What carb is this?

[AJBit187]

Hey crew!

I’m rebuilding my son’s 2007 CRF50 that he outgrew a long time ago to hand down to one of his sisters. He only rode it for a few months when I picked it up in 2013. I never got a full list of mods from the previous owner but it was a pit bike when I bought it. 

That said, I noticed it had a rough idle so I ordered a new OEM carb and just got around to opening it to find that this carb is much smaller than what’s on it. Can anyone tell me what carb and size this is? Should I go back to a stock one?

Edited July 23, 2019 by AJBit187

[CRF James]

Appears to be a knock off PZ19. Whether you should you use or go back to stock will depend on what has been done to the engine, exhaust, and airbox.

Post some pics of the bike so we can try and figure out what’s been done to it.

[AJBit187]

Thanks for the info!

I haven’t done a top end, but it looks like it’s been apart before. Not familiar with this bike so not sure if you can tell much from these pics.

[AJBit187]

Is the pz19 the same size the XR70 takes? I saw talk about using that size carb after going to a big bore.  

[CRF James]

The markings on the head indicate it’s a stock head but the cylinder, intake, and exhaust are all aftermarket. A stock cylinder would be black and marked “49cm3”. As your cylinder is not marked it is kind of hard to know exactly what size piston is in there without opening it but considering the bike had a larger intake, carb and aftermarket pipe I would assuming it’s has a big bore kit.

 

Perhaps one of the other guys will recognize the cylinder.

 

[CRF James]

Is the pz19 the same size the XR70 takes? I saw talk about using that size carb after going to a big bore.  

 

Yes, the stock 50 carb is 13mm and the 70 carb is 17mm.

 

Whether you should put the bike back to stock or just work with what you have would really depend on your daughters age and riding experience. If she is 5 or 6 y/o with no riding experience, a 50 with a big bore kit might have a bit too much torque for a beginner and scare her away from the bike as the added torque makes that front wheel come up very easily.

 

[AJBit187]

Right. Yeah, I’ll have to also look at the cost of going back to stock vs just staying with the big bore, assuming that’s what it is. I’ll tear it apart soon and see what I really have here. Thanks so much for the help!

[KillerK]

This is most likely an 88cc big bore kit. Very common. I would stick with what you have. Essentially this doubles the horsepower which is not a bad thing. It will still be reliable and won't be harder to ride. It will just have a lot more torque.

If there is no smoking or other issue there is no need to rebuild it. If maintained it will outlast your kids.

If you do decide on a rebuild. TB or "trail bikes" have very inexpensive and reliable parts. 

[AJBit187]

Thanks for the info guys. I really appreciate it. So I ordered a PZ19 carb to replace the eBay knock off. The PZ19 I ordered has its own petcock. I’ve been doing searches trying to find a diagram or pictures on how everyone else has run hosing on these. Any ideas?

[AJBit187]

I guess what I’m confused on is the in/out of the petcock on the carb. 

[KillerK]

 

I just looked at my 2003. The on/reserve is built into the petcock.

It appears that the carb you have is for an older steel tank where the reserve/on is built into the tank and has separate lines coming out.

You should be able to plug one and put the fuel line on the other. You will just have to have it turned to on if fuel goes in the on inlet or vice versa.