Woken from a coma. Dies with ANY throttle.

[Agno]

Hey guys,

I decided to revive a 2001 250 that had been sitting for about 5 years. Aside from sitting for so long, It seems to have been very well maintained and has about 9k miles on it. I am not new to bikes and have taken on similiar projects before.

Here is a list of work performed so far:

Carbs have been completely disassembled, cleaned well, fasteners replaced, and put back to factory specs

Torn intake boots replaced

Oil and Filter changed

Air filter replaced and oiled

New ngk factory spec plugs

Gas tank flushed out and petcock replaced

Main fuel line replaced with clear tubing and an inline filter

Fresh Shorai battery


On first crank, it pulled fuel through the carb without issue and fired right up to a slightly unsteady idle. No choke was used and I let it warm up to operating temp. Got a good amount of smoke as the pipes burned off 5ish years of dust. I fiddled with the idle adjustment till it sat around 1500rpm.

Time to poke it a little...
DEAD

Every attempt to open the throttle, no matter how slowly, immediatly kills it. Revs just dive.
Usually at this point I would pop the carbs off and fiddle with the jetting. But taking these carbs off were a royal PITA which is why I was extra meticulous in rebuilding them and setting everything back to factory specs.

Any ideas?

[cuong-nutz]

How does run with choke? Vacuum hoses routed correct and not leaking? How were the float needles? Not sticking?

[Agno]

I should have also mentioned that the exhaust smells very rich.

Dies on choke.
Vacuum hose routing was going to be my next attempt to troubleshoot. But I'm pretty sure I plumbed it all according to the california hose diagram. Which vacuum hose might cause a rich condition?
float needles were replaced with some from a rebuild kit and appeared to function normally.

[Agno]

Would a gummed up emissions system cause these symptoms? I was looking for a reason to cap all that off anyway.

[ducatiman]

keep your focus on the carbs. A bike dormant for 5 years is going to have deep carb issues, requiring a pro quality cleaning. Did you DIY? Did you utilize ultrasonic?

[Agno]

Yes, I cleaned and rebuilt the carbs myself using a rebuild kit. Everything that could be disassembled was. Including the float system, which received new float needles. All passages that I could find were cleared using various widths of guitar string.

I didn't use any form of ultrasonic cleaning but I was pretty dang meticulous as this in not my first rodeo with carburation. The vacuum operated slides were functioning well and nothing really seemed too bad to begin with.

I guess my main question is what would cause a very rich fuel condition in this situation?
Gonna go through and replace/re-plumb the vacuum system next chance I get. After that I will attack the emissions stuff. Any thoughts here?

[Motofool]

Originally Posted by Agno

....... Any thoughts here?

Too rich during idle may indicate:

- Fuel level in bowl higher than specified.

- Idle screw opened too many turns.

Two things may be happening when you open the throttle:

- Fuel: The diaphragms do not lift the needles and excess of air cools the combustion down and extinguishes it.

- Spark: Increased pressure in the combustion chamber prevents an originally marginal spark to jump between the electrodes of the plug.

[ninjunk]

I don't know jack about the 'california emissions' system. but if it anything like a carbureted car emissions system there is a controlled air leak through the PCV valve and a controlled air leak through the EGR valve, both of which could cause you to run lean and experience the 'dies with any throttle' condition. An air leak through the PCV system will have you burning some oil fumes and can cause a rich smell, although its really more of a burning oil smell, in the exhaust.

The 'dies with any throttle' can also be a plugged secondary metering system (unlikely) or a plugged pilot jet (INCREDIBLY LIKELY) no matter what taking those carbs off is enough of a PITA that i avoid it like the plague.

'only runs on choke' and 'dies with throttle' are two symptoms that mean the secondary metering system is not doing its job in one way or another. Sometimes it seems like it just needs a lot of vacuum to prime or something.

First thing i'd do is plug off the line that goes into the big fitting on the engine side of the carb with a vacuum cap. The line that goes to the emissions junk. Then i'd 'piss' the carbs, open the bleeder screws and let them run for a minute. Maybe even drain the tank and put it in your car and re-fill with good gas.

If you can get it to idle, just let it sit there and idle for like 10 minutes until its good and hot, then you might be able to baby the throttle up to full throttle and just whack it up to 10,k rpms a few times... the 'italian tune up.'

[Ghostt]

If no ultrasonic cleaning was used, did you at least verify that ALL fuel circuits were clear with a air compressor?

[cadd]

A/F ratio screws taken out and cleaned as well? When I deep cleaned my carbs, I forgot about those. Had to take the carbs out again. Not fun!

Have you tried spraying some starter fluid by the boots on the carbs (the two from airbox to carb and the two from carb to motor)? Any changes in rpm?

[Ghostt]

Stupid question time, what is your engine idle set at? 1300~1500 RPMs?


Idle mixture screws tuning how-to,

Your initial setting should be 3 full turns out from the bottom, remember just slightly tighten them, don't go all Conan on them.



Then warm it up, slowly turn 1 side pilot screw in until the rpms drop, then back out till RPM's peak (and no further)* Twist throttle...see how it reacts...tweak to taste.
Repeat on other side... test ride. You're looking for best throttle response and transition from just cracked to 1/4 throttle opening or so.*

Thats a quickie, 10 cent tutorial on setting pilot screws.**

[Agno]

Thanks for all the helpful ideas guys!

After fooling with the bike a bit more I became suspicious that the diaphram part of the carbs may be the issue. Pulled the carbs, disassembled the top and immedietly found the issue. For some stupid reason I had run the needle THROUGH the plastic retainer piece at the bottom of the diaphram spring instead of UNDER it. This caused the needle to be pushed up without any resistance. That is what was causing the instant severe rich condition on throttle.

Put it back together correctly this time and she runs like a dream.

[csmith12]

[ducatiman]

actually a very common assembly error

[spooph]

Glad you got it figured out! I was going to say, with your list of to-did's, there can't be much that's wrong... Post of some pics of the zombie.