GT750 Crank Rebuild (bill bune, miss matched rods), issue?

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rngdng
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Re: GT750 Crank Rebuild (bill bune, miss matched rods), issu

Post by rngdng »

Suzukidave wrote:If your later ( 74 and later ) engine has the proper crank without the thrust washers on the crank end of the rod there should be thrust washers on the rod small end . You just have to be sure there is the extra space in the piston for the thrust washers , if someone had fitted up early style pistons there wouldnt be space . The thrust washes are available from Suzuki .
Also, certain people who sell suzuki pistons will tell you that old or new pistons can be used in any bike 72-77. He says that if you want to use early pistons, just throw away the small end washers. He also claims that using late pistons on an early cranks is OK. We know what opinions are like.....


Lane
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tz375
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Re: GT750 Crank Rebuild (bill bune, miss matched rods), issu

Post by tz375 »

One possible answer might be to use an early narrow piston in the center but to locate the conrod, the crank would still need to be stripped to fit early type big end thrust washers.

And if the crank has to come apart, it might as well be fitted with a correct late style rod.

I did just take an old scrap rod and results were pretty much as expected. It drilled easily through the copper coated steel until the drill bit reached the hardened inner core of the small end. Then I switched to a carbide cutter and it popped through into the small end leaving a small amount of swarf that was easy to clean up with a 1/4" carbide ball cutter.

BUT that was a single rod. I would hate to try that on a rod fitted to a crankshaft.

My conclusion is that the incorrect rod must be replaced with an later style.

The small end thrust washers should have dropped out as you removed the piston pins. They are stepped and easy to recognize.
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JSJamboree
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Re: GT750 Crank Rebuild (bill bune, miss matched rods), issu

Post by JSJamboree »

Suzukidave wrote:72 & 73 cranks have thrust washers on the big end and none on the small end , also the pistons will be more narrow at the small end . 74 and later.. no thrust washers on the big end and thrust washers on the small end with matching wider gap pistons
Those pics were perfect, thanks a ton.
tz375 wrote: I did just take an old scrap rod and results were pretty much as expected. It drilled easily through the copper coated steel until the drill bit reached the hardened inner core of the small end. Then I switched to a carbide cutter and it popped through into the small end leaving a small amount of swarf that was easy to clean up with a 1/4" carbide ball cutter.

BUT that was a single rod. I would hate to try that on a rod fitted to a crankshaft.

My conclusion is that the incorrect rod must be replaced with an later style.
Thanks for the test, that's pretty much what I had assumed. I'll let you know what I hear back from Bill's team.

Going to call bill this afternoon to see what they say. They should either machine the rod or replace it with a new style rod. Need to see if they found something wrong with the one that was part of that crank TZ was mentioning earlier or if they just didn't use it for one reason or another. If it doesn't have the openings, with the thrust washers (which it has to have, since they didn't tighten the large end), it'll never get oil mist to it and it'll blow pretty quickly.

Ive learned alot here about the 750 crank, and what not to do. thanks for everyones help, once again :up:
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JSJamboree
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Re: GT750 Crank Rebuild (bill bune, miss matched rods), issu

Post by JSJamboree »

Just talked to Josh from Bill Bune, he knew what I was talking about and the potential issues with the oiling. He was surprised it made it out like that. They are going to take it back (reimburse shipping) and look at it and the other rods that they had again.

Thanks to everyone who helped me know what I was talking about :lol:
Last edited by JSJamboree on Mon Apr 06, 2015 12:15 pm, edited 1 time in total.
pearljam724
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Re: GT750 Crank Rebuild (bill bune, miss matched rods), issu

Post by pearljam724 »

That's good business. A lot of businesses today lack integrity. Even, when it's their fault. Happy, to hear.
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GT750Battleship
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Re: GT750 Crank Rebuild (bill bune, miss matched rods), issu

Post by GT750Battleship »

:up: Hi,great result,as stated,"how did it get out off the shop" :!:
Cheers,
Roger
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rngdng
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Re: GT750 Crank Rebuild (bill bune, miss matched rods), issu

Post by rngdng »

Bill Bune has always done me right. They are a class shop.



Lane
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Too many bikes, too much time, ENOUGH SPACE, FINALLY! Never enough money.........
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JSJamboree
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Re: GT750 Crank Rebuild (bill bune, miss matched rods), issu

Post by JSJamboree »

Update:

Spoke with Josh again from BB. The 'old' style rod was the best out of the lot, but the extra 'new' style was in good condition as well. What he said was most of the cranks he builds are for drag bikes, generally the racers would rather have the old style if its at all better. Doesn't really make sense to me, as you are still losing out on proper oiling, and running 10k RPMs would really put a hurting to it. In any matter, they tore it back apart, verified that the 'new' style rod I had sent was in good condition, and put it back together on their dime.

BB team was very professional throughout the process. The only hassle was carrying around the 50lb box back to the shipping center.
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Suzukidave
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Re: GT750 Crank Rebuild (bill bune, miss matched rods), issu

Post by Suzukidave »

Despite the hassle of the shipping back i feel this was the best way to go :up:
the older i get the faster i was
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tz375
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Re: GT750 Crank Rebuild (bill bune, miss matched rods), issu

Post by tz375 »

That's all good news.

Interesting that some racers prefer early style rods. It makes me think that they are stronger than the later style slotted rod. Either way the big end is fine. It's only the small end that could be lacking lubrication. There is a huge difference between running a bike for ten seconds and running it for hundreds of miles at a time.
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JSJamboree
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Re: GT750 Crank Rebuild (bill bune, miss matched rods), issu

Post by JSJamboree »

tz375 wrote:That's all good news.

Interesting that some racers prefer early style rods. It makes me think that they are stronger than the later style slotted rod. Either way the big end is fine. It's only the small end that could be lacking lubrication. There is a huge difference between running a bike for ten seconds and running it for hundreds of miles at a time.
It wasn't that they preferred the old style to the new, it was that they didn't care which style was used. They just wanted the absolute best. Josh said there wasn't anything wrong with the late style rod we had sent, just that the early style rod was best. Got it back yesterday, sat it in the lower case to ensure everything lined up, its all good to go. Now I just need to clean the lower case, and start motor assembly!

Next up, getting the cylinders honed and some new pistons... To go forged or standard...
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