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TTR 90 experts, PLEASE HELP!

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I have been working on my sons 90 for two weeks and can't get it straightened out. The fuel valve went bad over the winter and let gas into the carb. The bike will start, but it will not idle, and it spits and sputters under throttle. If you remove the airbox cover, it still will not idle, but will run like a scalded dog. I have cleaned the carb 6 times, new air filter, new plug, new gas. I need help, my son is DYING to ride. I'm ordering a new pilot jet to try and fix the idle prob, but I am 1 turn out on the fuel screw, and can't understand why it runs so well without the airbox cover. Please help. I've read every post here I can find, but nothing seems to help.

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I know this may sound kinda stupid, but it happened to me not to long ago. Check the breather hose from the gas cap, or remove or completely loosen the gas cap. There needs to be a passage of through the cap to insure the gas flow into the bowl. Also do you have FRESH GAS in there? All these little bikes will run like a champ if you use them often. But as soon as they sit a while they can be problematic.

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Ok, I tried it with the gas cap off and no change. I shut the gas valve off as i was revving it and right before it quit, it ran really good...like it is too rich. I checked the plug and it is very black. The jets are stock and the fuel screw is 1 turn out. How can it still be running rich?

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Its hard to know without the bike in front of me, but have you gone throught the following list.

New Gas .....check

Clen/New Air Filter......check

Clean Fuel Valve and Hoses.....check

New Plug.....check

Clean/Fresh oil....check

NEW JETS....check (not cleaned NEW!)

Fuel Screw clockwise all the way in and 1 1/2 turns out .....check

Exhaust pulled and inspected with no obstructions....check

Carb cleaned and operating properly....check.

Plug wire firing properly ....check

I personally have had problems with bad gas. Wether it is old or just an off brand that I wasn't sure of. I always use 91 octane and drain it after 2-weeks of sitting. After that I can't trust the gas. I have seen a number of posts from guys having hard start/idle problems here lately and I have noticed most of them are from cold weather states. This may also be your challenge. But I would be real patient in what you do from here. Nothing real drastic. Just the simple stuff. Most of the time its is just something simple and you just have to run across it to find it.

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Thanks for the info, so far I have done everything on the list except change the oil and new jets. The jets are on order, and I'm fixing to change the oil this afternoon. I've done everything else on the list. It has to be something simple, but I can't understand why it runs great with the airbox cover off? I cleaned the carb again last night with no change. After the oil change, I'm going to try and adjust the air screw out in small increments to see if that will help. It's just odd because it ran fine when it was parked after fall last year. Thanks again.

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Well it sounds like it needs more air in the fuel mixture if the airbox cover off is working. Still sounds like jets. But unless you actually ream those jets out with somithing then its probobltythe jets. The passage is to small and too long to just get it with solvent and copressed air. My brother uses some tool from his tatoo gun to clean jets, I use some real thin wire from old stereo headsets. but replacing them is always the best. Oh and thanks for serving our country......really appreciate it.....every day. My buddy Jeff White is and MC Officer and I know sometimes its a small world.

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You're welcome. I really enjoyed my time in the Corps. As for the bike, I'm totally baffled. I changed the oil today, just in case, and no change. I have been playing with the air screw, but it made it worse. I did run a wire thru the jets, but new jets are on order anyways. I'm going to check the valve adjustment now, but since it ran fine when we parked it, I can't imagine that's it. How do you tell if the choke is working properly. I know when you pull the choke out, it's pulling the end up, but how do you tell if it's closing when the choke is off?[/b]

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Did anyone suggest checking the float height? It sounds to me like it's set way too high.

I didn't see it in your "did-it" list.

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USMCVET SMAC has a good point. Check it!

SMAC what is the protocol to check that correctly?

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The manufacturer specified method involves measuring tools and looking up specs. If you don't have a manual, this can take some time.

The layman's method is:

drain carb

remove carb

open carb bowl

turn upside down.

if float lever is level with the body of the carb it's good. Do not press on the floats, just let gravity do it.

if not, adjust tang on float lever so it is level.

if you didn't clean the carb lately or haven't cleaned the float valve lately, now is an excellent time to do it. Remove the jets/valve, soak in carb cleaner (except parts that are not metal, remove O-rings!), blow out with compressed air and reassemble. Check the float level again just to be sure nothing was changed.

replace bowl

replace carb

turn on gas, if gas pours out over flow, you either set it too high or you have a bad float valve. Not over flowing does not mean your float valve is good though, it could be going bad. I've had that happen.

ride it - it should idle nicely and when held at or near WOT for extended periods of time will remain constant if it starts to die, it's too low, then repeat above.

I recommend the second one, it's just easier and you won't have to look up float height specs.

Good luck.

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I've got the carb apart again soaking. I checked the float height and it was dead in the middle of the specs in the manual. I got my new jets in today, so I'll put it all back together tonight and report on the results. Thanks for all the suggestions. This forum rocks!

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It's fixed, it's fixed, it's fixed! Thanks to all who helped, it's finally running right. The new pilot jet helped alot, and I talked to a mechanic today and he told me to check one of the little holes where the air comes into the carb. I had blown air in there, but that apparently wasn't enough, after soaking all day, I finally got it cleared. Should've seen my little boys face when it fired up and stayed running. Thanks again, maybe I can return the favor to someone one day.

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