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post #1 of 9 (permalink) Old 08-14-2008, 01:03 PM Thread Starter
 
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Erratic idle speed

My wife has a 2002 VN750, low mileage (<2000 miles). She doesnīt ride it often enough, had to have the carbs cleaned (dealer service) 2 years ago. Since then Iīve kept it well dosed with SeaFoam etc to keep the carbs clean and try to ride it occasionally to keep semi-fresh gas in it. I can't ride it all the time because I also have to ride my Yamaha Warrior and Venture to keep them running ok.
I rode the Vulcan to work this past week and the idle is screwy. Starts ok w/ choke and it takes off/runs fine. After it is warmed up and off choke, if I slow down at a light or stop sign, it may idle down fine to ~1100 rpm, or it may idle down real slow: plateau around 3000 or 2000 rpm for 5 seconds or so and then slow down to 1100; or it may stay at the elevated rpm levels. It is not consistant, one time it may idle down fully, next time I slow down it may stay at 3000 or 2000 rpm. It may be the same several times in a row or alternate several times back and forth. The choke cable isnīt sticking, no fuel leaks.
I'm not sure where to start looking, I don't want my wife riding it unless it is behaving correctly. Any suggestions or possible solutions are welcome.
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post #2 of 9 (permalink) Old 08-14-2008, 09:42 PM
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I've seen some other threads with similar problems. Seems the best advice is to look for air leaks in the system, especially around the carb boots. Once its warm and things expand air entering into the system can cause the idle to increase. Hope this helps.

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post #3 of 9 (permalink) Old 08-14-2008, 10:55 PM
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It could be that the mechanism that brings the throttle to idle is hanging up somewhere. There are several levers that move the carbs throttles together and if they hang, the carbs don't return to idle.
It could also be that the dealer put the carbs together wrong. It's a common error if they took the diaphram assemblies apart.

Jim W
93 VN 750 "Ursula"
Moved R/R 08Sep06
R/R rewire 17Feb07
New R/R, Installed 14Jun08
New Stator installed 10 Jun08
Maintenance Free Battery 12Jan08
21480 Miles
VROC #8542
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post #4 of 9 (permalink) Old 08-15-2008, 10:45 AM Thread Starter
 
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Thanks for the replies.
Just what I need to pull out my hair: air leaks and hung up linkages due to the dealer. :-(
At least I have a direction to start examining things. These are the general "usual suspects" and I was wondering if there might be a pecularity to the Vulvan 750 with the conjoined carbs before I started dissecting.

Thanks again, at least I know where to start looking now. I'll let ya'll know how it turns out.
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post #5 of 9 (permalink) Old 08-15-2008, 01:24 PM
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Quote:
Originally Posted by waterdog View Post
My wife has a 2002 VN750,...(snip)... try to ride it occasionally to keep semi-fresh gas in it. I can't ride it all the time because I also have to ride my Yamaha Warrior and Venture to keep them running ok.
Ahhh, so many bikes, so little time.

Anyway, it sounds kind of like something is hanging up, though hard to say for sure without hearing/seeing it. Cable or linkage/lever like mentioned above. Just because a dealer did the work, doesn't mean things were done right....unfortunately.

Let us know what you find, and if needed, we'll keep trying to help.
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post #6 of 9 (permalink) Old 08-15-2008, 03:57 PM
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When my '89 did this, it turned out to be loose carb boots. The PO used plastic cable ties on the boots. I switched to hose clamps, and the problem has not returned.

Chris
Wayne, NJ
1989 VN750-A5
VROC #27781
-Replaced/Fused Stator & Replaced/Relocated R/R (15K mi.)
-MF Battery
-De-Goated/Re-goated
-Coastered
-Splines Lubed
-Stebel Nautilus Horn
-AutoMeter 2" VOM
-Silverstar Headlight
-Refinished Gauge Rings and Mirrors(Flat Black)
-Refinished Swingarm/Lubed Pivots
-K&S Turn Signals Clear Cover/Amber Bulb
-Kenda Kruz 110/90-19 front 170/80-15 rear
-Clear Alternatives LED tail light
-Plexifairing III
-Willie & Max Saddlebags and SissyBar Bag
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post #7 of 9 (permalink) Old 08-15-2008, 08:16 PM
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Chris, did you use normal automotive type clamps or did you have to order the OEM ones? My left side clamp bit the dust awhile back and I'm too cheap to order a new one so I used the cable tie method but if a normal hose clamp will work, I'll do that.

Jim W
93 VN 750 "Ursula"
Moved R/R 08Sep06
R/R rewire 17Feb07
New R/R, Installed 14Jun08
New Stator installed 10 Jun08
Maintenance Free Battery 12Jan08
21480 Miles
VROC #8542
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post #8 of 9 (permalink) Old 08-16-2008, 01:05 AM
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I tried to use OEM clamps, but they were way too small in circumference. I triple checked the PN to make sure they weren't the wrong ones. Apparently you REALLY have to work to get them on. Cindy told me she had the same issue with them. I went with standard hose clamps in the end, and they are working great. Much better than the cable ties.

Chris
Wayne, NJ
1989 VN750-A5
VROC #27781
-Replaced/Fused Stator & Replaced/Relocated R/R (15K mi.)
-MF Battery
-De-Goated/Re-goated
-Coastered
-Splines Lubed
-Stebel Nautilus Horn
-AutoMeter 2" VOM
-Silverstar Headlight
-Refinished Gauge Rings and Mirrors(Flat Black)
-Refinished Swingarm/Lubed Pivots
-K&S Turn Signals Clear Cover/Amber Bulb
-Kenda Kruz 110/90-19 front 170/80-15 rear
-Clear Alternatives LED tail light
-Plexifairing III
-Willie & Max Saddlebags and SissyBar Bag
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post #9 of 9 (permalink) Old 08-16-2008, 09:53 PM
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This something that you might want to check for the fast idle. The carbs are vacuum operated. I found out that my airfilters were not passing enought air thought them at idle for the slides to go back down. Had to much oil on the filters and also the filters were too close to the inlets (didn't have the cages that the filters mount to). Got some cages from someone here and took some oil off of the filters and my fast idle stopped.
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