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Saving a 1980 750 twin. 22 Mar 2019 17:40 #800866

  • DoctoRot
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Work was slow today so I drew up a degree wheel and laser cut /etched it. I only had this scrap of acrylic so it was kind hard to see the marks so I filled them in with ink and sprayed white behind. The ticks are very fine, and dimensionaly accurate, should be easier to see at 14" in diameter. Hopefully I'll have time to button this up tomorrow.
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Saving a 1980 750 twin. 22 Mar 2019 18:06 #800869

  • Dr. Gamma
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We used to call them "government jobs" when we got to work on our projects on company time!!!!!
Can't beat getting paid while you work on your own projects!!!!!

Looks like some real good work there on your degree wheel!!!!

Give yourself a big pat on the back for that one!!!

14 inch degree wheel, that should make it pretty easy to get just what you want for a reading!!!

A large diameter degree wheel makes it real easy to get a half of a degree reading!!!
1972 H2 750 Cafe Racer built in 1974.
1976 KH400 Production Road Racer.
1979 Kz1000 MK. II Old AMA/WERA Superbike.
1986 RG500G 2 stroke terror.
1986 GSXR750RG The one with the clutch that rattles!

Up in the hills near Prescott, Az.
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Saving a 1980 750 twin. 23 Mar 2019 18:37 #800939

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I used my longest wrench (18") to turn it over and I am still getting small variations. I checked the intake 20 times and i was getting lobe centers varying from 105.7-106.3 with a target of 106. The exhaust had a variation of 107.5-108.4 with a target of 108.

The only thing I could think it could be at this point is the cam chain sprockets are worn as they are used. The other used sprockets I have are in worse condition. Do you think its worth the hassle of tracking down NOS sprockets and slotting them for 1/2 a degree lobe center variation? I'm not sure this will fix it because if the cam sprockets were worn out they would still be engaging at the same place every time. The lobe centers vary so erratically it makes me think its variation in the NOS cam chain. Or it could be the tappet spins a few degrees every-time the spring compresses and this is causing the dial indicator to move ever so slightly.

Right now if I average my findings the lobe centers are perfect. I doubt half a degree either way will make a significant difference in running.

I'm at my wits end here. what should I do?

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Saving a 1980 750 twin. 23 Mar 2019 18:42 #800940

  • Nebr_Rex
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Leave it alone, you ae starting to split hairs.
2002 ZRX1200R
81 GPz1100
79 KZ1000st daily ride
79 KZ1000mk2 prodject
78 KZ650sr
78 KZ650b
81 KZ750e
80 KZ750ltd
77 KZ400/440 cafe project
76 KZ400/440 Fuel Injected

www.dotheton.com/forum/index.php?topic=39120.0


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Saving a 1980 750 twin. 24 Mar 2019 19:37 #800986

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This engine is finished! I did a bench test and its making 180PSI on both cylinders, with no starter clutch slippage!

couple things from the final assembly: A bootleg rotor holder i made out of an old drill vise I use for welding and a kz1000 tappet holder i adapted to the KZ750 so i can swap shims without removing the cams. gonna try and slap this sucker together tonight.
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Saving a 1980 750 twin. 24 Mar 2019 19:51 #800987

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180 psi is good and it probably increase during break in.


.
2002 ZRX1200R
81 GPz1100
79 KZ1000st daily ride
79 KZ1000mk2 prodject
78 KZ650sr
78 KZ650b
81 KZ750e
80 KZ750ltd
77 KZ400/440 cafe project
76 KZ400/440 Fuel Injected

www.dotheton.com/forum/index.php?topic=39120.0


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Saving a 1980 750 twin. 25 Mar 2019 13:10 #801027

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very nice.

leon
skiatook,oklahoma 1980 z1r,1978 kz 1000 z1r x 3,
1976 kz 900 x 3
i make what i can,and save the rest!

billybiltit.blogspot.com/

www.kzrider.com/forum/5-chassis/325862-triple-tree-custom-work

kzrider.com/forum/5-chassis/294594-frame-bracing?limitstart=0

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Saving a 1980 750 twin. 26 Mar 2019 01:02 #801054

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Engine is in the frame and everything is going back together. I installed the new RS34 carbs. I would like to retain the airbox, so I made these Delrin flanges to lengthen the carb body to fit with the airbox boots. This got me looking at the airbox itself. The K&N filter looks like it can flow plenty of air, but the cap that holds the filter on has a long down tube which is quite narrow in diameter (40mm). I'm thinking about trimming this all the way back to the cap and making the opening there as wide as it can be and still hold the air filter (about 55mm)

Worst case scenario I end up using pods but I would prefer to use the airbox if i can. Thoughts?

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Saving a 1980 750 twin. 29 Mar 2019 08:42 #801224

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Crap, the petcock is right where the throttle cables now live.
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Saving a 1980 750 twin. 29 Mar 2019 17:23 #801261

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Can you move the throttle hardware to the other carb body so it's in the middle of the pair? It kind of looks like the mounting bosses are on the other body.

Or maybe replace the fuel valve with a tiny elbow, and use an inline valve.

www.amazon.com/Motion-Pro-12-0036-Inline-Valve/dp/B000WJA33I
'78 Z1-R in blue , '78 Z1-R in black, '78 Z1-R in pieces
My dad's '74 Z1
'00 ZRX1100
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Saving a 1980 750 twin. 29 Mar 2019 17:46 #801263

  • ThatGPzGuy
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My GPz750 airbox has the same type of inlet for the filter. I cut it shorter and drilled larger holes through it as well.
Jim
North GA
2016 Yamaha FJR1300ES
1982 GPz750 R1
1974 Kawasaki H1
1976 Kawasaki KZ400
1979 Yamaha XS650 cafe'
2001 KZ1000P
2001 Yamaha YZ426
1981 Honda XR200 stroked in an '89 CR125 chassis
1965 Mustang
1967 Triumph GT6
1976 Bronco
"If you didn't build it, it's not really yours"
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Saving a 1980 750 twin. 30 Mar 2019 11:54 #801291

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Thanks for the responses

DOHC wrote: Can you move the throttle hardware to the other carb body so it's in the middle of the pair? It kind of looks like the mounting bosses are on the other body.

Or maybe replace the fuel valve with a tiny elbow, and use an inline valve.

www.amazon.com/Motion-Pro-12-0036-Inline-Valve/dp/B000WJA33I


All the shafts are drilled for the throttle to be on the outside, I might be able to move it to the middle but it would take some fabrication. If i cant ind an easier solution I will check it out.

I thought about using a in-line valve but then I would loose the reserve feature which is a bummer on a street bike. I think a different petcock might work, it only needs a little bit of clearance for the cable to squeeze by.


ThatGPzGuy wrote: My GPz750 airbox has the same type of inlet for the filter. I cut it shorter and drilled larger holes through it as well.


I just chopped the whole thing off for now. I'm toying with the idea of fitting a bigger filter in the stock airbox with a custom cap.

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