Carb Issues: you're not alone.

[Ninjinsky]

One of the cool things about joining this site was discovering how many others suffer the same carb maladies as I do.

While it is reassuring it does suggest that there is no magic fix (except a fuel injection kit) and that I am stuck with it

I have become so weary of these kind of recurrent carburation issues over the past 20 years of Ninjette ownership that I am about ready to sell it. In all other respects it has been a great bike but the annual idle battles are just too much.

It is always the same routine. all is fine for months and then one day you pull up at the lights and the idle just falls and falls until it dies. You get it home strip the carbs and there is NOTHING wrong in there, no water no dirt all jets are clean, and yet it will not run right again until you have stripped and reassembled it ---twice.

[csmith12]

Hmmm....

[quarterliter]

Have the carbs ultrasonic cleaned. There are passages you are missing or vacuum hoses that are connected incorrectly

[Masterwhipper]

More often than not it can be an issue with the idle screw. I had the hardest time starting my bike and cringed so hard when my bike would die at a stop sign or intersection. One day I looked it up, turned the knob to the right a bit and it runs like a dream.

[Ninjinsky]

Originally Posted by quarterliter

Have the carbs ultrasonic cleaned. There are passages you are missing or vacuum hoses that are connected incorrectly

I have 2 pairs of carbs both exhibit the same phenomenon. I don't think I have missed passages they are pretty traceable.They have been filled with carb cleaner and blown both ways
The only departure from standard is the removal of the anti icing warm water loop but that shouldn't affect it in summer and some models don't have it

Vacuum plumbing is definitely correct. Do you think ultrasonic cleaning will move something that an airline can't? I have never tried it

Masterwhipper, The idle screw is set to run about 1100 cold and gives me about 1400 warm so I don't think it has enough latitude to drop to stall when warm.

[Ninjinsky]

It all gets a bit like this

Link to original page on YouTube.

[krapzed]

Perhaps its time to upgrade to a 300?

[Ninjinsky]

Originally Posted by krapzed

Perhaps its time to upgrade to a 300?

Crossed my mind, krapzed, but most likely is an EX500
Something like this should slot in seamlessly.
http://www.sportbikerider.us/Pics4/K...500-1990-2.jpg

[fast1075]

The single most common problem with the carbed 250 is from the bike sitting, especially with fuel containing ethanol. The problem can be solved by proper cleaning in most cases.

Herein lies the problem. One person's "clean" is still "unclean". The vast majority of the problems are in the tiny, tiny pilot jets, the air bleeds, and the transition passages.

My bike had all of the carb problems when I bought it. Surging, erratic idle, hanging idle, hard to crank, etc etc.

It takes good cleaner, diligence, and attention to detail to properly refresh and adjust a carb. Scraping the mung out of the float bowl is not sufficient.

There are cases where the carb is so fouled internally, that it is not possible to get it clean with a reasonable amount of effort, but that usually applies to one that has sat literally for years, and the mung is completely hardened.

The only issue I have with mine relates to all vacuum slide carbs. Going from WOT to closed throttle (hard decel), back to WOT gives a momentary stutter because the slide reacts slower than the butterfly (momentary lean condition).

Tips to keep the carb in good condition once it is in proper order.
(a) Don't let the bike sit. Ride it at least once a week, and not just around the block. Fresh fuel flowing thru the circuits help keep the mung from building up.
(b) Use ethanol free fuel if possible.
(c) Give it the occasional dose of an ounce of Seafoam, or ChemTool with a fill-up.

[Ninjinsky]

Thanks fast I will consider the ethanol situation and find out what my local supply is.
When I clean the jets I look through them with a jewelers loupe to ensure all is clear and blow all passages in the body with carb cleaner and an air line.

The bottom line is none of the other 10 or so bikes I have owned, over the years have had any carb troubles Only the ninjette. So there has to be a design weakness somewhere. Ninjetters always seem to be having Idle probs.
If it wasn't such a PITA to get the fueling correct I would consider a carb change to some other type. I'm sure someone here did that recently

[quarterliter]

I would still try and have them ultrasonic cleaned. It will clean places you don't even know about.

[flitecontrol]

Spray carb cleaners just can't do what Berryman's Chem Dip or similar carb soaking solutions can. Soaking the carb puts the cleaning solution in long term contact with the deposits that may have accumulated; something the sprays can't. I used to soak carbs for at least 24-48 hours before purchasing an ultrasonic cleaner.

The ultrasonic cleaner makes carb cleaning faster, and more effective. Below are some before and after pictures of a CMX250 carb I'm currently cleaning. The "before" shots are the carb as received. The "after" shots are once it has gone through the cleaner with just a solution of water and dish washing liquid. This is done to remove the grease and dirt from the carb. Removing the dirt and oil prolongs the effective live of Chem Dip, which is the solution the metal carb parts go through in their second, and final, trip through the sonic cleaner. Do not put any plastic or rubber parts in Chem Dip. It will destroy them!

Note: Chem Dip is flammable, and the sonification process produces quite a bit of heat. Use it in an ultrasonic cleaner at your own risk!

Before:

[Hero Danny]

@flitecontrol

You should do a full write up, you can never write enough information.

What rubber parts on the carbs? From my understanding there's just the 2 rubber caskets on the float cover. Are there any extra?

I had the same issue as OP with my pregen, finally fixed it after consulting a youtube video on how to fully and properly clean the carbs. Check and/or replace all vacuum lines.

[Waldo1]

Sorry for the thread Jack. I moved this to a new thread

[Ninjinsky]

Originally Posted by Waldo1

I bought a little pencil looking tester which is supposed to sense the spark in a spark plug wire. The left cylinder has constant spark but the right is showing intermittent. This is constant with my inductive timing light. Makes me wonder if the cap is bad. Or maybe the CDI.

Any help would be greatly appreciated.

I did have a misfire once that was caused by the ht lead pulling out of the coil slightly It all looked okay from the outside but had slid maybe a quarter inch.
You might think it would be obvious but it is an invisible fault until you unscrew the connector.

[Hero Danny]

@flitecontrol Actually if my memory serves correctly, does the floats have a needle with a rubber tip to it? If so, then my guess if you decide to use your method that thing should be completely out of there to avoid it getting damaged.

[flitecontrol]

I haven't been inside the Ninja 250 carbs, so can't be sure about all the rubber or plastic parts they may have. Since mine is exhibiting signs of needing the carbs cleaned, that's something that will probably happen sooner rather than later. If no one has done a pictorial on disassembly and cleaning of pre-gen carbs, I'll try to do that.

Speaking of motorcycle carbs in general, you are correct in that many float needles have a rubber tip. In addition, there is often a rubber tip or O-ring on the carb drain screw, the idle screw or air/fuel screw (terminology differs), and any other O-rings or gaskets the carb may contain. Many floats are made of plastic. Again, parts containing plastic or rubber should never be soaked in Chem Dip or any similar carb cleaning solution.