Vintage Dirt Bike Q & A

Tired of fooling with my stock Keihin. Can I replace with this? Info appreciated. Thanks ...Van

SIZE: 32mm, SPIGOT O.D. MOUNTING: 40mm, INTAKE BELL O.D.: 58mm, MIKUNI #: VM32-33
Part#: 13-5003

_________________
1980 Honda CR125R

A Mikuni TM34 (T34 02E) flat slide carb is a straight forward bolt on fit
(I know this because I've done it) can't recommend jetting spec but all I know is a mikuni main jet of 410 is the equivilant to a keihin 175 (stock main jet for a 1980 CR125).
Mikuni measure there jets by flow rate Keihin measure by bore size.
I've never used my bike with this carb but I did run it up once with it and it sounded pretty sweet.

Thanks Spannerman! So it would fit my stock intake and air filter box? Is there some kind of conversion chart between the two brands that would show ballpark compatibility that you know of? Appreciate the info. I'll look that carb up ...Van

_________________
1980 Honda CR125R

Yes it will fit with no modifications to the airbox or intake though you may need to fiddle with the throttle cable,you also have to flex the airbox boot slightly forward,I found it easiest to mount the carb on to the airbox boot an secure ,then push the carb into the intake boot.

Here's a keihin/mikuni jet conversion chart,

http://www.allensperformance.co.uk/jetsizeconv.html

I was advised to start with a 410 main and work down (get 3 or 4 jets between 410 - 300)
the mikuni runs a higher float level so the jets tends to be leaner than the Keihin.

hope its some help.

Interesting site. Thanks again! ...Van

Spannerman (or anyone else out there), what are your thoughts about the VM type compared to the flat slide?

_________________
1980 Honda CR125R

I bought a VM 32mm and runs nice now after i had to muck about with the needle height to make the bike run slightly richer.

I also bought an oversize flange from Donny at Vintage Elsinores and it all goes together lovely with stock airbox

You may need to buy a slightly longer than stock throttle cable though.

Hope this helps

Ruairi, where did you buy it, how much did it cost and do you have the specs or model/part number? Was this for a stock 1980 CR125? Sorry for all the questions ...Van

_________________
1980 Honda CR125R

I've noticed you've been talking about a 32 mm carb

The 1980 CR125 run's a 34mm carb and can go larger, I'm running a 35mm.
The 1979 CR125 run's the 32mm carb.

Thanks. I was unsure if the stock carb was 32 or 34. Do you think the carb below would give satisfactory results for moderate trail riding?

http://www.bikebandit.com/partsbandit/product.asp?pf_id=5081424&dept_id=2107456

_________________
1980 Honda CR125R

Hi Van

Sorry to mislead you slightly. My 32mm was for my 1976 125 Elsie.

I bought it from Donny at Vintage Elsinores who I can recommend.

Try their website http://www.elsinores.com/

best regards Ruairi

I theory any carb will work provided its the correct fit and size.
That carb looks fine provided its the correct fit and JETTED TO SUIT.
IMHO that carb is jetted way too lean.

I'm curious whats wrong with your current carb ? The stock 34mm Keihin isn't noted for
being troublesome, with stock jetting it should run very well.

Well the thing and all of it's parts are 27 years old. The rubber parts are deteriorated, some stripped threads here and there. Replacement parts cost a fortune. Not worth re-building. Yep, that Mikuni does seem to be jetted a bit lean. Wonder why that is and for what application it's for. Guess I could order larger pilot and main jets. Still pretty cheap compared to the price of parts I've see for the original Keihin. Thanks. ...Van

_________________
1980 Honda CR125R

I went to that web site. They show a 32mm Mikuni for 1979- 81 CR125 but give no specs....Van

_________________
1980 Honda CR125R

Spannerman, what would you think about the carb and jetting of this 34mm listed at the link below for my stock 1980 CR125? Thanks....Van

http://images.google.com/imgres?imgurl=http://www.psep.biz/images/fue-intake/mikuni%2520carbs%2520copy.jpg&imgrefurl=http://www.psep.biz/store/mikuni_carburetor.htm&h=295&w=450&sz=27&hl=en&start=2&um=1&tbnid=Wo_dkVOTzWca6M:&tbnh=83&tbnw=127&prev=/images%3Fq%3Dmikuni%2Bcarb%26svnum%3D10%26um%3D1%26hl%3Den%26sa%3DG

_________________
1980 Honda CR125R

Better than that other one however whatever you end up with you will end up spending a lot of time jetting it to suit.
I now know of a stock 1980 CR125 carb for sale here in the UK ready to go (it was offered to me but I'm sorted now),
I've not seen it but I've been assured its a good one.
I can email you the guys email address if your interested but be aware the exchange rate is against you at the moment.