Anyone raced a GS450

[Guest]

I am thinking of converting my GS450 cafe racer into a track bike and competing in the Classic Motorcycle Racing Club (CRMC) air cooled up to 500cc clubman class and was wondering if anyone had actually raced one in the past. The current class leader is a much modified Z500 twin....

Any guidance on successful 450 modifications would also be gratefully received.

Thanks

[hardline_42]

I am thinking of converting my GS450 cafe racer into a track bike and competing in the Classic Motorcycle Racing Club (CRMC) air cooled up to 500cc clubman class and was wondering if anyone had actually raced one in the past. The current class leader is a much modified Z500 twin....

Any guidance on successful 450 modifications would also be gratefully received.

Thanks

You should join the WERA forum. PM a gentleman by the name of Rich Graver. He's done some very interesting things with the GS450:

[Pod70]

Thanks for the lead. A very interesting looking bike but many of his modifications may not be allowed as they use parts sourced from bikes built after the cut off date but I'll follow it up and see what I can glean

[hardline_42]

I'm not sure what the regulations are in the class you plan to race. The bike I posted was raced in WERA light superbike, IIRC. It's got a GSXR front end, GS500 swingarm, GSXR wheels, Keihin CR carbs and is probably pushing close to 600ccs.

When is the cut off date for sourcing parts for your bike? Any of the larger diameter front ends from the bigger GS bikes can be swapped onto it. A dual disc front end in 35mm or 37mm with emulators/springs would greatly improve the handling along with good shocks out back and the best race rubber you can fit on the stock wheels (or run GS400 hubs laced to your choice of rims).

[Pod70]

I need to speak to the eligibility officer for full clarification but the cut off date is 1986 which excludes gs500 parts also major frame mods are not allowed so no mono shock conversions. I already thought about changing the wheels to gs250 hubs laced to alloy rims and fitting a front end from one of its bigger brothers but need to see if the weight gains of the extra disk and caliper are worth it.
I really need to check how far I can push the engine tuning as again the usual gs500 carb and cam swap are not permitted. Might get away with the 650 twin's cams though.

[rapidray]

Pod, are you in the USA? If so, call me. I can help you a LOT if I know what your rules are & you can give me a link to them so I can read them. There are usually LOTS of gray areas in rule books! !!!
Ray.

[Pod70]

Hi Rapidray, i'm in England but the good news is that I was at a race meeting today and had a chat with the eligibility officer. Basically there is no problem with using gs500 carbs and cams as you can re grind the cams to any profile and the carbs are in keeping with the originals. The only real restrictions are that the capacity must not exceed 500cc, the frame can't be modified apart from de-lugging and shortening the seat rails. The forks must be conventional (not upside downs) and less than 38mm in diameter. You can modify the fork internals and change the calipers but they must be from a pre 86 bike. I'm pretty much decided on the chassis side of things.

The main area I need help with is the best ignition system to run on a race bike (total loss or aftermarket?) The starter motor will be removed so I'd like to lose or seriously reduce the size of the battery.

Any engine tuning suggestions are much appreciated

[GregT]

Use GS500 pistons - but if you're going to use any sort of warmer cam, you'll have to get them cut to at least match std 450 valve cutaways.
Pic here of just that. Std cutaways will let you use up to around .420in lift with no clearance issues - bigger than that, you're on your own....

Use a dyna S, that's going to be quite adequate for racing. I ran mine with fixed ignition for a while - started and idled fine on 38 deg. Total loss with a smallish battery - 8 amp hours or so - will do a days racing. If you remove the alternator - and you should - it's necessary to make up a sleeve for the end of the crank to block off the oil gallery which lubes the starter clutch - and leave the bolt in the end too.

On the frame, as an absolute minimum, remove the sidestand lug....

[nikosg]

@Hardline42 that is an amazing build!

Do you have any more pictures/info/build thread on it I could check out?!

[patrino]

Pod70, you mentioned battery size, if you're allowed to, you should look into running one a lithium-ion battery. I've been running one in the total loss setup in my GS1000 race bike. I'm running a Dyna ignition on mine too.

The batteries are VERY light and only cost a bit more than a standard lead-acid battery.

I'm running the "AntiGravity" brand and have friends running total loss with the "Ballistic" brand.

Some brands require a special charging unit, so be sure to look into that too.

I have not used the "Shorai" brand but have heard a few negatives about them, specifically their terminals are a bit janky.