Engine mods and other upgrades for a 92 GSXR 750?

[Upshotknothole]

So I've got a US 92 GSXR 750 in the best and fastest paint scheme Suzuki ever made. I need to swap the emulsion tubes and give it a tune up, but I want to make it a little bit more exciting again. Basically I want it to be more like the short stroke 88 750 I had in my youth with RS36s that was all top end power.

It's currently snowing where I live, I'm bored and there are a few things I've been wondering about doing for a while now to this bike. First off, I want to keep it 750 based, I've already got a 7/11 and an 11/12. I want to keep one bike that revs fast and has a peaky top end.

955 big bore kits. I know there are a few people on here that have done them. Do they still keep a similar power band? Do they suffer from using stock cams? I've given up on ever finding hotter cams for this engine.

Carbs, eventually it'll get flat slides, but I've been holding off for now in case I do bore it out to 955. I've got a spare set of RS38s in my garage, but I don't want to completely kill the bottom end. So I'll stick with the stock 38 CVs until I figure out what I'm doing with it.

Crank, recently saw a lightened and balanced crank on APE's web site which got me thinking more about the big bore kit. Guessing lightening the crank will help with keeping the engine peaky with the larger pistons.

Head, should probably at least have a port and polish. Oversized valves as well or can I try and keep the costs down slightly?

Suspension wise I need to swap the front end, probably for a 750W. I've also got straight spoke W wheels and a braced swing arm waiting to go on it. Just need to get the wheels powder coated to match the paint.

Fairings have been the biggest pain in an ass. Who knew that a single year, single country model paint scheme would be so hard to find. The black plastics aren't that hard to find, but the sticker kit just doesn't exist anywhere. Thinking about getting a full set of aftermarket from Fiberman in Ireland. I've already got Airtech fairings on another bike and I'd like something a little nicer. Then get them painted in a similar pattern to stock, still heavy on the 90s vibe.

That stupid hunk of glass over the headlights. The M/N 750s were fat pigs, and the headlight glass definitely contributes to it. I've heard if you sit it on the oven door and let the glass get really hot for awhile, it'll soften up the glue enough to pry it off. I've got a 750W headlight with a bunch of broken tabs that I don't mind sacrificing as a first attempt. Has anyone done this? Any pointers? Then I figure some clear acrylic cut to shape over the headlight opening in the fairings will be good enough.

I probably won't get to this thing until next winter, have 3 other bikes in pieces taking up all the spare room in my garage currently that I need to deal with. And when it comes time to do the engine work, I've got a spare 1127 that I'll throw into it with the stock CV 38s just to see how it feels as a 7/11. Thanks for reading all of my ramblings. Before it really gets nice here again I do plan on doing a tune up, replacing the emulsion tubes as they've been shot for the past couple of years and doing the valves. Hoping that will pep it back up a little.

[Joseph]

Yeah i did the oven door deal

You can just buy a headlight protector cover fixed on with little tabs 

https://www.slipscreens.co.uk/product/suzuki-gsxr750-wn-wp-gsxr1100-wn-wr-headlight-protector/

Edited March 3 by Joseph

[Upshotknothole]

3 minutes ago, Joseph said:

Yeah i did the oven door deal

You can just buy a headlight protector cover fixed on with little tabs 

https://www.slipscreens.co.uk/product/suzuki-gsxr750-wn-wp-gsxr1100-wn-wr-headlight-protector/

Thanks. Any suggestions for getting the glass off? Like I said, I've got a donor W unit that I don't mind sacrificing before trying anything on my good one. Do you think propping it up in front of a propane heater in the garage would work? I'd imagine a heat gun won't be able to get enough heat into all of it to get it off. Do you have any photos of yours after you did it?

I'll go ahead and order up one of those covers before I start.

[Joseph]

Spatulas for plasterwork are a good tool for the job (a couple of narrow 1-½ inch wide blades) it's a difficult job to do even once heated up, that glue wasn't designed to leave its place

Propane heater should be good. A heat gun won't allow heating of the whole thing, and you really want to get it all up to temp evenly all round (the heat gun is also too hot for the needs of the job)

I put the oven on at 210-220°C to do mine

Just noticed you have the american 92 bike, the link i posted is for the WC '92

Edited March 3 by Joseph

[Upshotknothole]

15 minutes ago, Joseph said:

Spatulas for plasterwork are a good tool for the job (a couple of narrow 1-½ inch wide blades) it's a difficult job to do even once heated up, that glue wasn't designed to leave its place

Propane heater should be good. A heat gun won't allow heating of the whole thing, and you really want to get it all up to temp evenly all round (the heat gun is also too hot for the needs of the job)

I put the oven on at 210-220°C to do mine

Just noticed you have the american 92 bike, the link i posted is for the WC '92

They're similar enough that the job will be the same and I found the 91 M headlight cover on that site. Thanks for all the tips, was it pretty easy to change out that glass lens for the LEDs once the main glass is off? I wouldn't mind swapping in something a bit more modern. I'll post up when I start attempting to do it.

[Joseph]

To fit those hi power led strips I designed a plate that was laser cut, tabs welded, then fit to the headlamp bowl, both were powedercoated black and then reassembled the whole package

[Upshotknothole]

10 minutes ago, Joseph said:

To fit those hi power led strips I designed a plate that was laser cut, tabs welded, then fit to the headlamp bowl, both were powedercoated black and then reassembled the whole package

Cool, I'll look and see what I can figure out with my W unit. I'm guessing the weight savings in the headlight was noticeable with it off the bike once the glass was removed.

[BillyR]

id be tempted to use some R6 wheels, so light theres a noticeable improvement in chuck-a-bility. 

[Upshotknothole]

2 hours ago, BillyR said:

id be tempted to use some R6 wheels, so light theres a noticeable improvement in chuck-a-bility. 

I want to keep it semi period correct looking and the W wheels make it easy to keep using the stock speedo drive. My 7/11 has all K series 1K wheels and suspension and benefits greatly, but this one I don't really want to use anything newer than W parts. This is my one and only roughly period correct bike.

[Joseph]

8 hours ago, Upshotknothole said:

I'm guessing the weight savings in the headlight was noticeable with it off the bike once the glass was removed.

I think it weighs something like 8 kilos ? The glass is around 8 or 9 mm thick it's very heavy indeed

9 hours ago, Upshotknothole said:

They're similar enough that the job will be the same and I found the 91 M headlight cover on that site

Best to use the right one though, it'll just slip into the fairing hole and can rest against the plastic headlamp frame too, then you can make a period style fixing of it onto the fairing

[Upshotknothole]

12 hours ago, Joseph said:

That looks pretty good and I can totally live with that in exchange for dumping all that weight off the nose.

[clivegto]

Turbo is the best upgrade any Suzuki can have 

[Upshotknothole]

Just now, clivegto said:

Turbo is the best upgrade any Suzuki can have 

I already have a build that will eventually get the turbo treatment. This one I want to see how far I can push an NA 750.

[clivegto]

11 minutes ago, Upshotknothole said:

I already have a build that will eventually get the turbo treatment. This one I want to see how far I can push an NA 750.

Fair enough, there is a gsxr750 turbo that does very well at the salt flats. 

[george 1100]

31 minutes ago, Upshotknothole said:

I already have a build that will eventually get the turbo treatment. This one I want to see how far I can push an NA 750.

955cc, lightened crank, Carillo rods, big valve head, Yoshi st2 cams, fcr39's , decent exhaust system , two oil coolers 

[Upshotknothole]

2 minutes ago, george 1100 said:

955cc, lightened crank, Carillo rods, big valve head, Yoshi st2 cams, fcr39's , decent exhaust system , two oil coolers 

So those Yosh cams are a problem as it's a shim head, and it doesn't look like Carillo does oil cooled 750 rods anymore. Also the parts site here in the states that I've used a lot is listing the same part number for all GSXR 750 rods from 88-95, which doesn't seem right. I'd have thought all the 749cc engines would have the same rods unless the Slabbies had different cranks. If Slabby and long stroke slingshots use the same rods, I might have found a set for sale.

The big bore, lightened crank, carbs, exhaust, and oil coolers are the easy part. Even stock I'm leaning towards adding a second oil cooler to it.

[george 1100]

Maybe use a dot head with 30/26 oversized valves and use the st2 cams or get your cams reprofiled. $$$

[BillyR]

Do the 750's respond well to a decent porting job? 

[george 1100]

23 minutes ago, BillyR said:

Do the 750's respond well to a decent porting job? 

There's a lot to be gained with oil cooled heads. The factory castings and valve seat/pockets are mediocre 

[Upshotknothole]

8 hours ago, george 1100 said:

Maybe use a dot head with 30/26 oversized valves and use the st2 cams or get your cams reprofiled. $$$

I think for now I'll try and focus on the bottom end and getting the head ported and polished. I can always look into a head swap later on. I really picked the worst year of all the oil cooled GSXRs to try and restore.

Do Slabby 750 rods work in 749 slingshot engines? I found one set of NOS Carillo rods for an 87. 37mm bottom, 18mm top, 110mm length C to C. It seems like they do, just want to confirm.

[Upshotknothole]

On 3/3/2024 at 1:57 PM, Joseph said:

Spatulas for plasterwork are a good tool for the job (a couple of narrow 1-½ inch wide blades) it's a difficult job to do even once heated up, that glue wasn't designed to leave its place

Propane heater should be good. A heat gun won't allow heating of the whole thing, and you really want to get it all up to temp evenly all round (the heat gun is also too hot for the needs of the job)

I put the oven on at 210-220°C to do mine

Just noticed you have the american 92 bike, the link i posted is for the WC '92

How hard was it to get the inner glass off the headlight housing? The reason I ask is I was reading up on doing a projector swap on my truck headlights and it got me thinking about doing these as well. The glass has to be removed and they fit into the headlight from the front and have a plate that fits into the stock bulb holder. Just wondering if it would be possible to retrofit them onto the bike. It's supposed to be nice out this weekend so I might try and start pulling my busted up headlight apart to see if this is doable or not.

Ignore the fact that this is a truck headlight and not a GSXR headlight.

[Joseph]

It required quite an effort, the glue must be something like windshield glue, its very sticky and will stay on your skin, then the whole thing is hot so not great to hold tight.

Then the trick is to lever it out without deforming the plastic frame which of course is warmed up and malleable.

To be fair, when i did it, it was to put in that custom light and re fit the glass.

In your case i'd heat it up to soften the glue enough, then put it in a bag, smash the glass with a heavy hammer and then you can easily take out the parts from the frame without putting too much pressure on the plastic 

[Upshotknothole]

5 hours ago, Joseph said:

It required quite an effort, the glue must be something like windshield glue, its very sticky and will stay on your skin, then the whole thing is hot so not great to hold tight.

Then the trick is to lever it out without deforming the plastic frame which of course is warmed up and malleable.

To be fair, when i did it, it was to put in that custom light and re fit the glass.

In your case i'd heat it up to soften the glue enough, then put it in a bag, smash the glass with a heavy hammer and then you can easily take out the parts from the frame without putting too much pressure on the plastic 

Breaking the glass does seem like it would speed things up a bit. I'll play around with it and see what I can figure out. Thanks