Idle troubleshooting

[USMarine]

I recently got my 94 ninja 250 running and think that I have done everything that I can do but want some input on it before I take it in to the shop.

The bike starts up fine but if it's on full choke it idles at 5k RPM. I can adjust the idle screw to where it sits at 3k fine without any choke but if I go below that it has a lot of trouble staying in one spot and bounds from 1500-3000. Lastly if I rev the engine to around 6-7k RPM it will bog down after hitting that high rev as if it is going to die then creeps back up to 3k. The engine also has a slight tick but its kind of loud.

I have cleaned the carbs twice now and all of he fittings are tight, cables aren't caught up, boots are sealed, butterflies are closing.
The only thing I can think of is that I'm using gas that's been sitting all winter.

[jkv45]

Originally Posted by USMarine

I recently got my 94 ninja 250 running and think that I have done everything that I can do but want some input on it before I take it in to the shop.

The bike starts up fine but if it's on full choke it idles at 5k RPM. I can adjust the idle screw to where it sits at 3k fine without any choke but if I go below that it has a lot of trouble staying in one spot and bounds from 1500-3000. Lastly if I rev the engine to around 6-7k RPM it will bog down after hitting that high rev as if it is going to die then creeps back up to 3k. The engine also has a slight tick but its kind of loud.

I have cleaned the carbs twice now and all of he fittings are tight, cables aren't caught up, boots are sealed, butterflies are closing.
The only thing I can think of is that I'm using gas that's been sitting all winter.

I would say the gas could definitely be the problem. Draining the tank completely, as well as draining the floatbowls (and looking at what came out) is a good first step.

If that doesn't change things, it's time to pull the carbs again. It sounds like something may not be right. You should have removed the caps on the idle mixture screws, removed the screws, cleaned the passages, and have them set to 2.5 turns out.

It sounds like the idle mixture could be off or the passages are partially plugged. There should be a spring, washer, and o-ring on each screw. Sometimes the o-ring breaks apart and plugs the passage. The carbs should also be synced when you have them off.

When cold and on choke, have it set so the engine will run about 2000 to 2500 RPMs, and back it down as soon as it will idle without it.

[USMarine]

It seems a sign though I have done everything meantioned already except for checking to make sure the Orings are still intact. I'll try it and let you know, thanks.

[Triple Jim]

Are the valve clearances known to be set correctly?

[ducatiman]

Immediately purge the fuel. Our modern ethanol fuels can break down in as little as weeks, the resultant jelling (turning solid in time) clogging both tiny and large carb circuits. Tank and petcock damage are realistic as well, if unstabilized fuel is left to sit for long periods.

the magic word is STABILIZER...its use essential over winter storage.

At this time though, you must "revisit" all circuits within the carbs and confirm delivery system (petcock, carb float system) is, in fact, delivering. Compressed air, carb cleaner mandatory (remove the diaphragms before spraying!)

[USMarine]

I don't have any specials tools at the moment to be able to do anything to the valves or most of the engine.

As far the fuel I replace it and added a system cleaner which helped but I think needs a tune up which will require a visit to the shop. Due to a new job & schedule that will take a week or two but I will keep the updates coming.

Thanks for all of the support or help!!

[Triple Jim]

Adjusting the valves doesn't really take much in the way of special tools, and if they're out of adjustment, there's no point in trying to get the idle right.

[ducatiman]

a FULL SERVICE at a dealer normally entails checking valve clearances

Above and beyond, they'll eventually diagnose a carb clean as well.

I'd suggest getting an estimate for both before proceeding, could be expensive. If the dealer is decent...they should be easily able to supply an advance estimate via phone.

Best to be forthcoming and on the same wavelength as the dealer....that way there are no "surprises". Finances and logistics can become complicated once they get your bike apart.