GT750B Refresh

This year will be my third summer with "Alf".
Alf is my GT750B (so called because of the first three letters of the registration) and uniquely for me I bought him already restored and other than changing the tyres (as the originals were good but 19 years old and rock hard) all I've done is put fuel and two stoke in and enjoyed the experience.

Alf was one of the last GT750's registered in the UK in June of 1978. The first owner went to his local dealer only to be told that all the GT's were gone and he would have to have a GS750 (launched in 1976 remember and sold in parallel with the run out stock of GT750A's & B's). Not one to be easily put off, he went home an phoned Heron Suzuki (no searching on the internet then) who found him an unsold bike in a dealer in west London.

This B was one of a batch of (I think eight) that were ordered by the Suzuki's Swiss importer, who subsequently backed out of the order due to the success of the GS750 there. As was their policy at the time, Heron Suzuki would happily mop up any unsold stock that Suzuki might have presumably for a substantial discount. So the bikes came directly to the UK and had their speedo's changed from kph to mph. Otherwise, they retained the Swiss spec, which differed from the general export spec by having a long rear mudguard with mud flap, the dog bone rear light of the earlier models, smaller GS400 style indicators but still without the side reflectors of the earlier bikes and an additional spring on the side stand to make it (unsuccessfully) self retracting. Alf also has a factory friction steering damper but I think that was an extra rather than part of the Swiss spec.

The first owner used him for about 3000miles, then parked him in his back garden without even a cover for protection. The story goes that his dog would go out every morning and take a leak against Alf. This carried on for years until one leg of the centre stand rotted through, Alf fell over. At that point the owner decided to sell him in the sorry state that he then was. He was bought by a guy in Kent who got him running and used him for a while in the horrible rusty condition, before selling him to a mate who intended to restore him. This never happened so he was eventually sold back to the second owner, who did restore him about 20 years ago. He was then sold to a guy in West London who didn't have him for long, until I managed to snag him before he got listed on eBay.

I never had a GT750 back in the day. I can remember the B model when they were new, but I was 14 at the time and remember earnestly debating the relative merits of the GT750 and GS750 with my equally bike mad mate whilst pressing our noses against the local Suzuki dealers showroom window.


So whilst I've generally enjoyed the ownership experience, there were a few area's that niggled me. One was that the chain a sprockets were well past their best, but worse still is the horrendous surging (bucking) that the kettle is renowned for. The surging makes town and group riding absolute hell and the tight spot on the chain does nothing to help the situation.
As he is ridden not hidden, there are a few area's that were starting to show the passing of time by looking a bit tatty.

This is Alf on a chippy run to Leyburn where he drew quite a crowd (although it still seems like 1978 in Leyburn so they probably thought he was new)
IMG_1244 by Mitch Plackett-Smith, on Flickr" />

So, time to break the habit of a life time and get cracking with these jobs before spring actually arrives!

Stage one

IMG_1735 by Mitch Plackett-Smith, on Flickr" />

Wolfie wrote:

That's a great story, I can't believe that people just abandon good stuff without the least bit of protection and simply watch it rot away?

Looking good again now though.

I agree Graham, having gone to all the trouble of getting it, to then not use it much and just leave it seems most odd.


One of the cosmetic jobs is the side panel where the satin piant is falling off.

IMG_1737 by Mitch Plackett-Smith, on Flickr" />

Wolfie wrote:

Falling off??

That looks more like its been rubbed off by flapping trousers.. You could try shorts this Summer..

It'll need to warm up a bit first

Stage two - carbs off for a good dose of looking at


[img]IMG_1736 by Mitch Plackett-Smith, on Flickr[/img]

Alf looks great, I like the finish on the motor... looks just like it should, not too glitzy and over-restored.

Rob62 wrote:

Alf looks great, I like the finish on the motor... looks just like it should, not too glitzy and over-restored.

Thanks Rob. I agree, they weren't very blingy back in the day, so they shouldn't be now.

So, the carbs are off and don't look too bad on the face of it.

[img]IMG_1760 by Mitch Plackett-Smith, on Flickr[/img]

The plan is:-
Strip and replace all seals & wearing parts.
Ultrasonic clean the bodies
Fit 0.5mm air correction jets in the pilot circuit. There was a Suzuki mod back in the day that involved 0.9 or 0.8mm jets instead of the 1mm ones fitted by the factory, but it is thought that 0.5 is more effective at reducing the surging by restricting the air getting in on a closed throttle.
Change the pilot jets to correct the richness off idle as a result of the smaller air jets. Nothing to do with the surging, but a fix to fix the issue caused by the other fix.

More of an issue is this
[img]IMG_1748 by Mitch Plackett-Smith, on Flickr[/img]

There should be a foam seal between the airbox body and the cage that supports the air filter element which appears to be AWOL.

[img]IMG_1747 by Mitch Plackett-Smith, on Flickr[/img]

The foam seals on the covers have seen better days

[img]IMG_1749 by Mitch Plackett-Smith, on Flickr[/img]

And the filter itself is past it's best and starting to crumble away.

The airbox seals are high on the list of causes of the surging, so this wont be helping!

So another issue not helping the general riding situation and the surging is the gearing.
The B had different gearing to the L M A Kettles at 14t front 40 rear.

Mine has the 40t rear, but a 15t front making the gearing a good lump higher than standard or even the 15/43 that the earlier bikes ran.

It seems the 14t gives the chain a really hard life due to the small circumference so it wasn't unusual to find a 15t, but I'm going to change to a 43 rear as well, with the longer chain that this requires.


Looks like postman Pat has been busy delivering parts while I've been away
[img]IMG_1750 by Mitch Plackett-Smith, on Flickr[/img]

Keep at it. Spring seems close today with the nice weather....

Wolfie wrote:

Yeh, it was lovely out.. hope it's the same again tomorrow, will be visiting the Venue for next weeks shenanigans with Mr Swiv...

I've cured the surging on the H2 with 34mm Cabs only to run into other issues with these now  

Are 34s an option for the Kettles?

There is a guy on the Kettle Clinic experimenting with the slide carbs from the J/K model on a B. I think they are 32's and it is said that the early ones don't surge. The results seem inconclusive at the moment.

why do bikes most 2 stroke bikes surge/(kangaroo) nowadays?
mine and tlc's both do
synchronised kangarooing at 40-60mph on part throttle

On kettles the main reasons are
Air leaks
Tick over too high
Pilot jet blocked
Pilot screw set up wrong (although they work differently to Yamahas)
Carb sync
Un-even cylinder compression
Might not help at all I guess

both mine and terry's have reed valves yet kangaroo like mad!!!

wolfie I thought your h2 was blue?

The red triple looks awesome!
Have you thought of fitting boost bottles or balance pipes to the inlets.....it works on the bigger yams i believe...and they have reeds fitted as standard. All modern strokers (90’s race rep types) have a boost bottle of some description..

ive had a balance pipe fitted for years, ive got reed spacers too

This
[img]IMG_1780 by Mitch Plackett-Smith, on Flickr[/img]

To this

[img]IMG_1781 by Mitch Plackett-Smith, on Flickr[/img]

In an evening

haha... nice work, cant beat the smell of petrol in the house

Before the reeds.... if you have a spare set of inlet rubbers you could knock some up and give it a try..... just a balance pipe joining all three inlets may work, doesn’t necessarily have to be connected to a larger bottle. Surely one of the triples guys will have already tried it?