Hello Xt'rs

new here,

i am based in milan, italy and road race vintage stuff like CB500/4 and a 750/810 Gpz in the national series.

in order to get more (and cheaper) track time, bought a nice condition 1990 XT600E with 25K km that i am in the process of turning into a supermoto.
It is not meant to be a racer, just something to train with in a track i have near home (Castelleto di Branduzzo)

Pista

Not going to mess with the motor much, it's sweet running, so just a foam air filter and straight through exhaust.

TZR 17" with a 300mm disc wheels are on the way, gonna fit a GSXR caliper for braking in the front.

A few questions then:

15/45 is the stock gearing, I will surely want to shorten as this is a supermoto track only bike. does anybody have any experience with supermoto track gearing for an XT? Bike will not be used for any street riding, just SM track and a slow one at that.

suspension set up. I will lower and stiffen the front springs, any numbers as to a baseline ride height and spring rate? any ideas for a reasonable shock change that doesnt include a 1000$ ohlins?

any recommendations regarding jetting changes for a foam filter and open race exhaust? The bike has the usual stock double carb jobbie.

Will post pics when the bike starts take shape. right now its a plain XT600E....

Grazie mille in advance

TG

The carb runs rich stock, so if you need any jetting go up one number in idlejet, and I bet you're pretty close, if you only use it for track, a k&n should breathe better, or atleast thats my guess?

As for gearing, it depends on the track. Try with stock gearing, and take it from there. Its easy and cheap to add a 14 tooth frontsprocket, to try that out aswell.

Wilbers and hagon have shocks at around 4-500euro that seems good. A friend of mine has a wilbers on his xtz660, it was tons better than the old worn out shock =)

thanks jens

track is 90% slow, like mostly 2nd gear turns save for a staight with up to 140km/h in a supermoto. in th ebottom of the link i posted there's a nice telemetry video

14 front is surely a start but as i have to put a new chain, would hate finding out later that i cut it too short for bigger rear sprockets...

will check into those shocks but been looking today and the stock one looks rebuidable. might give it a try

tnxs

TG

As far as I recall, you can go 14-47 on stock chain. So a 14 for a starters might not be so bad afterall.

I dont think you will need it much lower, otherwise I think you will hurt youre topend too much.

Try messing around at www.gearingcommander.com You can see which sprockets gives you what speed, at different rpm's its good stuff.

Cant wait for the pictures

yep, i know gearingcommander, it's really nice, the data on the GPZ750 was entered by me

but i just discovered that kedo have an even more useful gearing calculator that lets you know also axle displacement according to sprockets and how many links you run in the chain!

just what i needed!

KEDO Ketten-Rechner

If you have access to an older kick-start XT600 / TT600 / XT550 /SRX-6 engine, consider swapping in the primary drive and clutch basket. The gearing is shorter in the older bikes. The lower primary gearing not only lowers the overall gearing, but results in better acceleration.

Offset from the triples isn't correct for 17" front wheel. Bike will be twitchy with stock forks. If you can swap triples or forks for something that less offset/ more trail, the bike will work better. I went to an entire front end from a MZ Mastiff for mine. If you can get more trail in the front, a longer shock will be better for the rear. On mine, I have an earlier, longer XT600 shock that has been revalved and a stiffer spring.

Good luck!

thanks for the useful info joe

wheels arrived and its easy to see how much steeper the rake is now, so sure, trail is going to be shorter too. know this from my road racing too, get too steep at the front and you loose feedback at the bars and bike gets nervous.

think i am going to hit the track first and then see how bad it is.

keeping this project kind of low key, so cant see myself getting too deep into motor things, or swapping front ends, too many other projects on the table!

that said, for all i know, it doesnt matter where you lower gearing, primary gear or final drive, at the end of the day its all about motor revs vs rear wheel drive revs. the TZR 17" wheels i got already came fitted with a 45 sprocket, so for now will only change the front sprocket for 14, hit the track some and then see.

cheers & grazie

TG

not much missing, need to sort the 17mm axle in the front (stock is 15), paint rear fender and tank white and maybe do some side panels to tidy things up.

should hit the track in a matter of weeks i guess...

BTW, weighted the thing and it's around 145 kg. dont how much the stock bike weighted but it surely feels lighter just pushing it around

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Sweet looking bike! I really dig the new wheels. What did they come off of? And what did you do for the chain alignment and getting the proper sized rotor? I too am looking to get a spare set of cast wheels and fit them to the XT and try some racing at a go kart track here in the states

the guy who sold them to me told they where off a Yamaha TZR 250 or 125, a small race replica bike sold in europe and Japan. Front offset is not a big problem as its easy to make spacers for the wheel and then caliper.

Back end is more difficult as after you center the wheel, you still need the right offset between tire and sprocket, guess i was just lucky with mine but if i need to tweak, i might need to put the sprocket carrier a bit further away form the hub

will post some pics to explain the mods

I would have guessed Suzuki GS500E/F wheels based on the looks of it, as the TZR250 have twin discs up front, and the 125cc model have the disc on the right side of the wheel.
It should be cast into the wheels though.

Love the look of the bike, I'm well tempted to try and make up a set of 17" wheels for my XT.

Im pretty sure its 156/168 dry/wet. Mine is 180 wet with 23ltr of gas, handguards, bashplate ect.

Thanks and well, just checked, turns out both wheels are branded "yamaha/Brembo" in the same casting. guess that makes them TZR125 wheels as that bike was made in Yamaha Belgrada near Monza back at the time.

front disc might have been on the right on the TZR but the XT brake brackets are on the left , need to check tire rotation direction now that i think of it

I didn't notice that the front wheel is mounted opposite to the back wheel until you mentioned it. Next time I'll take a closer look before commenting.

well, was almost ready to hit the track, had even registered to a Supermoto day, then on the weekend before the first ride broke my ankle in a road accident with my VFR.....

:P

oops, project/ride on hold i guess.

sucks a bit