Topic: Leaky CB750K4 after 836 rebuild

[HondaMan]

Is the screen missing from your oil pump?

I'm curious to know if your single-fuse ATC holder gets warm (hot?) when running. I tried 3 different brands in my K2, and the first 2 melted the rubber holding the clips, the third one actually melted the fuse(!). I unplugged them and plugged the [same] fuse into the Honda clips instead (added some insulators to them) and all has been fine since then (that was in 2009). The problem is/was due to lack of hard physical alignment of the female clips in the rubber single-fuse holders, and the circuit running near the max allowed for the type of holder.

[andy750]

Thanks Hondaman for the questions - screen is definitely there I felt it with my fingers must be the camera angle.

I have had my fuse holder for about 15,000 miles and never had an issue - not even a blown fuse. New harness around 25000 miles ago. Same DynaS for last 50,000 miles. Must have got lucky


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[andy750]

Pre-lubed is always best


Removing the old washer



Finally...home at last



Mmmmm



Mike managed to secure some new lash caps and then installed rockers and timed cam today...

From Mike today “Cam timing is all set.....cam came out very very close to recommended numbers. Overall lift close as well. Went very quick....one adjustment and I was done. Ready to button up”

Exciting!!

Now consider all this is getting done as Mike is ALSO working super hard on the triple RC engines which are a thing of beauty - the amount of work is unbelievable. Mike lives and breathes CB750 engines...so impressive to watch him at work.

Lesson #8 complete!

[andy750]

While replacing the leaking alternator cover also replaced the defunct starter motor that died after 87000 miles



Came out relatively easy and no real issues getting it back in.


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[754]

Where are the markings on the cam, on the end ?

[scottly]

Where is the supplied assembly lube on the cam lobes??? It's more important than on the cam journals!!

[calj737]

Where is the supplied assembly lube on the cam lobes??? It's more important than on the cam journals!!

I'm sure Mike knows that and its simply a matter of lack of photos. 

[andy750]

Cal is correct I didn’t photograph that part. Sorry for any confusion

[MRieck]

Where is the supplied assembly lube on the cam lobes??? It's more important than on the cam journals!!

I'm sure Mike knows that and its simply a matter of lack of photos. 

Thanks Cal.....of course there is lube on the lobes....and tach gear.....and rocker arm shafts.....and valve stem tips etc.
I was pleased with that CX-1 cam in regard to hitting the cam #'s....they were very close to the timing card. LC was 103 In 102.5 Ex. Lift listed @ .340...intake was .331 with .004 of lash and exhaust .334 with .005 of lash.
 We will be installing one of the CYcleX No Leak cam cover gaskets. They fit very well and work even better.
 Put some fresh oil/filter in with ZDDP to help that new cam out and Andy is on his way

[andy750]

Made some great progress last night

Leak down test showed excellent readings on all cylinders





Then it was checking piston to valve clearance using a MikeR homemade tool- passed the test!



Cam cover on with a no-leak Cycle-X gasket. When installing the #4 exhaust discovered the spigot bolt was stripped



Frame kit back in





Alternator and gear shift covers get new Cycle-X gaskets



Getting close



New oil ready...



Test drive Sunday?

Thank you Mike!


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[andy750]

It’s Sunday! Amazing how it all comes together at the end...

Filling the head with oil

 



Exhaust back on, carbs on, airbox on





Oil in - check



Changed oil filter. Ready for start up. IV line attached







Starter button...click...aftermarket solenoid failure...lucky Mike had a F solenoid to replace...thank you Mike. Starter button...vrooom! No smoking, no noise, nice and smooth and sounded good!!!

Test drive time! Round the neighbourhood, up to 4500rpm nice and smooth, oil pressure at 80psi....very very nice!





And so far leak free success so far!

Huge thank you to Mike for getting me this far after a disastrous start to the summer. Mike really went all out and gave me so much of his time to get this bike running and leak free. His attention to detail, careful checking is second to none. Ive been telling my colleagues at work I’ve going to Mechanics class at night and this is how it’s felt - a unique learning experience.

I now have a running bike for the Fall. I can’t wait for the extended test drive! With 87,000 miles on the clock this bike just got a wee bit more life injector into it.

Cheers
Andy

[MRieck]

You are most welcome Andy....you love the CB750....it's easy to see and feel. Engine does sound very nice....quiet valve-train for a CB.

[PeWe]

Andy, you are a "CB750 non leaking assembly specialist" now? Open evening classes for others....
Nice feeling when it works as intended.

If you will get oil weeping cases, usually seen up front and around oil filter. The additional breather hose drilled into clutch cover work fine.
I had oil weeping cases with 836cc (holiday high speed cruising back in the 80's), much more with 1000cc (short speeding on country roads).
Thanks to Mike's video earlier this year I got the idea.

[Jerry Rxman Griffin aka MuthaF'er]

Ahhhh, the sorcerer's apprentice.....

[andy750]

Epilogue:
Took a Lyft from work this evening carrying helmet, tool bag, wearing leathers and headed for Mikes...time to ride the bike home!

As always Mike super helpful concerned about potential oil leaks - none so far....had a chat...then it was heading out into the dusky night....feeling the silky smooth engine as navigated the dark twisty country road at a healthy 45-50 mph keeping the rpms up...nice feeling riding at night on country roads.

Took a detour to ride the highway got yo-yo 85...buttery smooth the whole way..could have kept going but time was calling...headed east to home. Big smiles with every twist of the throttle.

Home....no oil leaks! Looking forward to more test miles! Almost a year to the day since I got the rebuilt engine it’s now looking like a strong leak free 836 engine fingers crossed!

Thanks for following along I’ll update my CB750K4 thread with any more updates. Thank you Mike!!!!!!!!


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[andy750]

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[754]

 Sounds like you are set to go.  Did the valves get shortened for the lash caps ?
I know most cams run more clearance than stock, but what exactly is going on in this pic ?
 I  never seen that method ..

[robvangulik]

Testing clearance valve>piston?

[MRieck]

Sounds like you are set to go.  Did the valves get shortened for the lash caps ?
I know most cams run more clearance than stock, but what exactly is going on in this pic ?
 I  never seen that method ..

Just the intakes have caps Frank and they have been shortened .040 (cap crown thickness).
 Checking valve to piston 10 degrees before (exhaust) and after (intake)TDC on compression stroke.
The piece I made to protect the tappet cap threads is an old tappet cover with the center cut out on the lathe....works great.

[trigger]

MikeR is an excellent teacher and his knowledge of engines (any bike)  is just amazing! The stud nuts were not very tight when we came to remove them....and the head gasket (Vesrah) was leaking oil all over the place...NEVER use VESRAH head gasket!!!!!!

I have never had a problem with Vesrah head gaskets in all the years i have fitted them. I did notice that you never had the extra O rings on the 8 head studs and i don't think it was torqued down correctly in the first place. 

[andy750]

I won’t argue with you on that Trigger and glad your experience with Vesrah is better than mine. The head nuts were not tight.

[PeWe]

Old gasket was an MLS as I could see. No need of o-rings. I add the 2 o-rings for the oil feed up to head. Gasket dry. It work fine. Both surfaces must be smooth as it becomes with grit 400 paper (I had to remove all old machining marks with a few rounds of 240 prior to 400). MLS does not compress much or any as noticed 24 hours after first tightening of head nuts, tighten them again, 20 ft lbs. The MLS rivets needs to be removed or hammered flat + drill dents on mating surfaces on head, cylinder. It will not tighten if not when rivets are between the head and cylinder surfaces.

Tighten all bolts for cam holders can reveal bad threads. I use max 10Nm for good threads with time serts. 8Nm work fine too. Valve cover got tightened with 5Nm last time, no leaks. Honda gasket. I have sealed the holes for cam tower studs (in plug cavities) from outside with JB weld when head was off.

[scottly]

For what it's worth, I've Never waited 24 hours and re-torqued a head, nor re-torqued after heat cycling the engine, on any motor, and I've never had a leak. To be honest, I've only done it once on a SOHC 750, 39 years ago, and it still is leak free.

[PeWe]

Re-torque work fine on fiber gaskets.
I never did it in the 80's either. Torqued extra, 28Nm (20.65 ft lbs). Started to re-torque 5 years ago.
My K2 build has rather soft head gasket. Torqued 3 times until it stopped.