Bottom end rebuild

[Zman]

I just did this on a 2004 DE300 and I put the bearings in my freezer for a few hours and then I put the cases on an old cookie sheet and placed them into my weber gas grill set on 150F. I used an IR thermometer to confirm and it took about 15-20 minutes to get up to temperature. Onc bearing dropped right in and the other bearings went into the case bores with a minor tap from a deadblow hammer via an aluminum bearing driver tool. It was very easy.

[zeuszuki]

C3 clearance on your mains

[Zman]

I got them strage from Gofasters, but I beleive the ball bearing was a C3 but I think the roller bearing on the ignition side was just a 4 digit number with no letters.

[Mc_Grath]

I am about to open the engine to replace the main bearings, the left one already lost its tolerances and is making sound with only 90 hours in the bike. It is a 300 '11. I won't use original main bearings so I was wondering what do you recomend ceramic or steel GMP? Too I need to know the size/type of bearing I need so I can start ordering them before opening the engine. Thanks.

[Mc_Grath]

Sorry I forgot to mention too that I have heard that the bearings are the same as the honda Cr 250 ones, is it correct? both bearings? because I can find pretty cheap kits for honda

[Jakobi]

I've got an OEM set. I got a good price on the complete set. All bearings, trans, water pump, mains, etc. I'll pull the sizes off the mains for you if I get a chance. In hindsight I really should have just waited until I had them all pulled and then taken them into a bearing shop for spares. For the record all the OEM ones are SKF. The 2010/2011 models have the sealed LSH main. Not sure about 2012/2013 models.

[Mc_Grath]

Thanks Jacobi, but don't worry, I already found the sizes, Only the one of them is compatible with the honda ones but I am going to buy them local in a bearing shop, Just wondering if that closed roller bearing? would not be better to replace with a regular one (open and balls) since this closed one is the one that has failed with so little hours on it..... What you guys think?

[Jakobi]

GMP suggests that open is much better. I'd agree. Every other brand uses open ones and it was just 2010 that GG went closed. Maybe a test?

[ditezz]

I have used a heat gun for heating cases for bearing installation / removal and they are particularly good for heating hubs when changing wheel bearings.You can adjust the temp on mine and it also has a digital temp readout.Works a treat as you can direct the heat specifically where you want it and less chance of burning the crap out of yourself as you might do using a oven or barbeque

[GMP]

Yes, its related to lean premix ratios and future DI concerns. Just introduces another potential problem IMO especially with ethanol in the fuel. If a seal on the bearing fails, it spins out the grease, adequate oil cannot migrate in, bearing seizes or fails. Not widespread, but it has happened. I'd go open at the first oportunity. The previous roller/ball combo was fine.

Mains are NOT the same as Honda CR250, rod kit is. A quality ball bearing like an NTN, FAG, SKF, etc. (not a Chineese knock off) with a C3 clearance spec is fine. The two part roller is a very heavy duty bearing, its just more of a PIA to get the inner race on and off the crank as the fit seems tighter and its smaller. An M306 heavy duty is excellent as well and cheaper than ceramic. I have a local supplier who does a lot of ceramics and hybrid ceramics for MC and kart engines of various types so I'd probably go that way. Ceramics run cooler and are supposed to be less needy of oil.