650 crank treatments

Aiming this mostly at ape jay but welcome to others knowledge. Building an all out 650 for the strip, 810 kit with highly modified 750 head. I have done these over 10 yrs ago and we had significant trouble with the bottom ends holding up. If I had to guess, the rod journals seem soft. I guess what I'm asking is has anyone ever tried any kind of surface treatment such as ticn coating or other to prevent premature crank wear. I know we use to spin these things a little over 13,000 in the past and remember someone saying that keeping the rpm's down makes them last much longer. If so, what should the rpm ceiling be.
Thanks in advance.
Les Holt

You are right about the soft journals. We used to have them hard chromed, but haven't done that in years. Nwith our strokers, we are nitriding them. I am sure this would work on the 650 and be a lot less money than chrome.

Jay

nitriding is a heat-treating process for those unfamiliar with the term.chevy used to use a heat treating process on hi-end big block forged cranks called tuff-triding but the penetration was not deep enough to allow the crank to be turned or machined on later rebuilds without removing the hardened surface most new aftermarket hi-end forged cranks use the ni-triding or other process to beef up journals ,if it will hold up to a blown big-block chevy it should hold up pretty good on a 80-90 horse motorcycle crank!good luck,happy wrenching!

What exactly is happening that leads you to the conclusion that the rod journals are "soft"? Are the bearings spinning in the rod? If so, is that due to the crank bearing surface deforming (becoming oval shaped) or the rod big end stretching and pinching the bearing at the parting line?

I suspect it is not the hp but the rpm that is causing the problem, the stock GPz750 turbo puts out around 115 hp and I believe Lorcan is running ~200 hp. The GPz750 Turbo and the GPz750 share the same part number for the crank, while the standard 750 and the 650 (with HyVo cam chain) share the same part number. Maybe Lorcan knows the difference between the cranks (GPz possibly factory hardened?).

I think that if you limited the rpm to 11k, the bottom end would last a lot longer

Post edited by: steell, at: 2005/12/22 10:43

Actually, the older 650's,"non hyvo chain" have a tick more stroke in them. The reason I say soft is I have machined on them in the past to lighten and was amazed that they were not very hard. With the newer cam technoligies I'm sure I wont have to spin it as hard. Although I am going to have it nitrited.
Thanks

les holt wrote:

Actually, the older 650's,"non hyvo chain" have a tick more stroke in them. The reason I say soft is I have machined on them in the past to lighten and was amazed that they were not very hard. With the newer cam technoligies I'm sure I wont have to spin it as hard. Although I am going to have it nitrited.
Thanks

Yes, don't think it was the bearings as chroming the journals always fixed the problem. I am takling about little turbo 650 dragsters that ran mid 8s.

As for the 750 factory turbo, we do a lot of work with Mike Chestnut from Horsepower Unlimited, and he has not had crank problems on those radical 750 turbos he does.

Jay

Post edited by: APE Jay, at: 2005/12/22 15:32

Well maybe a good solution would be to use a GPz750 crank then? Use the HyVo chain and the 750 head and cams would be a bolt on

I would use a gpz 750 crank but I just hate the fact that I can't accurately degree cams. I guess you could call me anal rententive in that aspect. I'm one of those that just HAS TO KNOW where things are. Not a good guestamate for lack of better words.
So, more to the point, do you recomend nitriting or hard chrome. I know in the old days hard chrome didn't like the flex that was subject to cranks.
I will say this, I WAN'T TO TURBO AN OLD 650 but I am what some would call Poor. I can't afford to go through parts to find out what works and what doesn't.
Again, thank you gentlemen, VERY MUCH. Things have changed in the last 10 yrs. Maybe it's the OLD MAN syndrom, you know, " The older I get, the faster I was".
Les Holt

I think the week link in the 650 bottom end is the bearings. Being just led without brass blacking they are a little soft. I had great success having the rods peened and polished, the small end bushed and a thousandth taken off each side of the big ends to let the oil out easer and to keep it cooler. I also used Chevy small block rod bolts.
Mark

Not a real geinious on bearings but I do believe that the reason you have multible materials is not only there properties but the way that bond. I don't think you can get the babbit mat'l to bond to the steel shell without some sacrifice of integritity. Unless you want your bearings really thin. I'm probally wrong and darned sure won't argure my thinking but I will bet that their bearing design isn't much different than what is used in some very high horsepower applications. I do know that a bearing has multible purposes, It has to withstand high amounts of cylinder pressure, be able to absorb contamanites "bet I spelled that wrong", and produce a friction free environment between it and its mateing partner.

Dang, just read my post and realized, Jack Daniels and posting doesn't work well together. I would have stopped but I am going to let you know, I do have my moments. SORRY!!

Oh, try Jack Daniels and RootBeer, You might find that it's going to get you in trouble, just like me
Les Holt

les holt wrote:

I would use a gpz 750 crank but I just hate the fact that I can't accurately degree cams. I guess you could call me anal rententive in that aspect. I'm one of those that just HAS TO KNOW where things are. Not a good guestamate for lack of better words.
So, more to the point, do you recomend nitriting or hard chrome. I know in the old days hard chrome didn't like the flex that was subject to cranks.
I will say this, I WAN'T TO TURBO AN OLD 650 but I am what some would call Poor. I can't afford to go through parts to find out what works and what doesn't.
Again, thank you gentlemen, VERY MUCH. Things have changed in the last 10 yrs. Maybe it's the OLD MAN syndrom, you know, " The older I get, the faster I was".
Les Holt

the way to degree cams with a hivo camchain is with a spare valvecover that has had the ends of one side cut off thats the way I did it when I ran the J model drag bike. I always thought of fabing a bridge that would hold the camchain at the right level but was waiting for some aftermarket Co. to do it.

I like keeping the RPM's down. 11,500 at most. KZ650's were not made to run at 13,000 rpm.