Suzuki GS750 Mikuni VM26's on a Zephyr 750 & GPZ750 cam's in Zephyr750 head

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15 Oct 2024 02:56 #905126 by Mepb750
Hi,
Currently figuring out how to attach Suzuki GS750 VM26's to a Zephyr 750 head.

Have the Z900/1000 rubber carb manifold's, elongated holes, bolts straight on.

Suzuki throttle bracket looks similar to Z900 and overlaps the rear cam tunnel bolt.

Bought a Z650 (KZ650) throttle bracket, it fits around the rear cam tunnel bolt.

Sure this has been done before and found a thread about it, but the actual question is about which cables/throttle tube to use, cannot find a clear example. At the moment I have 80's GPZ750 unitrac cables and throttle tube.
,
My bike is in the avatar , its a bit of a bitsa, 1979 Z650 frame, JMC chrome swingarm, later gpx600 forks, re worked micron fork brace, GPZ750 wheels.

Engine currently in bits, early 80's KZ750 cases (actually fits my frame, GPZ unitrac motor that came with bike had be bogged in) , GPZ750 barrels, 90's Zephyr 750 head.
My 80's GPZ750 unitrac engine needed a lot of cylinder head work, but luckily I found a Zephyr head that has been reconditioned, stripped it anyway and its all good for less than the price of a new set of valves and it has the Z900 look, will have to file the square fin profile to something more rounded , think it will look more at home in the Z650.

Question 2, I have read something about cam circles being different in some engines, so what do I check to determine if my GPZ unitrac cams will work correctly in my Zephyr head, it has same cam cover style as the Z900's.

Have added a few pictures below.


 

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15 Oct 2024 06:45 #905130 by Street Fighter LTD
Welcome to KZRider
Dave


Original owner 78 1000 LTD
Mr Turbo Race Kit, MTC 1075 Turbo pistons by PitStop Performance , Falicon Ultra Lite Super Crank, APE everything. Les Holt @ PDM's Billet Goodies . Frame by Chuck Kurzawa @ Logghe Chassis . Deep sump 5qt oil pan. RIP Bill Hahn

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15 Oct 2024 07:09 #905132 by Wookie58

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15 Oct 2024 20:35 #905164 by Injected
Welcome from Canada.

For longer throttle cables on a 650 you can try those from a KZ1000 USA model, higher bars than Z1000 and Z650 UK bikes which provide more length.

As for the cam info on 750's see this : (bottom of pic)






 

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17 Oct 2024 00:53 #905191 by Mepb750
Hi, Thank you for the cam information, took the base circle reference, did a search and found a posting on how to measure it.
Apparently it's the  exhaust cam that has the smaller base circle.
quote from other post
" only the exhaust cam on the 83-86 Unitrac zx750's have a smaller base circle. The intake cam has a "normal" base circle exactly the same as any other kz750 or kz650 intake or exhaust camshaft."

www.kzrider.com/forum/2-engine/612384-ho...e-1983-gpz750#819840

Will  go measure it, its a unitrac motor I stripped, so it might be it is the smaller exhaust cam in which case I cannot use it in my later Zephyr750 head.

Thanks again,
 And hello everyone, that's a really nice looking GPZ fuel injected bike in the UK.




 

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17 Oct 2024 01:23 #905192 by Mepb750
Quick update, using the rough method, caliper at 90 degree across the lobe, my exhaust cam is roughly 1mm shorter than the inlet cam, so it is a unitrac smaller base circle one.

Off to buy a set of zephyr 750 cams which will match the head I have. 

Have to check what the power difference is, not too fussed about top speed etc, I usually ride around the surrey hills /country roads, so 60/70 mph on a good day is about it, way too old to play with the modern plastic missile brigade, they look great but suspect my back would last about a mile with clip-ons.
Thanks again.

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