250 Dang hard to cold start 05' ttr250

Hey gang. Wonderful weather we've got in Texas lately.

So this has been an "issue" since I bought the bike, but cold starting this thing is a pain. I replaced the starter, got a nice LiFe battery, and it still slugs to start. If I push start it, it seems to work a little better. I can start off by choking it, and it sounds like it wants to fire over, if I keep it on choke, it wont start, then taking the choke off after about 4-6 5sec starts it will just barely crank over, then I've got to hold the throttle up or else the backfire through the intake will kill the motor. The backfire seems to happen only at very low rpm, after it gets nice and warm, the idle changes a little bit higher which will keep it from stalling. I would really like to think that it's all centered around the carburetor, but I don't know a whole lot about small motors right now.

Anyone else got some wisdom to share? Thanks!
 

SRAD97750

Moderator
Staff member
Carb cleaning is the best place to start.
Just pulled a carburetor for the same issues yesterday. (Hard to start) I didn't find anything when cleaning, so I went through the normal procedure and it starts and works like a charm now.

My carburetor cleaning goes as follows.
Pull the bowl, fill with 1/2" of liquid carb cleaner. Rub bowl clean.
Pull Idle, main, and jet tube, mixture screw/spring and soak them in the bowl.
Spray out body with carb cleaner. Through all the jets and passages, both directions.
Reassemble. I like to start with the idle mix screw at 1.5-2 turns from lightly seated and adjust later when the motor is HOT.

This whole process takes less than 15 minutes if everything goes to plan. -BIG DAN:thumb:
 
Do you think by chance that the backfire is possibly just from a dirty carb? Also, would it be worth it to purchase a rebuild kit?
 
These bike are jetted very lean right from the factory. You will need to go up 2 sixes on the pilot jet and one size on the main jet.
Do a load test on your battery to be sure it is good.
Check all your ground cables.

Paw Paw
 

SRAD97750

Moderator
Staff member
Yes, a lean condition causes backfiring though the carburetor. And lean is a symptom of a dirty carburetor.
I've never needed a rebuild kit unless something was missing.

This may not cure your issues, but it is where you have to start. -BIG DAN:thumb:
 
Yeah, hoping its not the valves, so I'm wanting to start on the carb. Do y'all know where I can look for the jets? It seems like they should be a somewhat universal part, I was looking at some jet kits on amazon, but I'm not totally sure if that's what I should be looking for.
 

SRAD97750

Moderator
Staff member
You should be looking in the carburetor... The only way to know what's installed is to pull and clean the existing jets, write down their size for your future reference.
While they are usually 'lean' from the factory, a stock bike will run and start just fine with stock jets, otherwise they couldn't sell them.

I would get the carburetor clean and reassembled, and try again. It is usually just that easy on a small 4T.
If the issue persists, valve spec should be checked, but unlikely, as it would be harder to start when hot, not cold as you describe.
-BIG DAN:thumb:

EDIT: As the service manager at a Piaggio/Vespa dealership in 2005 one of my main jobs was to keep all 80 scooters on the floor able to be started cold, otherwise they couldn't be sold. You can never underestimate the power of a simple carburetor cleaning for hard starting when cold. Even if you cleaned it yesterday.
 
Clean carb jets , use guitar strings , or wire from a common wire brush . Pull out wires with pliers ..... I make small scratches on wires with pliers to help clean . . Been doing it for years . That is a lot of carbs ... never have I replaced a jet ,,,,,,,,, except for performance enhancement ....... And check valve lash ....... Very important if air filter not properly service ., and passing dirt ...
 
Cool! Thanks for the tips and tricks y'all. I've been using this bike a good amount lately on some crappy ranch trails, and the thing idles high enough to where it wont stall going 10mph uphill in 2nd gear, and on a straightaway following my buddy, I'm on my brakes almost the entire time. I would adjust the idle screw, but because it starts out great and idles fine, and as it gets to operating temps it starts idling higher, I think I'll just wait on messing with the screws and take it apart, hopefully that'll solve the 5 different issues I have with it. Oh and by the way, I knew where the jets were located lol, I was just wondering where I should buy replacements if need be
 

SRAD97750

Moderator
Staff member
Oh and by the way, I knew where the jets were located lol, I was just wondering where I should buy replacements if need be
That was never in doubt.
Carburetor jet types and sizing # schemes vary from manufacturer to manufacturer.
I am redirecting you to the specific jets installed on YOUR carburetor, so that if you were to go browsing for jets online, you would know what you're looking for.
I have no idea what's swimming in that fuel bowl of yours.-BIG DAN:thumb:

An example of types of main jets, numbering would vary by manufacurer.
 
That was never in doubt.
Carburetor jet types and sizing # schemes vary from manufacturer to manufacturer.
I am redirecting you to the specific jets installed on YOUR carburetor, so that if you were to go browsing for jets online, you would know what you're looking for.
I have no idea what's swimming in that fuel bowl of yours.-BIG DAN:thumb:

An example of types of main jets, numbering would vary by manufacurer.
Ah! My bad. Well anyways, I cleaned out the carb. Turns out, the smaller (idle?) jet was clogged, so I had that cleaned out, and let the carb sit in the good ol' bucket of carburetor parts cleaner for about 30 mins, put everything back together, and it'll actually start not too bad now, it doesn't backfire anymore, and doesnt change idle when getting to operating temperature. So far so good, not getting my hopes up for it just yet, seemed to easy to fix it, but time will tell.

On a side note, any idea how wide of a tire I can put on here? The front oem is 80/100-21 and the rear is 100/100-18. I definitely dont want to sit up any higher, trailing on crappy hill country terrain is already sketchy enough as it is, ideally I'd like to sit a little bit lower, and have a wider tire.

By the way, thanks for all the ideas and help y'all've given thusfar, it is much appreciated.
 
Study up on tire sizes ... there are charts that tell what the numbers mean ....... 18 is rim size , other numbers are width , and height . NOT All tire manufactures use the same dimentions , so choose carefully ... Also look at rubber compound ratings , hard , soft , interrmediate ....
 
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