Raising Compression

I am in the process of tearing down and rebuilding my 750 Seca motor. Has anyone tried using thinner head gaskets or milling the head to bump compression. I figure with a stock 9.2:1 It should be possible to see real gains from a bump to 10:1 or so. Obviously, using higher grade fuel would become necessity but has anyone tried this in XJBIKES.com land?

 

I am taking the level of response to this question as an omen that I should leave well enough alone as far as any "big squish" fantasies I may have had. I am still interested in squeezing any easy power gains from the motor but I think I will trust the Yamaha engineers in this case.

 

I checked with everybody in the whole wide world.

Nobody's tried the Thinner Head Gasket yet!

 

Why not give it a try. I'm sure the info is out there to determine how much to shave off. Easy math if you know bore stroke and cc volume. The worries are intruding on runners, valve clearance @ TDC, and timing adjustment.

Can you adjust the timing in these? ya gotta be able to...

 

To make adjustments to the Timing ... you have to Modify the Ignition Pick-up Plate ... extrapolating the four holes which mount the Pick-up Plate to the Case.

The Stock Timing is already set to the Maximum "Safe" degree of Advance to have the Engine perform within its design parameters. Advancing the Timing beyond that which is already Marked on the Rotor could wind-up costing you an Engine.

The TCI, based on the information sent to the Unit by the Magnetic Pick-ups ... Advances the Timing to 37.5 Degrees & 5,000 rpm's -- Stock.
Running the Advance higher than that Value could cause the Engine a catastrophic failure should the Cylinder Head Gasket fail and compression be lost at high rev's.

Throwing a Rod would be highly likely if not a certainty at above 5K with no compression to slow the rise of the Pistons on Cast Connecting Rods.

 

Wouldn't you need to retard timing with the increase of compression? I'm thinking of it in the same terms as adding boost. Tho if its set I would imaging its set both ways... ya dont get to advance or retard...

What about an aftermarket ignition like an MSD box... they sometimes have the ability to advance and retard timing. The only x-factor then becomes the wigit that you described advancing timing at high rpm...

i apologize as my knowledge of these engines specifically is pretty minimal.