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The TTR250 FAQ web pages -> TTR250 -> Carb stuff -> carb ????
Post Info TOPIC: carb ????
The TTR Kid


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carb ????
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Hello I am have a few problems with my TTR250. She's just reving high and because I haven't seen this carb before I'm confused.. basically when I got the bike running she was running high on revs and I couldn't found out how to adjust it to a nice pop pop pop. It's just reving above normal and getting hot quick! So I found a screw with a leaf that looks like a daisy at the bottom of my carb pointing downwards that has a ridge indicating it is entering a screw up into my carb. Please note this is on the left where the carb enters engine side. . I twisted it and I didn't notice too much full in and out.. I'm no expert bit I'm sure if I move an air fuel sceew the bike with let me know I am by picking up revs or lowering .  I'm also wondering if it has any thing to do with the accelerator cable and return cable. Am I right in thinking that if I just adjust the accelerator  so it's a little slack at the end that it will be in idle ? Or do I have to use the return one to to make it come down. . I've uploaded a photo of the carb screw here. Please help before my big powerful new but old TTR blows up I haven't rid it comfortably yet I have to slow eninge down with brake . Thanks

 



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mossproof


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Welcome to the forum Reg!
The screw you describe is the fuel screw. On a standard engine (no mods to exhaust or airbox) it should normally be somewhere between 1.5 and 2 turns out from the "completely screwed in" position. Often it doesn't seem to make a huge difference to engine speed whatever you do with it! I think you are probably having issues with lean running thanks to a blocked pilot jet and/or pilot circuit (the bore holes in the carb body) Don't run it like this too long - it will make a mess of the piston!
The little internal filter that hides behind the float valve could also be restricting the fuel flow to the bowl. Take EXTREME care removing the float pin. Read up on it first -
There is a good thread on rebuilding the carb. This is how the master does it:

ttr250.activeboard.com/t63835786/carburettor-deep-clean-and-rebuild/

Or here:

ttr250.com/Carb/TTR250_carburettor_strip_and_rebuild_guide.htm

Have fun!

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The TTR Kid


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Thank you for your reply and help I shall follow your advice. I already cleaned the carb out but I'll take another look.
I noticed you said about the screw must be 1.5 to 2 turn out on a bike with no mods to air box or exhaust, I was running it without the big cover for the filter. Would that be the issue maybe? I'm sure I'll find out soon :) thanks

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ttboof


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Before you take it apart again 

Try a bit of wd40 or similar around the rubber inlet manifold on the head of  it's leaking air it might increase the revs as well 



-- Edited by ttboof on Thursday 27th of May 2021 10:09:19 AM

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The TTR Kid


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Yes I also noticed that my rear air flow rubber was dented away front the metal band a that tightens around it. ! Letting ever such a small gap I'd imagine.
Thanks :)

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mossproof


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The rubber often separates from the metal boss that bolts to the head, allowing air in as Les suggests. Creates the lean running high revs.

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ttboof


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The carbs are a matter of clean and clean again 

The rubber inlet is a common problem as well 

A leak on the inlet to the carb prob won't cause the issue but would let dirt in dust over time 



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