KDXRIDER.NET

Hi All -

I recently rebuilt an 84 KDX200 motor (all new bearings and seals, except for lower connecting rod bearing, which was within spec by rod movement).

After breaking it in and jetting it, I rode it "hard" over the weekend in a CC event.

Started and ran great for about 45 min, then stopped suddenly.. I'm running down the electrical problem, but have a different question for you experts:

I noticed when removing the flywheel, that the crankshaft play (side to side / in and out ) has about 1.2 mm movement. I don't recall that after rebuilding the motor and can't find that spec in the manual.

Is that excessive, and what could cause it other than the crank sliding inside the crank bearings, which I thought was an interference fit. Any thoughts?

Thanks for your help with this.

Did you replace the main bearings?

Yes - with a set from All Balls Racing

Hi All -

You can disregard this thread.

I spoke with Jeff Fredette and he confirmed that there should be no movement of the crankshaft axially. So I'll be resplitting the cases to replace the main bearings and will do the seals also. This is not a good review of the All Balls bearing and seal kit for the 84 KDX200!!

What was your process to replace the bearings? Sorry to sound like I am questioning your technique, just ruling out a possibility.

I placed the bearings in the freezer overnight and then press fit them into the cases. The crank was able to be placed in the bearings with little effort, which should have been a clue, but I don't believe there was any axial movement of the crankshaft after reassembling the cases.

I've done dozens of main bearings this way, including an 86 KDX200 using an All Balls kit, with no issues. I'm assuming it's either a tolerance issue with the bearings or an issue with the metal used in the bearings. I'll know later today when I split the cases and will post what I find.

I'm certainly open to install suggestions - I'd rather not have to split the cases a third time within 6 months!!

Some of those All Balls kits are cheap chinese bearings, its possible you had one fail.

It sounds like this is not your first rodeo, so I suggest some Koyo bearings.

The plot thickens - I removed the bearings I had installed over the winter and they were actually Japan made Koyo bearings. They both slid easily over the crank by hand at room temperature.

I'm fairly certain the cases had never been split before I replaced the bearings a few months ago, so the crank was original, and I didn't modify it when it was apart then.

I went ahead and ordered a replacement set of OEM bearings from Fredette - I'll let you know if they perform any differently.

Wow. What are the numbers on the bearings you had in there?

Is it an OEM crankshaft?

The bearing was a Japan KOYO 6305 C3. And the crank was OEM.

Hopefully the set Fredette sends me will fit a little tighter.

Do you have calipers and micrometers to measure it and the crankshaft ends?