Triumphrat

Mental Trousers · 10-01-2009, 07:16 PM

Last night I picked up a 2000 TT600 track bike. The reason it's an interesting project is because it's dropped a valve (right outside cylinder sitting on the bike) and rather than replacing the head, barrel, piston etc myself and another Triumph owner (who also happens to be a motorbike mechanic of many years) are going to simply tidy it up, bolt it back together and run it as a 3 cylinder/450cc under New Zealand's Formula 3 regulations.

I don't know about anywhere else in the world but here there's a good number of former 600cc bikes terrorizing Formula 3 grids. It's something that's happened just recently, ie the last year, after Chris Osbourne (a former MotoGP mechanic) decided he didn't want to be like the sheep who ride SV650's and wanted a fun project. That bike went on to place 2nd in the National Formula 3 Championship a few short months after it first hit the track as a 450.

The unique thing about this project is that nobody has done it with a Triumph before (at least not in New Zealand) so there's going to be lots of late nights fiddling and tweaking and mulling things over a few beers etc. I really can't wait

The suspension is going to the best Ohlins man this side of the equator (Robert Taylor at CKT) so the chassis/suspension side of things will be straight forward. But if anybody has any suggestions about how to get the most of the TT600 engine/electricals etc I'd be grateful for the advice.

Of course the most important and pressing issue right now is what should I name it

Will · 10-02-2009, 12:48 AM

Running a four as a triple? I have not heard of it, but if you can figure out the balance issues, I suppose it would work. Are you planning to leave the dead cylinder in place as a counterbalance of sorts? If you do, then I suppose the easiest thing would be to pull the coil, seal off the appropriate injector and then just use TuneBoy to tweak it around until it works like you want.

It sure is an interesting idea, and if it runs away from SV650s, then it might be worth looking into seeing what the local tech guys would say about it. It would have an interesting exhaust note, and it sure would be different.

Mental Trousers · 10-02-2009, 01:39 AM

The most common thing to do is leave the piston and conrod in place with just the oil ring so there aren't any balance issues (other than the slightly lumpy firing). Pull the valve gear, weld up the valve guides, block off the intake and exhaust, remove any unnecessary bits and retune. Basically aiming to minimize any friction and pumping losses.

What I'm thinking of doing is blocking off just the intake and leaving the exhaust open so we can use the dead piston to scavenge the other cylinders.

The main thing that people are finding with the 450's is that they can use proper sized tyres and the bikes are far more amenable to racing than the SV650. Better suspension, better chassis, better weight distribution, better wheel base, just better all around.

kiwifour · 10-02-2009, 02:34 AM

Well done that man! I wondered who had bought that bike, seriously considered it myself although I'd rather be riding than tinkering.

Ohlins don't have a listing for the TT600/S4 but Robert Taylor fitted a K6 Ohlins shock from one of Shaun Harris's bikes very successfully on my S4, and Ohlins springs and Racetech valves on the front. Huge difference. Always happy for an excuse to ride up your way if you want to have a look.

Good luck with the project.

Mental Trousers · 10-02-2009, 04:27 AM

Cheers mate

I know Robert can do some magical things with the front end. Brent (my mate who is helping me out with this project) sent his Daytona 900 to Robert after a wee off and it came back transformed. I haven't checked very thoroughly but a fair chunk of the front ends appear to be common between the 2 bikes so the mods he does should be sweet.

Mental Trousers · 10-03-2009, 04:14 AM

Got some photos today. Thankfully the previous owner already had a spare head for the bike so I won't have to worry about any problems with the old one, even though that cylinder will be dead.

Definitely putting a new cam chain in though. That sort of thing isn't good for them. In fact it may well have been the reason for that intake valve parting company.

BombFactory · 10-03-2009, 02:14 PM

Those valve seats look fine; just lap the valves in and go!

This will be an interesting project indeed. Just a thought: I'd be tempted to build a permanent bob-weight that bolts around the fourth rod journal so you can get rid of the piston and rod altogether.

One problem I see with running only the oil ring is that you will get piston rocking/slap. I think you could delete the scraper ring, but you'd need the top compression ring to keep the piston square to the wall.

I also think the rings are somewhat dependent on the compression in the chamber to help them seal and scrape the oil down, so no/little compression might eventually result in a good amount of oil leaking into that chamber and then out the exhaust at higher rpm's. Running a bob-weight on the crank would allow you to block off the intake, exhaust, valve guides, and spark plug hole, and you'd get rid of the unnecessary friction the rings and rod bearings cause.

Mental Trousers · 10-03-2009, 06:43 PM

Good points there BombFactory.

Another problem is that the bore is most likely damaged as well so it would have a bearing on how much oil got into the top of the cylinder. We haven't dropped the engine out yet don't know what it did to the liner. However, from the looks of the piston if the bore does have any damage it'll only be very minor.

I'll have to find out how others have handled these problems.

Could you explain what you mean by bob weight? I'm familiar with the way Ducati balanced the engine in the Supermono but not sure what you mean by bob weight.

BombFactory · 10-03-2009, 07:17 PM

Machine shops use a bob-weight when balancing crankshafts. It is a removable weighted clamp that takes the place of the complete piston/rod assembly (rings, wrist pins, bearings, etc.) and the estimated weight of the oil that clings to the assembly. Each journal gets one while being spun up on the balancing machine so the machinist can accurately balance the crank as if it were in the running engine.

There is a specific calculation for how much bob-weight is needed depending on the number of cylinders, the weight of the assembly, etc., as there is rotating and reciprocating mass to be considered. A local machinist learned in the skill of balancing engines should be able to give you the formula for figuring out how much weight you need to attach to the journal, or he may even be able to calculate it out for you if he had the piston assembly and engine info.

You could build a steel half-moon rectangle with threaded bosses and then use the connecting rod cap for the other half. Instead of having studs, you could through-bolt from the cap side into the threads of your bob-weight. It would be a matter of bolting the two halves together (while off the crank), weighing it on a gram scale, and grinding/filing off material until you reach the proper weight. Red Loctite and maybe even safety wire the bolts, and the crank will forever be fooled that there is a piston assembly on it.

Mental Trousers · 10-03-2009, 08:53 PM

Awesome. Sounds like something to do at a later date. For now I just want to change as little as possible and get the thing running, then take it from there.

There's lots of possibilities, but there's also lots of unknowns. What I do know is the SV riders are getting pissed off that they've spent tons of money on fast bikes but guys are turning up having spent 1/5 the money they have and beating them. So a 4 cylinder running on 3 works and can be competitive.