TOPIC:

I have a full set of V blocks and a true table to match with a dial indicator so I was going to true it myself, I also have a vertical vernier to check the rod heights (TDC reference). because the original crank has twisted I have no choice but to get it welded, I was aware that it only requires a 1/2" to 3/4" seam weld but I for one am not good enough so I'll look for a professional.
In the meantime I'll give the Z900 crank a go and see if the vibration increases to an annoying stage.

I would like to thank everyone who responded to this Topic as usual your information was great.

PLUMMEN wrote: Packing it up and sending it to gardner or falicon would probably be kinda pricey from your location,Can you get your hands on a good used 77-78 1000 crank where youre at?

PLUMMEN, Australia is not the best place for parts, that's why we normally would get them through the UK or US, I'd get my hole ripped for a 78 crank in good condition. Sending it to the US ?? very pricey. as stated in my previous reply I'll true it and find a good welder who will be able to spot weld the pins and then have it re-trued in case.

The Z1R has been put together and running about two weeks ago, the Z900 (spare) crank has been checked and fitted. My report is as follows -
The Z1R crank was smoother at certain speeds and at low speed it had more torque in top gear. The vibration issue is not as bad as I first thought, the current vibration is not distracting or annoying.
Midrange to topend power the Z900 crank spins up quicker to the rev limited 10K. It had its first drag last week against my brothers bike and it appears to be slightly quicker but without timing it this cannot be verified.
Overall I'm extremely happy with this crank. Is one better than the other? only time will tell.

Great News Bozo !!!
Lighter crank should have a acceleration edge, Price is less rotating mass for launch and sometimes more vibration
Dave

I'll agree to the launch part. Not only was the shorter stroke a mistake but lighter crank too. I spend most of my time in the lower RPM's, not close to red line.
Steve

Steve if thats the case I definitely found when going through tight bends I had to use the gears more below 4,000rpm if I wanted accelerate (casually not racing), but above 4,000rpm it is noticeable, also when standing at lights on idle, previously the mirrors were perfectly clear at 1000rpm, now I have to idle around 1,200rpm to achieve the same result.
The other noticeable part was with the Z1R crank above 120kph hard acceleration it vibrated more than the Z900 which had a harder but smoother pickup.
I might add that the carbies have been synced with all butterflies (ZRX carbies - 36mm CV's) even and the idle jets adjusted to suit. Compression's are fairly equal +/- 5psi. Shims adjusted etc

The engine seems to have less buzz than I remember so long ago. If we had tight twisties I could use the RPM's more. The 1X cams were supposed to improve low end but I might have been defeating the purpose. I know the 903 cranks are lighter compared to the 1015 but I'm not sure the 750 crank is lighter than the 903 maybe with the exception of the slightly shorter rods. The only way to know for sure would to weigh them and compare. That's not likely to happen anytime soon. I'll just have to be happy with what I have for now.
Did you have the pins welded on your 903 crank? I hope so.
Steve

Steve, I mentioned previously I did not have the pins welded because no-one in Western Australia was comfortable enough doing this, I am on a budget so sending it elsewhere was hard. After talking to a couple of ex drag racers they questioned why I need to weld with an engine that has a mild cam etc (yes I know that's what I thought about the Z1R crank before it twisted).
I hope I didn't make the wrong decision, only time will tell. At this stage with the rev limiter fitted and my riding not as aggressive as when I was young (that is debatable) I should be ok

I bought the bike in 75, rode the piss out of it until 87. In 78 I went 1015. Never twisted a crank. I understand the !000 cranks could do this but never heard of a 903 doing it.
Steve

A bad backfire could do it and you cant predict that
Dave

Street Fighter LTD wrote: A bad backfire could do it and you cant predict that
Dave

Dave, thats the first thing I was asked, "did it backfire", but no this happened while doing around 140kph touring and all of a sudden it went rough. I assume it was just on the border line of twisting and at that time it decided to go.
Around 1" twist from cyl 2 referenced to cyl 3 crank so it twisted in the centre. In this case 3 & 4 were backfiring after the twist.