Crank shoulder repair options

[GlennP]

Eric,

Upon inspection of my GG crank, it appears the shoulders were machined incorrectly in production, and the inner races of the main bearings are only a slip fit. There is indication on the primary side of some slippage, as the crank surface is highly polished where the bearing sits. The fit of the outer races in the cases is fine. Besides pressing GGNA for a replacement (which I will do anyway)what are my options and what would you suggest? Is there a suitable Loctite compound for a crank application, or is a build up and re-machining required? If the later, could you recommend a shop providing such a service? Thanks.

 

[A.J]

I would pursue the loctite if you can not get a new crank from GG.They make some really amazing stuff and they have a link on their web site for tech questions/applications. The make a few different kinds of bonding products for cylindrical part assemblies.
Having said that, I am having a similiar problem on my bike but the cases are a slip fit to the bearings instead. I tried loctite 620 this summer and it seemed to work but when I disassembled the cases last week I could see that the bearing had been moving. I am not sure if I had it clean enough and also when I tightened the primary gear onto the crank, the crank centers itself in the cases and that may have broken the bond.:think
Anyway, I am going to make sure it is clean and give it another go, it is definitely less costly than any other options and I have heard a lot of good things about the stuff.

 

[GlennP]

AJ,

Thanks for the reply. What will help in your case is to "dimple" the bearing bore case surface with a center punch. This will raise the surface in spots, increasing the interference fit. Use the loctite as well. In my case, the crank is too hard to do this. This advice was given to me by a very knowedgable tuner.

 

[georgieboy]

GlennP, where does GGNA stands for.(i am a dutchie, so be kind with me)
and i also have read yr other thread about the bearings specs.(dealing the same problem).
I really thing that eric must answer this one, or any other highschooled mecanic with this kind of experience.
It really $#$% when you find out it is bad engineering. Hope you get yr answers soon.

 

[GlennP]

No problem, my grandfather was from the Netherlands.

GGNA is Gas Gas North America, the US importer. If they refuse to discuss my problem, I will come up with a more colorful name.

Its not bad engineering, but bad machining/QC.

 

[WoodsRider]

Originally posted by GlennP
Its not bad engineering, but bad machining/QC.

What's that, a Spanish bike with a quality problem?
Say it isn't so. :scream:

While your at it, ask GGNA for a service manual. You'll probably get a new crankshaft before we ever see a service manual. ;)

Good luck and keep us posted.

 

[GlennP]

By the time I get this job done, I could write my own service manual. Just the luck of the draw I guess.

Actually, the motor is quite simple and rugged inside. If your a good mechanic, a through spec sheet would be adequate. Besides the crank, everthing else looks great.

 

[Sage]

they're built like that so you can change your crank in the woods using a tire iron man! :)