Bottom end rebuild

[desertgasser300]

http://www.usabearingsandbelts.com/

These guys had every bearing I have ever needed to rebuild the bottom end of the Gassers.

[Mc_Grath]

Thanks for the answers guys!!!

[Jakobi]

Ok.. so I have all my parts ready to rumble. I've decided I might tackle the job over the next round of days off so the easy jobs first will be removing the engine. I'm going to fab up a simple brace which will allow me to mount the whole engine to the vice. Will give a solid platform to work from. Priority at this point will be getting the cases split and crank out ready to be sent away for rebuilding and balancing. Depending on how I go for time I might be able to get the old bearings out too. Maybe drop some fresh ones in. We'll see how I feel as the job progresses. It'll be slow for sure being my first time at it.

I've read the shop manual and it all makes good sense there so I'll follow it and plod along at snails pace. I think I have all the tools required too which is always a bonus. *fingers crossed* all the bearings drop in and out easily. On reassembly I see that it says to use thread locker on some nuts/bolts. Which colour is recommended for internals? High temp red?? Or just the medium blue? I have both but would rather use the right one.

Any other tips?

[pscook]

I strongly recommend you purchase a 6mm helicoil set. I discovered that almost all of my clutch cover threads had to be repaired, but I don't know if that is from the previous owner or the butter-like consistency of the engine case alloy. However, just having a set on hand before you start will build good karma with the engine god(s).

I wouldn't use any thread locker stronger than blue just because you might own this bike for another several hundred hours and have to get back into it. That being said, proper torque application will provide good holding strength so the blue should suit you fine. Unless, of course, the manual gets specific. This assumes you have a lightweight torque wrench, not some yard-long beam style with 1/2" to 1/4" reducers. Use a torque wrench with the right range, as you don't want to work at either the very bottom of the range or the very top. The target is the middle 40% of the torque wrench range (20% below half, 20% above).

Just remember to freeze the bearings and crank 24 hours prior to assembly, and don't warm the cases more than 150* F. Heat gun works well, but I like the "whole package" solution, such as a warm oven for 20 minutes or fresh out of the parts/dishwasher.

Last tip- beer is post, coffee is pre. I find that I swear to a greater selection with a good shot of caffeine, alcohol just makes me say "eff it."

[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?