Bottom end rebuild

[Jakobi]

All over all of the above Phil.

Have a thread repair kit on hand. Touching wood that I don't have too many issues with things not going as expected.

The manual calls for low torque values on a lot of things around 6nm. No issues as I have a 1/4" drive gearwrench (30 - 200 in/lbs) which is pretty accurate. I've always used it for the upper internals with 4Ts and when fine tuning triple clamp torques. Most other things I'm happy to do by feel.

Case temp the manual said 150C I thought? I'll double check that. I like the dishwasher idea. Two jobs done in one!

[adv rider]

Motion pro does make crankshaft tool for pulling the cases together. Although I use the previously mentioned temperature methods

[Jakobi]

Thanks everyone. Great info. I'm not going to bother with a tool to pull the crank back in. Will just use some temp.

[swazi_matt]

Originally Posted by 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.

I am busy with a rebuild of my bottom end (preventative maintenance) and see that the GG agent sent me NTN sealed crank bearings. The ones in the bike have close to 300hrs with no issues so I don't see an issue putting these in but wanted to ask if it would be better to remove the seals before installing them? or is there more of a difference with open bearings?

[Jakobi]

Definitely pull the seals out Matt.

My mains had started to dry out a bit at 260hrs, but also had no issues. However, without a seal the oil will be able to get in and lubricate the bearing well beyond the life of the seal and grease. My other thread shows what can happen if they do fail though.

[swazi_matt]

Thanks Jake. Will do. Was worried that the internal cage might be different

I have also drowned my bike properly a few times - wonder if the bearings would still be working if they were open?

[Jakobi]

Be hard to know for certain, but honestly I think if the drowning was bad enough (sediment/sand/mud etc) that the big ends would be negatively impacted by it, then you'd also be seeing significant ring and piston wear as well.

[swazi_matt]

Thinking about it though I guess the air filter did its job - am sure the big end bearing would show significant wear if the grit got through.

While on the topic of drowning I saw a bike this week that was drowned and they didn't know how to resuscitate it so they pushed it to the road and took it home full of water. Only managed to get it to their mechanic a week+ later ... it's going to be a bit expensive. Definitely glad I know the tricks for post drowning- the trip home ensures all moisture is evaporated

[stian]

Anyone got a option on the flywheel-side bearing? The one in my 06 is a 2-piece plastic bearing. Ill rather use a explorer bearing, as in a normal ballbearing, also used in the clutch-side.

My local shop got SKF bearings for the most.

[Jacob 'Berg]

Originally Posted by stian

Anyone got a option on the flywheel-side bearing? The one in my 06 is a 2-piece plastic bearing. Ill rather use a explorer bearing, as in a normal ballbearing, also used in the clutch-side.

My local shop got SKF bearings for the most.

As stated previously, use an open bearing with no seals. Let the fuel charge do it's job and lubricate the crank and bearings. Contact Bob at North Tahoe Motorsports and he will set you up.