Dunstall GT750

Retro, Wild, Cafe, etc. The stuff only your imagination can come up with.

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tz375
Moto GP
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Location: Illinois

Re: Dunstall GT750

Post by tz375 »

It really comes down to fitted diameter.

That Shinko is much taller than say a stock tire - partly because it's closer to old school aspect ratios and partly because it's fitted to a skinny 2.5" GS rim. That pinches the tire somewhat and has a fitted diameter of 675mm.

The closest BT45 comes with a 80% aspect ratio and that makes it a little smaller.

The differences are not night and day type, but are just enough to add up.

Stock GT seat height is supposedly 33" and I don't have a stock bike to confirm that. The Dunstall is closer to 34.5" So I need to trim that out in pieces. Seat foam will get me 1"-1.5". Lower profile tire will get another 1/4" and I will also see if I can mount the tank/seat unit 1/4" lower with new brackets.

The whole thing could be mounted over an inch lower if the tank were lowered and thinned slightly or replaced with a new custom tank. That is not happening any time soon. I'll just make those small changes to mounting brackets, shave the foam and see where that gets us to.

Time to order a set of chrome plated drag bars. It has black alloy bars but that makes the front end very dark with all the black up front.

Then I need to sell it off and clear some space for the next projects.
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busa1300
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Re: Dunstall GT750

Post by busa1300 »

Streetbike or dragbike project?

Two stroke for sure.... :up:
MY TWO STROKE ADDICTION
TZR250SP 3XV2...
RS 250 Cup bike
RGV VJ21 L
RGV VJ22 FL
RGV VJ23 T
RZ 350
GT 750 J....sold.....
SX-R 800
KD 80
JR 50
RZV 500 R
https://www.youtube.com/@wedgehorsepower9869/videos
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tz375
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Location: Illinois

Re: Dunstall GT750

Post by tz375 »

Street. When I said "drag bars" I mean flat/Vincent shaped handlebars - not wheelie bars.
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tz375
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Re: Dunstall GT750

Post by tz375 »

I may go down to a 120/80-17 to make the rear end look more balanced and svelte. I fitted a BT45 that size to a similar GS rim on a prior GT750 project. That would also drop the back end enough to allow me to revert to the 320mm piggyback shocks and still drop the seat height.

All I need to do to get the current tire looking right is to have the wheel widened and inch or two....... :roll:

Or I could fit that Avon cantilever 130/65-18 on almost any rim and have a wider, lower profile set up, but that one is like old school Dunlop KR73/76 "triangulars" in that it's designed to have a lot of tread on a narrow rim. Modern tires are designed to fit on much wider rims than our old bikes.

Back to the interwebs to find the right tire at the right price.
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tz375
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Location: Illinois

Re: Dunstall GT750

Post by tz375 »

Pulled the forks off today and polished them and all the stainless hardware. Looks 100% better.

Fitted the rebuilt calipers and a new master cylinder and banjo bolts so the whole front end is all nice and fresh again. I cannot believe how much better it looks already.

I asked my son for his opinion of the bike and he said that he like to see the motors on these bikes, so now I'm thinking about making new side pieces for the fairing to show off the motor better.

Still going back and forth as to whether to fit different carbs and pods or to keep the OEM carbs and airbox. No doubt I'll change my mind a few more times. And of course I keep thinking that if I have to remove the head or block to re-polish them, I might want to think about porting it more aggressively while I have them off. No rush on that idea. Lots of time between now and go to market time in the spring.

The ports were cleaned up when it was bored but it's just a minor clean up job to work with the Omar's three into one exhaust. I do have a lift plate that needs a good home or I could just replicate the Phat Trakka porting. It's mild and easy to ride and make around 80hp.
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busa1300
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Posts: 352
Joined: Wed Apr 11, 2012 7:17 pm
Country: USA
Suzuki 2-Strokes: RGV RGV RGV RGV ......
Location: Northern Indiana

Re: Dunstall GT750

Post by busa1300 »

tz375 wrote:
Then I need to sell it off and clear some space for the next projects.
Is that a street or drag next project ?

As far as tires, .....Avon has the AM23 in 130/80/17 in bias ply....I have a set of AM22/AM23's on my RZ350 and a set for one of my GS1000's....excellent vintage race tires.
If you like that style of GS wheel, look for a pair of GSX400S (Katana) wheels. They are a wider 17/18 combo that should bolt right up.
https://page.auctions.yahoo.co.jp/jp/auction/p655671040" onclick="window.open(this.href);return false;

But if you spend too much extra time changing it to sell.....you might end up liking it too much to sell....
MY TWO STROKE ADDICTION
TZR250SP 3XV2...
RS 250 Cup bike
RGV VJ21 L
RGV VJ22 FL
RGV VJ23 T
RZ 350
GT 750 J....sold.....
SX-R 800
KD 80
JR 50
RZV 500 R
https://www.youtube.com/@wedgehorsepower9869/videos
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tz375
Moto GP
Posts: 6204
Joined: Mon Nov 03, 2008 10:47 am
Location: Illinois

Re: Dunstall GT750

Post by tz375 »

Thanks for the link Busa. I had a set that looked like those on the last 750 I built.

Well that was easy. I replaced the fat 130/90-17 with a 120/80-17 and boy, what a difference a day makes. The new tire looks so much better and drops the back end down to where it should be, even with the slightly longer shocks. It's also much lighter than the 130.

The thing that stopped me from making that change much earlier was the reluctance to swap out a brand new tire.

Just waiting for the powdercoat parts to come back and I can button up the front end. I also need to send out some parts to have the old chrome stripped and have them polished and re-plated. I have had mixed results with that in the past and thin parts can be problematic, but let's see what happens.

Busa, you are right that before the bike was OK and now it's starting to look really good. I may have to hang on to it.
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