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Hey guys, a buddy of mine gave me a Walbro yesterday and I wanted to see if I could use it. There are numbers on the side of the carb that say it is a WT 275. It just seems so small for a carb for our bikes and not sure if it will be worth the time to try and adapt it to make it work.. let me know what you guys think..
 

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As long as the mounting holes on the carb line up with those of the intake manifold/gasket or the reed block then you should be fine. I was pretty amazed at how small the WT813 carb is when I put it on my Zenoah, but the performance gains you'll experience are pretty ridiculous.

Consider running a boost bottle with it. From my understanding it doesn't have an internal accelerator pump, so it could potentially bog down under low throttle. I couldn't find the carb on Daves motors to get any more info, but it looks like it should bolt right up. I assume your bike is reed ported, which I know significantly less about, but if the holes line up and there aren't any leaks or gaps it should work fine.
 

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So I did a bit more research on this carb. The WT275 is commonly used on Ryobi's small 2 stroke engines (string trimmers/tillers) and from what I've found none of the engines list over 37cc. That's not to say it won't work, since most of what I found were people complaining about it leaking from the diaphragm, which I take to mean the carb was pushing more gas than the engine could burn. It was replaced by the WT685.

So I'm not sure it was designed to work with a 47/49cc engine, but check it out. You may find that it works great, or find that it leaks from the diaphragm due to some engineering mistake.

Or play it safe and trade for the 14/14 which will definitely fit.
 

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Discussion Starter #6
So I did a bit more research on this carb. The WT275 is commonly used on Ryobi's small 2 stroke engines (string trimmers/tillers) and from what I've found none of the engines list over 37cc. That's not to say it won't work, since most of what I found were people complaining about it leaking from the diaphragm, which I take to mean the carb was pushing more gas than the engine could burn. It was replaced by the WT685.

So I'm not sure it was designed to work with a 47/49cc engine, but check it out. You may find that it works great, or find that it leaks from the diaphragm due to some engineering mistake.

Or play it safe and trade for the 14/14 which will definitely fit.
I was finding the same thing when I was punching that number on Yahoo, Ryobi kept popping up.. as far as a bolt on Im not sure at this point, I will be checking on this later but dont they usually need a smaller hole at the bottom of the intake for Idle purpose(sorry not really sure of the use or name of it) but I have seen on the cat-eye and the x-1 carbs right below the intake there is a smaller hole that you have to align with on the carb, dont you need that same set up for this type of carb? thanks again for the info!
 

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I was finding the same thing when I was punching that number on Yahoo, Ryobi kept popping up.. as far as a bolt on Im not sure at this point, I will be checking on this later but dont they usually need a smaller hole at the bottom of the intake for Idle purpose(sorry not really sure of the use or name of it) but I have seen on the cat-eye and the x-1 carbs right below the intake there is a smaller hole that you have to align with on the carb, dont you need that same set up for this type of carb? thanks again for the info!
To be honest I don't know the difference between carbs built for a reed ported engine and those for a piston ported engine. My X7 didn't have a hole below the intake and technically it's just an evolved cat-eye. I assume the hole at the bottom would be dependent on whether it's a barrel or butterfly carb. If you have a butterfly then the engine will be able to idle thru the intake even with the valve closed, but with a barrel they may need the extra hole to provide enough air for idle when the barrel is closed.

Which style of carb is it? I couldn't see the valve style from the pictures and am not familiar enough with this carb to just know.
 

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Looks like a 13mm carb, to small, even the 16mm Walbros WT 603 & 813 have a 12.7mm venturi. I have had alot of trouble already w/ Walbros on my Cag, cause the fuel & air has to travel thru the whole engine to get to the top. Its like a lag at the start, while the 813 w/ the accell pump works great on my scooter.
Measure the back hole of the carb, thats is the size, if its 13mm its a 13. My 26cc engine has a 10mm walbro on it.
My best 2 & fastest engines are running Sam's 12mm stock carb, Swirl bored to 17mm in the front and 14mm in the rear w/ a .70mm main jet. He bores thru the carb body, they suck aititle air around the sides of the piston, which makes it idle alittle high, but they work great.
 

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Discussion Starter #9
Looks like a 13mm carb, to small, even the 16mm Walbros WT 603 & 813 have a 12.7mm venturi. I have had alot of trouble already w/ Walbros on my Cag, cause the fuel & air has to travel thru the whole engine to get to the top. Its like a lag at the start, while the 813 w/ the accell pump works great on my scooter.
Measure the back hole of the carb, thats is the size, if its 13mm its a 13. My 26cc engine has a 10mm walbro on it.
My best 2 & fastest engines are running Sam's 12mm stock carb, Swirl bored to 17mm in the front and 14mm in the rear w/ a .70mm main jet. He bores thru the carb body, they suck aititle air around the sides of the piston, which makes it idle alittle high, but they work great.
it does seem to be an extremely small venturi and a carb altogether.. I didnt think it would be worth my time to try and adapt it. I held it up to the stock manifold and it wouldnt be a direct bolt on..
 

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Do you have a ruler or something you can measure the front and back holes in the carb. Looks like a Purge card, no bulb have to run a metal line from the cases to the carb, I believe. Looks like you could bore out the front some. Try to get the size of the small inside part of the carb.
Most of them carbs have a 12.7mm venturi, and 16mm rear, and 13 to 19mm up front. You need a different manifold to mount a Walbro to a Cag. See the alum intake manifold in the photo $18 at PB Parts. Make sure you measure the center of the bolts holes on the carb and that it matches the manifold if you order one.
 

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