new BS owner Michigan. 100cc race bike.

[jbm]

hello!
I'm in Michigan, and I just bought a nicely patinated and pretty complete TMX 100. I have been looking for a 100 to build into an inexpensive class killer(100cc 2t/125 4t) for our local concrete banked 1/4 mile oval.
 http://thunderdrome.com/
this is not my first bike. I've mostly been building/restoring vintage italian bikes for a few years, but couldn't find something that would compete with modern bikes in some pretty limiting classes. so i did my research, and the tmx 100 looks like it will be VERY competitive with modern bikes, and parts availability seems to be very good.
my initial plan is to follow most of the tuning tips that are documented in the bridgestone tuning guide, but i would love some input into whether or not all of the information in that guide is viable and accurate. Any additional tips would be much appreciated!
thanks,
jeff



 


 

[old smokey]

Hi Jeff,
Welcome to the site. I can't offer any help on the TMX100, but if one turned up close to home at a good price I would consider getting it for going around the neighborhood.

[Bikenstein]

Welcome to the site, Jeff. Looks like you guys have a blast at the Drome. I think you chose a good bike. I'd love to see some videos of your TMX racin' on that track when you get it runnin.. Do they still make PBR?

[jbm]

yep. they still sell PBR, and I still buy it.

[Mike Anderson]

Hi,
Welcome to the site. Did you buy the TMX that was for sale on e-bay over the weekend? It looked like a pretty nice bike. Good Luck
Later Mike

[jbm]

yes. the one in wisconsin, not the one in michigan. ebay #330758060803

[scrambler]

I have to admit I am jealous of Thunderdrome.

[rocketman]

 Worthwhile project Jeff.   Unless you have a lot of spares, I would recommend staying closer to the factory stock side.  A good expansion chamber, fabricated or store bought is a must. Concentrate on compression, carb tuning and timing. The competition tuning manual is pretty basic and time tested by now so I feel confident that if you stick to it closely and don't go overboard cutting everything up, you should be good with the results. Whatever you do, do not overcut the rotary valve and keep in mind modifications can rob the bike of lower end. EZ does it.  Thanks, Mark.

[rocketman]

About your gearing Jeff. I'm pretty sure you want to be able to get high gear. You may have to gear it low enough to leave the line in second. Mark.

[jbm]

thanks for the info. I will be very conservative with the rotary valve mod.
Is there a known good store bought expansion chamber out there that fits this bike?
i was looking at gear ratios, and it shouldnt be an issue of getting this into 4th gear.will probably be bump started in 2nd anyways...

any recommendations on carburetors? the modern vm22 has a flange mount.. the tuning specs mention a 300?! main jet on a vm22.

[jbm]

well, they changed the classes two weeks before the race, which will not allow me to run the 100 TMX.  :'(
so I had to scramble pretty quickly to find something in the barn that would be competitive.
fortunately I had a rusty '64 BS 90 sport in the barn . it's nice to have a barn full of bikes to pick from!
the 90 is now running well.  it started out a "little" rusty. working to make it look a little better, dunno how much i will get done cosmetically before the race.


I will post race pics and pics of the completed bike.

[Bikenstein]

Man, I'd love to get somethin like that Thunderdrome goin here. I know of Four old tracks within a 30 or 40 mile radius from here that used to be wide open. I guess I could build one on my land, run em around the field then down through the beaver ponds up the hill through the woods and back over the lake dam. Second thought, forget that. I would like to get somethin goin on one of those old tracks though. Looks like good family fun. Any suggestions on gettin people interested? My BS's are a "little" rusty too. Building my shop now so I'll have a good place to work on em.

[jbm]

if you have the land, build it. they will come. the thunderdrome is a velodrome. it's fun, but it only really good to small displacement bikes.
you could easily build this on <5 acres
 

[jbm]

looks a little better now.
good enough for the race.loaded up and ready for tomorrow

[Bikenstein]

The bike looks great. I'd love to see some video of the races tomorrow. Have fun

[jbm]

[Bikenstein]

Smokin! Do you have to lean in the turns or do you ride straight up like the bicycles on this track? From what I understand, a velodrome has banked turns so that you ride through at a 90 degree angle to the track. What kind of speed are you gettin out of the 90?

[jbm]

it's a 45 degree bank.very steep.looks scary as a spectator. maybe 20 ft wide. like a mini-taladega . you dont lean into anything. riding it feels flat. trying to get to 50mph(3rd gear). revved out at the top of third gear(screaming). the power loss to shift to 4th with stock sprockets makes 4th gear a no-go. next race will be running a bigger rear sprocket. should make a HUGE difference(ie we'll get into 4th gear, and get up some real speed). hard to prep for the drome on the street.