What makes a 250sx engine hard to start...

[Seabass]

What makes a 250sx/es,trx250 engine hard to start after it's warmed up a little? Brother has an '85 trx250 that is really hard to start after it has been warmed up. His 250sx was the same way. I think it's the coil going...or is it a carb issue maybe?
Any help appreciated - thanks.

[TeamGeek6]

Can be anything from loss of compression, fouled or fouling plug, weak ignition (CDI or electrical connection affected by engine heat) or carb too rich. A combination of weak ignition and rich carb is what to expect. A cold engine needs more fuel to start so it follows that if its rich, itll start easier cold.

Try getting it hot (like where it is hard to start) and throw in a new spark plug. Do it quickly so the cylinder doesnt have much time to cool. If that doesnt show anything, check the carb jetting and fuel level in the carb bowl. And look at the spark arcing against the spark plug, it should be white.

[bigredhead]

Well.. funny you ask cuz my SX has just recently started doing this .

I found that opening the throttle just a tiny bit will help it fire but during the last few trips once hot.. just like you mentioned.. it will start but not easily like it should.

Anyone else ???

[MO350X]

Mine takes a little while to start cold, even using the choke.
You crank for about 20-25 seconds before it'll fire when it's cold.
But when it does start, it purrrrrs.

And hot start?
You so much as BREATH on the start button and it fires right up.

Gotta love these 250SX's, though. :beer
What a cool ride.

[nimda78]

with the age of these toys, my experience is after the cylinder heats and expands, the rings cant swell enough to make up for wear. and is simply at a loss of comression. electronics for the most part rarely fail. even after 25yrs++

james

[Tri-ZNate]

Mine used to do it and since the electric start doesnt work I had to kick for a little while before it would start. Try holding it full throttle for a kick, then after 2 kicks it should start. Make sure the choke isnt on either :rolleyes:

[conig]

depending on the year or if it was added. There was a cold start "option" I don;t know if thats the correct way to decribe it. It was basically the smae jets that came on the 87 carb but it was a larger pilot jet I beleive. I have seen it searching before on here.

If you have it it would explain some of your scenario. My red has it and it fires first kick when cold and then I have to crack the throttle alittle bit when hot. I don;t run a battery becuase I keep loosing them to the trail.

[bigredhead]

Either way... mine used to fire right up warm or cold.. but lately has been giving me problems starting when hot.... only started lately.

I would say it started since i last replaced my plug now that i think of it ......... might try another one for fun.

[conig]

would valve adjustment affect jetting?

[Maine_Triker]

Holding the throttle slightly open when starting a warm engine helps big time on my Big Red. (250es)

In 1985 there were a few 250cc models that had a defect in the carb, causing a cold start problem. Honda produced a "kit" to fix this problem, but not everyone brought their trike to the deasler to have the "kit" installed. These kits are VERY rare nowadays.

I have no clue what causes the problem with the warm starting.

Phil

[Seabass]

with the age of these toys, my experience is after the cylinder heats and expands, the rings cant swell enough to make up for wear. and is simply at a loss of comression. electronics for the most part rarely fail. even after 25yrs++

james

I thought of this as well, but wouldn't it smoke a lot more onced it's warmed up? This bike does not smoke at all. It just seems to run a little choppy and is hard to start when the engine is hot.

"In 1985 there were a few 250cc models that had a defect in the carb, causing a cold start problem. Honda produced a "kit" to fix this problem, but not everyone brought their trike to the deasler to have the "kit" installed. These kits are VERY rare nowadays."

I had this kit on my '85 Big Red. It really imrpoved cold starting - I never had a problem starting it when it was warm either - it was actually easier to start.

I keep leaning towards an electrical problem. I'd like to get my hands on it and try a spare coil or spare plug - see what that does.
Thanks for all the replies.

[1984kxtTECATE]

My SX is harder to start cold, but when it is warm ill open the throttle just a hair. Now when my tri-z or Tecate gets warm i always have to opean the throttle a tad to get them started.

[MO350X]

depending on the year or if it was added. There was a cold start "option" I don;t know if thats the correct way to decribe it. It was basically the smae jets that came on the 87 carb but it was a larger pilot jet I beleive. I have seen it searching before on here.

If you have it it would explain some of your scenario. My red has it and it fires first kick when cold and then I have to crack the throttle alittle bit when hot. I don;t run a battery becuase I keep loosing them to the trail.

The first thing that came to mind with my cold start issue is a lean condition.
The "cold start option" you describe fattens things up a bit.
But fattening up the cold start produces a wee bit fat hot start, necessitating the "cracking of the throttle for hot starts".
Interesting, VERY interesting.

I'll try and find the '87 250SX jetting combination.
That would be easy to duplicate.

Thanks for all the input, folks! :beer