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post #1 of (permalink) Old 08-02-2007, 10:54 AM Thread Starter
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ts 250 backfires

I have a Suzuki TS250 (1978) that won't run and backfires through the carb when I try to start it.
The timing is set to the mark, I just rebuilt the carb, gelled the tank, and replaced the piston.
It ran pretty good for a while, but now it usually won't start. When it does, it will only run for a few seconds and giving it more throttle causes it to die.

Any ideas would be much appreciated.
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post #2 of (permalink) Old 08-03-2007, 04:30 AM
 
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Cool Sounds like you need to adjust your carb?

As a good rule of thumb;
"Coughing" through the carburetor, indicates a too lean a fuel mixture vs. Black smoke seen from the exhaust at idle or a feeling of sluggishness off idle a fuel mixture that is too rich .

Hope this helps?
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post #3 of (permalink) Old 08-07-2007, 09:21 AM Thread Starter
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F(!)**ing carburetors.

I tried turning the air screw in some and that seems to help. It would start for a sec then die most times.
That's an improvement.
I ran out of threads before I could get it to idle, but that adjustment was just slightly helping the real problem anyway.
So off comes the carb again and more good times.
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post #4 of (permalink) Old 08-09-2007, 11:15 AM
 
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Cool More on Carb. "tuning"

Check out the advice / info I offered "Mutt" on https://forums.off-road.com/dirtbike-...fo-needed.html
Methinks it'll help
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post #5 of (permalink) Old 08-09-2007, 09:41 PM Thread Starter
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I took off the carb this morning, and checked the float level with digital calipers and it is dead-nuts on.
And the floats do float.
My carb is made to go richer as the pilot is turned inwards.
After I put it back in, it started for a minute but was popping the whole time.
After that, it would not start, despite trying the pilot screw in a lot of different depths.
There was a (approximately) 3" by 3" patch that I welded onto the exhaust just after where it leaves the cylinder. Is the expansion chamber's shape "super-critical"?
My plan for tomorrow's session is to do a good check of the air passages in the carb body.
Any thoughts would be appreciated.
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post #6 of (permalink) Old 08-10-2007, 01:50 AM
 
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Red face It's not the Xhaust! ... time to recheck that carb!

Your "patch" on the Xhaust shouldn't be too much of a problem, and certainly won't exhibit the symptoms you currently have, (Altho' a better way to remove dings from your expansion chamber in future, would be to fill the dinged area with water, and then pop it into a freezer ... placing it in the freezer so that the dinged area is completely covered by water then allow it freeze over ... then remove it, defrost and repeat the exercise until the ding has been pushed out).

Back to your "problem" tho' ... as the problem "mysterously appeared", after you gelled your tank and rebuilt your carb, (I'm assuming that you gelled the tank as it was rusting?) ... I would hazard a guess that you have something, (rust? ... or even some resin if you didn't allow it to cure properly?), stuck in one of the jets and or carb passages? ... or even in the reed valves?

As an interim tho' ... Check your reed valves ... Recheck your pilot jet and it's passage through to just in front of the venturi ... and if all checks out OK ... then try raising your needle and see where that takes you?
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post #7 of (permalink) Old 08-11-2007, 09:56 AM
 
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As long as it works ... :)

"Experience is simply the name we give our mistakes" - Oscar Wilde
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post #8 of (permalink) Old 08-28-2007, 10:51 AM Thread Starter
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getting better

Ok.
I was a little confused aqbout the idle jet/screw thing, but now I've figured out the reason it wouldn't run.
The plug was being fouled by excess oil.
I had adjusted the oil pump per the manual, but it was putting in way too much.
Now it is at the minimum setting and the plug no longer fouls.

I have a question though. There is a screw on the bottom of the carb, nearest the cylinder. The manual does not seem to mention it.
Where should it be set?
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post #9 of (permalink) Old 08-30-2007, 02:12 AM
 
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That's yer' mixture adjustment

It should be about +- 2 turns out ...

Hold the throttle a little above idle and adjust it ... the motor revs will pick up up slightly when you have it set correctly
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post #10 of (permalink) Old 09-09-2007, 12:25 AM Thread Starter
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Thanks

Okay, that explains why it ran okay when I had it set at 1.5 turns out.
But the big problem turned out to be the seal on the right side of the crankshaft.
I found that my plug was fouling. I tried various settings, all the way up to no oil supplied at all. Just straight 91 octane was fouling the plug.
It was leaking oil into the "dry" area.
I pulled it apart and the problem was obvious. A $7 seal that I should have replaced the first time around.
The new seal is on order.
Thanks for your helpand patience!
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