misfiring and cutting out - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 10 (permalink) Old 08-30-2012, 11:58 PM Thread Starter
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misfiring and cutting out

I have what I believe are partly plugged pilot jets. Bike starts up fine on choke, but starts misfiring when you close the choke. Both cylinders are firing, because both pipes are hot. It has an erratic idle. When you give it gas, it first stumbles and then takes off. It runs fine at much above idle, but when you stop, it starts running rough again. This is the first time it has ever done that. I have always kept stabilizer in the gas, and sometimes drained the carbs. It does sit a lot. I thought about draining the carbs, and filling them up with Seafoam (read that on here) but I think the float will not let them get full enough to reach the pilot jets. Can I pour the Seafoam in through the carb vent hose, or will it just run into the cylinders?
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post #2 of 10 (permalink) Old 08-31-2012, 12:37 AM
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Can I pour the Seafoam in through the carb vent hose, or will it just run into the cylinders?
Yes y ou can inject the seafoam as you propose. also highly recommended procedure. Another problem you might be having is a carb boot vacuum leak.
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post #3 of 10 (permalink) Old 08-31-2012, 12:00 PM
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What Slim said, and have you ever syncronised your carbs?

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post #4 of 10 (permalink) Old 08-31-2012, 01:46 PM Thread Starter
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I have checked the carb sync a few times, it was always right on. I'm convinced this is plugged jets, because the bike sat for over 3 weeks without being started. The main jets seem fine, because it will go 75 mph perfectly smooth, with no power loss. The idle is the problem. I'm hoping I can get it running right without having to go through the hassle of pulling the carbs to clean them. There are no leaks between the carbs and engine. And it was running and idling fine before it sat there for 3 weeks.
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post #5 of 10 (permalink) Old 08-31-2012, 02:29 PM
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Do not think 3 weeks would be a long time for bike to sit and cause fuel to go bad. Look back on Wolfies suggestion and blow the jets out backwards. The throttling jets are teenie tiny so it would not take much of trash to cause a clog. After so many rpm's the mains take over anyway. Does it run fine on the low end with the choke ingaged?

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post #6 of 10 (permalink) Old 09-01-2012, 04:05 AM Thread Starter
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Ok I got it to running good again. I drained the carbs, and filled them with Seafoam through the vent hose, then one that goes in the right air cleaner, and let them sit overnight. I tried to start it on the Seafoam, it wouldn't run, but did fire several times. My idea was to suck Seafoam up into the jets. Then I drained out the Seafoam, poured 16 ounces of Seafoam in the tank, and filled it up with gas. I ran it out of gas with a combination of town and highway riding, then refilled the tank with gas and another 16 ounces of Seafoam. It idles fine now, and does not have the just above idle stumble anymore. I'm sure it was just gas residue in the jets. I think I'll start draining the carbs every time it needs to sit more than a week.

Still not sure what you mean by blowing out the jets backwards. Can you explain that?
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post #7 of 10 (permalink) Old 09-01-2012, 10:26 AM
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Quote:
Originally Posted by suitcasejefferson View Post
Ok I got it to running good again. I drained the carbs, and filled them with Seafoam through the vent hose, then one that goes in the right air cleaner, and let them sit overnight. I tried to start it on the Seafoam, it wouldn't run, but did fire several times. My idea was to suck Seafoam up into the jets. Then I drained out the Seafoam, poured 16 ounces of Seafoam in the tank, and filled it up with gas. I ran it out of gas with a combination of town and highway riding, then refilled the tank with gas and another 16 ounces of Seafoam. It idles fine now, and does not have the just above idle stumble anymore. I'm sure it was just gas residue in the jets. I think I'll start draining the carbs every time it needs to sit more than a week.

Still not sure what you mean by blowing out the jets backwards. Can you explain that?
I think he means blowing aerosol carb cleaner in through the carb bowl drain.

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Hope this helps

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Last edited by OlHossCanada; 09-01-2012 at 11:06 AM.
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post #8 of 10 (permalink) Old 09-01-2012, 11:19 AM
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actually, I am meaning place a hose on the float bowl drain nipple and using a turkey baster or other kind of syringe inject seafoam right into the carb body. by using the drain port, the fuel will backfeed through both the pilot and main jets.

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post #9 of 10 (permalink) Old 09-07-2012, 10:45 PM Thread Starter
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That sounds like a good idea, I'll do it. I have already drained the gas out of the float bowls several times, and have not found anything big enough to see.

Now I have another question. I poured a whole 16 oz bottle of Seafoam into the tank, and filled it up with gas. We have ethanol gas here. I know that is way more than it says to use on the can, but it runs fine at highway speeds, with plenty of power and no misfiring. It was idling good to, until I put all that Seafoam in. I'm going to run the tenk empty, and put in plain gas. Could that much Seafoam cause it to misfire at idle, and hesitate when you blip the throttle?
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post #10 of 10 (permalink) Old 09-08-2012, 10:24 AM
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Yes. You are using too much SeaFoam. SeaFoam has close to 20% Isopropyl Alcohol in it. They recommend max 2oz per gallon of ethanol gas.

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