GSXR 750 Slabside Race Build

[maxwin]

As promised here is my new build thread, I will be updating the other one with my dad's antics as the year progresses.

Usually these threads start with a picture of a ropey bike that is to undergo a great transformation, I however don't have a bike, just a garage full of parts.

Thanks to @dupersuncfor the frame and tank, and a useful box of bits

The rest of the bits came from fleabay and a doner SRAD.

 

I started the build a few weeks ago when I could spare the time, first up was to rebuild one of the motors I had purchased for a mere £250.  Only catch was 4 broken exhaust studs, these proved to be a real PITA.  I managed to Tig 3 of them out but the 4th needed some extra attention...

With the motor stripped down I was pleasantly surprised with the condition, all tolerances were well within limits and the general wear was very little

This time around I've decided to go a little deeper on the rebuild and balance the pistons and con rod, and like usual by the time i realised it was a bigger job than I had imagined I was already too deep!

Piston assemblies 2 and 3 were 3 grams each heavier than 1 and 4, that's 6 grams out of balance which at 11,000rpm would definitely be noticeable.

Con rod weighing jig took a good day to construct, started out with a simple setup but just couldn't get repeatability, the above works very well

Removed the excess weight from the seam that runs around the rod with a sander.

Decided to take the excess piston weight from the area that has been machined at the factory behind the skirts, that swarf is from the con rod jig not the piston

Pistons all balanced up to within 0.1g.

Also had my dad do his lapping duties on the valves .  The valve guides look golden so may be APE bronze ones which would be a bonus!

I'm pretty much ready to start putting it back together now, just need more hours in the day!

I managed to get a few extra jobs in while looking after my 18 month old boy, Mrs aint happy lol

Frame Bracing

I had originally decided to brace the frame but have scraped that idea for now as one of the clubs I'm running with don't allow it on ally framed machines, however I did put in a bit of time designing an efficient bracing profile which I'll leave here.

The 2 cross braces would need to be designed to account for the fuel tank and the exhausts, the front engine mounts need beefing up and the rubber mounts would be need replacing with tight fitting polyurethane.  The large plate attaches the head intakes to the top of the frame which makes a huge difference to the rigidity.

Over all this is just over 4 times more rigid than stock, the Yoshimura style bracing is only about 1.6 times over standard.

Obviously its 3D model and some big assumptions have been made so take it with a big pinch salt  

Below is the standard frame, deformation is exaggerated.  You can see that the weak link is the front frame loops

More to come!

[R1guy]

[KATANAMANGLER]

We missed you...

[dupersunc]

Awesome stuff Ben.

Really like the analysis on the frame. 

The twisting of the lower front rails is paricularly interesting .  Explains the issues I've been having.

 

[Gammaboy]

8 hours ago, maxwin said:

The 2 cross braces would need to be designed to account for the fuel tank and the exhausts, the front engine mounts need beefing up and the rubber mounts would be need replacing with tight fitting polyurethane.  The large plate attaches the head intakes to the top of the frame which makes a huge difference to the rigidity.

Over all this is just over 4 times more rigid than stock, the Yoshimura style bracing is only about 1.6 times over standard.

Obviously its 3D model and some big assumptions have been made so take it with a big pinch salt  

Below is the standard frame, deformation is exaggerated.  You can see that the weak link is the front frame loops

 

A more practical way of achieving that front cross brace while still fitting the exhaust may be to run a V brace from the top of the front legs to the centre of the crossmember, and then another down from the centre of the crossmember to the corners of the lower rails. All depends on where the exhaust wants to be I guess.

 

Edited January 9, 2018 by Gammaboy

[MeanBean49]

Could you not make some plates that fasten to the cam caps on the motor. Make it a stressed member. Easier than all the cross bracing

[MeanBean49]

Also swap the front rubber mounts for solid material.

Or the other thing i was thinking of, putting the bracing internal, ie, frrom the lower left spar up and backwards onto the upper right spar and the opposite for the lower right spar.

And then one cross member between the to spars to stop them seperating.

Would potentially save loosing space where exhausts and oil coolers need to be

[dupersunc]

3 hours ago, MeanBean49 said:

Could you not make some plates that fasten to the cam caps on the motor. Make it a stressed member. Easier than all the cross bracing

I shall be trying this on my Slingshot build. I agree on the solid front mounts

Anything plastic will melt. 

@maxwinhave you got any FEA.  Screen grabs with the bracing added. It would be interesting to see how the stresses are distributed too once the bracing is added.

[nlovien]

+1 - these pics are handy for any bike build 

[maxwin]

Update!

As I'm not bracing this bike and there is a bit of interest in the frame bracing I will start a new thread in the oil cooled section.

Pistons loaded in and crank on.

Crank halves back together and torqued up.

Head is ready to go back together, nice new Viton stem seals fitted

One carb was dull after the ultrasonic bath, probably could have done with a soda blasting I'm guessing.  No time at the moment though to mess about, must push on!

Damned accelerator pump rubber boot degraded, had to buy two from Suzuki... 25 quid!! delivered that is

I removed the carb fronts to clean them and while i was at it decided to try and eliminate a bit of the slide play.  I installed some Teflon tape to the main body surface (pictured), it has removed most of the play and has a silky smooth operation.  I will keep a close eye on it as I test the bike just to make sure it stays in place.

More to come.

[CockneyRick]

On 1/9/2018 at 7:18 AM, MeanBean49 said:

Could you not make some plates that fasten to the cam caps on the motor. Make it a stressed member. Easier than all the cross bracing

Although i'm trying to picture this in my mind, from previous experience the cam caps are a weak point in engines i've messed with.

M7 thread & poorly tapped into the cam caps which i always thought were made of wensleydale!

I usually ended up tapping & helicoiling em cos they were so poor!

[dupersunc]

25 minutes ago, CockneyRick said:

Although i'm trying to picture this in my mind, from previous experience the cam caps are a weak point in engines i've messed with.

M7 thread & poorly tapped into the cam caps which i always thought were made of wensleydale!

I usually ended up tapping & helicoiling em cos they were so poor!

I think he meant the caps in the side if the head where the rocker shafts go.

[CockneyRick]

Cam plugs! That makes more sense.

Although like the sliders you can get to protect lump always seemed a bit iffy, could end up wrecking head for sake of some other cheaper bits?

[maxwin]

It wouldn't be a mod I would do for the road, but for a race bike its probably worth the risk for a bit more rigidity.

[CockneyRick]

Really? So you would risk the head if you chucked it down the track?

 

Although this is NOT my area of expertise, just a thought  

Edited January 16, 2018 by CockneyRick

[maxwin]

I would be more worried about stress cracks, but I assume there is a fair amount of redundancy built into these old bikes.

[CockneyRick]

Fair enough, going on the above posts, you know what you are doing  

[MeanBean49]

Sorry for my poor wording, i was on about the cam plugs. I was thinking you could use the gsxr hex head plugs and drill/tap m8 threads into the plugs and use both to secure a thick plate that bolts securely to the frame. The LHS could be welded on. Just an idea, somthing im going to have a go at when i get round to chucking a slingshot track bike together

I think done right using both plugs it would add rigidity to the headstock and also provide better protection to the engine/head in the event of a crash. You could even have a nylon block on the plates as a crash bung.

A lot of modern sportsbikes are made this way so no reason it wouldnt help

[dupersunc]

2 minutes ago, MeanBean49 said:

Sorry for my poor wording, i was on about the cam plugs. I was thinking you could use the gsxr hex head plugs and drill/tap m8 threads into the plugs and use both to secure a thick plate that bolts securely to the frame. The LHS could be welded on. Just an idea, somthing im going to have a go at when i get round to chucking a slingshot track bike together

I think done right using both plugs it would add rigidity to the headstock and also provide better protection to the engine/head in the event of a crash. You could even have a nylon block on the plates as a crash bung.

A lot of modern sportsbikes are made this way so no reason it wouldnt help

Shall I get a couple of sets done.

 

[MeanBean49]

9 minutes ago, dupersunc said:

Shall I get a couple of sets done.

 

I think it would at least be worth a try

[Mole28]

1 hour ago, dupersunc said:

Shall I get a couple of sets done.

 

I'd be up for trying them if you made some up. 

[Gammaboy]

There's a couple (aircooled) of bikes running in historics down here with a headstock brace that picks up off the bungs in the end of the GSX heads - haven't heard any tales of woe re: them destroying the head when they get laid down. I think if the ends of the head are at risk, you've got bigger issues!

[maxwin]

One of my least favourite jobs, putting the spring retainers on...

But soldiered and not the head is one and torqued up.

Time to dial in the cams, I've made a couple of tools to use as a piston stop and a secure holder for the degree wheel...

The degree wheel is paper an card, I used Autocad to draw and print it.

With it all set up I have worked out that the duration is taken at 6 thou lift on these standard cams, also calculated the intake cam is 4 degrees out (advanced) and the exhaust is 2.5 degrees out (advanced) so next job is to slot the cam pulleys.

[KATANAMANGLER]

That looks just like my home made positive stop tool I downloaded a good pdf degree wheel printed it, cut it out and laminated it. Worked a treat.

[maxwin]

Had an industrious Sunday, while stuck indoors watching the child I managed to get all the vinyls cut and backed ready for the fairing  (when it arrives)

Going for a variation on this one

Fairings are coming in black so a bit of red paint, the vinyls and happy days.

Still some room for a few OSS decals if there's any going