Carb Clarification.. I'm Done with mine

[FastCletus552]

Are all carbs basically the same? Meaning if my bike has a carb ID that's 28mm, would any 28mm Carb work? Its for a trials bike (beta techno 250 2 stroke), so it has to have some kind of difference than a carb of the same size like maybe for a YZ250, or does it?

I bought my bike in parts (project bike) It came with the carb but one can only assume its the right part. I bought a rebuild kit for a Mikuni VM 26 (research told me that that's what it might be) and it didn’t fit so I assume I have a VM 28. (which was the other option) NOONE carries parts for this carb. I want to buy a new carb. One that is more common and is easily accessible to parts but want to be certain a new one will fit my bike. I’ve spent way too much time trying to figure this out. Any help is appreciated

 

[usedtobefast]

Not very standard and switchable.

The carbs have a model number on them, if you find that exact same model number (say on eBay), then that should bolt up with no problems, but all the carb internals could be different ... jet sizes, needle, slide ... all might be different.

If you have details of your carbs jetting (like a manual) you could compare that to what you buy and adjust.

But just having a 28mm carb on a bike and buying some other 28mm carb may or may not work. And probably not.

Maybe find an eBay carb for some other trials bike ... that might be a better shot at it. That would make it a better shot in the dark.

 

[usedtobefast]

Looks like some good info on trialscentral.com and trialstribulations.net and thumpertalk (of all places)

And there is trialstoreusa.com, but they would want to sell you a brand new one. But might be worth calling them, maybe they have some tips/hints, like what else might fit that is more common.

Also, on eBay, do not buy one of those super cheap carbs from China ... they tag them with whatever you look for ... like you search for beta techno carb and they stick that on the line saying it fits a Beta. Just not true and junk.

 

[buellistic]

Just my 2 cents.
I bought a older Suzuki King Quad. For 500$
The carb had a broken diaphragm.
The dealer wanted $600 for a new one. I said No Way..
I found a cheap carb on Walmart for $60. Did Alot of Visual. Comparisons
Before buying..
It Works Great!...

If you go this route do Not search by bike.
Only carb size...

 

[FastCletus552]

I ended up just picking up kehin version of the Mikuni. checked all measurements. I might need to make a couple adjustments but from the carb folsk I talked to this one will work. MIght need to adjust jets, but thats easy. Lets hope this works!! I need to ride

 

[elemetal]

PWK 28mm will work, you may have to mess with fitting the rubber boots on either end but a quick check of the PWK dims and the Mikuni you have will verify that. Also check body length, trials bikes aren't too forgiving with space.

You cannot swap a 4t carb for a 2t carb but can swap the 2t carbs assuming they fit. Needles for PWK are "D" series; pilots usually around 35; MJ around 120.
It is very common for trials bikes to come with Del'Orto carbs because they provide very smooth power; higher class riders/bikes usually come with a PWK 28 for quicker response. At most you have to add a rubber sleeve at the airbox boot to reduce diameter, they do that with the 125's for sure.

trialscentral is the go to info source for all this type of stuff and as stated above, ADVrider has a good trials section as well.


Just saw your response after I posted, you made the right move.

 

[OaklandF4i]

The carb on the Beta Techno is either a Del Orto (some) or the Mikuni VM26-208 (most). Thats what is suppose to be on there. There should be some markings on the carb body to identify it.

A carb is measured by the opening diameter closest to the engine. There may be many different models of any one series of a carb from Mikuni or Keihin in any particular size. The series carb you have is a VM, in a 26, and a 208 model. Models in the same series and size may vary in height (bottom of bowl to top of slide) and length (intake to air box) amongst other differences anyone manufacturer might specify for their bike.

So to answer your question, no, any 26 or 28 mm carb will not always fit (size) and there may be slight internal differences affecting its running.

That said, most of the basic internal parts of any particular size and series are often interchangeable, ie VM26. Sudco keeps a part list for the VM series to help you online. Or call them.

The Beta Techno is was a pretty popular trials model, there should be a lot of folks on the TrialsCentral.com forum that could help you identify the carb and even where to source the parts. Or ask one of the guys in the stickied trials thread at the top of this forum what is the best online source/forum for Beta info.

If there are no markings on the carb anywhere on the body, I would a suspect chinese knock off. If it has markings, you should be able to identify it. Then reach out to a trials or beta specific forum for the best place to source the parts.

Just my suggestion. Good luck. :thumbup

Edit: Boom...... Luke to the rescue. He knows his stuff and would certainly listen to any suggestions he has. arty

 

[KooLaid]

that's the problem I often see with the chinese knock offs. They'll look the same but then you'll get goofball sized threads and porting is just different sometimes. I've had successes and failures with them.