CR 125M Problem. No Grunt whatsoever

[YZ250H]

Interesting Big K.  God knows how old the carb is.  The slide deosnt show obvious signs of a lot of wear but ...
I accidently bought a new boot for theairbox to a Mikuni.  I also have a gem reed valve manifold with reeds.
Maybe I should just bite the bullet and get the Mikuni.

Thoughts ??

[huskibul]

   Needle and needle jet are critical in the little zingers ! and if not adjusted/jetted right(too rich) they get a real flatspot ,they also get worn and throw it all out ! new mikunis work too 

[PCMAX]

I had a similar problem with my CR125 last year, it would start & idle OK but wouldn't go well with my weight on it. When i checked the compression it was down around 8 PSI. Turns out one o the rings was jammed in the piston groove. Have you checked the compression?
Also about 2 years back my RM was running like a dog. This turned out to be a piece of rubber from the back of the airbox getting sucked into the carby inlet whenever I gave it a fistfull. Are you sure there's nothing restricting the airflow?

[bigk]

I would use a Mikuni and the gem seeing you have it. If you are to run the Keihin get a 45 pilot if you can. You'll go nuts otherwise.
K

[mainline]

Nothing stuck up the muffler?

[YZ250H]

Nothing stuck up the muffler?

Checked for sausages and bananas.  All clear 

[Ted]

So it free revs but doesn't move when put in gear. Check that you fitted the chain Tentpeg

[09.0]

You have ridden one before haven't you? They have zero bottom end...

[Simo63]

So it free revs but doesn't move when put in gear. Check that you fitted the chain Tentpeg

ROFL 

[oldyzman]

Big K would you generally say to go with the mikuni even on slightly later CR's like a 125RZ
Brett

[midway200]

      Check the needle and i'm betting it has the wrong one in it. It happened to me once and for the life of me couldn't work out what I had done . I had got an M2 needle mixed up with an M1 while stuffing around and it had a richer profile. I couldn't tell until I lined them up side by side. The original CRM1 needle is fatter in diameter on the bottom to mid.  Hope this is of some help.

[JohnnyO]

Big K would you generally say to go with the mikuni even on slightly later CR's like a 125RZ
Brett

Brett a 32 or 34 Mikuni is a better carb for the 74-77 CR125's but there is nothing wrong with the Keihin on the 125RZ and RA models, the RA carb is 2mm bigger than the RZ carb and a better choice.

[GMC]

Piston in backwards?

The bike starts Ok on the kicker (second or third kick).  RUn "OK" and revs out well when not in gear. 
Trouble comes when you try to ride away.  It just dies in the arse completely.

My KDX was like this when I first fired it up, in the end I found the main jet was way too big.
It had the correct number, I suspect it had been drilled out.

[oldmxracer]

Fuely type stuff running out around the exhaust flange.

If "fuely type stuff" is actually fuel, me thinks you're having float/needle seat issues.

[YZ250H]

So it free revs but doesn't move when put in gear. Check that you fitted the chain Tentpeg

Helpful input as always Teddles - thanks

I checked and the chain is in fact connected.  Likewise the gear lever is set in such a position as to select gears freely.   

Methinks If I go for the new mikuni I can get most of these issues in one hit (probably cheaper by the time I but new needle and seat and hunt around for jets).

I will try this first.  Will let you know how I go.  Is the joint in Townsville the best or somewhere else ? 

30mm or 32mm ??