Topic: bad head gasket

[cd811]

I noticed tonight ,I got a bad head gasket ...#4 is throwing exhaust out the side ...it sure didn't last long ...I cleaned all surfaces...Honda gasket...torque to spec in proper sequence...back to drawing board...any suggestions or experiences

[bwaller]

What pistons are you using to make 811cc and what is the compression ratio supposed to be? In the 70's I ran some modified 350 twin pistons for a while, (I called it an 810) and the compression was through the roof literally. I'm not condoning the use of these by the way. I changed head gaskets by the car load... usually I modified the stock gasket. For sure heavy duty cylinder studs will help and although I have never used copper or aluminum head gaskets I expect these would handle higher compression. Maybe someone else can pass judgement on these.

[cd811]

from what I understand..the 811 is just some 350 pistons(stock)(if I remember right)...when I put it together I needed new rings, so I research I and the guy is still in business( i can not remember the co. name)anyway...the guy was real nice and he said that  the pistons were honda 350 piston(like ya said)...so he gave me some honda part# and I went to my honda dealer and BAM they worked perfect...I don't know what the compressin ratio is...How did ya modify the stock gasket?

[bwaller]

I enlarged the hole of the stock gasket to match the bore and recrimped the larger metal sealing ring from a larger bore gasket 350 or 450 twin, but it was a real pain. This was over 30 years ago. Those modified 350 pistons do yield some extra power, but does not lineat the powerband by any means and no matter how much material is removed from the piston crown the compression is still really high. Do you notice any detonation? Larger bore head gaskets are probably available individually but wait to hear from some of the guys as to what to expect from copper or aluminum because I think this would be the better approach.

[cd811]

oh man!!!!!!!!! I didn't even think about the bore size...now i don't know what

[volthause]

For super-high compression, using a metal headgasket makes sense.

I've seen car engine builders running insane amounts of boost actually groove and o-ring around the bores. Crazy, but cool.

[crazypj]

I use solid copper head gaskets, had problems with aluminium gaskets. You just have to put up with the oil weep from ends of cylinders where the oil feeds to cams (but you can reuse copper when weep gets too annoying)

[dusterdude]

cd,try a cometic head gasket,see how that works for ya.

[MRieck]

cd,try a cometic head gasket,see how that works for ya.

Yes. The Cometic head gasket for the 836 kit will work for 810 or 811cc's. I have used both the graphite and CMF. Heavy duty studs really help too. APE sells them.

[howardstapley]

Find the thickest head gasket you can to drop the compression down some and (I don’t really recommend this but it does work) put a thin washer on each of your plugs. I’ve only done this on cars but when we built a 383 up, the compression was just too much so with a combination of these things it helped allot.

[bwaller]

crazypj,   has the oil weep you mention anything to do with the copper gasket or is it just a matter of the o'rings not holding up. Has anyone tried a different o'ring material like teflon for example? #$%* there must be enough advancements in materials to allow us to use a better o'ring that can withstand more heat !! I hate oil leaks and need to contact Cometic about a gasket for this 592 I'm getting to and was hoping to use copper.

[Lumbee]

...carl, do a compression check after your next rebuild...that should give you an idea of the compression...if its something crazy like 200 or something then u'll know it might be to high...

[cd811]

the 811 is a action4 kit...the guy that builds those thing(really nice guy) says he uses oem gaskets...that what I had on there...I think my main error was I did not go back and retorque after I had run it...I understand (NOW) that that is critical
Cometic ...I know nothing about that

[bwaller]

In a perfect world you could pull the valve cover after a bit and retorque.... but of course pulling the engine to accomplish this usually means it doesn't get done, I've never done it. That's where the heavy duty studs help.  Since you need to buy a gasket anyway go to cometic.com and as was mentioned buy the CMF head gasket for the 836. The stock gasket is too small for your bore. It's up to you how far you want to go, but I can tell you from experience the compression from this set-up will tax a gasket.

  Good luck
 

[MRieck]

 The fire ring of the stock head gasket isn't sealing with that bore...plus the piston could be hitting the fire ring as it is sitting inside the cylinder. Here's Cometic's site  http://www.cometic.com/

[cd811]

ok...I've decided to order the Cometic head gasket(43.35)...they were closed today...I will try again Monday...I also think I shound replace the rubber o-rings while I'm there ,right?(91303-035 times 2, right? 16mm?)ok, my next question..be honest..do I really need to replace studs and base gasket with upgrade?

I really am grateful for all the help

[Big Jay]

I made the original 836 kits using 350 step 4 pistons. However, we had to machine the domes down and remachine the valve pockets. It was a true 10.5:1 and ran good on premium pump gas.  Did literly thousands of these. Also used CB450 pistons with wrist pin bushings to make the first 1000cc kits.

Others then made the 836s too when they found out what to use. If you ever need rings for a cast 836 kit and it says ART in the piston, the rings are ( were ) available from Honda.

Jay

[cd811]

yea, thanks,I put new rings on it at rebuild...paniced for a while until I found out...walked right into honda and ordered them...what head gasket did ya use?

[Big Jay]

yea, thanks,I put new rings on it at rebuild...paniced for a while until I found out...walked right into honda and ordered them...what head gasket did ya use?

Way back then (1970?) we had gaskets made by commercial gasket companies. Now, Cometic has it all covered. They don't usually cally much stock in the motorcycle line. I just checked and we are out too.  But, Wiseco will probably have it. If you call Cometic on Monday and they are out of stock, call Wiseco ( 800-321-1364) and ask for part# W4934.

Jay

[crazypj]

crazypj,   has the oil weep you mention anything to do with the copper gasket or is it just a matter of the o'rings not holding up. Has anyone tried a different o'ring material like teflon for example? #$%* there must be enough advancements in materials to allow us to use a better o'ring that can withstand more heat !! I hate oil leaks and need to contact Cometic about a gasket for this 592 I'm getting to and was hoping to use copper.

Yep, the 'o' rings fail, the copper gasket works really well.
 If you find a source of teflon 'o' rings let me know, they will take up to 400 deg f. I remember dowelling the oil feed to support 'o' ring on one head, worked fine but quite a lot of extra work getting things lined up
PJ

[bwaller]

crazypj, I'm going to look into this alternative o'ring material.

[Jerry Rxman Griffin aka MuthaF'er]

I've been running a 810 Yoshi kit since late 70's. Obviously Yoshimura rings are not available. Someone mentioned that he'd had his rings sized by someone that was very helpful. It has been MANY years but I may have used the same company. HASTINGS Piston Rings !! Super folks. Sent a piston in & it was returned with the info I needed No Charge !!! Turns out as someone mentioned the Yoshi 810 kit used the old 350 twin rings. Say 1968 to 1972ish.