CR 125M Problem. No Grunt whatsoever

[Husabergpete]

I Used Hatrick in Townsville last week for a 38mm Mikuni for the CZ - $132 plus some spare jets and a bit of super fast post.

Spoke directly with Tom who was happy to discuss a bunch of jetting options.

Got everything in 3 days.

Pete

[YZ250H]

Thanks Pete.  Sounds like the go.

[JohnnyO]

Yeah TD Hattrick is the place to go. 32mm

[YZ250H]

Thanks JO.  I think this will save me a lot of buggerising around.

[09.0]

I have a carby or two to try different jets.

[bigk]

Done LOTS of CR125M/M1's and have found a standard jetted 30mm Mikuni (TD Hatrick) to be a direct replacement for 28mm Keihin with no jetting other than maybe needle clip position, to work great on standard engines. Of course some inlet air boot mods are necessary for perfect fit. I usually a 16mm spacer on the cylinder with Suzuki inlet manifold & air boot. The spacer seems to give them more bottom end as well. Obviously if you use the gem reed you may not need to space things. You can also purchase a specific Mikuni inlet manifold to suit the CR's now as well. Tested lots of pipes as well and found that '76/'77 CR125 M2/M3 & Circle F work best. You can almost use the word torque & Elsinore in the same sentence with either. Send your email and I can shoot you some photo's.
Cheers,
K

[YZ250H]

Wow.  You blokes really do have a vast amount of knowledge.

I think I will go for the Gem reed set up since I have it here.  There will be little or no heat insulation / vibration insulation from the barrel.  Is that an issue.  What gaskets to use ?

I might do a mock up and post some pictures.   Am I adding additional complexity by putting the Gem reed setup on it?  I'm pretty there are no performance mods to the barrel.  On the first oversize (!)

Thanks for the offer of the carbs Brad.  A lot of information here to digest. 

[Lozza]

Try ATV Unlimited for a mikuni with a big packet of jets for a $100 odd

[YZ250H]

These are the bits I have collected.   Looks like now is the time to use them 

[JohnnyO]

Only trouble with those cr125 Gem reed valves is they are a bit restrictive and you may lose some outright horsepower in place of the better bottom end. None of the privateer race teams used then back in the day. DG, FMF etc..

[35elsinore]

I put a 32mm mikuni from townsville on stock M1 and made the world of difference. I havent touched the jetting at all from what Tom sent. slip it in and rev the shit out of it. Happy days
Cheers Troy

[JohnnyO]

I put a 32mm mikuni from townsville on stock M1 and made the world of difference. I havent touched the jetting at all from what Tom sent. slip it in and rev the shit out of it. Happy days
Cheers Troy

Yes I'd go for a 32 also..

[YZ250H]

UPDATE :

Stoked to announce that after owning this beast for three years it is finally running as it should.

The new Mikuni carb did the trick beautifully.  I ended up leaving the gem reed valve off.  Still doesn't have much pull off the line, but once you do get it off the line it flies .

Thanks everyone for your help.

For future reference I ended up on :
VM32 from TD Hatrick
Main #240
Pilot #45
Jet Holder #P8
Needle Jet #159
Needle 6F21
Slide 3.0 (standard fitment for that carb)

[enzo906]

Maybe the old carby jets were drilled and not what they appear?
A lot of us used Methanol in those days and other exotic combinations of Fuel to make 125's make more power
your old carby may still be worth keeping, find someone with needle drills and do the go no go test to see what they actualy are.?

[YZ250H]

Yep, I've still got the old carb, an NOS manifold and NOS Carb Boot.  Will put them in the CR125 box in caseI want to sell it one day