Vintage Dirt Bike Q & A

Hi guys.
Firstly I'd just like to introduce myself, I'm Dave, from Bendigo in Australia.
I don't own a CR125M, but I do own an engine for one...
I've recently purchased an unfinished project which is a go kart fitted with a CR125M engine.

I'm unsure what year engine it is - where the engine number is located has been broken off - refer to pic.

If you could assist me with your expertise, it'd be much appreciated.
I'm trying to rebuild the carb, it was leaking fuel so i removed it to try & figure out why, the old seals are all hard and cracking.
I need to find a carb kit/gaskets etc, but i', unsure what year I should be looking for.
All the carb kits I've seen online seem to show a round float bowl seal - mines more rectangular, however going by other pics I've seen it does look like it's the original CR125 carb.
Markings on it that I've found are "Keihin Japan", and "056A" with something small underneath that, that I can't quite make out.
Also, could someone advise what the hose fittings I've pointed out on the carb connect to? And is the number 3 arrow the choke?

Thanks!

If that's the original carb, it's a 1975 motor (the '74 carbs are stamped 005A, '76-'78 are 083A). Confirmation can be found on the ignition components; all but the coil should have date codes stamped on them, probably 4A or 4B.

It would be a good idea to replace that carb, since at a minimum it will need a choke assembly and rebuild kit, and most likely a needle jet if you want it to run reasonably well (that's nearly $100 US plus shipping, if you can find the choke and needle jet). A complete used carb (004A / 005A / 056A / 060A / 092B will drop right in, 083A needs the manifold too) can be found on eBay for a reasonable price if you're patient, and may run just fine.

The round O-ring in the rebuild kit IS the bowl gasket; you'll have to glue it into the bowl like the factory did (I've done it twice, section by section - it's a real pain). Pre-formed gaskets are now available on eBay, I think they're $10 each or so.

The small brass hose fittings are for carb vent and overflow hoses. Eventually you'll want to connect hoses to them and run them below and behind the motor.

When's it's running well, that kart should be a lot of fun.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

Cheers thanks for the help Ray.
I had a look at the CDI unit, but cant make out what the sticker used to say so no idea what year it is.

I've had a bit of a look but can't find any of the carbs you mention on ebay etc, or the preformed bowl gaskets.
Are there any common, easy to fit replacement carb's that people use?

Dave,

Here's the float bowl gasket:

http://www.ebay.com/itm/honda-1973-1984 ... _611wt_920

... and here's a good rebuild kit.

http://www.ebay.com/itm/New-Carb-Repair ... 1701wt_824

Sure, there are plenty of other carbs you can put on that motor. It can be quite expensive, but if you get the new carb jetted right it should run really well.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

Thanks a million Ray!
I'll be sure to update with more photos & some video's once we get the thing going.

I'll most likely take it to a local bike mechanic who specializes in classic & race bikes to get it all checked over
and tuned up.

Dave