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6-speed Transmission Swap Instructions 01 Feb 2021 09:27 #842786

  • ac4
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Thanks for this,been very helpful.I am builing a 750 together with 750 LTD engine cases and zephyr 750 crank,pistons,cylinder and cylinder head.I started with a GPZ 600 gearbox,now have a Z 550 and GPZ 550(ZX550) too.As the LTD engine cases only fit in the older z's I'll use the 550 output shafts,guess the 600/zephyr 550(same part number on kawasaki.com)would be better with wider back tyre.I'm using your idea with the clutch basket,a friend of mine is machining the clutch basket.Just got zhe plastigage to check the crank bearings in the LTD engine cases,so sometime in the not too distant future it might be together,have to do some other stuff first,like head and foot gasket on a gt 550(european version of 550 spectre).

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6-speed Transmission Swap Instructions 02 Feb 2021 06:47 #842824

  • Daftrusty
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ac4 - It sounds like you are well on your way.
Please keep us up to date with your project, so we know how the trans swap works for you or if you have any issues.

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6-speed Transmission Swap Instructions 04 Feb 2021 02:02 #842955

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Thanks again!Quick question,is there any reason not to decide later to use a zephyr/zr //Zx750 style clutch with the bearing cup fitted with the pushrod type clutch?I can't think of any ,have both options open then..

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6-speed Transmission Swap Instructions 04 Feb 2021 12:48 #842969

  • Daftrusty
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ac4 - You have to decide which clutch release mechanism you are going to use before installation of the transmission. The pushrod style uses the bearing roller cup with the hole in the end for the pushrod as where the zr550/zx550/zx600 transmission uses a bearing cup with no hole in the end.
YOU CANNOT USE THE PUSHROD BEARING CUP WITH A PULL STYLE CLUTCH RELEASE!
The hollow center of the transmission shaft is "pressurized" with oil in order to lubricate the clutch release plunger and ball bearing (or puller in a pull type) If the push rod bearing cap is used with the puller style, then oil will pour out the end of the bearing cup instead of pressurizing the transmission shaft and lubricating the clutch release mechanism. You would also have a jet of oil squirting out of your engine case as well....not good.
If you do decide to use the pull style clutch release, then take note of the following issue that was discovered....
A member (Fishrider) over at the Zephyr-Zone forum is currently doing a 6-speed swap in his Zephyr 750. He identified a possible issue that I will to explain.
It is know that the 550 input shaft is shorter than the 750 shaft, hence having to machine the clutch basket in order to make it full bolt on. But it was found that the shorter shaft may not fully support the pull style release mechanism (plunger/pusher). There is roughly ~6mm less shaft for the plunger to ride in, which under normal driving conditions should be fine. But, when the clutch lever is pulled then the plunger is pulled even farther out of the transmission shaft.
There is however, no risk of the plunger being pulled completely out of the transmission shaft!!

The pusher/ puller only moves about 5mm to release the pressure plate. So at full extension, that leaves roughly 13mm of the plunger still riding in the transmission shaft. And the more I have thought about this.....when the clutch is activated, the plunger/puller stops free wheeling and becomes stationary, which means it is then no longer being supported by the transmission shaft anyway. So as long as the plunger dosen't get pulled completely out the shaft (which I am almost 99% certain it cannot) then when the clutch is released, it will slide back into the transmission shaft and become supported again. I am attaching photos to help illustrate what I mean.

Difference in length of input shafts and how it relates to the pull style release plunger


The difference in the amount of support between the 750 and 5500/600 shafts. Picture courtesy of Fishrider


So in summary, I don't think using the pull type clutch release mechanism with the shorter 550/600 6-speed transmission is an issue at all.
But as of me writing this, I do not have definitive proof that it is not an issue. So to whomever installs a puller style clutch release, please double check the clutch release action to ensure that every thing works as it should. And then please let me/us know your results.
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The following user(s) said Thank You: ThatGPzGuy

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Last edit: by Daftrusty.

6-speed Transmission Swap Instructions 21 Apr 2021 09:10 #847150

  • ac4
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Motor is together,just need a frame to build it into:)I went for the pushrod clutch.Motor is turning nicely on the crank and the gears are all selecting nicely...Incidentally the GPZ 550 final drive cover is the same as the older 750 cover,and that has the later style clutch,so no problems with oil coming out of the final drive cover.(I also got the GT550 back on the road,running much better with grinding the valves)
I was looking at various parts,I wonder if the later 600s have a longer clutch shaft,so it wouldn't be necessary to machine the clutch basket.I think I mentioned I used the GPZ 600 clutch and 550 output shaft.
Will let you know when it's running in a bike:)
Thinking about building a 650 now too:)
cheers,andy
 

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