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Fouled spark plug and exhaust smoke

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My son has a 2000 TTR125. The plug keeps fouling (black, wet) when doing a cold engine start. It starts fine when the engine is hot. I had to clean the plug with carb cleaner to get it to start. The guys we were riding with think the jetting is too rich. I put in a new plug and it started fine but I noticed smoke coming from the exhaust. Because of the smoke I am thinking that there is some oil going past the rings causing both symptoms. Does anybody have any thoughts? Thanks.

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When you pull the plug and it's wet, smell it. Is it gas or oil? Touch it. Is it gas or oil? After the bike has been running and is warmed up, pull the plug. How does it look now?

Is the bike new or used? From the dealer my wife's bike was way too lean, and we had to richen it up some (increased main jet size, moved needle clip down one notch), but we did the airbox mods too.

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You didn't leave the choke on did you?

If you leave the choke on, there is no problem...if you leave the gas on, then that could be a problem.

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The choke cuts off an air jet in the carbuerator causing it to richen the mixture. If you leave the gas on and it does that its probably the float.

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The choke cuts off an air jet in the carbuerator causing it to richen the mixture. If you leave the gas on and it does that its probably the float.

Hmm...Well, yeah if you are riding. I guess I didnt understand what you meant by that. I think I understand it correctly now. 🙂 BUt leaving it on while the bike is off and ther is no gas flow, it would cause no problem.

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White or black smoke?

White, could be the rings. Burning oil.

Black, most likely too rich. Generally, if the motor runs better hot it is too rich.

However if the rings are bad, it too gets better when the engine is hot. Metal expands and seals better.

I would check jetting specs and compare with "normal" ranges posted somewhere on here. Check compression and then valve clearance. Does it take a long time to kick start it when cold (many kicks)?

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sounds like oil burning to me. there's not many things that can be wrong with it. coudn't be coolant so just look to see if you have low oil or check jetting

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doesnt it smoke blue if its burning oil?? I've always thought smoking white is from moisture.

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I'm thinking either stuck or mis-adjusted float, or possibly the pilot jet has come unscrewed in the bowl...

Either way, I'm betting it is a carburetor problem too. I don't think it's necesarrily a jetting problem as far as the wrong jets in, but maybe something to do with the jets as I already said.

Also, check to make sure the fuel screw is still there and adjusted at around 2 turns out.

It's either that or a float problem.

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You should include a bit of history on this kind of question....

Has the bike ever been running well? What happened between then and now ?? Any Mods..... or more inportantly, and maintenance ? is the Air Filter clean ?? Did your son clean and oil the filter ? Too much oil on the filter ? Was the plug replaced before the trouble... was it replaced after the trouble ??

I would do this... make sure the air filter is clean. Replace the plug. Make sure you have good gas ( no carosene ).

Then, if this doesn't help, take the carb off and clean it. Spray it out with a carb cleaner. Make suer you get all of those little ports and holes.

Whatever you do, don't make any adjustments to floats or jets until you know that you have a clean base to start from. Once you know it's clean, then you can move on.

Jeff

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You should include a bit of history on this kind of question....

Has the bike ever been running well? What happened between then and now ?? Any Mods..... or more inportantly, and maintenance ? is the Air Filter clean ?? Did your son clean and oil the filter ? Too much oil on the filter ? Was the plug replaced before the trouble... was it replaced after the trouble ??

I would do this... make sure the air filter is clean. Replace the plug. Make sure you have good gas ( no carosene ).

Then, if this doesn't help, take the carb off and clean it. Spray it out with a carb cleaner. Make suer you get all of those little ports and holes.

Whatever you do, don't make any adjustments to floats or jets until you know that you have a clean base to start from. Once you know it's clean, then you can move on.

Jeff

Ditto.

Make sure you have good gas ( no carosene ).

Yeah...no diesel either 🙂

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WOW - I didn't expect so many responses - THANKS!

Here is some more info and what I have found.

We just purchased bike used so I have no history.

There are no mods (airbox, exhaust, etc.)

The smoke is white.

The plug is black and wet. It appears to be gas.

I cleaned plug on the trail with carb cleaner to get it going when cold.

Compression is good.

The air filter is clean and properly oiled.

Changed plug after the starting problems and it is much better but after inspecting plug it is now black.

We went on another ride this weekend and the day started out with gas pouring out of the float overflow tube. I had him ride it for a couple of minutes it stopped.

Because of the gas pouring out I think the post about the float may be right. My next step will be to completely clean the carb to make sure the float is not sticking and none of the holes are plugged. I will let you guys know how I make out.

Thanks again for all of the responses.

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400MAN,

We would very much like to know how your "carb rebuild" works out. It could help one of us sometime.

Jeff

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400MAN,

We would very much like to know how your "carb rebuild" works out. It could help one of us sometime.

Jeff

Jeff - I am out of town until next week and won't be able to try anything until then, but I will post my results, hopefully the solution!

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my cousin had a 350 quad and his float would sticking. i borode his quad and got 20 miles back into the bush and it wouldn't run properly and then it stalled 🙂 . i drained the carb a few times and it ran for about 20 seconds then it stalled again 🙂 .

then i tapped the carb and it started it ran! then every like 20 minutes(when it stalled) i had to tap the carb and it worked. :D

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my cousin had a 350 quad and his float would sticking. i borode his quad and got 20 miles back into the bush and it wouldn't run properly and then it stalled 🙂 . i drained the carb a few times and it ran for about 20 seconds then it stalled again :D .

then i tapped the carb and it started it ran! then every like 20 minutes(when it stalled) i had to tap the carb and it worked. :D

It is borrowed! :D

That would suck if you had to stop every 20 minutes. 🙂

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ya i suck at spelling... ya it did suck having to stop every 20 minutes.

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Well - I completely disassembled and cleaned the carb. I set the float level per the service manual (it was quite low - 1/2"). Same results. :applause: It also will not idle and I have the idle screw (on the side) in all the way. It just dies if you don't hold the throttle on partway. I took the end cap off of the muffler and it seems fine there. I thought the packing may be plugged but it does not appear to require packing. The only thing I think I will try is checking the ground at the coil. Any other suggestions before I take it to the dealer? Thanks to all.

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Well - I completely disassembled and cleaned the carb. I set the float level per the service manual (it was quite low - 1/2"). Same results. 🙂 It also will not idle and I have the idle screw (on the side) in all the way. It just dies if you don't hold the throttle on partway. I took the end cap off of the muffler and it seems fine there. I thought the packing may be plugged but it does not appear to require packing. The only thing I think I will try is checking the ground at the coil. Any other suggestions before I take it to the dealer? Thanks to all.

Did you go over all of the parts and make sure everything is in the carb that is suposed to be? By chance may have lost or fallen out when cleaning or opening it to clean it out :applause: Cant think of much more :eek:

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