Topic: Head gasket leak (pics) OR: The Debacle.

[gregimotis]

Fixed in Three.

Heavy Duty studs (APE race parts) - 80.00
Machined faces (local shop) - 120.00
3 Honda gaskets - 80.00
Three tear downs - 15 hours
One high revin', partly legal run up a mountain road - 40 miles


One Leak free CB750

Thanks for the support, now I'm going to go fill a glass with two or three ounces of relax-juice.

[Jerry Rxman Griffin aka MuthaF'er]

Third time's the charm! Congrats. Now you're a pro. No short cuts next time. Keep us informed of the status.

ps You can be the guy to tell all the future head leak guys to do it properly and spend a few more bucks (initially) or don't waste their time. 

[Terry in Australia]

Well done mate, I'm glad it worked out ok, but hey, you put the effort in and you got the desired result. Kind of a lesson in there, hey?

[gregimotis]

Thanks for the support. 

I am now the owner of one of the fourteen oil leak free CB750's in the known world. 

[sinister902]

boy am i glad i read this thread, Im about to embark on my own teardown for a headgasket, possibly rings as well.....If i may ask(and probably sound stupid)....are you able to remove the cylinders and re-install them without removing the pistons/rods/crank from the bottom end? or does the WHOLE DEAL have to come apart? im afraid to see what the crank bearings look like or to break a major bolt down there so if i can get away without touching them i will do my best to do so.

[mystic_1]

Yes, you can tear the motor down to the pistons without splitting the crankcases.  Once the head is removed the cylinder just slides right off.

mystic_1

[gregimotis]

Yes, you can tear the motor down to the pistons without splitting the crankcases.  Once the head is removed the cylinder just slides right off.

mystic_1

And the cylinders aren't very hard to get back on over the rings.  Two people with dutiful care can do it without any special tools.

[sinister902]

Yes, you can tear the motor down to the pistons without splitting the crankcases.  Once the head is removed the cylinder just slides right off.

mystic_1

And the cylinders aren't very hard to get back on over the rings.  Two people with dutiful care can do it without any special tools.

thats what i wanted to hear! thanks guys!.....hopefully the same holds true for NEW rings, i suspect my top rings to be in multiple peices on at least 2 of the cylinders...

[adpage]

I am going through the same oil leak/multiple re-build issue (750 K4).  It is driving me crazy!!  I had both the head and cylinders decked, new cometic head gasket, service bulletin o-rings on the oil return passages.  I torqued the head and let it sit for 24 hours, then loosened 1/4 turn and re-torqued as previously posted: 5lbs, 10 lbs and 15 lbs.  Everything was running great for 150 miles.  Then, my worst nightmare!!  Oil on my fins coming from the head gasket area.  It is not a terrible leak, but it is definitly noticible.  (drips on the cement when parked)

My question:  Do I need to re-torque the head bolts?? 

Your comments are VERY APPRECIATED.  THIS FORUM IS GREAT!!!!!

[gregimotis]

I feel your pain, my e-friend.

First make sure you know what's leaking, then get a honda head gasket, and heavy duty studs from APE race parts.  Torque to 22.5lbs per instructions on this thread.

My (learned the hard way) advice - don't just torque your head bolts and cross your fingers, drop the cash and be done with it forever.  Eat Ramen for a while if you have too, it makes you tough.

[adpage]

22.5 ft lbs?  My 750 K4 Shop manual says 13-15 ft lbs.  When I put it together, the first torque I went to 15 ft lbs.  After the 24 hours, 1/4 loose, I then re-torqued to 16 ft lbs (made me feel better)

[andy750]

Adpage,

I also feel your pain, and have been through it with my own K4. Engine rebuild at 50,000 miles and with Vesrah head gasket I was good for 10,000 miles of leak free head. But after two long distance trips that involved serious riding it leaked. Pulled the engine at 62,00 miles and had a minor top-end rebuild using stock studs. Put engine back and leaked on test ride!! Pulled again and replaced with HD studs. Now at 64,200 miles and just completed a 1250 mile round trip 2-up with some serious hard riding - no leaks :-) (also used cometic head gasket). So....try the HD studs and follow Gregs advice. Its worth it in the end.

good luck
Andy

[adpage]

Thanks again Andy (Nice color bike ), but what is the difference with HD studs?  It doesn't make sense to me.  The studs themselves can handle the extra torque (linear stress), but I would be worried about pulling the threads out of the lower case.  HD studs will have the same issue, wouldn't they

I still want to understand where the 22 ft lbs for torquing a head came from?

Thanks To All!!

[Jerry Rxman Griffin aka MuthaF'er]

Adpage,

With the bigger stronger Heavy Duty studs you can get more torque on them. ie 22ft lbs which will sandwich the head gasket down tighter. The stock studs will stretch upon abuse/reuse.

[adpage]

RX, but isn't 22 ft lbs the same torque no matter which studs are installed?  I guess in my mind, if I torque my stock studs to 22 ft lbs, it will have the same effect regardless if they are stretched or not. ( I hope I am explaining it clearly)

Are the stock studs going to break if I take them to 22 ft lbs? 

[gregimotis]

When you install the HD studs, you torque them into the crankcase at 6-8lbs.  Then you torque the head bolts to 20-22lbs.

My understanding is that the limitation on the original studs torque rating is not how much stress the threads can take, but how stress much the studs themselves can take before they begin to stretch and become less effective.  With the heavier studs, you can torque down considerably harder - that extra five or seven lbs takes some real pulling on your wrench, so have the case tied down when you do it.
Get your studs from APE race parts

[adpage]

Ok.  That sounds reasonable.  Not to be a pain in the ass, but who came up with the 20-25 ft lb torque spec?

[mystic_1]

Ok.  That sounds reasonable.  Not to be a pain in the ass, but who came up with the 20-25 ft lb torque spec?

The manufacturer, although it actually says 20-22 on mine:








mystic_1

[martino1972]

does this stud thing and stuff also count for a cb650??
every time i take a ride my left shoe is nicely polished and shiny from oil...

[bert96]

Greg,
At Mike Reick's suggestion, I used Hylomar on the pucks.  No leaks after 2+ years.

 What's that??? Hylomar and where did you buy it?

[adpage]

Thank You Mystic!!!  That is why this form is so great!!!

Now the big decision.....ride this season and call it a winter project(the leak is not terrible just a couple of drips) , or jam it out in a weekend and listen to the wife complain. Hmmmmm