Carb Alternative for RXB150 or other YX engined pit bikes

[Goob]

I have been messing with setting up the Mikuni 26mm carb that was supplied with my bike. It is a pain in the butt that you have to take the carb off to adjust the pilot fuel screw. I tried a small 90 degree screwdriver ratchet from Harbor Freight, but couldn't get the blade engaged.

There is some confusion on my part because this carb is sometimes called a VM26, but a real VM26 is actually a 30mm carb that I am considering using on my TT250. They are completely different.

https://www.scooterpartscatalog.com/...or-114-20.html)

https://www.denniskirk.com/mikuni/26...prd/165142.sku

However, there is a true VM carb, that has better access for adjustment and easier to find parts. This is the flange mount VM22.

https://jetsrus.com/photos/photo_mik...dimensions.JPG

https://www.denniskirk.com/mikuni/22...prd/165139.sku

However, it has a 49mm on center mounting flange rather than the 48 mm for my stock 26mm carb.

Has anyone used this true VM22 on the YX or similar engine? Is a different manifold needed for changing to 49mm or for clearance issues?

[culcune]

Contact Pete at Kronik Racing. He is the Vader 125 guru, but prior to dealing with Vaders, he was dealing with pitbikes and racing them.
www.kronikracing.com

[Goob]

I have been doing more searching.

I found TboltUSA.com. Others probably already know of them. They have lots of parts and tech information. They sell SSR and other pit bikes.

This is what I will likely do: a true VM24 carb with a spigot manifold adaptor.

https://tboltusa.com/store/tbparts-m...rb-p-1369.html

https://tboltusa.com/store/26mm-carb...oot-p-599.html

This way I get the good jet access in the bottom of the bowl and pilot screw adjuster where it is accessible.

Also, I am getting the VM26 (which is actually 30mm) for my TT250, so I will be able to use the same jets and become very proficient at tuning.

[Goob]

Originally Posted by culcune

Contact Pete at Kronik Racing. He is the Vader 125 guru, but prior to dealing with Vaders, he was dealing with pitbikes and racing them.
www.kronikracing.com

Thanks. I sent Kronik an e-mail regarding my VM24 with adaptor idea to see what he thought and if he has anything similar to recommend.

[Goob]

Originally Posted by jeffrey

Yes a Mikuni VM26-606 with the adaptor to mount the spigot carb to the intake flange. I have two of them one on a Pirahna 150 on a Honda trail 70 replica.

Jeffery,

Is the VM26 too big? It is really a 30mm...the same as I plan to put on my TT250. If I read the Mikuni convention right the VM24 will actually be a 26mm, which is what I have now.

Also, the VM24 is a bit smaller...matching more closely to what I have. The fit is pretty close, especially at the top near the fuel petcock. But, I guess I could relocate the petcock. I am OK with the performance as it is. I just don't like the carb.

https://jetsrus.com/photos/photo_mik...dimensions.JPG

Is your Pirahna 150 a stock YX engine? If so, how did you set up the jets (main & Pilot) and needle position? I am in Denver, 5280ft, so your settings may not apply, but I would have a starting point.

Thanks a bunch!

[Goob]

Originally Posted by jeffrey

Yes it is stock I never messed with the jets just mounted it up and it ran fine. I only have a red pod filter and a header on the engine. All the parts exept the header came from tboltusa.

Cool Man! What altitude are you at? So, no clearance issues?

I will go for the VM26 with adaptor.

This is great because once I change out my TT250 to VM26 I will have only one type of carb to mess with. Right now it has a KOSO PWK (Keihin knockoff) 30mm flat slide on it that I think is too much for a stock CG250 engine. But, it runs good, so I can wait on this change out.

The carb at Dennis Kirk is $84, but that doesn't include the $14.50 worth of main jets that Tbolt gives you for $110. Only a $11.50 difference. So, I'll buy from Tbolt as I like their site and they have a lot of parts and good info.

[dirtbkr188]

Just an FYI, the Genuine Mikuni spigot mount carbs are measured at the ID of the flange intake (Letter A in the jetsRus photo in the original post). They are straight bore carbs, meaning the measurement at the spigot opening is the same as the measurement where the carb throat and venturi meet (at the throttle slide). A VM26-606 is a 26mm opening, you'll find that a Genuine VM24 will measure 24mm ID.
The various flange-mount Mikuni-clone carbs that come standard on a lot of Chinese pitbikes will measure to be quite smaller than the intake opening, and usually have a rounded rectangular bore size at the throttle slide.

[Goob]

Originally Posted by dirtbkr188

Just an FYI, the Genuine Mikuni spigot mount carbs are measured at the ID of the flange intake (Letter A in the jetsRus photo in the original post). They are straight bore carbs, meaning the measurement at the spigot opening is the same as the measurement where the carb throat and venturi meet (at the throttle slide). A VM26-606 is a 26mm opening, you'll find that a Genuine VM24 will measure 24mm ID.
The various flange-mount Mikuni-clone carbs that come standard on a lot of Chinese pitbikes will measure to be quite smaller than the intake opening, and usually have a rounded rectangular bore size at the throttle slide.

Thank you.

I have had folks on the CR Dual-Sport blog tell me the VM26 is a 30mm. I think your information is more document oriented, so likely correct.

So, I think at 26mm this should work with the RXB150.

I am also considering it for my CSC TT250. Right now I have a KOSO 30mm flat-slide on it, which gives good performance, but at the cost of fuel mileage. I am only getting 60mpg and would like to approach 70mpg. This is a commuter bike, so mileage trumps power.

[ss27gogeta]

Did you go with the tbolt vm26 setup for your rxb 150 I'm looking at doing a diffrent carb setup on mine as I'm having a lot of issues getting my stock carb dialed in and would like a carb I can get parts for eaisier.

[ss27gogeta]

Double post

[ss27gogeta]

https://tboltusa.com/store/tbparts-g...ni-p-1220.html

is this the kit I need.

[ss27gogeta]

Originally Posted by jeffrey

Yes, Your engine has the KLX head. That is alot of money and you don't need the intake or the throttle cable I got by with just the adapter and carb. If your intake has 48mm bolt spacing at the carb then I think you could just get the carb and adapter.

Thanks I went ahead and orderd the kit. After buying the carb separate and the boot spacers and gaskets. it was only about a $20 difference. And they did not have the carb in stock by its self either only had the kits left. Hopefully this gets my rxb runnig right finally.