My Custom GT750's

[Suzukidave]

Painted engine subframe made from a modded GT750 frame to attach the GT750 engine to the 99 GSX-R frame , it weighs about 9 1/2 lbs .

[water cooled]

Dave,

That turned out great! Nice job blending everything...its going to look super!

[ja-moo]

Very cool........ Do you have a weight for the frame?

[Suzukidave]

The weight for just the engine subframe is around 9 1/2lbs .. i am sure it could have been made lighter with aluminum or CM but this was the only way i could come up with that i could do myself . for the entire GSXR frame i dont have a figure on the weight .

[tz375]

Dave,

That looks good. How does the subframe attach to the main frame at the rear?

[Suzukidave]

There are 2 tabs that bolt up to the lower GSXR engine mounts

[tz375]

Very tricky Dave. I should have known you had that all worked out. I was hoping for a design snafu to gain a little more time at my end.

[Suzukidave]

Thanx guys and Richard this part of the build has been done for over a yr now just needing paint whats holding up progress is putting the engine together and what final machine work i need to do to the block to set the squish .

[tz375]

Dave,

That's the easy bit. Build the bottom end, fit the pistons without rings and bolt down the head and measure squish at all 4 corners at the same time. Then remove the block (where did you put the puller plate) and machine the right amount off and then assemble for real. Set the timing with the head off and a dial gauge, pop the head on and then the fun starts.

[Suzukidave]

Yep .. thats the plan it would be cool if the squish came out right

[two-stroke-brit]

Yep .. thats the plan it would be cool if the squish came out right

please enlighten me ,is the squish you talk of where the piston crown compesses the fuel/air mix into the decresing area of the cylinder head?.
ifso how do you alter it (alan pulsifer had this done with good results.)
cheers mark.

[Suzukidave]

Good question .. the squish needs to be as close a possible so the design of the head "squishes " the mixture away from the edges of the combustion chamber into the middle where the flame front is controlled by design to burn evenly and without detonation . This clearance is controlled somewhat by rod stretch so it can only be set so close and thats .048" for the GT750s.

[two-stroke-brit]

so to measure the squish ,could you use a two part rubber compound that stays flexible but retains its shape from when it sets .(we have this at work to mold and measure inacsesable areas on the parts we make.?}.
if not how do you mesure it?.
and then do you have either weld and remachine the heads or skim the head to achive the requred squish.?.
thanks mark

[Suzukidave]

Mark the more popular way of doing the test is to use non acid core solder thats fatter than the clearance you are aiming for , cut 2 pieces several inches long .. bend them into a L shape and insert them thru the plug hole so the pieces lay the same direction as the piston wrist pin to the edge of the piston left and right . Rotate the piston across TDC several times to flatten the solder , and then remove each piece one at a time so the thickness can be checked and recorded . If the clearance is too wide shaveing the head or the top of the cylinder block the needed amount can be done and if its too tight a thicker copper head gasket can be used . But as a added problem if setting the correct squish results in too much compression then you may need to have the chamber in the head reshaped to increase the trapped volume .

[tz375]

Alan P's motor has a stock head with a quiescent chamber i.e. it has no squish band so it is impossible to set squish clearance. I believe that SCR may have done some combustion chamber matching to get them closer to the same volumes and he may have skimmed the head to increase compression. His chambers had significant variances from one to another in volume and I suspect that Scott C was trying to get them all closer.

Squish bands are the "flat" annular area around the outer edge of the head and are almost parallel to the piston crown. Squish band thickness is set to create a certain value of squish velocity i.e how fast the gases are squirted out towards the plug. Squish velocity (MSV) is related to squish band width and depth plus engine speed.

On Dave's bike the compression in that squish head was a little high for the street, so that had to be reduced and the squish band thickness was worked out given a few variables.