rocker box blues

kiwidave

kiwidave

Registered User
anyone else had this issue? Driving me nuts


Recently reassembled my 1985 Evo motor after having cylinder bases skimmed for true flatness etc.

Now the base gaskets are dry, head gaskets dry, but i have a nasty oil leak out of rear jug: it was quite a steady drip-drip, almost a drizzle, when hot from rear of the jug, between bottom rocker box and head. Onto the pipes for smoke effect.

I have done the gaskets *carefully* THREE TIMES now. Same way I did the front jug and that is oiltight. First using James Gaskets with Hylomar, as I have always done; second time with the factory's newish one-piece metal gasket betwen head and lower rocker box, with Hylomar

After taking advice from Phil and other vastly experienced peeps (thanks! ;) ) .............. the third time I installed gasket DRY.

After I had used valve-lapping paste on glass to flatten the lower rocker cover (it did topple when I pressed one corner, before this), cleaned the gasket surfaces for half an hour, did the one-piece metal gasket bone dry, torqued every bolt criss-cross to spec and checked it twice...I was super careful.

when engine is at temp it now leaks 50% *LESS* from the same spot (between head and lower rocker cover, at the rear near exhaust port), but still leaks too much to ride.

(it's definitely NOT the rocker box rubbers, pushrod tubes...it's VERY DEFINITELY leaking from where the head meets the lower rocker box, at the rear, just above the exhaust port)

We have a good old-school factory-trained mechanic in the neighbourhood with a home workshop who is at his best on 1970s/1980s Big Twins and his thoughts are now that the head may not be flat either. So on Friday when off work I will be handing head and rocker to him for absolute truing. He has valve spring compressors etc that I dont have.

Anyone ever have this problem and have a rocker box that maybe warped when hot giving this?

It's doing my head in!!
 
Re: rocker box blues

true it is unusual to warp with heat, knowing you it was all torqued up to the book, if it does warp then why?.
nope that doesnt sound like the problem to me, is the rocker box getting pressured perhaps?

the only warp that beast should experience is a time warp:D :D
 
Re: rocker box blues

Good way to go Dave,at least you will know they are flat,its very difficult to flatten off manually without dipping the surfaces around the edges.

Brit bike ally rocker covers and ally cyl heads are notorious for warping,castings etc on my FXR look a fair bit stronger tho.

Good luck

Chill
 
Re: rocker box blues

if all that fails dave ,fling it together totally dry ,and use clear sillicone, itll do the job till next years pull down;) monstersa been riding his like this for about 3 yrs now;)
 
Re: rocker box blues

Could the cylinder have been trued without a torque plate fitted?
 
Re: rocker box blues

definitely not Roger. I mean, OK I wasn't there, but the guy who did it even boasts of having the only Ironhead torque plates in the UK. He is super meticulous and used to build top-fuel motors. He takes NO shortcuts - we even joked about people who get rebores done at shops without torque plates - he said it DOES happen :eek:

Also...it was leaking bad by end of last season, before the skimming
 
Re: rocker box blues

I think you're doin the right thing Dave by havin the head top and rocker bottom flattened.The fact that it was 50% better after the rocker box lapping suggests that the head does require lapping too.
Good luck M8:)
 
Re: rocker box blues

It could be worth checking the obvious, like the length of the rocker box screws.
IE Are they too long or bottom out before they should, thus you are not actually clamping the joint down fully.
 
Re: rocker box blues

Thanks Steve but everything torques correctly to spec and there are no ''odd job'' bolts or screws in there

I am crossing fingers that Ralph can get me two surfaces flatter than Twiggy by the end of next weekend.

Two Scotsmen badly need me to show them how to get a real colonial suntan............ :D
 
Re: rocker box blues

I was thinking more on the lines that there could be an obstruction ie crap in the bottom of the threaded hole, thus the screw would not fully go down but you could still achive the correct torque setting without actually clamping down the rocker box fully.

A outside bet but possible which could also be exasperated with removing material from the head and box or by thinner gaskets!
 
Re: rocker box blues

UPDATE


my friendly local neighbourhood factory-trained mechanic who now works on bikes from his house reports the gasket surfaces were far from flat and he has now lapped them back to flat.

I am away at work six days out of the current seven so yesterday, with a million jobs to do at home as well, it was well worth taking the head and rocker boxes to him :)

What a relief. Long as it stays oiltight on start-up on Tuesday!
 
Re: rocker box blues

:eek: :eek: :D :D :D

sander8pz.jpg
 
Re: rocker box blues

kiwidave said:
UPDATE


my friendly local neighbourhood factory-trained mechanic who now works on bikes from his house reports the gasket surfaces were far from flat and he has now lapped them back to flat.

I am away at work six days out of the current seven so yesterday, with a million jobs to do at home as well, it was well worth taking the head and rocker boxes to him :)

What a relief. Long as it stays oiltight on start-up on Tuesday!
Click to expand...

Superb Dave:) I had faith in ya' rol on June 12
 
Re: rocker box blues

kiwidave said:
UPDATE


my friendly local neighbourhood factory-trained mechanic who now works on bikes from his house reports the gasket surfaces were far from flat and he has now lapped them back to flat.

I am away at work six days out of the current seven so yesterday, with a million jobs to do at home as well, it was well worth taking the head and rocker boxes to him :)

What a relief. Long as it stays oiltight on start-up on Tuesday!
Click to expand...

Aye yuv been worryin aboot feck all!!:eek: :eek: :D Had us worried tae, Davie said he wid guide the baeth a us tae Calafell:D Couldnae find his ar$e in the dark usein baeth hons:rolleyes: :D

As Davie said, lookin good for 12 June;)
 
Re: rocker box blues

Stuarty said:
Aye yuv been worryin aboot feck all!!:eek: :eek: :D Had us worried tae, Davie said he wid guide the baeth a us tae Calafell:D Couldnae find his ar$e in the dark usein baeth hons:rolleyes: :D

As Davie said, lookin good for 12 June;)
Click to expand...


A could find your a$$ wae ma foot nae problem:eek:
 
Re: rocker box blues

AT LAST - OILTIGHT!!!!! :D

After four top end teardowns in 6 weeks, the rocker boxes on the rear cylinder are not pissing oil. Thank Christ for that....

The truth is......the gasket surfaces on the lower (inner) rocker box and the head were *FAR* from flat.

The top rocker box was warped, so there was no seal at all on that square-gasket tower on the top of the rocker asembly.

All down to 80,000 miles of heat cycles, I guess.

My friendly local expert spent six hours getting the surfaces true and refreshed my worn-out valves and seals for a magic price.

I did a quick test ride this morning and for the first time in bloody ages, no puff of smoke off the pipes from a drip of oil.

I did the top-end gaskets twice before deciding I couldn't be totally at fault. The third time after thinking I had flattened the lower rocker cover gasket surface. Wrong! Nowhere near enough.

See you on the road :D
 
Re: rocker box blues

Good news Dave, see you out and about sometime.
Tony
 
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