Topic: Crack Repairable or Need New Valve Cover

[Ace Blackwell]

All,

Working on the bike today and noticed this leak.  I removed the tappet thinking the seal had gone bad.  Replaced and started engine and I could see oil seeping from the crack. 

So I'm trying to see if this looks repairable or if I just need a new one.  Assuming they are out there to get.

Thanks

Also, I'm aware the screw seems gummed up.  Not sure why, I've never had the valve cover off in the 30 years I've owned it.

[bryanj]

Weld or replace. What bike would help

[nanahan]

I would replaced that screw with a new one.
How does the rest look?


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[BenelliSEI]

Those cracks go right up to the inspection cover. I’d find another cover and a new set of screws.....

[Bodi]

Again, what bike? On engines with the cover just a cover (750 for sure, maybe others?) welding will be ok. For engines with the valvegear in the cover maybe not.
Welding oil soaked cast alloy is fiendishly difficult though. Welding such a small area... moreso.
Without any pressing need to use that cover I would search out a good used one. If the valvegear is in it, the cam "bearing" surfaces should be fine in a non matching cover as the cam rarely if ever works against the cover bore. Chain and tappet forces are all downward. For main cases with tight bearing tolerance the cases should definitely be matched but for the valvegear cover it doesn't normally matter, production tolerances were close enough for the relatively loose fit needed..

And - that screw is way past worn and belongs in the scrap bucket along with any others in that state.

[BenelliSEI]

Ace..... I’ll assume  that’s your cb750F? Since you’ll  need to pull the engine to replace that cover, try this first. Pull off the tappet inspection cover, and take out the screw. With a Dremel, carefully clean the cracks and create a small “V” in the surface of the cracks. Blow it all very clean with brakleen spray. Mix up a small amount of two part JBWELD” and paint the cracks, filling the little valley you ground in with the Dremel tool (use a tooth pick). Before it sets, tighten in a new screw. Don’t get any in the threads for the cap. When it’s dry, apply second, thin coat again. It might seal, and save you a lot of work......,

[ekpent]

 Wonder if that got broke by somebody beating on the screw head with an impact driver or something. Take out that screw and the chunk might just fall out like a rotten tooth.

[Ace Blackwell]

Thanks all.  If it matters the bike is a 77 550F.  I should have posted but though it was list under my profile picture

Benelli I think I’ll try that before pulling engine.  Not much to lose. You said if I replace, I’ll need to pull engine. Granted I don’t know how much clearance is needed? When I had the tank off this weekend working on harness, it seemed like there would be enough room if I got the cables out of the way.

Assuming I may need to replace, are these things hard to find or bike model specific, meaning it will have to be a 77 550F. A 550K or 76 550F won’t cut it.

[jonda500]

Any '71 to '78 CB500/550four cover will work - ppl here favour the later ones ('77,'78 I think) as they have the rocker shafts pinned so they can't rotate and chew out the soft alloy cover
John

[ekpent]

 Benelli was assuming I believe you had a 750 hence the fact the engine would have to come out to remove a valve cover. 550/500 you do not need to pull the engine to do that.

[754]

I assumed it may he 550 by your pic, but...but many of us have several bikes.l
 So make it easy, post what it's for..btw for 750  valve cover are often 40 to 70 bux, not worth welding.