Apologies in advance for probably the dumbest questions to appear on this learned forum. Where do i find the power jet in the TA21A carburettor? looking at the bottom of the carb body with float bowl removed there is a central group of 3 orifices. One holds the main jet, needle jet holder/emulsion tube, one holds the slow/pilot jet. On my carbs the third holds a thick brass tube that extends almost as far down as the main jet, with no slot or hex shape to facilitate removal and it is resistant to gentle twisting with pliers. It is also not readily apparent in the parts diagram. The carb model number is on the float bowl only. Do i even have the right body?

Also, can the needle be replaced without removing the whole slide operating mechanism? The manual says not to remove it unless necessary and there are two security screws which require a special tool holding the back plate to the carb body so i think they are serious about not removing the back.

By way of context: trying to fit the jetting kit which requires plugging the power jets.

Thanks for all help.

http://www.nsr250.net/forums/viewtopic.php?t=14575&highlight=power+jet

I think it's the same for TA21 carbs
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Why do things simply when you can complicate them

Thanks again RobH! I think that screw is referred to in the manual as a "plug". I had a peek under there but could not see anything that looked like a power jet but i'll look again. That seems consistent with the manual and the parts diagram.

Ha, some good light and magnifying glass and found the little blighter! Thanks RobH, right again.

Needle jets are removed from under the top plates
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Why do things simply when you can complicate them

OK, I'll have to look again. It looks like there is some kind of retainer plate holding the needle down and it bends out of sight with no obvious way to remove it. what am i missing?

The needle retainer is indeed just a spring clip. Hold the throttle wide open, and just pop the retainer up with a small flat bladed screwdriver or similar. Once you've done it, you won't believe just how beautifully simple the mechanism it is!

I just knocked this up to illustrate how the retainer sits on top of the needle. It's not 100% accurate, as it's 1AM and I didn't want to go rummaging for an actual holder to measure up, but I'm sure you can get the idea! 😉



The standard retainer pushes down on the "fixed" head of the needle, and the kit retainer pushes down on a circlip. The kit retainer has a brass bush to take up the difference between the thick head of the stock needle and the thinner circlip used by the adjustable needle.
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Andy.
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Thanks Andy. Yeah i actually managed to figure it out last night, after a closer look and you're right. Beautifully simple. I have to say this is the most complicated carburetor i have dealt with but it is all falling into place.

Continuing saga and nothing online about these carbs. This is about the float valve seat. The fellow who worked on this bike reported carbs leaking fuel hence this inquiry. The old seats themselves look ok after polishing with a Q-tip in electric drill, but i am not convinced there is no leaking between the seat and carb body. In fact i tried a little pressure test by blowing on the fuel line with fingers blocking the float valve seats and air flows freely. Seems to me that all fuel should have to pass through the float valve so this seems to indicate a problem. Please tell me the seats are removeable because i have already tapped one out to take a 1/4" NC bolt. can't shift the seat. I will try to make a puller but it will have to rest on the posts that hold the pin for the float valve so can't put much pressure on there.

Any tricks, suggestions much appreciated.

Better idea for a puller will be a tube to fit over the seat and brace against carb body.

I think you're making a mountain out of a molehill!

Luckily for you, T2Racing have replacement float valves and seats available now, but seriously, I've never seen a seat that couldn't be cleaned up with the lightest touch with a Q-tip and a dab of Brasso, and personally, never even needed new float needles! The biggest problem has been the rubber float bowl gaskets not sealing.
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Andy.
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Hi,

As Andy mentioned, T2 Racing in Japan sell float valve seats but they also provide a service whereby they would change them for you if you sent your carbs which isn’t easy in your case.

There is a very useful video on YouTube “ fix a lawn tractor that floods, Briggs and Stratton carburettor repair video.

Was considering changing mine till I found out the cause was a damaged float valve tip.

Good luck.

of course, a 10mm 1/4" drive socket. Just hope the threads will hold in the brass.

Thanks Andy. I have the new seats and needles. was debating whether to change the seats but just want to be sure there are no other issues when setting up the jetting. Besides, I'm into it now because i've already tapped the seat, so no going back.

Too late now then! So, in for a penny, in for a pound, as they say!
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Andy.
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