So i was taking apart my primary/derby cover to change all the bolts from silver to black but now i see that one of the threads on the primary that holds the derby cover is stripped and the coresponding hole on the derby cover itself had a small crack. What do i do im going to heilicoil the threads. But do u think i need a whole new derby cover? Your guyss input would be much appreciated

 

These are the pictures

 

Leaving a Cracked anything ain't good. I'd change it. That's just me.

 

It's the top hole, right?

If it's the top hole and it wasn't leaking I think I would run it if you liked it. There probably isn't a reason for oil in the primary to overwhelm that spot with oil or pressure, hence, if it hasn't leaked it probably won't.

Otherwise, you could come up with a serviceable one easy and cheap enough one way or the other.

 

I see it now, this is a talisman!

If it isn't PC'd black to match your primary then there's your answer; the God's say pick a new one and PC it black.

Gosh, that was so simple, don't know how I missed it before

 

insert a helicoil and replace the derby...and have peace mind knowing it was repaired right.

 

So..... was it over tightened? I agree with all the above, not a cause for worry, untill you start seeing oil come out - if ever.

 

I'd Helicoil the hole and run that derby cover without hesitation. It's at the top and the "print-o-seal" on the gasket is inboard of the screw holes. Maybe keep an eye out for a replacement at the swaps and if you find a really nice one for cheap replace it just for peace of mind but the cracked one may run fine for 50 years.

 

Really? It's bad enough that some clown overtightened the cover enough to screw up the primary. Now you want him to just ignore the cracked cover because it may not leak? Just think how the next owner will feel when he removes the cover, finds the crack, then finds the helicoil. Remind me never, never, never buy a used bike from a few of you guys.

 

You're jumping to assumptions and conclussions, and way out of line.

You have no clue as to how it was damaged. It wouldn't surprise me if it happened during manufacturing.

It's the top hole on the Derby cover. Not any other bolt, not the bottoms, not the sides, it's the middle top bolt. That is important.

The OP didn't say "Hey fellas, how can I disguise what is probably a meaningless crack in the least crucial point of the derby cover so I can pawn it off on some schlep".
After stating how he was going to fix the bolt hole in the primary he then asked in other words, is it ok to use the derby cover.

I don't think the primary creates pressure inside due to it's size and there really isn't a hole lot of oil in it and gravity, spinning of the chain, and lack of created pressure will doubtfully make oil over come the gasket, and thus leak out of that spot.

If by rare chance it did, we're not talking no cataclysmic failure here.

Maybe the OP really likes that derby cover.

Nobody but you came up with this nonsense about selling some problem to someone else.