Carb problems?

[radioflyer]

Hey guys! Got a problem with the ninja. Been having trouble starting it. I removed and cleaned the carbs yesterday, pilot jets, main jets, etc. Nothing seemed really gummed up but i ran a wire through all the passages anyway. I took the mixture screws out and cleaned the passageway then set the mixture screws at 2 1/4 turns out. Put it all back together and everything was fine. Started right up and took it for a long ride. It ran out perfectly. Tried to start it this morning and it will not start. Tried starting fluid and got it going but it will not idle. When I try to blip the throttle it either dies or accelerates very sluggishly. Maybe I'm in over my head here. The bike is all stock.

[csmith12]

Welcome Ivan!

What is the status of;

Airbox/Filter
Spark plugs
Fresh gas?
Fuel filter
Petcock (good working order?)

[radioflyer]

I have the stock airbox and filter. Gas is fresh Shell 91 octane. Carbs are getting plenty of gas to the float bowls so i think the petcock and fuel screen are ok. Spark plugs are somewhat dark. I'm wondering about a vacuum leak. Since the bike was running fine yesterday, I can't see how the problem can be anything internal to the carbs

[FvnnyL3tt3r1ng]

How does it react to choke?

How did you keep it from dieing while riding it?

If it does idle, what is the engine response when blipping?

When you put your idle mix screws back in, they don't always have the same height as the other one even if you do screw them in the same number of turns. You may have set them to different heights which would affect idle/starting or maybe you just set them too rich????

I'd put the needles flush with the carb bodies and then adjust them both the same number of turns, versus screwing them in all the way and then out the same number of turns.

[radioflyer]

I just finished taking the carbs apart again. One pilot jet looked blocked again. other jets looked fine. Ran wire and carb cleaner through the one pilot jet and blew air through all the jets and passageways. Checked the diaphragms and needle jets. Checked the fuel filter. Put it all back together and it started and idled ok after i reset the idle screw. Responds to choke normally. Can blip the throttle quickly and it will rev up and come right back down to idle. Now for the fun part. Took it for a ride and it cuts out and misses badly starting about 5k on the tach. Will not really pull further than that. Almost didn't make it up a small hill. Just parked it for today. Will try again tomorrow. Any advice would be appreciated.

[dino74]

Soak it in Berryman Chem Dip.

I've tried to clean a carb with wire and spray but there are some places you just can't reach. Its a pain to fully disassemble the carb but the chem dip stuff works.

[DaBlue1]

Has the bike been sitting in the rain lately?
Have you checked the snorkel to see if it was blocked?

BTW, the bike will run better on 87 octane. 91 octane is of little to no benefit.

[Motofool]

Originally Posted by radioflyer

........ i think the petcock and fuel screen are ok...............One pilot jet looked blocked again..............

Some filter is not filtering correctly.

Before repeating the cycle one more time, clean that tank and replace those filters and fuel hose.

[radioflyer]

Ok, went through the carbs again this morning, everything looks spot on. It starts and runs fine...up until about 5K on the tach under load. I'm thinking that this is probably not a carb issue. It actually feels more like an electric cut-out, as in cutting fire to the plugs intermittently. Does anyone have any experience similar to this?

[csmith12]

I have seen coil temps causing random stuff like this but still not feeling it's that.

[n4mwd]

Originally Posted by radioflyer

Ok, went through the carbs again this morning, everything looks spot on. It starts and runs fine...up until about 5K on the tach under load. I'm thinking that this is probably not a carb issue. It actually feels more like an electric cut-out, as in cutting fire to the plugs intermittently. Does anyone have any experience similar to this?

I have an almost identical problem, but no solution yet. I had a plugged carb so I swapped with a known good carb. Within a few days, the known good carb was plugged up too. Gas goes through a 30 micron filter in addition to stock.

I am grasping at straws here, but I wonder if the rubber gas hose from the petcock could be bad and possibly shedding internally? The alcohol they put in the gas is known to do that.

EDIT: It seems like there is suddenly a rash of people having carb trouble. Could be the timing between age and when they started putting alcohol in the gas.

[radioflyer]

Been riding the bike and thinking about the problem some more. It runs sterlingly well from start up and take off and up to about 5k rpm. Isnt this the point that the diaphragms would normally be lifting the needle jets? Maybe this is not happening? I have triple checked the main jets to be sure they are clean and open. But if the needle jets are not opening, that fuel the bike needs to keep accelerating would not be there. I have had the diaphragms out and checked them, they appear intact with no visible tears or holes. Cleaned the needle jets and am using no shims under the needles. I have visibly checked all vacuum hoses and they appear fine. I do not really understand how vacuum acts on the diaphragms to lift the needle jets. Does anyone else think this is the right track? I have a hand held vacuum pump...is there any way to pull a vacuum on one of the hoses and test the diaphragms rising?

[n4mwd]

To test the diaphragms, do two things:

1. Push up on one slider and let it go. It should close slowly with a hissing sound. If it snaps back, then something is wrong.

2. Use compressed air and blow (from about 1 foot away) into the roundish oval shaped intake vent on the airbox side of the carb. The diaphragm should rise.

Other than that, I don't know how to test them. There is another diaphragm on the left side of the carb that works with that stuff, but I don't know how to test it or exactly what it does.

But in a nut shell, when the engine vacuum gets strong enough, it causes the needles to rise. The result is that it throws in more gas. I am told that if the diaphragms were bad, you wouldn't be able to blip the throttle at any RPM.

I also know that 5000 RPM is a magic number when it comes to these carbs.

[n4mwd]

One other thing. Hopefully, I'm preaching to the choir here, but make sure you don't use RTV to put it back together or the RTV will come loose and plug everything back up. Gaskets only.

[radioflyer]

Thanks n4wmd! I appreciate the testing info. Took the carbs off...again. Tried pushing up on the slide and letting it go. I could hear suction both on the way up and on the way down...and they came down with a cushion not a snap. Then like you said I tried blowing compressed air into each of the kidney shaped ports above the venturi from about a foot or so away and sure enough each slide rose and raised the needle jet. So...the good is that I now know the diaphragms are good and working... the bad is I now am back to having no clue as to why the bike won't accelerate past 5k rpm. oh yeah...not using any kind of sealer on the carbs...just the gaskets.

[Asspire]

gotta pic of your plugs? video of it running over 5k? and does it do it all the time or WOT?

[radioflyer]

Pulled the plugs, they look maybe a little dark...but ok. Tried to insert pics below. Do not really have any way to do video. Bike runs well up until 5k rpm. Don't really have to be accelerating hard, just running through the gears, when it hits 5k is starts missing and surging and bucking. You can just hold it there or open the throttle wide open, it doesn't seem to make a difference...it just misses and surges. If i back off the throttle some so that the rpm drops it goes back to running smooth.

[n4mwd]

Does it matter what gear, if any, you are in? Neutral, 1st, 6th, etc.?

[radioflyer]

only seems to do it under load in any gear. Can rev it wild in neutral.

[n4mwd]

I'm afraid I don't know exactly for sure, but on a motorcycle carb, there are different circuits for different RPM's. The main jet is what typically kicks in around 5000 RPM.

But since you said you cleaned it and all its pores, its hard to imagine that anything could be wrong with it. Is it possible that it clogged up again?

I assume that you also have an inline fuel filter to block this stuff. Nevertheless, its possible that the alcohol in the fuel is chipping away at the hose. Maybe time for a new one that is alcohol resistant.

[radioflyer]

Ok...more thinking and testing today. Double checked everything internal in the carbs...everything looked ok. Got to thinking how to get the bike to ride past the 5k rpm point. Decided to over-shim the needle jets to the point that they were flowing fuel no matter what. Put three washers under each needle and put it back together. Cranked it up and after a short warm-up it idled about 3k rpm. (lol) Took off on a ride. Bike had no problem running right past the 5k rpm point and I actually ran it all the way to 10k rpm with no hesitation at all several times. I guess this proves that with sufficient fuel flow the bike runs out fine. So it must not have been getting sufficient fuel flow before. The question is why? At least this seems like progress. Next I think I will try dropping back to two shims and see what happens.

[n4mwd]

Maybe its time for a new carb from ebay or get the EFI kit.

[radioflyer]

Took the carb tops off again today and left two shim washers under the needle jets. Cranked it up and reset the idle...about 1k rpm... and took off on a ride. Everything seemed normal... bike started with first hit on the starter button, idled well, took throttle well, could blip it and it revved right up and quickly came back to idle, revved well past 5k rpm in all gears. Hopefully problem solved. Thanks to everyone for their ideas and help!