Topic: Taking a dremel to a new head gasket?

[turkey2143]

Hey Sohc-ers, has anyone ever cut an aftermarket head gasket that didn't quite fit before?

I know that cutting the base gasket is fine because it's paper and doesn't hold any real pressure, but I'm a little more skeptical about the head gasket, even though the major cylinder pressure is held around the stiffer metal rings.

I had the head and block decked to make the mating surfaces are nice and flat; because this is a Vesrah head gasket, I'm not sure if I should take the chance or not, and plus there is a cam chain tensioner slot in my block that will not be be touching the gasket.

I want to cut out a path in red here, is this asking for leak-city? The green is the empty space in my cb650 block where the tensioner sits, and the gasket pictured is for a 550. The green helps to illustrate my gasketless spot that would be a gap in between my head and block...bad??

Should I just pony up the money for a $72 OEM CB650 headgasket from bikebandit? Or does anyone know where to get a cheaper aftermarket one?

[vames]

Dunno the real answer here -- but seems like this could shed some weight from your bike, which would be fantastic for performance. While you have the dremel out, get rid of that center stand.

[vrenlos]

I'm talking with no sort of backing on this, but it looks like you'll be cutting it pretty close around those edges - does the stock gasket follow the same contour on the part below those "cut-outs" you plan on making?

Also, take a look at servicehonda.com (look up the part number for the gasket you need first then check there - I usually look up part #'s on my local dealership's site: cycleworldnj.com)

Best of luck!

[turkey2143]

The stock 650 gasket doesn't have that gap at the top and follows the contour of my green lines, as well as the cut-out, so it'd be a perfect fit.

No luck looking for the gasket on servicehonda, I may end up getting one from cometic after checking my valve to piston clearance today.

And to vames: after cutting this gasket, it'll probably weigh about 3 grams less than the stock 550, so I guess I am pretty excited 

[scunny]

I take it the fit was bad, needing to invert the gasket to line up the firing rings. I've come across 2 like that, first one still hangs in the garage and the second I had to massage 2 of the stud holes to fit, no problems after 8 months riding but will be getting an oem one for the winter.

[turkey2143]

The fitment is just fine and dandy, it's just that in the head gasket for a 77' CB550, the cam chain tensioner slot is in a different spot than it is on the 80' CB650. The firing rings line up perfect.

What I'm worried about is the little spot at the top of the picture that sits outside of the green line I drew that would be exposed. Would this cause a leak?

[turkey2143]

bump

[cobra2411]

Is the gap in the green box open to the outside? If so you'll likely have a leak. If it just makes a pocket that's sealed it shouldn't be a problem.

My opinion is that it'll work. If that's all I could get I would run it.

However is it worth possibly having to pull the engine for $72... That's your call.

[754]

I suspect the red are is where your camchain slder is held with a pin. If it is and you cut it out there will be slop, and it will mark up the head.

[turkey2143]

I seem to hear that I have to pull the engine to replace the head gasket a lot, but when I took the jugs off both my 550 and 650 parts bike I got them both off without taking it out of the frame (albeit very carefully with very little room to spare)

I'm going to risk it I guess because $72 is a 6 hour valet shift for me, there will just be an unsealed pocket like cobra mentioned, withno real path for anything to leak out.

I think 754 thought I was chopping off my cam chain slider pin, but it's the head gasket that I'm trimming.

Thanks for the input guys

[scunny]

it's the 750 that you have to pull the motor.

[turboguzzi]

aftermarket, cometic included, often suck. had to enlarge holes in a cometic as some were way out of spec.

I'd say that the cut  is doable, would add a dab of sealant only around the area were the gasket is really narrow for safety.

a picture of the gasket sitting on the problem area could help us help you

[754]

Let me put it another way..if the chain slider pin moves around it will wear against the gasket...if you trim that out, it moves more and wears into the head..

[turkey2143]

Glad I don't have a 750, but turboguzzi, would you add the dab of sealant in the gaps where there is no sealant? Or do you mean a thin crankcase-thick layer underneath and on top of the thin gasket?