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post #1 of 11 (permalink) Old 07-09-2013, 01:56 PM Thread Starter
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another high RPM idle thread

Hey y'all-
I hate to do this, but I need some opinions.

I have put over 7,000mi on my '96 vn750 since I got it a year ago(doubling its mileage!). It has always cranked & ran wonderfully. I kept a dose of seafoam in each tankfull throughout the winter, and rode fairly regularly. I remember one 70 degree day in January!

Now, since this spring, I quit dosing with seafoam. I thought more frequent & longer rides would not warrant the seafoam...

At times, ever since I've had the bike, it would rev up when stopped at red lights (at idle). Sometimes I would lean the bike to the right & turn the bars to the right, & it would settle back down @1000 RPM. I looked at the cable routing & tension and they seemed ok to me. I ignored this since it did not happen often.

Now, last weekend I was returning from another fine ride, when I stalled it stopping for the neighbor's lawn mower in the drive. When it cranked back up, it began the high idling again. I rode to the top of the hill & killed the engine like I always do to coast on in. I heard a backfire on shut-down which has never happened before. Ever since that day, it revs up to 4000 RPM as soon as it is getting warm from cold start.

I performed Wolfie's back blow carb cleanout procedure once on each carb yesterday with no difference afterword. I think I may need to remove carbs & give a thorough cleaning...

If I get the bike back to running like before, I will not abandon the seafoam ever again!

So, what do y'all think?

edit: Oh yeah, I have tightened the carb boots once before when I saw black soot at the cylinder side of them. There were no symptoms at that time, though. All rubber seems to be in good shape, too.

Last edited by sculpinyakker; 07-09-2013 at 02:03 PM.
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post #2 of 11 (permalink) Old 07-09-2013, 02:19 PM
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I'd visually check the choke on the carbs to see if it's engaged. You could have a stuck choke cable?

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post #3 of 11 (permalink) Old 07-09-2013, 02:33 PM Thread Starter
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Yeah, I did. The little brass plungers fully retract into carbs when choke is off. Also, the throttle cables are not tight or bound. I can hear & see the throttle levers hit stops on the carbs (if you follow me..?)

I'm not very confident messing with engines, but I will have to do any work needed, myself. I may superdose with seafoam & make small runs around the house, hoping for good results. I really dread tearing into the carbs. A local Kawi mechanic says he has learned of one bike with carbs more difficult than these...

As my luck would have it, after a solid week of rain, it's maintenance time!
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post #4 of 11 (permalink) Old 07-09-2013, 02:50 PM
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Well if you got a change by moving the handlebars I suspect you have a sticky linkage or a sticking cable.

Spray the crap out of the linkage with WD-40 and lube both cables (not with WD40)

The throttle should snap back loudly when you let go of it when it's opened.

I'd check the carb boots again....start the bike and spray some of that WD40 at them...if the RPMs go up, you got a leak.

Never stop using SeaFoam....

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post #5 of 11 (permalink) Old 07-09-2013, 03:25 PM Thread Starter
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Thank you Thtanner & Knifemaker for your replies.
KM, I'll do as you suggest.

I guess I should tell you guys that I also am guilty of spraying carb cleaner on the carb boots & cylinder heads to clean the soot I talked about earlier... I did spray off with the water hose soon after though.

I now wonder if that may have caused the boots to deteriorate. I'll give them a good look & see.

Thanks again
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post #6 of 11 (permalink) Old 07-09-2013, 06:51 PM
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^Don't know about the effects of carb cleaner on the rubber boots, but I do know if you sprayed any on the carb linkage you would have washed away any grease or oil on them. Spraying it with water AFTER this would make it worse.....

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post #7 of 11 (permalink) Old 07-09-2013, 06:55 PM Thread Starter
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Update

I got home from work and cranked her up and soaked everything between the cylinders with wd-40. No change in engine speed. I did worry about starting a fire though, when the stuff ran onto the pipes!!

While pondering my next move, I remembered the PO put a new tank on and had it painted. I always thought this had something to do with how I rode 8-9 miles with the gas turned off one time

Now, yesterday while doing the Wolfie carb blow, I had the gas valve off. When I finished that procedure, I went for a test ride and didn't turn the valve back on. I didn't make it to the end of the drive before She ran dry and died. Must have been enough carb cleaner in there to get that far??

So, since the gas shutoff is working now, I wonder if something broke loose from it and clogged the carbs up?

Although i may be loosing it, I'm about ready to just pull the carbs and give them a once over.
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post #8 of 11 (permalink) Old 07-09-2013, 06:57 PM
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I hope that you're talking about the external boots. You can get away with that, but if it's internal rubber, bad juju. I learned the hard (and expensive) way about that...

Reminds me, I need to lube my linkage...



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post #9 of 11 (permalink) Old 07-09-2013, 08:08 PM Thread Starter
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Yeah, outside. The only time I've peered in was undoing intake side boots for wolfie's blow job.

Km, I still think linkage and cables are working right...
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post #10 of 11 (permalink) Old 07-09-2013, 08:59 PM
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I have the same issue with my bike. I'm pretty sure it's a carb problem. I'm going to pull the carbs, do a complete cleaning, and replace the float needle valves. Unfortunately I can't get to it for about the next three weeks.

I think that a good cleaning will resolve it but we'll see.

I've checked the entire throttle and choke linkage and it works fine. It's gotta be in the carb.
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