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yz80/TTR125 carb swap ?

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i have swap over my TTR125 20mm carb with a YZ 80 26mm it is running well but is a little lean on the needle jet i have rung up plenty of mikuni dealers and they tell me i need to know a series number for a p-4 needle jet and don't know what p-4 needle jet would fit can someone please tell me the series for the p-4 needle jet that fits the 26mm carb as i have searched the net high and low and still cannot find it.

:thumbsup: can someone please help me out as it is very frustrating. :ride::applause:

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The P-4 is in the Yamaha YZ80 K model carb. Should be available from Yamaha.

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Can you please tell me what jet needle to use? I have a 5DL1 needle will this work with the P-4.

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Did you find the correct series for the needle jet? I've been unable to find it also. I guess I could bore out the stock one a bit and try it.

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The Yamaha and I mean the Yamaha YZ80 carb is a lot different from the Mikuni carbs sold as VM26's. If you have a Yamaha version needle and needle jet out of the K series bike will work well with a bit of testing of clip position and main jet on the TTR depending on other mods. To get that needle and needle jet it has to come from Yamaha.

The diameter of the needle jet holes are in the Mikuni manuals that can be found on various carb websites. They are a pretty precise dia.

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The last generation of round slide carbs from the YZ80 make great improvements to the TTR for little $$$ and fit right up with no modification. (2.5mm can be milled off the engine side for a perfect fit, but is not necessary.) They are particular about jetting, but make very good power. Look on Ebay and in junk yards for a clean model from 1982 to 2001. They are all basically the same and can be had for as little as $20. Strait from a YZ, they will be very rich on top and bottom, and lean in the middle on the TTR. A good place to start with rejetting is a 20-22.5 pilot and 140-150 main. The best needle is still undecided, but any of the richest Mikuni 4 or 5 series needles could work. (The stock YZ needle seems to fall just on the rich side of the middle of the charts in the Mikuni catalouges.) Slide sizes could also be changed. The YZ's slide is a #3. A #2 or even #1.5 could work well? Many folks have opt'ed to replace the stock O-0 needle jet with a P-4 size and keep the YZ needle. This seems to work well too. But remember, jetting will be different on nearly everyone's bike, so what works great for one, may not work as well for another. These are all just generalized places to start. Getting your bike finely tuned is half the fun. But overall, the YZ80 carb mod is very much worthwhile for the added power and response.

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The last generation of round slide carbs from the YZ80 make great improvements to the TTR for little $$$ and fit right up with no modification. (2.5mm can be milled off the engine side for a perfect fit, but is not necessary.) They are particular about jetting, but make very good power. Look on Ebay and in junk yards for a clean model from 1982 to 2001. They are all basically the same and can be had for as little as $20. Strait from a YZ, they will be very rich on top and bottom, and lean in the middle on the TTR. A good place to start with rejetting is a 20-22.5 pilot and 140-150 main. The best needle is still undecided, but any of the richest Mikuni 4 or 5 series needles could work. (The stock YZ needle seems to fall just on the rich side of the middle of the charts in the Mikuni catalouges.) Slide sizes could also be changed. The YZ's slide is a #3. A #2 or even #1.5 could work well? Many folks have opt'ed to replace the stock O-0 needle jet with a P-4 size and keep the YZ needle. This seems to work well too. But remember, jetting will be different on nearly everyone's bike, so what works great for one, may not work as well for another. These are all just generalized places to start. Getting your bike finely tuned is half the fun. But overall, the YZ80 carb mod is very much worthwhile for the added power and response.

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Has any one tried a cr80, rm80, or kx80 carb? I know the forks off of all the 85 two smokes work, but do the carbs. Until then I will look for the yz80.

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The Yamaha and I mean the Yamaha YZ80 carb is a lot different from the Mikuni carbs sold as VM26's. If you have a Yamaha version needle and needle jet out of the K series bike will work well with a bit of testing of clip position and main jet on the TTR depending on other mods. To get that needle and needle jet it has to come from Yamaha.

The diameter of the needle jet holes are in the Mikuni manuals that can be found on various carb websites. They are a pretty precise dia.

Hey thanks. I've got the main and pilots, so for now I'll just try running the stock YZ needle in the richest position and see how it does. Hard to find the needle jet from that carb, even from the dealer.

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The stock needle in my '86 YZ carb is a Q-2, not and O-2, meaning it will run richer than a P-4, not leaner.

Anyone used the Q-2 needle jet in a YZ80 carb on a TTR with a 150 kit? I can get a Q-0 from the dealer to lean it up a bit, but the P-4 seems hard to find. I'm goint to try the leanest clip position and see how it does

Thanks

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I dont know if anybody has said anything or answered your question fully yet, but if you havent figured it out, call up Sudco. They seem to know there stuff if you get the right person. If you ask one, and they dont know, call back the next day and hope its a new one. Go to www.sudco.com .

Good luck I guess...maybe it will help you. I had a different carb that I used, it was not off of a YZ80, but it was an aftermarket carb that could be swapped in on one. I cant remember the model, but it kicked assss.

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The stock needle in my '86 YZ carb is a Q-2, not and O-2, meaning it will run richer than a P-4, not leaner.

Anyone used the Q-2 needle jet in a YZ80 carb on a TTR with a 150 kit? I can get a Q-0 from the dealer to lean it up a bit, but the P-4 seems hard to find. I'm goint to try the leanest clip position and see how it does

Thanks

Im in the same boat! What main and pilot did you use? I have the 150 kit, pod filter, and a WB pipe.

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hey foxmoto i have a carby that i bought straight from mikuni mine is a VM26mm basically the same on the yz80 what settings have you gone on your carb i have main=250 pilot+45 needle=5J6 needle jet=P-O but it's still lean in the middle so i tried needle 5DL1 and i still think i need P-4?? :thumbsup:

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i am going to try drill out my P-0 to a P-4 needle jet any idea how i could do it ?? what size drill bit ?? :thumbsup:

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Im in the same boat! What main and pilot did you use? I have the 150 kit, pod filter, and a WB pipe.

Well I have 140 amd 150 Mains. 17.5,20,22.5, and 25 pilots. I got these from Sudco. Waiting on the head to come back from PRC before I can test it.

I can post Sudco part numbers for the mains and pilots if anyone want them.

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hey foxmoto i have a carby that i bought straight from mikuni mine is a VM26mm basically the same on the yz80 what settings have you gone on your carb i have main=250 pilot+45 needle=5J6 needle jet=P-O but it's still lean in the middle so i tried needle 5DL1 and i still think i need P-4?? :thumbsup:

I am not sure what mine were, if i remember right, your main would be too big I think. Also, I bought my P-4 needle from Sudco. I wish I kept it, but I sold it for another $50 with my bike. I had extra parts and stuff too, but they went with it. I know for sure I bought a P-4 needle. I am 95% sure that that main is way too big. The pilot I think is in the range I had. I had 40, 45, and 50 I believe that I messed with. For some reason the main numbers dont come back to me. Hope this helps a little bit :ride:

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