Some GT750 crank rebuilding pictures

Suzukidave · Post by **Suzukidave** » Wed Jul 22, 2009 6:32 am

http://gt750.medial.com/crank/Hans/

Post by **Suzsmokeyallan** » Wed Jul 22, 2009 7:00 am

Nice support block base hes made there for the journals Dave, thats given me some ideas for making one. This way i can use my smaller 5 ton press for the job at hand when it eventually comes around.

Suzukidave · Post by **Suzukidave** » Wed Jul 22, 2009 7:10 am

I dont know Allan , i read that its a job for a 20 ton

Post by **Suzsmokeyallan** » Wed Jul 22, 2009 7:26 am

No Dave, you would never need 20 tons as you're only pushing a pin of around one inch diameter for each section of each journal. Besides the presses i have are from the late 60s 'old school' design and that figure is very reserved.
Compared to a new hydraulic jack at rated 5 tons my 5 ton press ramp is a 45mm diameter, much much like those of a 25 ton equivalent of today.
Usually to move a crank pin of the GTs size takes no more than 150-200 kgs/cm2 on the head to initially shift it from its pressed set position, after its moved it glides on the interference fit at an average of much less than that figure.

rbond · Post by **rbond** » Wed Jul 22, 2009 8:04 am

I take it Suzsmokeyallen, (long name) that you have rebuilt a few cranks in your day? Are you going to offer that as a service like Johnakay does with racks? If so, you have one customer here (later this year) for a GT500 rebuild. Already have the seals, o-rings, GT750 big end bearings and thrust washers.

tz375 · Post by **tz375** » Wed Jul 22, 2009 8:08 am

Allan, Dave's right. In my experience, it takes a good 20 ton press to split a crank and a very stiff table and jig.

Assembly takes whole lot less force, but it is surprising how much force is typically required to crack one loose.

I have split a few cranks in my time and I send all my Suzuki cranks to Bill Bune in MN and all my TZ cranks to Accu-Products in Ohio.

Post by **Suzsmokeyallan** » Wed Jul 22, 2009 2:17 pm

I've rebuilt about 80 or so single cylinder cranks in my lifetime so far and never needed a monster press to shift the crank pins. Its getting the pin to crank wheel initially shifted, thats the main issue, after that its pretty easy to keep it moving.
This press i'm talking about is a neat little affair that stands nearly five feet tall and uses an adjustable vertically moving plate rig to accomodate short to long items under the ram.
It has shifted many crank pins before so im not too worried its performance, if i need more effort i can use the much larger press i have.
The problem with the Buffalo crank is that its quite heavy for one person to hold and constantly manipulate its weight under the press for extended periods of time.
It will be very costly to send any crank to me given my location in the Caribbean, thats why i'll be forced to do my own crank rebuilds since theres no one i know of doing twin or triple cylinder cranks around here.
Ive got the Titan crank in line for seal replacement first so thats the one that will get the press work on it soon.

Post by **oldjapanesebikes** » Wed Jul 22, 2009 11:22 pm

First of all I have never done a crank myself so you are free to ignore what I say - but talking to the fellow in town that does do them the point he made was that you need a big capacity press for the initial disassembly. His point was that to avoid galling on the pins (and consequent issues on reassembly), you need something that can do the press in one motion.

He could be talking through his hat, but he does very nice work and has been doing crankshafts here in Calgary for a very long time - and he will be doing my next rebuild

tz375 · Post by **tz375** » Wed Jul 22, 2009 11:29 pm

Allan,

I hear you on that shipping cost. could be expensive. You are 100% correct that it takes a whole lot less to keep teh parts moving once they are cracked. I always found that twin cranks take a huge amount of force to start them moving and significantly less once they were moving.

It's far more than the difference between sliding and limiting friction. It's as if they almost weld themselves together over time.

I don't understand the comment about holding the crank. yes it is very heavy but it is never held. It does have to be caught though as it slides apart.

My crank jigs were always over engineered so the held everything nicely in place , but I had access to a good machine shop back then and a good machinist to do the machining

Please post pics and commentary on that 500 crank when you do it.

rngdng · Post by **rngdng** » Thu Jul 23, 2009 6:24 am

I don't remember who did it, but one of our members used threaded rods, and angle iron to split/rebuild a T500 crank.

Lane

Post by **Suzsmokeyallan** » Thu Jul 23, 2009 6:32 am

Richard by using the words "holding the crank" i mean you have to place it in the respective jig, press a part off, remove it change the cranks position and so on till its fully apart. This means you are constantly changing the cranks position and shifting it so you're getting the press points correct for disassembly and reassembly etc.
All this moving, lifting and repositioning on such a heavy item as the Buffalo crank does tend to get your wrists and arms a bit tired since you're constantly reaching into and across the press to lift the crank.

tz375 · Post by **tz375** » Thu Jul 23, 2009 4:00 pm

Think of it as the strength training part of your workout.

Suzukidave · Post by **Suzukidave** » Thu Jul 23, 2009 4:03 pm

rngdng wrote:I don't remember who did it, but one of our members used threaded rods, and angle iron to split/rebuild a T500 crank.
Lane

http://www.ozebook.com/compendium/t500_files/crank.htm

tz375 · Post by **tz375** » Thu Jul 23, 2009 6:53 pm

That's amazing. Dave, how do you keep all those references clear in your head?

Suzukidave · Post by **Suzukidave** » Thu Jul 23, 2009 6:53 pm

20 ton press at Harbor Freight on sale now for $199.00 http://www.harborfreight.com/cpi/ctaf/d ... mber=32879