GT750 Drag Bike

tz375 · Post by **tz375** » Sat Nov 15, 2008 10:20 am

There are two effects of weight.

First is the flywheel effect which makes a difference to how fast the motor spins up. For a bike that is relatively constant RPMs is less of an issue than say a road bike.

Second is that weight takes energy to move it. So the less weight on the bike, the better it is.

Your engine will still accelerate so both effects are relevant to what you are doing. You also remove the energy wasted rotating that points drive shaft.

The hardened drive pin can be pressed out. I can't remember how I got mine out, but it can't have been difficult.

9000 is rather high for a GT750, but Steve H used to tell me his ran to over 11 according to his datalogger.

water cooled · Post by **water cooled** » Sat Nov 15, 2008 2:04 pm

I'm leaving tomorrow afternoon to pick up the new dragbike frame for the GT750. A good friend located it for me on ebay and I was the only bidder.

By tomorrow night, I'll have a good idea if the GT engine will fit in this frame and/or what modifications are needed to squeeze it in there and have the pipes clear.

If the engine can be packaged in this frame, I'll have to finish the backbone fuel cell. A PMFR triple tree and swap-over of most of the existing components, along with the re-laced spoked rear wheel that Suzukidave found for me, it might make a nice light weight conversion...I think I found some GS850 forks...If they are the same dia. as the GT, that would be even better. Front rotor is on its way back after being thinned and drilled.

water cooled · Post by **water cooled** » Mon Nov 17, 2008 9:09 am

It looks like the dragbike frame will work out with some minor relocation of the engine mounts. The clearance of the pipes is very close to the frame rails and they appear to interfere slightly.

The total weight of the drag frame as shown with triple tree upper and lower is 39.5 lbs. so a fairly significant weight reduction over the stock GT frame, extended swing arm and struts...although a subframe assembly will be needed for the seat, rear fender and body shell attachment

The GS1100E forks appear to be 37mm measured off the triple tree and of course the GT is 35mm so it doesnt look like those will cross over...so I may need to build up the front end as a GS1100E or equivalent. I still want to retain the look of a GT where I can so it doesnt loose its identity.

tz375 · Post by **tz375** » Mon Nov 17, 2008 9:28 am

That is going to be a mean Buffalo

water cooled · Post by **water cooled** » Sun Nov 30, 2008 5:10 pm

Spent a little time on the front end. Got the master cylinder and reservoir corrected and rebuilt, removed the LH rotor, caliper and stainless brake lines and lightened the RH rotor (4.5 lbs) by thinning it and having the 72 hole pattern drilled. The rotor was done in Portland OR. I replaced the fork brace with one I bought from "Fast from the Past" (Paolo Tarozzi Stabilizer). Couldnt get it in time for Norwalk but it arrived the following week and it looks clean. I like it. Bought some speed bleeders and installed them. I had a lot of trouble with air leaking around the threads. Tried teflon tape but I was never really satisfied with the bleeding job I did. Since the master cylinder and calipers were all freshly rebuilt and the stainless lines were new, I used the DOT 5 Silicon and was very happy I did.

water cooled · Post by **water cooled** » Sun Nov 30, 2008 5:24 pm

Here is a better view of the lightened rotor...

water cooled · Post by **water cooled** » Sun Nov 30, 2008 5:42 pm

Here is a helpful link for many GT bikes...

http://www.fastfromthepast.com/servlet/StoreFront

The GT750 and GT500 use similar fork sliders so I bought the stabilizer for the GT500 PN 24-0010. I was able to use the existing dust caps. You simply pop them up off the aluminum fork slider, install the fork brace and slide them back down onto the brace where they stay. I like this fork brace becasue it can be installed and removed without having to remove the forks or wheel.

rngdng · Post by **rngdng** » Sun Nov 30, 2008 5:51 pm

Very cool fork brace! I like it. The frame looks great, as well. I can't remember, but I have either GS750 or GS850 forks on my TS400. They are longer than the GT750 forks by about an inch, and are still 35mm. They really appear about the same except for the length.

Lane

water cooled · Post by **water cooled** » Tue Dec 02, 2008 3:18 pm

Here are a few bits and pieces that came yesterday from D&G Chassis so I can move ahead on finishing the dragbike frame. The gas cap and neck for the backbone fuel cell, the bung to receive the Pingel fuel valve, 4130 rear axle and aluminum axle adjusting blocks. I know these parts wont help most GT750 owners but it took me a bit of time to locate this stuff...so on the outside chance that anyone else is building a GT750 dragbike...lol

water cooled · Post by **water cooled** » Tue Jan 20, 2009 4:15 pm

The air shifter kit arrived today and I am pretty anxious to start on the installation. This one is an electric over air system with DOT bottle from Murdoch Racing Ent. (MRE).

The setup still requires a single button handle bar switch to operate, so I started looking at MPS.

Also got new wheel bearings from All Balls for the GS spoked wheel hub that Suzukidave found for me. I'll do some cleanup of the aluminum hub, install the new bearings and then send to Buchanan Spokes for the wider rim (4.25") and order the slick and tube from Summit.

I think these chassis mods and upgrades should help lower the ET this year along with a few other changes I'm working on. AMA has 3 races lined up this year for the Super Eliminators (multi-cyl. two strokes): Michigan in June, Indy in August and Norwalk, OH in Oct.

Suzukidave · Post by **Suzukidave** » Tue Jan 20, 2009 10:44 pm

Nice stuff Kevin , with all the go fast goodies and lightened parts your ET's should come down alright

tz375 · Post by **tz375** » Tue Jan 20, 2009 10:48 pm

Kevin,

That's looking good

But let me get this straight. You ordered a GT500 brace for your GT750L forks and it fits perfectly?

Why didn't I think of that? That was rhetorical BTW - no need to answer it..

water cooled · Post by **water cooled** » Fri Feb 06, 2009 4:05 pm

Well, I'm begining to have serious doubts that I actually have stock GT750 forks.

My forks are most likely GT500's. They certainly appear to be shorter than stock. According to the Zedder crossreference, a stock 1974 GT750L and 1975 GT550M have the same outer fork tubes. When helping another board member, I realized that the Fork Brace mentioned above should have fit my 750L and someone elses 550M but unfortunately it did not...so one of us had the wrong fork tubes...

The reason the GT500 fork brace fit my 750 was because I provided Fast from the Past with the actual dims that I measured. They matched the dims up to a GT500 which is what I bought. I dont believe the GT750 and GT500 have the same machined dims where the fork brace mounts.

Sorry, if I caused anyone any inconvenience with the mistake...and I know that I did in at least one case.

tz375 · Post by **tz375** » Sat Feb 07, 2009 10:07 am

kevin,

No worries mate. That's why I always ask. Good point about sending them teh dimensions. maybe they will have one that fits my GT750L forks

jaybob · Post by **jaybob** » Sat Feb 07, 2009 11:13 am

We should have an answer for the 550/750 forks soon.....

I think Kevin has the GT500 fork sliders also as the brace he is using measures 60/61mm on the sliders and it fits fine

I ordered the GT500 fork brace to try on my 550. Needless to say it did not fit and was too big. The center measurement was right on but the clamps were too big for my sliders. The gt550 sliders measure 58mm.

So I have sent back the brace I ordered and included a sheet with all of my fork slider dimensions including the 8mm lip for the dust cap to Jim Hinshaw at Fast From the Past.

Jim was overseas last week but this week he is supposed to be back and he is going to send me a new brace to fit my dimensions.

I believe the part# 24-0029 will fit as I measured my forks with a dial caliper and the dimensions listed for that brace seems to match up well.

We will see what I get back hopefully this week.

the GT550 M forks measure as follows

58mm slider tops
175mm center width
8mm lip and 8mm recess for the dust boot.

Not sure about fender clearance yet but for me I am going to custom mount a new fender so it will not be an issue for me. However when I do get the new brace I will install it with my original fender to see how it all works out.

Jason

GT750 Drag Bike

Weight Reduction

Air Shifter Kit