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Saving a 1980 750 twin. 01 Jul 2020 13:09 #829535

  • 531blackbanshee
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nice work sir.


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!

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kzrider.com/forum/5-chassis/294594-frame-bracing?limitstart=0
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Saving a 1980 750 twin. 17 Jul 2020 10:52 #830877

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I remeasured the cylinder head volume. The new titanium valves have no dish and intakes are bigger so the volume is smaller than previous. cyl 1 is 46.4cc and cyl 2 is 47cc
maintaining my desired squish (0.035") this should leave me at about 10.25 -10.35/1 static compression.

-Vic
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'78 kz1000 LTD long term project

'80 kz750G project
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Saving a 1980 750 twin. 19 Aug 2020 15:09 #833241

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I downloaded the C5 ignition software and started playing around with it. its very simple to use. I decided to compare it to the stock curves and WOW what a difference! talk about turning the wick up

'76-'80 Stock ignition curve with points. idle = 5 degrees full advance 30 degrees @ 3750 RPM
'81+ stock electronic ignition. idle= 10 degrees full advance = 35 degrees @ 3750 RPM
C5 ignition curve. idle = 23 degrees full advance = 38 degrees @ 3000 RPM



-Vic
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'80 kz750G project
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Saving a 1980 750 twin. 19 Aug 2020 21:01 #833285

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What are you up to? Some searching turned up powerarc.com and c5ignitions.com.

I see an optical trigger with programmable timing maps. The only thing that jumps out at me that's unusual is the multi-spark operation.

So two questions:

One, why do the factory timing curves have an upper and lower bound. Is that the acceptable error in timing? Some sort of hysteresis?

Second, how are you determining the new timing curves and limits for the programmable system? Is the Power Arc software suggesting those values based on engine parameters?

Oh, one more. Does that Power Arc/C5 gizmo have the ability to read a throttle position sensor, so you can do a full load/rpm 3D timing map? Something similar to the K-TRIC system Kawasaki used?
'78 Z1-R in blue, '78 Z1-R in black, '78 Z1-R in pieces
'95 GPZ1100 (sold) , '00 ZRX1100

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Saving a 1980 750 twin. 20 Aug 2020 09:39 #833319

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So two questions:

One, why do the factory timing curves have an upper and lower bound. Is that the acceptable error in timing? Some sort of hysteresis?
I believe that is the case. acceptable error in timing., I personally found that TDC was off almost 2 degrees from the marks on the advancer plate.

Second, how are you determining the new timing curves and limits for the programmable system? Is the Power Arc software suggesting those values based on engine parameters?
This ignition curve came programmed from C5. they sold it specifically for the KZ twins. I ran this ignition, with this curve, on both the stock engine and my mild hop up, it worked well. With this new engine package I want to be able to modify the timing to get the most out of it without making it go boom.

Oh, one more. Does that Power Arc/C5 gizmo have the ability to read a throttle position sensor, so you can do a full load/rpm 3D timing map? Something similar to the K-TRIC system Kawasaki used?

I don't think it gets quite that complicated, but you can add in any sensor. It can only store 4 different maps. On the C5 site he uses a a MAP sensor to get vacuum readings to switch to 4 different curves depending on load. I haven't planned on messing with this but i probably will at some point.

www.c5ignitions.com/classroom--timing-maps.html
-Vic
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'78 kz1000 LTD long term project

'80 kz750G project
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Saving a 1980 750 twin. 06 Sep 2020 14:43 #834493

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I talked with a guy in Canada who has been racing and developing this platform. He has given me tons of good info including this tip to run the clutch from the belt drive engine. This clutch is different because it has an aluminum clutch basket, and the clutch is actuated from the right side of the bike. This not only allows a much larger countershaft sprocket by removing the clutch push rod, but also removes over a pound from the flywheel!

-Vic
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'80 kz750G project
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Saving a 1980 750 twin. 05 Apr 2021 23:04 #846247

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This project is pivoting. I have decided to build a track/race version with the big bore engine. I've started a build thread HERE if you are interested.

As for this bike I will be building a nice, fairly stock engine.

I had 3 spare engines lined up and I chose the best one from the bunch. Other than being stored with an exhaust valve open this may be the cleanest engine internally I have every seen. It must have had low miles because everything is barely worn, evident by the cross-hatching in the bores, and the small end of the connecting rods looks mint. Because of that I'm just going to clean it up and rebuild the top end.

I started by tearing the cylinder head down, polished all the fins back how I like them, sand blasted, re-polished the fins, and painted with Gun Kote Satin Black. After the paint is dry I wipe the fins clean with acetone before baking the paint. I then do one last polish with 320 so the fins are super bright. I find this process gives me really well defined fins and reduces the risk of damaging the paint during fin polishing significantly

I also took the time to polish the intake and exhaust runners and to blend in the valve seats. This is a common issue on these heads; the ports and valve seats are not aligned very well and leave a sharp internal edge. I'm no porting expert but I know that this is bad for flow. Other than that I mostly just removed the large casting flash present in the runners and tried not to remove much material as these ports are already too bg for stock displacement. I also took te time to port match the carb boots, and polish the combustion chambers.

Now its time for a thorough cleaning in the parts washer before going out for a 3 angle valve job and getting the head decked. I will be using NOS valve springs (the big ones, cant find the small ones) along with high quality teflon valve seals. 






-Vic
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'78 kz1000 LTD long term project

'80 kz750G project
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Saving a 1980 750 twin. 08 Apr 2021 09:25 #846380

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BEFORE/ AFTER


 
-Vic
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'78 kz1000 LTD long term project

'80 kz750G project
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Saving a 1980 750 twin. 08 Apr 2021 13:53 #846398

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Gonna be sharp!  
1973 Honda CL70-K3
1975 Kawasaki 350 F9-C
1983 Kawasaki KZ750-K1
1994 BMW K1100RS
2008 Suzuki GSX1300-BKK8 #1120

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