Head and base gaskets 750 bigbore

[Denisesewa]

Today I tore down the 1978 750 tracker to find the howling noise in the bottom end and found an inner main bearing toasted ( as I suspected so I have another crankshaft on hand) but I also found the head and base gaskets are thick copper which appear much thicker than the gaskets in the Athena bigbore gasket set I bought, I am worried about decreasing the squish and upping compression too much with the thinner gaskets.
I am guessing the bigbore kit is not from Mikes,( the cylinder does not have a bolt on camchain tensioner cover and is the large fin variety) at least he does not list copper head and base gaskets.
So, reuse the copper gaskets?
What bigbore kits come with copper gaskets?
Other ideas?
Any suggestions or advice would be greatly appreciated !

 

[grizld1]

Copper gaskets can be reused, but they should be annealed first to soften them. Unlike steel, copper softens when it is heated cherry red and quenched. I clean the gasket with solvent, hang it on a wire, heat it with two propane torches with flame spreaders, one in each hand, and dunk it in a bucket of water. I've had consistently good results with HK or Permatex copper bearing gasket spray on copper gaskets: two or three coats and let dry.

If you want new stuff, 650 Central sells copper head and base gaskets for 80 mm. bores in a range of thicknesses. Another source is Copper Gaskets Unlimited; Google for the URL. Even with new copper gaskets, best practice is to anneal before use.

 

[Denisesewa]

That's great info, thank you very much.
I am going to use your suggestions since there is .5 mm difference between the old thicker gaskets and the new ones which means there will be even more difference once the new gaskets compress.
Thanks again!

 

[Marlin72xs]

I am guessing the bigbore kit is not from Mikes,( the cylinder does not have a bolt on camchain tensioner cover and is the large fin variety) at least he does not list copper head and base gaskets.

Hey there. I just bought the Mikesxs 750 kit. Yes, it has larger fins, a no bolt on cam chain adjuster and it came with a non-copper head gasket. I'm in the process of installing it soon.

 

[ebb0tk]

Loan on thread. Does anyone know if the new OEM gaskets from yamaha are chemically treated?
Want to know if i can use copper spray on it?

 

[grizld1]

Permatex copper spray has worked well for me on OEM Yamaha and Vesrah head gaskets. Hang the gasket on a wire, give both sides two or three coats, and let dry. HK recommends against using its copper spray on fiber gaskets, and recommends its brush-on copper gasket dressing instead.

 

[ebb0tk]

Permatex copper spray has worked well for me on OEM Yamaha and Vesrah head gaskets. Hang the gasket on a wire, give both sides two or three coats, and let dry. HK recommends against using its copper spray on fiber gaskets, and recommends its brush-on copper gasket dressing instead.

Headgaskets. What about OEM cylinder base gaskets? Like the picture i attached. =)

 

[grizld1]

Sorry about that. Usually no sealant or dressing is needed, unless you have some dings or scratches on the case or cylinder base surfaces that you don't trust. If I'm working with a base gasket surface that's at all questionable, I use a tough sealant like Permatex Ultra Black or Ultra Gray.

 

[Marlin72xs]

The base gasket from mikes looks like basic paper. I contacted mikes and they said it requires no goop. It was "special". I haven't gotten to that phase yet, but since the o-rings at the base are no longer used, i feel compelled to put a very thin line of permatex in the corner where the o-rings were. Eh?

 

[TwoManyXS1Bs]

... since the o-rings at the base are no longer used, i feel compelled to put a very thin line of permatex in the corner where the o-rings were. Eh?

Could be a prudent move there, Marlin, if there ever was a history of problems. Or a waste of time if the sleeves are cast-in or fitted differently from oldschool.

http://www.xs650.com/threads/aseembling-engine-question-about-o-rings.33818/

 

[ebb0tk]

Sorry about that. Usually no sealant or dressing is needed, unless you have some dings or scratches on the case or cylinder base surfaces that you don't trust. If I'm working with a base gasket surface that's at all questionable, I use a tough sealant like Permatex Ultra Black or Ultra Gray.

Alright. Got a tube of ultra gray for 5$. Are u using it just on the imperfections? or are u using it on the hole joining surface just like when you seal the cases?

 

[grizld1]

Again, only use sealant if there are dings or scratches that you don't trust. If you have to use sealant, cover the whole surface as evenly as you can with a thin coat; you don't want silicone to squeeze out, form lumps, and find a home in an oil jet.

 

[Marlin72xs]

Excellent advice! Thanks.