Go Fast TM125 Tips Needed

[Graeme M]

OK, took the TM out to the DT for a run on Sunday and it went great. I fixed the problem with the front wheel, rejetted it to run nice and crisp, and replaced the rings. But... it is still way to slow compared to elsie125's ummm Elsie 125. Those CRs are fast!

I was very happy with its handling, in fact the only place it was no good was the uphill sweeper where it's too slow. But through the kink I could stay with Dennis on the KTM400 and even close up on a few of the young guys on their moderns. So she works OK, just needs some go.

How do I make it competitive for the Aussie DT Nats in September?

My plans are to take a little off the head (maybe 15-20 thou?), change to a 30mm carb, maybe go to methanol and get the gearing spot on. Worth it? Can I get this thing to go fast?

PS feeling much more positive about the little TM now I got it working. God it was bad at Wagga...

[David Lahey]

If you want a TM125 that shames CR125s, you should talk to George McKenzie (07) 32064230.

[Graeme M]

George is the man eh? Never heard of the guy. In Brisbane?

[firko]

George MacKenzie has been around VMX since the very early days. In his riding days he was one of the really fast blokes on Maicos but apparently a back injury prevents from him riding these days. He's a bit of a genius with an welder or a porting tool.

[David Lahey]

Yes George is in Brisbane
I'm a twinshock trials nut nowadays rather than a MX or DT person but I do get to hear a bit about what he gets up to with building race motors and exhausts for VMX type bikes as he is my Brother-in-law.
Some bikes he has built motors and/or exhausts for in the last few years that I have heard a bit about are Bill Holm's TM250 and TM125 and John Kemp's Aussie titles winning XL250-based Maico-framed Unlimited pre 75 4 stroke.

The TM125 is something of a specialty with George and the one he did for (I think it was Bill) is quite spectacularly fast. He is able to make Mk7 360 Pursangs quick too which is no small feat.

Maybe some other forum users who know about what George can do can speak up. Please do. I'm keen to have Graeme M thrash a few CR125 Hondas on a Suzuki.

Thanks Firko

David Lahey

[Lozza]

Having seen a few TM barrels it has 3 downfalls compared to the CR.1) Lack of transfer port area(by virtue of it's 2 transfers) 2) Ignition curve 3) Tiny carb.If you put it on fuel that will help but you will still be down compared to a CR on fuel.Good news is the fixes are simple and easy,ie cheap. Your after top end so on with a 36mm, track down a YZ 80/RM 80 or 100 ignition after that a stage 2 the transfers.

[Suzbulvarna]

Graeme,
The best thing to make it go faster is put a TM 400 motor in it!!!! and well picked up on the new Forum name or did you work it out from my email address I wonder who else will work it out.....are you going to Jack Hogg and if so who else from the Nations Capital is going any of the Kamp KTM crew Myers,Bill etc
Regards
Suzbulvarna

[Mike]

Hi Graeme, are you running 28mm Mikuni? Can you tell me what jetting, slide etc you used to make the tm run nice and crisp as I am about to set up a new 28mm Mikuni for my tm.  You might have done the hard yards for me already.

[Doc]

Graeme,forget trying to match the CR in outright speed..it's not so much the lack of horsepower as the lack of cogs contained within the TM gearbox. If it's running crisp concentrate on it's brakes and handling, go for a small 3.50x18 rear and run a lightweight front. 14/61 gearing. You'll only lose a few bike lengths on the straights there's more to a track than the straights. The best part about the TM is it will run consistantly all day 

[Graeme M]

Yeah, Chris, you're right about the gearbox, but in DT there isn't any more than the straights. It really is all about speed, and especially in Canberra there's no point in being quick through the tighter section if you don't have the go for the uphill sweeper. Elsie125 is quicker than me as a rider, but his CR is also miles faster than my TM. If I snapped mine on at the same time as him out of the bottom corner, he would pull me by a good 20m by the end of the sweeper.

I will definitely regear as you suggest, I'd already figured I could come back a tooth on the front (actually I think 2 on the rear is a better option, but no spare rears).

I like Lozza's suggestions, though a 36? I am willing to have a go at that, but what needs to be done to the inlet manifold to fit that size carb? Is there a bolt on part, or do you need to make an adapter? I guess given my bike is on a stock 26mm carb going to 34 or 36 would get me a whole lot more air in that cylinder...

Mike, I am running a 26mm Mikuni on stock jets except for a 150 main and one notch leaner needle clip.

What model RM80 CDI do I need? Any of them?

[David Lahey]

GraemeM
No matter how well you set up a bigger carby and fiddle with the gearing, it's not going to do well enough in the drag race stakes to compete with an Elsinore till you also fix the transfer port problem. Not just not big enough, but the left and right are way different sizes. It can be fixed. I've seen it done and the results are wonderful.
You will have to run methanol too if you are serious about this. Does anyone actually win races using petrol in 125cc DT racing?
David

[Graeme M]

Well, I am never gonna win any Aussie Champs, I am not fast enough a rider. All I am after is to be able to get in with the pack, which of course is wall to wall Elsinores. So my level of seriousness is tempered by a certain amount of reality.

That said, I will start by making a few of the changes mentioned here and take her out to a rec day in a month or two's time and see if there's an improvement.

I have plenty of time to get it sorted by the Nats, and if I can pick up maybe 5-6 Hp it would make quite a difference I think, maybe enough to make me happy.

Anyone know what the fast 125s put out? I guess a stock TM is maybe 18, I'll assume that with a fresh engine, pipe, free breathing airbox and a port job mine might be a little better than that, maybe 1-2 more? So, assuming mine might be close to 20, I would like to be able to get to 24-26. I'll guess a good CR would be in the 28-30 range?

[Lozza]

Nobody runs an EGT gauge or a det counter so you won't get near the alki burners. Petrol needs fine tuning, especialy with a 125 that is sensitive to changes in air density.28-30HP on petrol is do able.
What you need is torque
HP sells
Torque wins

[Graeme M]

Oh, I have no shortage of torque. I torque the best race you've ever heard, regularly win everything I enter...

Thanks to everyone for their thoughts and advice, some excellent ideas and info there. I'll report back in a few months time.

By the way Mike, I found these jetting specs for the 28mm carb on an RM125M, which I reckon would be a good starting point for you, as the RM-M and TM were not too dissimilar:

Main jet: #180
Jet needle: 5DP7-3rd
Needle jet: P-4
Cutaway: 2.5
Pilot jet: #50
Pilot air screw: 1 1/2 turns
Float level: 25 mm (0.98 in)

[Doc]

 ooops..dirt track eh..I never read the initial post properly sorry. I'll be taking the TM dirt tracking soon but at present it's very much uncharted territory for me also. This was the main reason I built the RM125S powered TM..it has a reliable 23-26hp, the 5 speed shouldn't be such an issue with DT. It pushes it up into pre78 but it's the sort of TM Suzuki should have built in the first place