all the information guys.. I have decided to have the local shop re-nikasil the cylinder and rebuild the crank. Hot rods makes a complete crank, but for 99 and newer :bang: . I'm replacing most of the bearings, as some of the bearings are still good. This motor was already torn apart.... eek, but I've got a manual and a buddy who is a master mechanic.

Should be good to go soon!

Thanks,
Nick

 

[weav6385]

How are the gears I wonder???