Kettle Clinic

and just for comparisons sake, a picture of the crank with a full starter clutch fitted, and what's left of mine..........

While you had it all in bits, I thought you might have had some titanium crank webs turned up to drop the engine weight to only one small planet equivalent!

Why all the mods to the starter clutch? Did I miss a post?

I've rethinking my starter motor options as the dynstarter hasn't really got the torque......

I am waiting for my stainless exhaust cone sheets to come back from the laser cutters. Then I reckon I have about 3 days of swearing at the exhausts as they get welded!

There's a lot more you can remove if you are stuck at home looking for something to do.

Here's one we prepared earlier, as they used to say. The drive part has been reduced to the boss plus three fingers and the gear has been drilled within an inch of its life. I didn't have any Ti bolts at the time, but that would have been a useful upgrade.

If you have excess cash, you could fit a set of BDK Ti engine bolts and a set of their alloy cylinder head sleeve nuts. They are really tasty but lighten the wallet more than they lighten the bike.

There are also 2 different designs of points shaft and the one with smaller diameter flange weighs a little less. And you could eliminate that shaft completely and narrow the side cover by 4 inches with the right ignition...

But what are you doing for a starter? I went kick only and threw out the gear, idler gear and starter motor as well.

dumped the starter motor - a 2 stroke doesn't need one. The alternator will be occupying the space vacated by the starter motor.

The driven starter motor clutch gear is going to be permanently attached to the idler gear behind it so the idler gear is no longer free-spinning. That in turn will drive the pair of small intermediate starter gears (running on a needle roller bearing conversion) which will then drive the alternator via a starter motor end shaft gear. Sort of working in reverse to how the starter motor sequence works.
Ignition is on the right side of the bike, so the points are already discarded, as is the stator & rotor assembly, replaced by an alternator.
I do like the look of your 3-fingered mounting boss for the driven gear - may I pinch that idea from you?
What you can see of the boss in my pictures is all that I could remove on my small hobby lathe - I was going to get it turned down smaller anyway.
Just a point - how did you ensure that the 3 fingers were identical ? If one was bigger than the other 2 wouldn't it run (slightly) out of balance?

Alan H wrote:While you had it all in bits, I thought you might have had some titanium crank webs turned up to drop the engine weight to only one small planet equivalent!

the crank is only part of the weight problem Alan - the barrel is the other, but I am working on that ............

Copy away. I might even have a spare one here.

Barrels are really heavy and not all are the same (but they are all heavy). Big ports make a small difference, but the casting is ridiculous and not hard to carve down a little.
This set are L models. The outer sides are thinned a little down to the recess for the water cooled badges and a lot was removed below the water jacket. People often ask if they are genuine TR750 (XR11) barrels. The answer is no, but they do make more than 80HP with stock BS40 carbs and JEMCo pipes.

The L barrels were ported for more torque not top end originally as I understand, even though the site link below says they are the same as J & K.
On the OJB site - https://www.oldjapanesebikes.com/GT750_ ... de/page-81 - is a bit about it that I'm sure you're already aware of, but just in case......

I can get a 550 engine in and out of the frame fairly easily if the top end is off, but I wouldn't like to try with a Hippo engine no matter which bits were unattached.

Good point that porting did change. That reference has to be right. I supplied those pictures and most of the details......

Porting changed to raise the exhaust port by 2.5mm and dropped the floor of the intakes rather too far. I have barrels from every year and they vary a bit from one to another but the big change was with the M model. JKL are all the same porting and MAB are all the same +/- manufacturing tolerances.

Interesting. I understood that many changes were made with the A model (A/B being same). I must do more reading of 750 year on year changes - it'll help me sleep if nothing else. At least they didn't have SCEM plated barrels in 'some' markets like the 550......