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Discussion Starter #1
The bike startes up and idles real good. If I just take a real short trip 1-3 miles, it idles normal when I come to a stop. But, if I take a longer ride and go faster, when I stop the at a light it has a fast idle for awhile. After some time it will go back to idling low again. I am guess that one of the cyclinders is filling up with fuel when I am going. The bike does run good when I ride it on the road. It does not backfire, also. How do I get ride of this fast idle after it hass been driven for awhile?
I tried last year to sinc the carbs by the yardstick method. Got them close at low idle.
 

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I'm no mechanical guru but your bike probably isn't warmed up completely in 1-3 miles. After the engine has warmed up thoroughly try adjusting the idle speed to 1050-1150 rpm by turning the idle adjustment screw.
 

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Discussion Starter #3
The idle is set correct. After it has run the long distance and sets for 5-10 min it will idle back to the same idle as when cold.
I think that it is loading up with fuel. Not sure what to adjust.
 

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Also make sure all the "boots" holding the carbs are on tight. A loose one can let in air and up your idle.

Mine did this when I first got it, I adjusted the air screw...which helped, but then I found that one of the clamps around the carb was not tight...and after checking and tightening them all, and re-adjusting the idle speed...no problem ever again.

KM
 

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Discussion Starter #6
Checked the boots and clamps, they seem to be tight. Could not move the clamps any, so I guess that they are tight. Have tried pushing the cable stop closed when it has been fast idling and it doesn't help any.
 

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Checked the boots and clamps, they seem to be tight. Could not move the clamps any, so I guess that they are tight. Have tried pushing the cable stop closed when it has been fast idling and it doesn't help any.
So you are saying you did not actualy stick a screwdriver into them and try and tighten them, you just felt to see if they moved???:doh:


KM
 

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Discussion Starter #8
Could not get to the heads without taking the gastank off. Put a screwdriver to the backside and pushed. there was no give or play of any kind. Also, took Carb cleaner and sprayed on them with the bike running and there was no change in idle. If they were suctioning air, they chould have changed idle when I sprayed them.
 

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Dont forget, Engine speed is controlled by AIR going in the engine. You are getting too much air in the engine for whatever reason. Keep this in mind while hunting.
 

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I also have had the same problem. I am still not sure if the problem has completely cured but it has not happened the last few times i have been out.
Another idea to check would be the choke. I would check to make sure that it is completely shutting off when you close it. If not that then i would refer back to a carb. clean. I have done alot of reading on these types of threads due to my problem which is identical to yours and they all refer to either an air leak or most likely a dirty carb. and something is sticking inside. So i would try that and if that's not it; when in doubt pull the carbs out.
 

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Discussion Starter #12
I think that I have found the problem. Was talking to one of the mechanes at work about this and he said to spray the carb cleaner when it was fast idleing and see if it then slows back to normal. Tried it the other night an it work, brough the idle back down. He said that the carb boot has a small crack in the rubber. When the rubber is cold it seals up, when it gets hot, it opens up a little. The spray seals the crack back up. I guess that I need to get some new carb boots. While I have the carbs off, I will give them a good cleaning also.
 

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Just a little tip for the future, tell us how old your bike is, how many miles , what has been added (or removed) and where you live.

If I had thought your bike was older, rather than suggest just checking the tightness of the carb boots I would have also suggested inspecting them for cracks...

Glad you solved the problem...

KM
 

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Knifemaker,
Just wanted to bounce this off of you. I took my bike for a spin..after adjusting the idle slightly up to about 1100 rpms....while riding ..it seemed a couple times the throttle didn't return fast enough to idle.....almost like it was sticking....is this common? i have an 05 750vn.....i was wondering what i should do if anything? other than that ..its running like a top after my ngk sparkplug/wire tune up and new mfb....
 

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Most of the time if the bike won't return back to normal idle after it is warmed up, but does so fine when cold, it is an air leak. Just like the OP stated, as the engine and all the rubber stuff around it warms, things expand and any pin hole in rubber boots, vacuum hoses etc. will open up. First thing to check "always" is your throttle cables, making sure they are free of any binding and returning the throttle to the stop. If all that is working smoothly, it just about has to be an air leak. On older bikes, many have discovered leaks in the hoses of the air switch which has been sitting on top of the engine for it's life, baking in a slow heating oven for years. Anyone here ever used a dehydrator to make jerky? Low heat over several hours makes the strip of meat dry out and bet brittle... I'm just saying...:smiley_th
 

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Calif Rider
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Try a good dose of Sea Foam in the gas and a good ride, what about the air filters? Have they had a good cleaning lately. Just my 2 cents.
 

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Eagle Riders 4146
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Most of the time if the bike won't return back to normal idle after it is warmed up, but does so fine when cold, it is an air leak. Just like the OP stated, as the engine and all the rubber stuff around it warms, things expand and any pin hole in rubber boots, vacuum hoses etc. will open up. First thing to check "always" is your throttle cables, making sure they are free of any binding and returning the throttle to the stop. If all that is working smoothly, it just about has to be an air leak. On older bikes, many have discovered leaks in the hoses of the air switch which has been sitting on top of the engine for it's life, baking in a slow heating oven for years. Anyone here ever used a dehydrator to make jerky? Low heat over several hours makes the strip of meat dry out and bet brittle... I'm just saying...:smiley_th
Try a good dose of Sea Foam in the gas and a good ride, what about the air filters? Have they had a good cleaning lately. Just my 2 cents.
Reviving an old thread. I'm having the same issue with off and on fast idle...about 4K. Not sure it's a matter of cold v warm/hot engine as it will sometimes happen at start-up, a couple blocks from the house, or after riding several miles.

A few weeks ago I had the choke cable replaced after it broke some months ago. I'd noticed the problem right away, but at first it would idle around 2K, and so I really didn't think anything about it. It wasn't until researching this forum that I learned the optimal idle speed is 1050-1150 rpm. When I pull up to a light, sometimes it will high idle while other times it will idle around 1K. It wasn't until the past few days that it started to idle at even higher rpms. On the ride in to work this evening I was really noticing it. I was going down the road at about 2K rpms when I engaged the clutch to see what it would do...it went right up to 4K.

It's running well otherwise; no sputters or hesitation when accelerating or cruising - highway or city streets. Even though this is happening at start-up too with a cold engine I'll still check all the rubber for leaks. I've already purchased a recharging kit for the K&N filters, and will give them a thorough cleaning and coat of oil this weekend along with adding extra Seafoam into the tank. Maybe I'll get lucky and it's just dirty filters and/or something sticky. Any recommendations on the amount of Seafoam to add? I've heard that there is no "too much" amount, but kinda of nervous with adding an entire bottle without first getting some feedback from y'all.

Thanks, Jimmy Mac
 

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Funny - I am the 2nd owner of my 86 Vulcan 750. I owned the same yr\model bike in 1990, at 20 yrs old. I loved it, but let it go because I just had to have that Ninja, lol. Now, at 47yo, and wiser, I nailed the same year, same model, in EXCELLENT shape, for a lowball of $800. Couldn't believe he took my offer! He bought it brand new in 1986, I even got the original title with 1 mile on it, lol. Both tires are brand new Dunlops. Oh, and it only had 24,500 original miles on a 31 year old bike! 1st thing I did once home was put in a little fresh gas, and took a 6 mile ride. Went pretty good. Registered the next few days, and proceeded to Napa to change plugs, and buy oil and filter. Bike had freakin Champion plugs.....Put in the infamous NGK's it called for, right in NAPA's parking lot. Performance and starting difference was instant! Only other thing I have done is install new auto cam chain tensioners from TOC. Absolutely silent now, VS just a hair of slap before the change. I must say though, like my bike in 1990, it is a finicky ride. You have to learn how to start it, and when to use choke, etc. If I shut if off, run in store, and come right back out, I use choke, and it instantly fires up. No choke equals a backfire, lol. 10 mins or so, no choke needed. Same as other bike in 1990. However, I have noticed the idle issue. After riding 10 or 15 miles, my idle is up to 1300-1400 rpm at a stop light, but if I just let out the clutch a tiny bit, not even enough to move, the idle drops down to 1100-1150rpm and stays there, idling smoothly. I see Seafoam is next to godliness, but never used it. I will be buying a can and dumping in tank to clean er out. No rust inside tank whatsoever. I also notice if I am cruising, and pull in the clutch, while coasting the RPM's don't drop as fast as I feel like they should. Seems they should drop right away, as I am disengaging driveline from engine by engaging clutch. Just curious if anyone has that infamous "Light bulb lighting up in your head" thing, guessing or knowing the symptoms and what I should do. I drive it every day, and love it, but strive to continually improve what I can. Any input is appreciated, Ride safe and watch those other people on the road! :) Mike
 

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There are too many variables to high idle. Choke sticking, throttle sticking, carb boots leaking, etc.

The best way to eliminate it as quickly as you can is to test for internal or external issues. If theres a leak wd40 will find it. Start the bike and spray everything on the carbs listen for changes in idle.

If the bike doesnt change it isnt air, its fuel.
 

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1985 VN-700
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High idle

I believe mine was because of the choke not returning to off. One carb was sticking. Is really an idle enrichment valve and not so much a choke. The cable ad lever would return to off, but one enricher was not returning to bottom.
 
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