Saving a 1980 750 twin.

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.

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!!!

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?

Leave it alone, you ae starting to split hairs.

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.

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


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very nice.

leon

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?

Crap, the petcock is right where the throttle cables now live.

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

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

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.