TOPIC:

Just ordered my 903 crank. Been watching it for a while. There's a 1075 kit I have my eye on but it's the old style cast Wiseco pistons. I'll make an offer and if it's accepted, I'll buy it. I figure I can sell the 750 Z2 crank and my 1015 pistons and make some money on the deal. If nothing else, the bike should be quicker with higher compression. We'll see.
Steve

Just in time for Christmas...... betting your gonna feel a big difference in power... am looking forward to hearing about it.

It took a while to gather the parts needed for my valve job one by one. The original Wiseco's were cast but they don't sell them anymore. The rings are the same so if I do get the 1075, I'll get new rings to go with them. Gives me something to look forward to.
Steve

your going to think you got hit in the ass by a train the first time you crack the throttle on your rebuild

leon

I hope so. Been squeezing as much juice out of this thing as I could get.I always knew something was missing.
Steve

Funny thing about it though, when I ran into Miller on his Honda Davidson in 87, I pulled on him when before he would walk away from me. He said "you're learning." That was with new cams and stock carbs. Obviously the lighter crank made a difference even with the loss in compression.
Steve

lighter cranks spin faster.

but compression makes torque and horsepower!

plus you'll be gaining back some stroke which will be more torque at the expense of less revs.

leon

YUP. A added bonus is if I left this crank in the shop, it would have burned with all the rest of my parts and had been stolen for scrap. It's valuable and can be sold for $$$ . I'm tempted to tear into it as soon as it arrives but I've waited this long, might as well get the other goodies I want as well.
Steve

Got my crank. Better than I'd hoped. I'll have Jeff weld it and put it in. Might just do that first then go with a bigger bore later.
Steve

Happy to here that you have finally found the crank what you had wanted but before you send it out for welding don't omit to check how true and also the condition crank side thrust bearings are as these 1973 to1978 cranks 15 pin shafts are not as strong due to smaller bearing pin size as against the 1978 to 1980 shafts and will not rev out the same as Z2 . I myself if building this motor would have stayed with the Z2 and raised the comp to 10 to 1 or better still got a good J crank an changed the centerpin to a 16 pin mark style.

In 40 years I have never had a issue with a 903 crank. In 78 I installed a 10.25/1 1015 kit and beat the hell out of the bike. Never had the crank welded. The 750 Z2 crank is identical to the 903 except the rods and possably the throws. In 87 when I did it not much was known about them. I had it welded figuring I'd go with a bigger kit sometime. Since then I've knocked the snot out of it with no issues. From what I've read the early KZ 1000 cranks were just as bullet proof just heavier to reduce vibration. As I understand it the late cranks have thrust bearing issues and have been discussed here recently. I will have Jeff check the crank and tack weld the pins. I will take a closer look at the thrust bearings.
Steve

Does the 750 crank have the same stroke as the 900?