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The TTR250 FAQ web pages -> TTR250 -> Repairs and maintenance -> New Owner/New Member Carb issues
Post Info TOPIC: New Owner/New Member Carb issues
digithead


Newbie

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New Owner/New Member Carb issues
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HELLO ALL!  Found you via Google. Im 67 and riding since about 10 years old. Started on those Honda 50 and 70's we all love.

Got a used 2003 TTR250 for $1400usd.  When I went to get it he agreed it had a idle problem. Would stall if you didnt hold a little gas on. But other then that rode and ran great and shifted fine.  I brought it home did a  oil change, flushed tank and fresh 93OCTANE Gas,  and a brand new battery and new plug and new air filter.  Idle was still bad without some choke.

So I have worked on carbs before, dont love it, but I do it. I tore it all done and cleaned like crazy. I have a full service manual too.

Put it back together, same issues, rough idle. No change. So I said screw it I'm buy a carb. Mine appears to be the original Y30P they all used. 

So I ordered this one from Amazon. 

https://www.amazon.com/dp/B0BZR88GTT?ref=ppx_yo2ov_dt_b_fed_asin_title

I installed it just fine. Pull 1 click of choke and it starts right up. Idles PERFECT! So I think I'm golden now.

BUT, heres problem. When I drive it and get beyond  1/4-1/3 throttle (mid range) it stutters and bucks. In garage, it runs fine and you can rev it to any RPM 

and NO STUTTER.  You have to drive to get the stutter/bucking. I tried driving and when its coughing mid-range gently pull some choke on to see if its too lean and maybe I can richen it. No luck. Pulling choke during its fits make it worse.

SO I pulled new carb and pulled needle to check it. From Factory it was set right in the groove 3 of 5, dead middle. I checked in old carb and it was slot 3 as well.

I checked idle mixture on bottom. I tried it a 1.5 turns out all way to 2.5 in small increments do different.

Dont know what to try next. ORIGINAL carb ran fine just poor idle. Now I have great idle and no mid band. A few times I got past mid band coughing and up

to a higher rev and it randomly would smooth out a little.

ANY THOUGHTS OR HELP APPRECIATED! I'M PULLING OUT WHAT LITTLE HAIR I HAVE LEFT AT 65!

 

 



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mossproof


Super Guru

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First, welcome to the forum! Hopefully the assorted experience on here will help you get to the bottom of the problem.

The carbs are well known here for having problems when old fuel has been left in them, especially with high ethanol content. Sounds like a pilot circuit problem to me, either the fuel screw passageways and/or the pilot jet blocked. The pilot jet in particular needs cleaning out with a bit of copper wire (hard enough to clear hard crusty deposits, but soft enough to not damage the brass jet.) Any of the passages in the body of the carb could also be blocked so a good blast of carb cleaner and air, or even better an ultrasonic clean, might be needed. Take care of the various 1-way valves - the carb rebuild threads are useful to show you what to watch out for.

BUT, rereading your post, it's not just that the idle screw is incorrect is it? You should be able to see just a glimmer of light under the slide if you look through the carb. Adjusting the throttle stop on the outside of the carb lifts the slide and might bring back the idle. Life is rarely that easy, but you gotta try!

ttr250.activeboard.com/t47674647/carburettor-pictorial-guide-to-stripping-and-checking-a-carb/

I have not heard of anyone having a lot of luck with cheap aftermarket carbs, (but I can't open your link to see which one you've got), but have you tried moving the needle? There is a good chance the internals of the carb are not the same even if it looks similar from outside, so it could easily need different settings. If you reckon pulling out the choke makes things worse, that implies over rich, so drop the needle down and see what happens. The "choke" on the TK carb is actually an enriching circuit rather than a butterfly in the inlet tract. Don't know what's in your Amazon special, but they don't always react in the way you'd expect. Have a play with the needle and see what occurs.

Good luck, and let us know your results,

Simon.



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digithead


Newbie

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thanks. So I looked inside and measured and yes my cheap aftermarket seems identical to OEM carb. Needle was set to slot 3 dead middle like the OEM one.
Big update though.
I didnt really drive it much before tuneup/oil change and giving it to grandson so I called him. He said it had the mid-power band stutter/buck/cough before!!
So I Think my new carb has FIXED my rough idle, but the OTHER PROBLEM IS NOT related (sorry).

I am going to try a new spark coil next. I have new carb, new plug, fresh gas. Spark is all thats left !


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Ttboof


Senior Member

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Posts: 173
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Hi 

I have stayed with the original carb , I put in a bit of carb cleaner from the Auto shop occasionally and have had no problems with it gumming up since ( i tend to put a bit in when I'm heading out and using the whole tank ). the flat spot can be a little difficult to fix with mine i dropped the Needle one notch and opened up the Air box a bit . 



-- Edited by Ttboof on Monday 22nd of September 2025 11:10:11 PM

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