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Just installed a CRF150F carb on TTR 125, not working properly...

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So, I put the CRF150F carb on, it's got a 40 Pilot and I think a 95 or 98 Main. Air screw is turned out 1 3/4 turns. It will start with full choke and sounds ok, but misses a little bit with some throttle. When I notch the choke down to the mid setting the idle goes high and then it dies after 3-4 seconds. It dies in 1 second if I turn the choke off.

Any ideas on what's going on here?

It also seems slow to go back to idle after letting off the gas. Did I get a bad carb?

Thanks!

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sounds like it could be an air leak causing it to run lean. spray some brake clean or carb clean around the engine and see if it changes the idle.

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I suspected an air leak. If it's leaking at one of the boots/manifolds, what can be done? I will try cranking down the clamp tighter.

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If the manifold is leaking and it happens a lot, tighten the clamps will only make it worse. You have two options buy a new one or what I do, is grind off all the rubber from it and replace it with some radiator hose. It's simple, easy and cheap. Plus you probably need to go bigger on the main. I used a 200x carb with almost the same carb and I ended up with a 120/122 main.

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Alright, so I moved the clip into the highest setting, and tightened the air screw and now it will run without the choke on. It still runs like crap. Plug is sooty black, but the main thing is how it doesn't return quickly to idle. Is that a sign of a leak? I put the hose clamp on trying to get it tighter, but not sure if it helped any. Here's a video of it sputtering and returning slowly to idle.

http://www.youtube.com/watch?v=WD92yWPYLVk

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Oh, SocalXR, got any pics of that radiator hose manifold replacement?? Do you think the rubber boot has a hole in it?

interesting fix wouldn't mind seeing this myself.

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Finally got it. I first put a 110 main in and it got better on top. Then backed the air screw out to 2.5 turns and a little better. Dropped the idle screw down to where it wouldn't idle unless you gave it gas and that mostly solved the hanging idle, but what it needed was a 42 Pilot. Once I put that in the idle was much higher so backed that down to a reasonable rate and she works like a charm now. Noticable power improvement over stock carb!!

Now I have a sticking rear brake problem. It did this once before in the heat of a battle and I figured it was just hot, but it did it just today while cold... Hmmm. Might be time to put the YZ swingarm and rear wheel.

All that said, it wasn't a leak. I spent a lot of time trying to find one, but it just needed a bigger pilot for the hanging idle issue.

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It was about 45 degrees this morning and TTR's are notoriously tough to start cold. On some days if it hadn't been ridden in a while and if cold you'd wear out the battery. Today I walked past and decided to check it... I hit the button and had instant fire.

Excited about it. Throttle response and power feel great. Got a buddy with a stock carb that I'll ride with tomorrow for side by side.

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I loved my 200x/150f carb over the stock unit. I was using my carb for mr xr120, so it was already closed to dialed. I ended up witha 115 or 118 main I think though. But yea 40/42 pilot and needle clip about 2nd from bottom. It gave it some needed umph.

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Thanks for the input here, guys. Haven't ridden it as much as I'd like just yet, but the broader, stronger power makes for more fun and easy wheelies up a nearby hill. Cool to feel the extra torque. Also, it was neat to see how just the slightest change in the orifice of a jet would make such a big difference and solve an issue.

One more thing, on the youtube clip up there, what's that little round, flying saucer looking thing attached to the carb behind the slide assembly?

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It some EPA thing.

Can they be removed or is it better just to leave them on?

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