GS450 - ambitious race bike build!

[Sprockets]

Well, here goes. First post so lets make it a good one

The Background

As with all good(?) ideas, this story all evolved from the pub where a friend of mine happened to mention he had a GS450 taking up residence in his back garden that he couldn't get running right. After some discussion and some more beer it was settled I could have it for the grand sum of £free! With that settled, more beer was had and a good time enjoyed by all! Later the following afternoon, a GS450 was dutifully delivered by his son. That was a result I couldnt remember! This is where I decided to put it in the shed until I was not hungover and could get it running......then I stumbled across an interesting race series. http://www.thunderbike.org.uk/ Basically a power to weight ratio class......thats when my troubles started!

The Story

I'm going to apologise from the outset. Original photos are thin on the ground, as I was just very anxiouos to crack on with (yet another) project. The first job was just to strip everything off and get to a frame, then build up from there! Basically, the project would end up with two areas running in parallel. Engine and chassis.....thinking about it, not much else really, but due to the power to weight ratio ruling both are closely linked! Basically I had two limits. 75hp maximum from the engine, which would put the minimum weight i could run at 122kilos if i could make this wonderful 75hp from an aging aircooled lump! Two ambitious targets....but targets none the less.

once the engine was out it was straight on the scales, as form lifting around the workshop i could tell it wasn't light.....I was correct..64Kg's without the carbs/exhaust....not good. Time to get it in bits!

Ok, heres a quick list of weights:

Balancer shaft: 2.515Kgs - Removed
Starter idler gears: 0.72Kgs - Removed
Starter and cable: 1.58Kgs - Removed
Generator and sprag clutch: 1.85Kgs - Removed
Stator windings: 0.74Kgs - Removed
Balancer drive gear: 0.345kgs - Removed

Total initial savings 7.75Kgs.

Thats not bad weight saving for free, taking the weight down to just over 56kgs.

the crank came in a 6.75Kgs, but that will be sent away for balancing as without the balance shaft, need to get everything spot on. Looking through my notes I have loads of other important dimensions and specs, but I will update as and when.

the brief outline of the engine spec is as follows:

big bored to 79.5mm using enlarged liners and GS1000 pistons (562cc)
custom piper cams
lightweight valves with bucket under shim
ported head
Balanced bottom end
approx 10.5:1 CR (TBC)
Homemade ignition system using 2 "yukon" coils
2xCRF250 flatslide carbs
modded casings to accept oil cooler and spin on filter

Not 75hp worth, but should be good for a wide useable 65-70.

Chassis

Ok then guys. Thanks for staying with me this far..

The chassis is the important bit. Basically, apart from the frame...not much is left. The front end is basically early R6 RWU forks, with R6 yokes and GS spindle (it's an easy conversion guys!) Gilles clip ons, R6 front wheel and braking system. The rear is a bit more complex. Suzuki DRZ 400 swingarm, Ducati 916 rear shock and linkage and bandit 600 rear wheel.......and yes, it all works! Luckily i own a lathe and mill, so all doable!

Gotta sort the swingarm by shortening it, the swingarm pivot is going to be moved by use of an adjustable plate being welded in, the castor is also to be tweaked by yet another oddball way. More info soon!

Cheers

-Gavin

[spyug]

Looks very interesting and th way you describe it easy peasy. I'm watching with interest.

Best of British luck mate!
Spyug

[Charlie G]

You have my attention. Welcome aboard.

Charlie G

[Flyboy]

Yes, welcome to the board, I am in for the ride.
Looks like you know your stuff and plenty to be learnt here.

[Tim Tom]

this is ambitious! Very cool project though. I've had many thoughts about undertaking something similar but I can't support that kind of project at my stage of life.

Best of luck with the project and keep us updated. I love older bikes brought back to life with modern bits, and to compete on a race track looks like a whole lot of fun too.

If there is anything brits can do it's build lightweight racers in the shed

[pete]

Welcome Gavin! Another one interested here... sounds like a barrel of fun just waiting to happen

[Sprockets]

Thanks for all the interest guys. Glad I'm not the only one to think this is a good idea! Thing is, I could have gone out and bought another R1/GSXR/CBR etc, but then I'm just the same as everyone else, with just the options of different colour fairings.

I'm just out of hospital at the minute, so should be relaxing, but in truth I'm just making lists and drawings for whats to be done/bought/made. It's a long list but until I can get out to the workshop, it's the best I can do at the minute. Should have some proper updates next week.

The next stage is to measure up the current chassis dimensions to see where I'm starting from before I can see where to go. I'll have the inclinometer and tape measure in hand as soon as I'm able, along with photos this time. Will also be giving the credit card a bashing with some pistons being ordered and some parts for the ignition system. Aiming for a rolling chassis by the end of the month. I've found I have to set myself deadlines to get stuff done, otherwise I end up with a pile of bits and nothing else!

Stay tuned!

-Gavin

[FiremanBob]

Wow. You make it sound so easy, all I need to do is buy a lathe and a mill.

Great project and you will have a lot to teach us as you go along.

[pete]

So what's the plan for the ignition system? I have recently found that the Dynatek DS3-3C should work for the 450's and I'm in the process of trying to prove it at the moment, but it's become nigh on impossible to actually get a chance to start the bike which is very frustrating.

[Sprockets]

Regarding the ignition system, it's actually rather OTT for a standard bike as this will include a datalogger aswell. The heart of which has just been ordered, based on a ST STM208 development board, which includes lots of lovely little extras I require. Basically it will read from the stock sensors, as the original is basically two seperate ignition systems combined into one unit (I disassembled the stock one to be nosey!), and I am going to use the same idea as I have enough processing power and interupts to achieve this, although it will read from a single table, which can be optimised on the dyno. It will be a 3d system, as the CRF carbs will have throttle position sensors. The actual coils will be the LS2 style "yukon" coils as these are very easy to drive via a 5v logic signal meaning no awkward power handling stages. the rest of the processor will be logging to an SD card, various other sensors. Front and rear suspension travel, wheel speed, brake pressure etc etc

A simplified 2d version could be easily made using a very basic microcontroller with the upgraded coils, or fire a standard set of coils with some more components. I'll gladly help if you want to construct such a thing, but my time is thin on the ground to build such a unit at the minute.

I know this all seems a bit excessive, but why not if it can be done! I also know what is required to win races as I work in the motorsport area, and ignition control and datalogging are high priorities.

Any questions, just ask. My mind is full and struggle to convey all my ideas correctly most of the time!

-Gavin

[pete]

Mate that sounds awesome! A bit of overkill for me given I won't be racing, but I'm definitely curious to see how that all fits together, so please share once you get to that point.

I was mainly asking due to the fact that the stock ignitors on these have a tendency to die and there are very few alternatives around, so I wasn't sure if that was your issue or if you were doing something fancy like you are...

[Sprockets]

If they fail that often, and an alternative can't be found I could build a viable plug in unit depending on what people were after. Pointless doing it for one. If you are after another unit, I have the original sat in the stores shed somewhere. All i did was open the back and peer in, nothing destructive as I knew what i would be doing for mine. Sort me out something for postage and it's yours. i have no use for it, and if it helps someone out, all the better.

-Gavin

[pete]

If they fail that often, and an alternative can't be found I could build a viable plug in unit depending on what people were after. Pointless doing it for one. If you are after another unit, I have the original sat in the stores shed somewhere. All i did was open the back and peer in, nothing destructive as I knew what i would be doing for mine. Sort me out something for postage and it's yours. i have no use for it, and if it helps someone out, all the better.

-Gavin

Interesting thought. I'm hoping the Dynatek will be a viable replacement once I've gotten it sorted and the guy at Dynatek is waiting for me to give him info on it, but other than that there are very few options currently.

I don't need that one myself, but probably post it in the parts for sale section and I'm sure someone will grab it, usually there's at least one person looking for that model ignitor...

I think it's the dodgy charging system that ends up killing them.

[Flaming Chainsaws]

When I had my GS450, I planned something similar. Basically a track bike with modern running gear with the appearance of a cafe racer. Unfortunately, it has been sold because of said ignition issues. Loved that bike too. But now I have a GS1100E to do that to.

Anyways, I will be watching with great interest. The European guys build all the cool bikes. You might want to check out Old Skool Suzuki as well if you haven't already. Those guys can do amazing things with these GS's.

EDIT: Judging from the frame, I assume that this is a GS450E/S?

[pete]

Hey Gavin, any more progress on this one?

Mine's been on the road for a couple of months now and the Dynatek is going strong.

My only issue is my stator just carked it but is at least putting out enough voltage to keep me riding...