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.
"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.