Author Topic: GTR tuning article  (Read 6854 times)

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Offline Gerrit

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GTR tuning article
« on: January 16, 2014, 06:30:02 AM »
My attention was drawn to a tuning article that can be downloaded as pdf through this link:

http://www.eurospares.com/graphics/Bridgestone/MSQFall1971Bridgestone350Racer.pdf

It was written by Tony Murphy and complements the Gordon Jennings "Son of Secret Weapon" articles rather nicely.

Offline paul

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Re: GTR tuning article
« Reply #1 on: January 16, 2014, 04:32:22 PM »
Had not seen this article in years. Motorcycle sport quarterly wasnt the biggest selling magazine. I recall another sister article to this one. The sister article had a photo of the big remote float mikunis supplied by Rockford Motors and some details about the custom frame used for Murphy's/MSQ project . Bob Barker and I think Tony Murphy went on to compete for   land speed records with another rotary valve wonder bike, CAN AM.

Offline Gerrit

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Re: GTR tuning article
« Reply #2 on: January 16, 2014, 04:37:15 PM »
Does anybody still have that sister article, I wonder?

Offline slawsonb

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Re: GTR tuning article
« Reply #3 on: January 16, 2014, 05:07:10 PM »
Good read! Thanks for posting Gerrit...
...bert

Offline scrambler

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Offline paul

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Re: GTR tuning article
« Reply #5 on: January 18, 2014, 04:52:13 PM »
Scrambler, thanks for reposting these Gordon Jennings Son of Secret Weapon articles. These are interesting and can be found on the manuals/articles tab of this website under 350 modifications.  I think there is another Motorcycle sport quarterly article about Murphy's project GTR.The article would be before this one. As I recall, that article  had a photo of the, one of a kind, remote float Mikunis that Rockford had supplied.

Offline Jeff Bar

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Re: GTR tuning article
« Reply #6 on: January 18, 2014, 04:54:12 PM »
Son of Secret all parts 1-2-3  are already posted on this site

http://bridgestonemotorcycleparts.com/index.php?action=downloads;cat=25

Offline scrambler

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Re: GTR tuning article
« Reply #7 on: January 18, 2014, 05:02:59 PM »

Online Mike Anderson

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Re: GTR tuning article
« Reply #8 on: January 18, 2014, 05:15:40 PM »
For anyone interested in trying these modifications, they work real well. The 350 when touched up properly is really a good performer. You can modify in varying amounts and get great results. Never got beat by the Kawasaki triples. Sometimes even ran fuel, they like it. Good Luck.
Later Mike

Offline scrambler

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Re: GTR tuning article
« Reply #9 on: January 18, 2014, 06:13:19 PM »
Hey Mike you bring up an interesting point comparing the GTR to the Kawi triples. I have a racing sidecar outfit that was built in 1972. It was road raced and also had a few runs at Bonneville. At that time it used a Kawasaki H1 for road racing and an H2 engine for Bonneville. There was a series of articles on it in Cycle Guide.

http://www.scramblercycle.com/1/post/2013/09/vintage-racing-sidecar.html



Currently it has a Kawi 500 H1 engine it. Its not the original engine that was in it when it was raced. I have been having thoughts about what I should actually do with it. It can't be road raced in its current form as the wheels are to small in diameter and to wide for vintage sidecar racing. In reality there really isn't much sidecar racing around unless I want to travel thousands of miles. So my next thought was to take it back to where it once was, Bonneville. Running something at Bonneville has always been in the back of my mind.

So lets get down to where the Kawi triple and GTR comparison comes into play. The way this frame is built I can really only run a 2-stroke because of height limitations. I could cut the frame and make modifications for a 4 stroke but almost hate to do that as then the custom tank on top wouldn't work. Your comment made me think about considering the BS350 as a possibility. While I do already have a Kawi 500 engine (actually probably 2 or 3 engines) they are expensive to build, parts are scarce and they did have their problems. I also have 2 or 3 GTR engines. All need to be totally rebuilt and parts aren't exactly cheap and easy to get for these either. But articles like the ones posted above are interesting and somewhat inspiring. I mean when was the last time a Bridgestone in any form made a run down the salt at Bonneville? (I know OldSwartout did, was it a recent run?)  If I were to make a run it would be at BUB and the Sidecar class with a 350cc engine is an open record.

Kinda tossing ideas around but thinking 2015 as the year to make something happen.



Offline slawsonb

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Re: GTR tuning article
« Reply #10 on: January 18, 2014, 08:13:35 PM »
Hey Scrambler, after reading some stuff on your site, made me think (and I don't know the answer), is there an sidecar ice racing class or opportunity. Not trying to distract you from the Bonneville goal, just a wild thought. I would personally love to see another BS pass or two at Bonneville!
...bert

Offline coxy

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Re: GTR tuning article
« Reply #11 on: January 18, 2014, 10:30:32 PM »
Kevin
I saw a h2 motor on ebay a couple of weeks ago in the states $2500 .

Offline scrambler

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Re: GTR tuning article
« Reply #12 on: January 18, 2014, 10:33:47 PM »
Crazy stuff.
http://www.ebay.com/itm/kawasaki-H2-750cc-motor-/181298587012

I have most of an H2 motor also but really don't want to risk using it in this.

Offline coxy

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Re: GTR tuning article
« Reply #13 on: January 18, 2014, 10:58:59 PM »
risk it as in destroying the motor? I think it would be a blast .

Offline scrambler

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Re: GTR tuning article
« Reply #14 on: January 18, 2014, 11:01:15 PM »
Yes I don't want the risk of destroying it or the cost of building one.

Offline coxy

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Re: GTR tuning article
« Reply #15 on: January 18, 2014, 11:09:13 PM »
once upon a time these motors were a dime a dozen

Offline scrambler

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Re: GTR tuning article
« Reply #16 on: January 18, 2014, 11:14:33 PM »
It's those crazies from Australia driving up the prices!   ;D

Offline paul

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Re: GTR tuning article
« Reply #17 on: January 18, 2014, 11:25:24 PM »
Scrambler,thanks for posting the picture of the Murphy bike in motion. Most of these Bridgestone race efforts seem to lack time and money for development.

Offline Gerrit

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Re: GTR tuning article
« Reply #18 on: January 19, 2014, 04:06:23 AM »
Personally I'd go for the H1 engine. Compared to GTR stuff, H1 engine parts are dead easy to find- pistons can be readily obtained from Wiseco and Wössner for example, conrod kits are also available. As for tuning, both Jennings and Murphy are dated and more recent and up to date tuning info isn't available for the GTR, partly because cylinders are very scarce and nobody will sacifice a set easily. However, H1s are still being tuned by enthusiasts using up to date info. Proper racing pistons aren't available for the GTR and as far as I know never were.
If you want to go the 350 route, use a Kawasaki Avenger engine. Although there is little up to date tuning info for A7s, parts are much easier to find. Also, I believe the A7 offers more scope for tuning. The only advantages the GTR has are its 6-speed gearbox and dry clutch- though a 6-speed gearbox is avaliable for the A1-R in England.

Offline reed

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Re: GTR tuning article
« Reply #19 on: January 19, 2014, 10:13:59 AM »
Kevin,
If you are going to do it use the Bridgestone engines what ever happens it will show some light on Bridgestone again!!
Thanks.
Steve.

 


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