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 Post subject: BIMOTA GT1 Project
PostPosted: Tue Nov 10, 2015 1:03 pm 
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Around the block

Joined: Thu Dec 05, 2013 12:32 pm
Posts: 84
Country: Austria
Bikes owned: GT750
Hello friends,
this is my first post on this forum. I am 55 years old and I live in Vienna, Austria. My passion is to restore, collect and ride classic or exclusive motorbikes, mainly twostrokes. Amongst several YAMAHA RD500s and 350s I also have a 1976 SUZUKI GT750 in original restored condition.

Image

Back in the 80´s I already had a Bimota seatunit on that same bike:

Image

I got a spare GT750 engine several years ago, tuned close to TR750 specs and I have planned to build a Cafe Racer from that for long.
Then, in my summer vacation, I read a book about BIMOTA and sa pictures of the HB1 which at the time was the most sexiest motorcycle in the world for me.
My plan was born to build a HB1 replica with a GT750 engine.
I already had bought a frontend, wheels and brake disks of a Z1000J (with 18" front wheel) and 3 classic AP Lockheed calipers years ago.

By pure coincidence I found a guy who was able to offer me a tank and seatunit very similar to the HB1 - it was not an exact mold (since only 10 of them were ever produced, no owner would ever give away a tank or seat for a mold!) but close enough.

I started with thinking how I could get the stock frame modified to replicate the typical HB1 layout with the main frame spars following the contour of the tank, and the very wide swingarm pivot area. I had some ideas, and contacted a framebuilder to check whether he could do the modifications.
He looked at it, and finally convinced me to build a completely new frame rather than modifying the stock one.

Off my parts went to The Netherlands: stock frame, fork, wheel, swingarm, dummy engine case with cylinder, shocks, handlebars, radiator...

As a reminder, thats a BIMOTA HB1:

Image

Now the frame build started:

Image

only 1 week later:

Image

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 Post subject: Re: BIMOTA GT1 Project
PostPosted: Tue Nov 10, 2015 4:10 pm 
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World Superbike
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Joined: Thu Feb 16, 2012 11:50 am
Posts: 2263
Location: The Republic of South Yorkshire
Country: England
Bikes owned: 2 x GT550s GT750, T200, TC200
Excellent. It's good to be different!
Good job your English is so good, my Austrian is nil!
Welcome to the forum.

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 Post subject: Re: BIMOTA GT1 Project
PostPosted: Wed Nov 11, 2015 12:46 am 
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Around the block

Joined: Thu Dec 05, 2013 12:32 pm
Posts: 84
Country: Austria
Bikes owned: GT750
Hello Alan,
In Austria we speak german ( kind of). Slight differencies like between US and british english.


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 Post subject: Re: BIMOTA GT1 Project
PostPosted: Wed Nov 11, 2015 3:09 am 
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Novice racer

Joined: Tue Dec 16, 2008 11:37 am
Posts: 972
Location: Trowbridge UK
Country: UK
Bikes owned: T500R, SV1000S, TS125, Seeley T500
Hello Wolfgang,

What a fantastic project :up: . it will be a very unique machine when you get it finished, I look forward to following your progress.

Cheers Geoff


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 Post subject: Re: BIMOTA GT1 Project
PostPosted: Wed Nov 11, 2015 4:55 am 
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AMA Superbike
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Joined: Tue Oct 14, 2008 6:47 pm
Posts: 1729
Location: Blythewood, SC, USA
WOW! Your frame builder is in Holland? Obviously knows what he is doing. That is going to be a beauty.



Lane

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If you stroke it more than twice; you're playing with it.

Too many bikes, too much time, ENOUGH SPACE, FINALLY! Never enough money.........


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 Post subject: Re: BIMOTA GT1 Project
PostPosted: Wed Nov 11, 2015 5:33 am 
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Around the block

Joined: Thu Dec 05, 2013 12:32 pm
Posts: 84
Country: Austria
Bikes owned: GT750
Hello Lane,
can you send me a larger pic of your blue GT750 in the avatar?


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 Post subject: Re: BIMOTA GT1 Project
PostPosted: Wed Nov 11, 2015 5:38 am 
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Around the block

Joined: Thu Dec 05, 2013 12:32 pm
Posts: 84
Country: Austria
Bikes owned: GT750
I need some advice about carbs. I am using the late A-version cylinder with the rubber carb mounts for the BS40 carbs. I would like to go to other carbs, like VM34 (no bigger than 34mm). These carbs have only 40mm diameter on the cyl. side, while the carb mount is the 44mm BS40 diameter. How do you recommend to fit the smaller carbs into the rubbers?
I try to avoid the milling and rewelding of the carb mounts of the cylinder

Please share your experience and ideas with me


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 Post subject: Re: BIMOTA GT1 Project
PostPosted: Wed Nov 11, 2015 7:49 am 
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Moto GP
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Joined: Mon Nov 03, 2008 10:47 am
Posts: 6076
Location: Illinois
Awesome work, Thanks for sharing. I have a set of small body 34mm carbs that I glued an outer tube over the intake stub to make them larger.

A smarter solution is to use 73 intake rubbers. The 34mm carb will hit the clutch cover and needs to be angled up a little to avoid that. I don't remember which intake stub has an angle. It could be GS1100 but I think it was a Kawasaki - ZX10 perhaps. I will check my notes later.


Last edited by tz375 on Wed Nov 11, 2015 9:32 pm, edited 1 time in total.

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 Post subject: Re: BIMOTA GT1 Project
PostPosted: Wed Nov 11, 2015 8:16 am 
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Novice racer

Joined: Tue Dec 16, 2008 11:37 am
Posts: 972
Location: Trowbridge UK
Country: UK
Bikes owned: T500R, SV1000S, TS125, Seeley T500
Hello Wolfgang,

I have a set of 34mm Mikuni's for my Seeley T500. The carb rubbers/manifolds were supplied by Allens ( http://www.allensperformance.co.uk/carb-kit/carburettor-mounting-rubber-manifold-dimension-information-page/ ) who also supplied the carbs. As you can see they bolt directly to the T500 barrels, any good for the GT750?

Image

Cheers Geoff


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 Post subject: Re: BIMOTA GT1 Project
PostPosted: Wed Nov 11, 2015 9:23 am 
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Around the block

Joined: Thu Dec 05, 2013 12:32 pm
Posts: 84
Country: Austria
Bikes owned: GT750
Hi Geoff,
sorry these wont work on my cylinders unless I do the machining - this is how my A-cylinder looks like:

Image


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 Post subject: Re: BIMOTA GT1 Project
PostPosted: Wed Nov 11, 2015 10:04 am 
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To the on ramp
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Joined: Wed Jan 01, 2014 2:04 pm
Posts: 493
Country: UK
Bikes owned: GT750 hybrids (x2) VJ23A RGV500 TS185 R250
Brilliant ! :clap:

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I'm addicted to brake fluid, but I can stop anytime.


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 Post subject: Re: BIMOTA GT1 Project
PostPosted: Wed Nov 11, 2015 10:46 am 
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Novice racer

Joined: Tue Dec 16, 2008 11:37 am
Posts: 972
Location: Trowbridge UK
Country: UK
Bikes owned: T500R, SV1000S, TS125, Seeley T500
Hi Wolfgang,

For the 38mm Mikuni's I used these manifolds (supplied by Pete Odell) and a pair of the "sleeve rubbers" (also shown on the link to Allens in my previous post). Allens list quite a range of these sleeves, there is probably on which might fit your requirements,

Image

Cheers Geoff


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 Post subject: Re: BIMOTA GT1 Project
PostPosted: Wed Nov 11, 2015 9:53 pm 
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Moto GP
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Joined: Mon Nov 03, 2008 10:47 am
Posts: 6076
Location: Illinois
The stubs on a GT750 are basically horizontal and with a straight tube, the right carb float bowl will rest on the crankcase above the clutch.

That is why the inlets are usually sawn off and replaced when fitting larger carbs. Lane (rngdng) showed me how to sleeve a 34mm carb to fit in a stock intake rubber but unless they are small body carbs, the right carb still rests metal on metal - even with a 3mm spacer (lift) plate.

I am almost certain that the fix is a Kawasaki part but cannot find the number. You could try a 13121-00A00 which I think fits a GS1100.

A 73 carb rubber would fit but still the metal on metal issue.

Just as a point of reference, 72 GT750 VM32 carbs are 43mm od. Small body VM34 are 40mm, BS40 are 49mm, regulra body VM34/.36/38 are all 43mm, normal VM32 are also 40mm.


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 Post subject: Re: BIMOTA GT1 Project
PostPosted: Thu Nov 12, 2015 5:51 am 
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AMA Superbike
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Joined: Tue Oct 14, 2008 6:47 pm
Posts: 1729
Location: Blythewood, SC, USA
wolfgangh wrote:
Hello Lane,
can you send me a larger pic of your blue GT750 in the avatar?



Image


How about this one?


Lane

_________________
If you stroke it more than twice; you're playing with it.

Too many bikes, too much time, ENOUGH SPACE, FINALLY! Never enough money.........


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 Post subject: Re: BIMOTA GT1 Project
PostPosted: Thu Nov 12, 2015 8:31 am 
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Around the block

Joined: Thu Dec 05, 2013 12:32 pm
Posts: 84
Country: Austria
Bikes owned: GT750
Lovely, that hits exactly my taste? Are these JEMCO pipes?


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