Topic: CB750 Rocker / Cam cap stripped bolts.

[rz350ypvs]

I was taking the cam/rockers out to fix a massive oil leak (leaking "pucks" in the head) and I ran into a huge problem. Most of the bolts that secure the cam and rocker assembly are stripped. They were almost loose when I took the bolts out, and some of the threads came out with the bolts (and one stud). The engine was rebuilt in the late 90's by a shop and I am not sure if they over torqued the bolts.

What is the best way to fix this? Will helicoils be sufficient? I read another thread about time serts, but wasn't sure there was enough room for the studs near the holes in the head where the "puck" seals it off.

Also, two of the long cam tower bolts are strange looking (see pic). I assume this is not factory??

I am repairing the engine for my dad who has owned the bike since brand new (1973). He wants it back on the road soon!

[rz350ypvs]

Also, I tested all the bolt holes and studs at 6 Ft/Lbs and the ones that held felt very questionable. Should I just repair all of them?

[flybackwards]

I just did the same thing - final assembly of the head - first time I put it together two bolts stripped out at around 4 ft lbs - I took it apart and heli coiled the two then put it back together and another two stripped. Third time was fine I liked the heli coils - they are small and proven tech - if you are careful it is not hard to do it yourself. Have at it do the lot.

Whoever ground that bolt - I have no idea why unless maybe to use it to cut the threads - I'm sure someone will know why.

[madmtnmotors]

I would helicoil all the bolt holes and replace those marginal bolts. As for the studs, a helicoil may be difficult to seal. With treads in the head intact thread sealer is used to keep these bottomless holes at the studs from weeping oil. They go all the way through into the cavity above the spark plugs. Be careful when installing the helicoils for the bolts that you don't drill all the way through on those into the cavity below or they will leak profusely since the oil feed for the cam bearings passes through the bolt bore in the tower. This puts oil under pressure around the bolts.

[bryanj]

Oil under pressure goes knowhere near those bolts but through drillings in the tower.
All the same those hoes need to be closed or oil will wick down the threads and leak out, various soloutions have been proposed on the forum so do a search and make up your own mind.
There is room for timeserts but they are more difficult due to needing a non standard 10mm tap

[Alan F.]

That ground bolt could have been a thread chaser?

PO probably thought he was including it as a favor? Should have bagged it with a note IMHO and gotten a new bolt to replace it.

[rz350ypvs]

Thanks for the replies. I guess I will pull the head and helicoil everything. Hopefully I can seal the studs that are open holes.

That ground bolt could have been a thread chaser?

PO probably thought he was including it as a favor? Should have bagged it with a note IMHO and gotten a new bolt to replace it.

There is no previous owner. It has been apart twice in its life by "mechanics" though.

[bryanj]

Should that be mainiacs?

EDIT forget the torque wrench for those bolts

[madmtnmotors]

Oil under pressure goes nowhere near those bolts but through drillings in the tower.

And four of those drillings in the tower pass through the cam bearing cap bolt (not stud) holes...



The bolt hole bores in the head are not bottomless, i.e. they do not go all the way through into the cavity below, but the casting at the bottom of these bolt holes is not very thick and easily breached. If the bottom of these bolt holes are breached it can be difficult to stop the ensuing oil leak. I still have a pair of jeans with oil stained shins from this very scenario...

BTDT