Head gasket: compressed thickness?

yamahama

'72 XS in Restoration
Messages
302
Reaction score
465
Points
63
Location
Florida
Anyone know what the std. xs 650 head gasket compressed thickness is assuming it is compressed to spec.?
 
upload_2020-6-11_14-5-37.png
 
TY...could not remember to even look. I'd rather be closer to 9:1CR than 8:1 reusing my original pistons and nice flat head surface looks untouched. I have access to 90 oct. non-ethanol and 93 oct. 10% ethanol pump gas. Been eyeing the Hughs' flywheel timed ignition.
 

Attachments

  • P6020456.JPG
    P6020456.JPG
    174.9 KB · Views: 138
Now there's a question! i honestly have no idea, but my initial thought was quite thin.

Well, I used to back into what my CR would be after getting my clean/fresh bores, pistons and rings in the bores set to a specific height to measure volume of liquid and cc the head. Then I could order/ make a gasket. But, just knowing how high up the head will be and the squish helps allot...just to know what's what.
 
Humm, I have a flat smooth, head surface as found...really don't want to mill...not that it's a big deal at all. unless a gasket is unobtainable to get me to the nominal original CR. Seems that's the case. Odd. I'm on the Mike's site now a bit confused by the $148 upper end gasket kit with some seals (Japan) vs just ordering a complete Athena
Athena P400485850620 Engine Gasket Kitand individual seals from Mike's. I need to go back and sift through the assorted seal discussions.
 
I see that "new" $148 kit Mike's has been hawking. Total rip-off in my opinion. Their Athena kit is over-priced as well. You can find it cheaper elsewhere. But, it's head gasket is thicker than stock. I've used them with no problems but now will be trying others that are the original thickness. Can't say I noticed any power loss with the Athena gasket though.
 
There is no need to mill the head. Vesrah head gaskets are made to exact OE spec. and are easily available. Ottoco makes a .040" head gasket that works very well, no issues with squish or valve clearances.
 
TY Grizld I poked around on the Vesrah site. They did not give thickness nos. for non-race applications. Nice to know there may be other options. I saw a guy on youtube make a 6-cyld. Kawa out of a 1978 4-clyd. and make his own gasket from copper sheet, a round saw cut, and file. The lower one gets the 'squish' on a higher compression set up...without touching at OT, it helps defete knock, pre-ignition.
 
Last edited:
I gave you the Vesrah thickness number, yamahama. I've used Vesrah gaskets for many years and have measured head gaskets from Yamaha and from Vesrah. Vesrah gaskets can't be distinguished from OE, and I suspect that Vesrah made the originals. Cometic also makes XS650 head gaskets, in fiber or copper. Copper Gaskets Unlimited in Tempe, AZ is another source. If you decide on a copper gasket, be sure to anneal it. The drill I follow is to hang the gasket on a wire and work with two propane torches with spreader tips, one in each hand, to heat the gasket cherry red, then drop the hot gasket into a bucket of cold water to quench.
 
I saw a guy on youtube make a 6-cyld. Kawa out of a 1978 4-clyd. and make his own gasket from copper sheet, a round saw cut, and file.
That weren't just any guy... it was :bow: Allen Millyard. :bow2:
 
Thanks Grumpy...I believe you and I think that is best Vesrah...I'll call Tempe to see what's what, I couldn't find xs 650 head gaskets listed. :agree:
 
Back
Top