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post #1 of 185 Old 08-15-2012, 2:26 AM Thread Starter
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Racing my '90 GSXR750 - again!

Been _extremely_ busy building an Historic racebike for this coming weekend. Three weeks ago I dragged my old '85 and '90 GSXR750's out of the shed and tried to determine which would be the easiest to get into race trim inside of three weeks. The '85 has way more than 100,000kms on her, and feels it, so I'm hesitant to go full race pace without building the engine, but she is already set up for the track. The '90 I bought new (the day my daughter was born - December 8th, 1989) and is in full OEM road gear, but I built the engine in '91 (totally stock) and I know it's strong. I raced her as a Production Superbike - all OEM including the muffler, I'm really looking forward to racing her again as a proper race bike :-)

I decided the '90 was going to be the more likely to get ready on time, although swapping the engine across to the '85 was still an option of last resort.

The Historic Racing Club is doing the State Titles as a single round this year as Wanneroo has been closed most of this season for building renovations. And the more bikes they can put on the grid the better the whole event is.

I first drained the oil and then stripped the bike down to a totally bare frame with just the engine, then spent several hours hand cleaning the engine and frame with WD40 and visually inspecting every inch of the frame and engine cases. I crashed her at more than 200kph in '91 and had never had her stripped down so this is an opportunity to find any damage I may have missed twenty years ago. With the carbs and headers off and plugs removed I thoroughly fogged the combustion chambers and ports with INOX to let it soak into the valve stems and rings for a few days before I start moving the internals.

I'm also weighing every component. The '90 model inverted fork legs weigh 9.05kg, eight years later my '98 GSXR750 inverts weigh just 7.35kg. The complete '90 5.5" rear wheel, new tyre, sprocket and disc weighs 16.82kg. My Marchesini 6.0" mag weighs 11.56kg with the same 6kg tyre, a bigger sprocket and aluminium disc. The complete '90 front wheel is 12.58kg with discs and a new tyre, the 929 is 10.86kg with 20mm bearings and Arashi discs.

The dry weight of the complete bike when new was 193kg. The frame (only with outer steering races) and engine (no alternator, starter motor, oil cooler or sprocket cover but still with manifolds and 530 sprocket) weighs 82.8kg. I weighed another '90 750 frame last year at 15kg, not as accurately as I like but near enough, making the engine around 67.8kg.
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"I won't forget that ride for a while. Maybe you're right. Living fast might be worth the final crash. Maybe that's the secret you fliers know." - Flight of the Intruder

Last edited by bladeracer; 08-15-2012 at 7:49 PM.
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post #2 of 185 Old 08-15-2012, 2:57 AM Thread Starter
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Re: Racing my '90 GSXR750 - again!

I removed the ignition switch from the top clamp (still had the tamper-proof bolts), greased the tapered bearings and reinstalled the fork clamps into the frame.

Then I stripped the swingarm and shock linkages and was very pleased to find the bearings and bushes shining like new ones. Polished the bushes on the buffing wheel, greased everything up and reassembled the linkages. I made a new aluminium bearing spacer for the swingarm pivot to replace the steel one to save 230gms, and I replaced the axle adjuster studs with stainless - I've replaced almost all the fasteners with stainless during this assembly. I also had to drill out a broken bolt in one of the race stand bobbin mounts. When I mentioned to a mate that I had to make some crash knobs he gave me six roller skate wheels so I'm mounting those on the axles and engine :-)

I replaced the original 40mm damper and remote reservoir with a 46mm '03 GSXR750 shock. It's 20mm longer and saves half a kilogram, but the spring is much larger diameter and just fouls against the front of the swingarm. So I spaced the top mount 8mm off the frame. The piggyback reservoir also means I have to remove the top shock bolt and jack the bike up a couple of inches to be able to access the air filter - hardly a big deal.
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"I won't forget that ride for a while. Maybe you're right. Living fast might be worth the final crash. Maybe that's the secret you fliers know." - Flight of the Intruder
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post #3 of 185 Old 08-15-2012, 4:54 AM Thread Starter
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Re: Racing my '90 GSXR750 - again!

Then I fitted the 6" Ducati Marchesini rear wheel. I replaced the 25mm bearings with 20mm ones to fit the axle and made up an aluminium bearing spacer. I expected to have to make new axle spacers but the originals were almost perfect so I just used those for now. Making aluminium ones will save another 150gms but I don't expect to find time for that this week. I'm running a set of new Pirelli Supercorsa treads I've had on the rack for a while, mainly because I was hoping to get some road time in this week to check the bike out. It's not looking likely now but I doubt I'll make the effort to swap new slicks on even though I also have new ones on the rack

I made a new caliper hanger and made it captive to the swingarm to do away with the torque arm, and save just over half a kilo. I also made an aluminium disc which is almost a full kilo lighter than the original disc despite my not bothering to drill it for lightness. I have to pull the wheel out again this week anyway to fit the chain guard so if I have time to spare I'll drill it then.

I got new fork seals but after polishing the tubes I decided they'd be wasted due to some fairly significant pitting. I don't have time to get them rechromed or get replacement tubes, so I reassembled the forks with fresh oil and I'll sort them out after the race day. The rulebook states no inverted forks unless they were orignally fitted, and the '90 GSXR750 was the only production bike with inverts at the time. If they were conventional forks I'd be allowed to run modern forks that are "visually indistinguishable" from forks of the era. But for inverts the book specifically states I can only run _original_ inverts. I have '88 GSXR750 forks I could run (and they're nearly 2kg lighter) but it just seems to me that if I'm going to race a '90 model then she has to be inverted :-)

The original discs are 310mm diameter so ideally I wanted a wheel that will run 310mm discs - like the 600RR and early 1000RR. To run larger diameter discs requires moving the calipers out on the fork mounts, but I decided there wasn't enough meat in the forks or calipers to do that without welding them up and redrilling them, and I don't have time to do that.

I was going to run the '06 1000RR front wheel off my 929 but to save having to change tyres I decided to run the 929 wheel. The wheel is wider at the hub than the original so I needed to make a new axle. I found a straight 20mm axle that was 25mm longer than required and made a sleeve out of a 20mm front wheel spacer to make the shoulder on the axle. I had to cut the thread 25mm further along the shaft before shortening the axle to length. I replaced the 25mm bearings with 20mm ones and made a 20mm aluminium bearing spacer and an axle spacer to replace the speedo drive.

I don't have any 1000RR 310's though and couldn't find any on Ebay or locally so I took the plunge and ordered the Chinese Ebay discs for A$180 delivered to the door - giving me eight days to get other things done before they arrived.

"I won't forget that ride for a while. Maybe you're right. Living fast might be worth the final crash. Maybe that's the secret you fliers know." - Flight of the Intruder
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post #4 of 185 Old 08-15-2012, 5:23 AM
 
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Re: Racing my '90 GSXR750 - again!

Looking great BR, when you changing your username?



Bike build Vblog latest Update
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My 900RR Winter Project
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post #5 of 185 Old 08-15-2012, 6:25 AM Thread Starter
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Re: Racing my '90 GSXR750 - again!

Quote:
Originally Posted by Lambchops View Post
Looking great BR, when you changing your username?

I thought it'd be easier to put Fireblade decals on the bike :-)
Just been painting this arvo. Doing the same colour scheme I did for her back then, sort of a step back in time :-)
I have done the front guard red this time though, mainly because the original guard was red, but also because it doesn't sit alongside anything else it was handy as a test piece for some different reds.

"I won't forget that ride for a while. Maybe you're right. Living fast might be worth the final crash. Maybe that's the secret you fliers know." - Flight of the Intruder
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post #6 of 185 Old 08-15-2012, 6:50 AM Thread Starter
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Re: Racing my '90 GSXR750 - again!

For some reason the pics got lost on that last post.
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"I won't forget that ride for a while. Maybe you're right. Living fast might be worth the final crash. Maybe that's the secret you fliers know." - Flight of the Intruder
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Re: Racing my '90 GSXR750 - again!

Sounding like shes going to be ace! Cant wait to see the completed pics



Bike build Vblog latest Update
http://youtu.be/2ISgxtQXs9o

My 900RR Winter Project
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post #8 of 185 Old 08-15-2012, 7:24 AM Thread Starter
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Re: Racing my '90 GSXR750 - again!

I'm running the GSXR1000 clip-ons which sit higher than the originals so I had to make a spacer for the steering stem to raise the top clamp 6mm. Removing the bar end weights and swapping the clip-ons saves half a kilo. The clutch lever mount is the same on both bikes so I left the 1000 one on the clip-on along with the grip. I didn't want to rebuild the original master cylinder so I swapped the GSXR1000 one on. I had intended to run the Goodridge lines off the GSXR1000 as well but after pulling them and giving them a good clean I discovered they were just chrome-plated steel fittings and banjo bolts, and already rusting. So I kept the stainless braided lines I made twenty-two years ago that still look as good as new. I also put the clutch cable on.

Next I inspected the harness, replacing two connectors before re-taping it and refitting it to the bike. Some of the boots on the plug caps were perished or broken but I managed to find replacements at the wrecker's. I only need electrics from the battery to the coils and I reckon I could save at least a kilogram by making a race harness, but I just coiled the excess harness up under the tank as I do plan to licence it soon after the race day.

I made a block-off plate out of 5mm aluminium plate to cover the hole left by removing the 3.7kg alternator. I had intended to pull the clutch and remove the alternator drive gear as well but it doesn't look like I'll have time now. While I was doing that I also swapped out the lower and rear engine mounting bolts for stainless ones and discovered one that had broken off in the hole, but it was an easy fix. I also swapped out all the fasteners in the area above the transmission before installing the airbox and carbs. With no time for tuning, I built a set of totally stock carbs rather than risk having to mess with jetting my original Dynojetted ones.

"I won't forget that ride for a while. Maybe you're right. Living fast might be worth the final crash. Maybe that's the secret you fliers know." - Flight of the Intruder
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post #9 of 185 Old 08-15-2012, 7:32 AM Thread Starter
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Re: Racing my '90 GSXR750 - again!

More pics.
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"I won't forget that ride for a while. Maybe you're right. Living fast might be worth the final crash. Maybe that's the secret you fliers know." - Flight of the Intruder
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post #10 of 185 Old 08-15-2012, 7:43 AM Thread Starter
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Re: Racing my '90 GSXR750 - again!

Some more.
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"I won't forget that ride for a while. Maybe you're right. Living fast might be worth the final crash. Maybe that's the secret you fliers know." - Flight of the Intruder
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post #11 of 185 Old 08-15-2012, 8:10 AM Thread Starter
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Re: Racing my '90 GSXR750 - again!

I used a wire wheel to get all the surface rust off the headers before giving them a coat of rust convertor, then a couple of coats of hi-temp caliper paint (500C). Then I wrapped the headers and collectors to minimise heat radiating from the exhaust system into the sump and oil.
To save some time I didn't bother cleaning the midpipe and simply sprayed it with caliper black as is - I can clean it up later on. The muffler was made for me in '92 by a good mate. I spent a couple of hours polishing it up on the buffing wheel and it came up pretty nice.
I plan to make some plates to fit between the midpipe and muffler with different sized holes drilled through them to quieten it down as it is very loud.
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"I won't forget that ride for a while. Maybe you're right. Living fast might be worth the final crash. Maybe that's the secret you fliers know." - Flight of the Intruder
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Re: Racing my '90 GSXR750 - again!

I mounted the CDI on top of the airbox and swapped out the bolts on the engine covers for stainless and installed the oil cooler. I'm running aftermarket oil pressure and temperature gauges. I normally just T the oil pressure sender into the OEM pressure switch, but this one is inside the pulse generator cover and there's no room for that. So I made adaptors to mount an oil pressure sender and oil temperature sensor into the engine. I used a standard tapered gallery plug (I don't understand those gas thread sizings so I don't know what size it was) for the oil pressure by running an M16 die nut down it to fit the main oil gallery and then drilled and tapped it with a tapered thread to take the oil feed line fitting. The temp sensor was harder as the remaining gallery plugs are M14, and the aftermarket plugs are hollow, which doesn't leave much meat after drilling for the M10 sensor. So I made an aluminium adaptor by cutting an M14 thread down some 20mm rod, then drilling and tapping it for the sensor. As I want to monitor the temperature of the oil before it gets cooled, I installed it into one of the front gallery plugs in the sump just below the hose feeding the oil cooler. A new filter and oil, put the starter motor back in and fired the engine on starter fluid just to confirm it was good. Even without the headers it was music to my ears :-)
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"I won't forget that ride for a while. Maybe you're right. Living fast might be worth the final crash. Maybe that's the secret you fliers know." - Flight of the Intruder
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post #13 of 185 Old 08-15-2012, 9:02 AM Thread Starter
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Re: Racing my '90 GSXR750 - again!

I made a front subframe to support the fairing and instrument cluster but still leaving room for me to fit the headlights in for road use. I also made up a new dash to take the oil temp and pressure gauges and the tach. I had assumed I wouldn't run the original instruments for reasons of weight, size and replaceability, but it just seemed right to run her original tach. A trademark of the original GSXR750 was the tach that starts at 3000rpm. I ran a toggle switch directly to the harness to do away with the ignition switch and mounted that on the dash as well. A mate bought a bunch of tiny LED idiot lights for the oil pressure switch and neutral light which I hope to get mounted before the day, although neither is essential. I was going to shorten the OEM GSXR1000 levers and weld the balls back on but another mate gave me a pair of ASV shorty levers that he'd taken off his own '90 GSXR750L when he bought it as he didn't like them. Although they're significantly heavier, to save me some time I installed them. I removed the light switch from the right switch cluster and put that on and hooked up the throttle cable to the carbs and replaced the bar end weights with plastic furniture caps.
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"I won't forget that ride for a while. Maybe you're right. Living fast might be worth the final crash. Maybe that's the secret you fliers know." - Flight of the Intruder

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Re: Racing my '90 GSXR750 - again!

Dash detail.
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"I won't forget that ride for a while. Maybe you're right. Living fast might be worth the final crash. Maybe that's the secret you fliers know." - Flight of the Intruder
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Re: Racing my '90 GSXR750 - again!

The rear master cylinder was weeping and the caliper pistons were dragging. As I don't use the rear brake I didn't want to waste precious time rebuilding the master or caliper so I pulled both off the GSXR1000 and put those on instead, with one of the front Goodridge lines as it was the shortest. I cut the new rear disc out of 5mm aluminium plate.

The front discs arrived from China and mounted up just fine on the 929 wheel. I ordered all new OEM seals for the front calipers, rebuilt them with new stainless bolts and polished the pistons on the buffing wheel to a near-mirror finish. To get the calipers aligned with the discs I had to grind 3mm off their mounting bosses.
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"I won't forget that ride for a while. Maybe you're right. Living fast might be worth the final crash. Maybe that's the secret you fliers know." - Flight of the Intruder
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