1974 GT750 Rebuild

[burgs]

Hi
Need a new water pump drive gear 17522-31031, old one has several cracks in the hub, not in the gear web, a hour of searching on the internet only found out of stock .
As an interim fix I will turn up a sleeve out of 6061 and interference fit over the cracked hub to hold it together.
Not sure a new gear would be worth it if it would only crack again, may look at making some up out of a better material, the chap I have make up gears for me might like to play with something like this , I usually machine the blanks and he cuts the gear teeth
This was a late discovery as when I removed the gear I thought it looked OK as I only looked at the front, no evidence of cracking, today I had a better look and yuk, on this one it was cracked in a different places, not a game changer but one I need to attend to before too many miles.

Burgs

[PaulD738]

I'm sure someone on here, maybe Astrax makes a steel replacement gear? No doubt someone will be along to say yay or nay

[Kettletimes3]

I have seen these for sale in aluminium on eBay some time ago.

[burgs]

I'm sure someone on here, maybe Astrax makes a steel replacement gear? No doubt someone will be along to say yay or nay

Hi
I don't think steel would be a good idea, Suzuki would have selected a plastic for several reasons, noise, less need for accuracy, better shock absorbing, cheaper to manufacture etc.
Steel on steel would need high accuracy for alignment and noise reduction for one, aluminum maybe but initial run in may produce some unwanted wear partials floating around.
Some of the materials available today would in my opinion be far better than the original materials of 1970's.

But I am always open to someone who has runs on the ladder

Burgs

[burgs]

I have seen these for sale in aluminium on eBay some time ago.

Hi
As per Paul's comments, I must say I feel a bit uneasy with steel or aluminium, there are some very good materials out their now, that would be far superior to the original Suzuki gear, strength wise, and wear wise, they are easier to machine and have very good mechanical properties compared to steel.
looking at the two gears I have here, there appears to be very little visual wear on the teeth, it appears that the web and hub are maybe too brittle, lack strength, maybe aging??

But as I said before if someone can put up a good engineering reply I will be willing to listen, never too old to learn

Burgs

[burgs]

Hi Again
Complete clutch assembly (A/B), arrived from USA today, compared to my clutch it looks pristine, little bit of what appears to be surface rust on the steel plates, but it wipes off with my finger so hopefully all good, roller bearing and race looks to be in good condition, all zinc plated parts show no signs of rust

Now got to sort out a new set of crankcase bolts, will take a bucket load to the local Nuts and Bolts place and see how close they can get, my gut tells me the original bolts were not all that good, never broke one going in but undoing them, they seem to break too easily, mind you this is only my second GT750 rebuild

Regards
Burgs

[teazer]

When you get the plated, ask the plating shop to bake them. During plating, hydrogen permeates the steel and makes it brittle. Heat treat (baking) at somewhere around 450F for a couple of hours bakes out the hydrogen.

On the water pump gear, the original material is molded around the steel hub and over time it shrinks (ask Alan to explain that).... and it cracks but rarely do they break. I haven't checked in a while but Suzuki used to sell that gear at least up until at least year so ask your local dealer first.

If Astrax has a metal replacement, go ahead and buy it. Chris Livengood (CLTech) in the US supplies aluminum assemblies but you have to send the center or a complete cracked gear so he can harvest the center.

For decades we used to fit aluminum timing gears to Triumph twins and they lasted longer than the rest of the bike, so that's not an issue.

[burgs]

Hi Teaser
I am hoping to get Hi-tensile plated bolts, never bothered to ask in the past if they were heat treated or not, I assumed they would have been seeing they are Hi-tensile?
I have some other bolts I am going to plate myself, these I will have to heat treat, I have a gas oven that I made up for pre and post heating alloy steels etc when welding that I could use, will have to drag the old engineering books out to refresh my knowledge, studied all this when doing my mechanical engineers certificate and diploma, but never really had any use for it.

Been there with the aluminum Triumph gears didn't make them go any faster but sounded good when you said you had them, aluminum with good lube system makes good bearing material, little end in my Manx was originally aluminum.

Nuts and Bolt man asked if I was kidding when I dropped the box of bolts off, but said he will go through them tomorrow, they usually have a good supply on hand and I have bought heaps of bolts off them when I had the engineering business going.

Burgs

[Peterg]

It is the onLy model to have

[burgs]

It is the onLy model to have

Looks very nice, hope mine comes up as good, notice you still have the original front brake hoses, or were you able to get a new set, or did you get the old rebuilt?

Removed the corroded cylinder studs through the week, was that a challenge broke my stud remover had to use Stillson,s to get them out, threads all ok.

Today have to paint the top case, and bake, need to do a weld repair on the thermostat housing on the head, side was broken out of the bolt hole.
Once I get that done I will re-machine the top face and drill and tap and fit 6mm Recoil thread inserts into the three bolt holes.
One of the four bottom bolt holes is stripped in the case where the coolant inlet manifold bolts on, and a 5/16" UNC bolt has been fitted at some stage, YUK, not sure what I can do here, not too keen on welding in this area, might have to leave it go.
Found one of the M8 bolts from crankcase has been broken but I cannot find the broken bit?
Hopefully I can start rebuilding the engine next week.

Burgs