Topic: Oil on top 3 fins of cylinder? Where is it from?

[HondaMan]

Umm...one important thing that I am not seeing above: did you install HD cylinder studs with the 836 bores? If not, it will still leak, later...

[1976cb750f836]

Did not install studs?
Didn't know it was required?
By HD stud, do u mean larger diameter,or stronger  steel?
Who has Them? Is it a bolt On?
Or is it a drill and tap install?
Do I really need them?
Thanks!

[Nic]

I don't have them on my 836 flat top pistons, I think I have the bigger O rings though. Never had leaks other than pucks.

[1976cb750f836]

Mine are Wisco,flat tops.
So I shouldn't worry bout the studs?
Have had no issues except oil seepage?
Runsgreat,way more tq than Before!
Thanks

[Nic]

Mine are Wisco,flat tops.
So I shouldn't worry bout the studs?

At this time I wouldn't. Hate to disagree with the master though

[disco]

I have the APE hd studs in my 836. They didn't add a lot of cost & after investing so much time & money, I thought it a good idea. I bought my set from Andrews Motorsport in NC.
Btw I've had no leaks so far, but have only about 600 miles on this engine.

[Nic]

When I was doing mine, about 4 years and 15,000 Kays ago I bought the ape studs and had to buy nuts separately thinking I would need hd nuts, jeez you'd think the studs would come with nuts? Anyway I bought HD nuts from I have no idea where but I thought they were a tad loose on the stud threads so I just left the stockers in there. The ape studs are still here somewhere.
While more torque on the head gasket would be a good thing I don't know of anyone back in the 70s ( when we were all doing yoshi 812 kits with a domed piston for more compression) who put HD studs in, I never even heard of them and I was a mech in a Honda shop, brfff, loosly speaking
Of course, back then we didn't even put sealer on the pucks, I dunno how different the pucks are today and as Mark has said, gaskets today are taller. 40 years on and there is so much more to know about these beauties.
I wonder how many blokes have used the Crusinimage gasket and just not bothered retorquing. I have 3 of them here but won't ever use em, I will buy the Yamiya gasket in future as I KNOW it is a good gasket. I must admit, I didn't measure the thickness though.
I have a Z900 as well and it has the Crusinimage 69mm pistons and the gasket needed retorque as well. I now use the Vesrah gasket on it simply because I bought one and used it and it did NOT require a retorque,
I have not idea if the Vesrah for the Honda is the same.
I have also read that on the later engines with the 8 rubber seals and pins that you don't need to put them in, I left them out and had leaky gasket, I put them back in and have not had leaky gasket but have had leaky pucks but I'm hoping now that all my threads are good in there I have fixed it for good this time but I won't be surprised if I get leaky pucks in the future, with the frame kit it's a mornings work.
I have 11x2.5 Orings between barrels and cases, no leaks, I do have the 10.77x2.61 Orings in stock but I just have no idea if they are in there between head and barrels, no leaks there either.
So to HD stud or not? I don't think it's a necessity? It hasn't been a problem for me after 15,000 Kays, I don't flog the engine though.

[PeWe]

My CB750K6 got HD studs 2013. I used the stock studs in the 80's with 836cc.
I torqued them 20.5 ft lbs, mostly to not retorque afterwards. It got minor leaks after some time. But most oil could come from the tacho seal.
I did not retorque after 24 hours as I have started to do lately after reading good stuff on this forum. My ongoing K2 build was retorqued 4 times until it stopped to compress the fiber gasket further.

The good thing with HD studs as APE or Kibblewhite is the stiffness, the do not flex as stock. Enough to tighten 20 ft lbs, max is 22.5. I snapped one APE stud with a bad calibrated wrench I have borrowed. I bought an own set and verified the other bolts, it needed 26.5 ft lbs to move further. I replaced all studs.

If you need tougher nuts, use std DIN6331 forged collar nuts, M8. Much cheaper than the HD nuts the tuning parts sellers provide. It need a 13mm socket. Nut is higher so Honda thick washer must be replaced by a thinner to us as much threads as possible. Socket need to be a slim 3/8" type. I have an 1/2" - 3/8" adapter with that socket.

I have those on my K6 build with kibblewhite studs, tightened 20.5 ft lbs. MLS head gasket and RCS base gasket did not compress much or any at the retorque 24 hour later.
My latest K2 build with 736cc stock CR has Honda std nuts tightened 20 ft lbs.

I tightened Honda nuts 20.5 ft lbs during the entire 80's without any problems.

[1976cb750f836]

Well,I do flog the he'll out of mine,especially now while I. Making jet changes.
Leak seems to be getting good worse?
I just want to be able to find it when it comes apart?
I'm betting on pucks,don't think I used any sealer on Them?
I think my book says to assemble them dry, I followed the Book?
Warm hear again in East tn, might hit 60deg.
Going to ride more!
Planning on teardown through Christmas holidays.
Thanks all!

[Nic]

One more thing, if you've had the 6mm studs out you need to put thread sealer on them as well or they will leak. This is imperative.

[HondaMan]

The studs in the 750 changed around the K3 model to become a better metal, slightly more tensile. If you have a K3 engine you can tell if you got the "new" ones or the "old" ones by twanging them: pull them back about 1/8"-1/4" and let them snap free to see if they vibrate and make a tone, of if they just straighten back up. The 'new' ones will make a slight "boing" sound.

The "new" ones were/are stronger than the older ones, and they also don't rust as much as the early ones. When removing them for HD studs, they don't break off as often, either! The older ones tend to rust and corrode pretty badly at the bottom, near the case. The early ones looked like they were cut and left unpolished at the top ends of the threads: the newer ones have a more finished appearance, which de-stresses them where the thread bolsters meet the shaft. This roughness makes them weaker there: this caused some of them to break when installing bigger pistons and heavier head torque to hold them down: the pistons from Powroll, Henry Abe and Wiseco, with their higher compression, most often caused the leaks at the head gasket. When run at hiway touring speeds (80+ MPH) the head gaskets would start leaking from the drain holes at the front of the cylinders, and after a while the oil would pressure itself out from the journals at the back of the cylinders, making a bigger leak.

The needed torque difference for the high-dome pistons was usually 20 ft-lbs (11:1 pistons), but sometimes the Wiseco versions were OK (10.25:1 CR) at 18 ft-lbs, at least in the newer engines. The stock studs reach max tension at 210 in-lbs (17.5 ft-lbs) or about 2 kg/m: you can feel it when torquing them down. They 'stop' then, or suddenly increase the resistance torque, as the stud is beginning to stretch. Sometimes, the studs would snap as the torque continued. The first HD studs I remember came from Rocky Cycle, and R/C supplied some too, IIRC. Later Action Fours made them, but theirs rusted even in the package for lack of some kind of plating, so they were not real popular. The most-accurate methods of bolt torquing, used in places like high-pressure tubing flange systems, uses dial indicators on the bolts to measure their stretch: you torque the nut until it reaches 'max' and 'stops', then watch the dial indicator until it stretches the bolts some extra amount over that point. This is the real maximum any bolt is supposed to take, and they will not then vibrate loose afterward because the threads and nuts are then distorted together...and they are then a real b!#ch to get apart, too!

[Nic]

Thanks Mark, as usual, great info, I guess i have the "better" stock studs yippi

[PeWe]

Is the root cause of the leak found?
If replacing the cyl studs, you need to remove head to get a chance to grip them enough with double nuts. Maybe cyl too if they sit like #¤%&&%. This brings new base gasket + head gasket + all 4 12 x 2.5 mm o-rings + a light hone of all bores.

Sure about correct head gasket? Stock gasket on 65 mm bore can't be good. The stock I have might work on 62 mm bore max.
I measured some of my new Head gaskets. They are all just under 1.5 mm thick.

Cruzinimage 65mm - 1.45mm
Yamiya 65 mm - 1.5 mm
DSS complete gasket stock head gasket (NE Brand) - 1.25 mm
Used Cometic 65mm - 1.1 mm
MLS 68mm - 1.2 mm - 1.45 mm around oil holes, embossed like o-rings. I use o-rings on such gasket

I bought a set of the most common o-rings to the engine, Viton. Viton feels harder and not that sticky rubber as Nitrile.
Honda can never have used Viton, right?.
Maybe Viton will keep up better since it feels harder and will not flatten when hot as Nitrile can? Nitrile has max temp of ~125C.
Viton will keep up the tension and not leak?

One more thing:
If using an old cyl + head with 8 smaller oil return holes and use later gasket with wider holes. Use o-rings here. 12.5 x 2 mm. I have found Viton 12.42 mm  X 1.78 mm I ordered with the other rings. I hope will work. Not in a build yet.

[1976cb750f836]

I'm still jetting and working other bugs out.
Going to ride as much as possible in hopes of seeing where the oil is coming from when I Teardown!
I still hope to only retorque qnd replace pucks?
Last week in year is teardown?
Thanks

[PeWe]

If you are sure that you use wrong head gasket, there is only one thing to do...
Use correct size of gasket, 65 - 65.5mm for 836cc. The metal ring around the 61-62 mm gasket hole will not have much surface contact either....

[TwoTired]

I've been avoiding this thread, cause I don't have much constructive to say.   But, I keep reading the tittle and I always answer to myself, "the middle east, probably".

Makes me chuckle a little bit.  Maybe others, too?


Anyway, I always thought putting an oil stop leak product in a wet clutch motor trans with tiny oil flow control orifices was a big no-no.  Isn't that stuff like shellac?  How to get it out of oil control orifices once its hardened up inside?  It's oil resistant, right?

Maybe it's only me that worries about such things...


Cheers,

[Nic]

Anyway, I always thought putting an oil stop leak product in a wet clutch motor trans with tiny oil flow control orifices was a big no-no.  Isn't that stuff like shellac?  How to get it out of oil control orifices once its hardened up inside?  It's oil resistant, right?
Maybe it's only me that worries about such things...
Cheers,

Good point.