saving a 1980 KZ750 twin

doc_rot

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irk miller said:
There's a circuit of tubes that feeds nozzles in each carb. The pump is always on #2, which also usually doesn't have a sync adjust. You sync the other three to that carb.
yeah, brain fart earlier. You are correct sir.
 

doc_rot

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I slotted a second set of cam sprockets properly on the mill because my original job that i did with the file was pretty rough and i wasn't happy with it. I also finished machining the starter clutch. I thought it would be tougher and need to be ground but a carbide cut it just fine.

I have been screwing around with my tool setup to time these cams. A lot of trial and error to get make a feeler that can touch the tappet AND not get in the way of the cam AND go that deep into the head, finally got it right only to break my dial indicator! I then borrowed a friends dial indicator only to break my tool holder! I was getting super irritated with my cheapy Chinese dial indicator setup anyway, I just couldn't get consistent numbers with it here for some reason. I did what any sensible human does when they get pissed at their tools and splurged. I got a nice Mitutoyo drop dial and a NOGA magnetic base. Ive never had so much trouble timing a cam.

TLDR; I don't want a pickle, i just want to ride my motor-sickle

https://www.youtube.com/watch?v=X4OKPMm-vfc
 

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doc_rot

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The new tool setup is soooo much better, I can zero the dial in 5 seconds as opposed to 5 minutes. The adjustability and rigidity is much better as well. However, I am still getting a small bit of variation on the degrees.

The indicated degrees will fluctuate +/- half a degree on my target, despite the dial coming back to zero every time. This means the lobe center can be as much as 1 degree off target. I have tried many things to try and tighten it up and nothing has removed this. I checked to see if the feeler was dragging at all and it clears everything completely. I called Web Camshafts up and they thought it could be variations in the cam chain or the OEM style spring cam chain tensioner. The cam chain is brand new, so im scratching my head. Right now the cams are very close to where they need to be, but they're not perfect.

After I got the cams timed I clayed the pistons to make sure there weren't any problems. You can see in my tool setup I cut off most of a spare cam cover so i could access the cam sprocket bolts without moving my tool setup. this made dialing in the timing much easier.

Any suggestions on what I could look at to remove the small degree variations? I'm stumped.
 

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cxman

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watching and reading with interest

i was minding my own business the other day and one of these followed me home
 

der_nanno

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With regards to the variations: turn the cam in both directions until you can take a measurement on the gauge and then split the value in half and set the cam to this position.
 

doc_rot

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Won't that give me an even less reliable number? If I rotate the engine backwards it will pull against the tensioner and introduce even more slop.
 

cxman

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do you have a spare set of cam sprockets you could try

i have seen wear on the sprockets give readings like that
 

doc_rot

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cxman said:
do you have a spare set of cam sprockets you could try

i have seen wear on the sprockets give readings like that
The other sprockets i have are in worse shape. these are in pretty good shape. I would expect it they were worn it would at least be consistently off, but the variations are erratic
 

doc_rot

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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!

It was suggested that a larger wrench to turn the engine over with a larger degree wheel would help get more precise numbers. This did help, but I still was having variations in the cam degrees. In checking the cam lobe centers I was getting variations of less than 1/2 a degree in either direction. Good enough.

couple things from the final assembly: A 14" degree wheel i drew and laser cut out of acrylic, filled in the etchings with ink and spray painted the back white. 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 engine in tonight.
 

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doc_rot

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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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irk miller

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Can't see why trimming that would hurt. Plus, if you feel you need a tube there, you could always flare a better sized tube and weld (if it's metal) or rivet it in the OG tube's place.
 

doc_rot

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Just a side mount throttle linkage. I think a different petcock might clear it just barely
 

doc_rot

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I will still run a Pingel. They have this super cool petcock that doesn't have a tang on it, just a knob, so you can orient it in any direction. I called their tech support, the lower body on this is smaller than what I currently have. I think it will clear. I also asked the dude how much wall thickness was there and he thinks I can safely shave off 1/16" of an inch if I need to.
 

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doc_rot

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I’m takin this bike on a road trip this summer so I fabricated a luggage rack, crash guards, and a better kickstand. Also got it running. The video really kill’s the sound. Makes it sound a bit “ farty”.

Sadly this will have to sit for 2 months until I’ll be able to ride it. I accepted an amazing job in LA so This will be in storage for a bit while I move. The bitter sweet part is I will loose access to all the cool tools I have had at my disposal. I have been working 1 or 2 days a month at my old college to retain access to their shops. That’s all going to stop now :(

https://www.youtube.com/watch?v=lvvkoq6FN-k
 

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irk miller

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doc_rot said:
I have been working 1 or 2 days a month at my old college to retain access to their shops. That’s all going to stop now :(
I feel you. I worked at Tyler School of Art (Temple University) in Philly for 6 years, if for no other reason then to have access to every studio, shop and tool that Art School had to offer. When I moved on, it took me 5 years and a move to the south, where I could live cheap and have a lot of space, to recover with my own shop and tools. I'll never have everythingTyler offered, but at least I'm functional again. Why does this sound like an AA meeting?
 

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