GT750 Frame Weight Reduction

water cooled · Post by **water cooled** » Mon Nov 02, 2009 1:06 pm

The stock GT750 frame uses a lot of metal plate to reinforce the steering neck relative to the other frame rails. Does anyone have experience removing some or most of these plate sections that are welded to the steering neck by grinding them off?

There is also reinforcing metal plate under the steering tube and down along the center frame tube that the radiator inlet passes through.

It looks like a weight reduction of 3 lbs might be possible. I'm sure there would be an overall reduction in the strength of the frame section but it might still be acceptable for straight line racing. Has anyone done this successfully?

Tom Garcia · Post by **Tom Garcia** » Mon Nov 02, 2009 2:34 pm

Didn't you get a moly frame?

tz375 · Post by **tz375** » Mon Nov 02, 2009 4:23 pm

Kevin,

that bracing adds a ton of weight and makes very little difference to strength or rigidity. I ground most of it off one of my frames, and then I replaced some of the tubes with Chrome Moly. Wall thickness of stock tubes is around 2.3mm. I replace it with 1.5mm (.065") where possible.

Are you planning to run the stock frame class again next year or move to the light frame class with that frame you got?

BTW, have you ever weighed a bottom triple clamp on that bike?

johnakay · Post by **johnakay** » Tue Nov 03, 2009 11:24 am

go on a diet that should reduce weight and ya feeeeeeel better for it.

Suzukidave · Post by **Suzukidave** » Tue Nov 03, 2009 11:29 am

This was all that was left of the GT750 frame my son and i modified for the Yellow bike .. about 34lbs .

water cooled · Post by **water cooled** » Tue Nov 03, 2009 11:33 am

Oh My GOD John..

tz375 · Post by **tz375** » Tue Nov 03, 2009 1:28 pm

Compared to a stock 52 pound frame, that's quite an improvement Dave.

Even with a light sub-frame, that would be a good place to start.

water cooled · Post by **water cooled** » Tue Nov 03, 2009 2:23 pm

Its very interesting...I see where you cut the frame and blended in something else. Very well done. I am particularly interested in that front end section around the steering neck.

A different radiator setup lets you get replace the middle frame rail that runs down the center line just under the gas tank. Very nice job! Thats an 18 lbs reduction with added braces and uni-shock mount...extra nice. Thanks for posting Dave.

Suzukidave · Post by **Suzukidave** » Tue Nov 03, 2009 3:27 pm

We cut away all the sheet metal and welded the frame tubes where they crossed and then also added connector tubes to tie the upper and lower frame tubes together to help prevent spreading under hard braking .

water cooled · Post by **water cooled** » Tue Nov 03, 2009 3:42 pm

Thanks Dave. I will post pictures of mine as I remove those hefty brackets.

Am I underestimating the weight at 3 lbs of metal to be removed?

Suzukidave · Post by **Suzukidave** » Tue Nov 03, 2009 4:05 pm

I am not really sure of total weight in sheet metal removed but it is pretty thin stuff .

Suzukidave · Post by **Suzukidave** » Tue Nov 03, 2009 4:14 pm

Teaser also has some writeup about the frame mods http://www.pinkpossum.com/GT750/phattrakka/part3.htm

water cooled · Post by **water cooled** » Sat Nov 07, 2009 11:44 am

If I cant get 1 or 2 lbs off by removing the plates, it might be worth it to me. I have about 12 lbs so far off the front end since the race at Norwalk in October and maybe an additional 4-5 from the cooling system modification.

Speaking of which...it occurs to me that I might be approaching the cooling system all wrong.

What if the stock water pump is pulled and shaft hole blanked off. A small, light weight pump can be housed where the starter motor use to be. Cap the inlet side where the lower radiator enters the engine by putting a flat plate in place. Reinstall the coolant bypass line located behind the block. Get rid of the radiator and coolant tubes all together. Move a pressure release (radiator cap) to the top of the engine coolant outlet at the back of the cylinder head, add a small expansion tank using the two temperature sensor bungs...then, reverse the flow to draw coolant from the bottom of the cylinders and dump it back up top through the bypass. I'm sure this will change the temperature gradient down along the cylinders but effectively, the cooler water is at the bottom of the cylinder and hotter water is at the top.

I think for a 10 second burst after warming up, it might work. The primary goal is to save weight by eliminating the radiator, water, and all drive gears associated with running the stock pump...

Any thought on this...

tz375 · Post by **tz375** » Sat Nov 07, 2009 12:33 pm

Kevin

Get a Davis Craig water pump - preferrably the auxiliary pump - the small one. That thing pulses the water through but only when it's hot enough to need

http://www.daviescraig.com.au/Electric_ ... ils.aspxto. My guess is that it will never need to turn on

I can't remember who imports them into the US, so you might be cheaper getting one from Demon Tweeks in the UK.
http://www.demon-tweeks.co.uk/products/ ... &x=15&y=10

Here's a Bosch pump:
http://www.merlinmotorsport.co.uk/p6900 ... eb479257e4

And teh cheap alternative is NO PUMP. just let it thermo siphon. After all, how hot can it get in 10 seconds

advant63 · Post by **advant63** » Sat Nov 07, 2009 6:45 pm

most mercedes have one or two of those bosch pumps that teazer posted.
it might be worth a walk through the local wrecking yard.

GT750 Frame Weight Reduction

GT750 Frame Weight Reduction

frame reinforcement