Carb idle problems

[n4mwd]

Rather than to continue hijacking another thread, I am posting here regarding my carb problems.

To bring everyone else up to speed.....

Basically, I had some minor problems with my carbs. They were hesitating and misfiring when I opened up the throttle in high gear from 30 mph. I bought two rebuild kits, cleaned the carbs and installed the new parts. The primary jet on one carb and the pilot jet on the other had minor occlusions that I cleaned out. I checked the float level and it was OK. Then put everything back together and back on the bike.

The problem with the hesitating from 30 was fixed - yeah! But now it wont idle. It runs and then dogs down and stalls. At first I thought the problem was the mixture screws (which were changed out in the process), but I have now discovered that the problem is actually a vacuum leak somewhere.

What I did was to put an unlit propane torch under the carb and the problem was temporarily cured and the engine revved up. I have a stock airbox so the only way for the propane to have any effect is by entering through a vacuum leak.

The problem is not solved entirely. Propane flows all over the place and there is no way to know exactly where the leak is. Tomorrow, I am going to remove the carb again to try to look for bad hoses.

So here's the question. Does anybody know an easy way to pinpoint a vacuum leak on a Ninja?

[choneofakind]

Try spraying some WD40 on the spots in questoin. That should get you a pretty good idea of which part is causing your issues.

[n4mwd]

Good idea. I'll go get some tomorrow morning and try it. That should narrow it down a bit. Honestly, I think it was cracked or something before I rebuilt the carbs. But rebuilding them must have made it worse because of all the handling. I say that because it never really idled smooth, but it did idle.

[choneofakind]

I'm betting you have a leak in the boots somewhere, not the carbs themselves.

[n4mwd]

I'll check those first. I did check to make sure they were tight. Have you heard of them cracking in other bikes or something?

[choneofakind]

Not particularly, but they're rubber-ish and old. They're just the first thing in my mind that would leak/crack/whatever after taking the carbs out for repairs and are the cheapest thing to check first

[Asspire]

you have to put the carbs in a ultrasonic tank to clean them out properly......

j/k

I prefer to spray ether or carb cleaner around the carb (propane is heavier that air so you need to point it on top of the carb). But I did have a similar issue, found it to be the hose going to the carb body was dry rot on the brass pipe it was on, I think it was the hose that goes just under the coasting enricher. I ended up replace every damn rubber hose my eyes set on.

hope that helps

[n4mwd]

Now that you mention it, the one on the right side was acting funny when I loosened the clamp to get it out. The clamp was stuck to the tube. I didn't think anything about it at the time and I didn't remove the tubes themselves so I don't know what is going on there. In retrospect, I should have pulled them and looked at them. I'll use the wd-40 and see if those are the culprits.

I'll get some RTV in case I need to patch them. That should hold them long enough for me to order new ones if I need to.

Thanks.

[n4mwd]

Originally Posted by Asspire

you have to put the carbs in a ultrasonic tank to clean them out properly......

j/k

I prefer to spray ether or carb cleaner around the carb (propane is heavier that air so you need to point it on top of the carb). But I did have a similar issue, found it to be the hose going to the carb body was dry rot on the brass pipe it was on, I think it was the hose that goes just under the coasting enricher. I ended up replace every damn rubber hose my eyes set on.

hope that helps

I wired them out so I know their clean. They weren't that bad to start with so I'm not worried about any clogs.

Anyhow, I think your experience with the coasting enrichener tube could be the same in my case. I had to loosen it and the top two tubes when I removed the diaphragms. That meant that I had to bend the enrichener tube a good bit. If it was already dry rotted, then that most definitely would have made it worse.

So I will be checking that too. Actually, I hope that's it because I don't have to pull the carb to get at it.

[n4mwd]

Despite my best efforts, I was unable to localize the vacuum leak. Its now intermittent. My suspicion is that its the intake boots. I'm going to change out everything, including all the hoses and clamps, and see if that gets it.

[setasai]

That stinks, If you can change out the TEE connections too and be sure to check the connection points on the carb body itself. I've heard those little tubes to crack on some occasion.

Change out each of the tubes one by one first. Just in case so that you wont need to take the carbs out unless it still doesnt fix it.

I had a vacuum leak once before and it was one of my vacuum caps. Did you cap anything off? The vinyl ones get all hard over time and need to be replaced.

[n4mwd]

There aren't any vacuum caps on this carb, but I will take a close look at the port connectors. Thanks for mentioning that.

I was wondering if it could be the vacuum diaphragms on top. I did remove them during the cleaning. They looked good, but it might be possible to get them kinked in there somehow if the engine vacuum goes in there.

[n4mwd]

Well I pulled the carbs and removed all the hoses. They were all pristine with no signs of dry rot, cracking or leaks. They also passed pressure testing. It was tempting to just put them all back on there, but I used clear yellow gas line instead. So far, this stuff fits good. The main intake boots were a little greasy from being sprayed with WD-40 so I washed them in soap and water. The vacuum diaphragms looked good but smelled like gas so I washed them as well.

One thing I suspect is that the intake boots aren't getting clamped enough. The boots have deformed over the years from the tight clamps, now the clamps don't squish far enough. They are bottomed out.

The result: The bike idles much better now. I have no clue what the deal is, but its idling. But now there is a new problem. Now I have a flat spot in first gear that wasn't there yesterday. Plus it seems real sluggish off the line. So it looks like I have more research to do.

Anybody know if the mixture screw will cause that?

[choneofakind]

mix screws and needle height.