Sputter and no power @ 50 mph - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 6 (permalink) Old 06-03-2008, 01:20 PM Thread Starter
 
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Sputter and no power @ 50 mph

86 Vulcan w/ 11,400 miles. starts good, idles good when warmed up.

here is the problem...

this is an intermittant problem - last sunday i rode over 100 miles with no issues (but had a lot of seafoam in the tank). now this problem is here a lot - but it does go away every once in a while (after stopping at a light or stop sign).

driving @ 50-55mph in 5th gear, the bike sputters, bogs, and pops under full throttle with no power. it will still stay at 50 and cruse, but try to accel and it has 0 power. down shift to 4th and floor it and it accels to 60, but not hard like it should. sometimes it goes away and the bike runs fine for a short amount of time.

1st - 3rd (even at low rpms) is fine - the issues are only noticed in 4th and 5th only

could the splines on the rear drive be messed up? the bike gets a vibe when it is trying to accel and it sputters.

my though is - if it is the splines, it will fail constantly and the rpms will increase with more throttle - not lack power and bog.

i have an appointment with the dealer in 2 weeks for a carb clean and rebuild, but if anyone thinks i should try something first let me know.

just a fyi... i can, but don't have time to rebuild the carbs myself (new baby at home) and i need this bike fixed quickly.
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post #2 of 6 (permalink) Old 06-03-2008, 01:47 PM
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You'll often find this condition if the carb vent tube (from the carbs to the right ear) bottoms out in the airbox. Cutting the tube at a 45-degree angle where it sits in the airbox is the quick and easy solution to that (can't completely seal itself against the box). See if that helps.

C
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post #3 of 6 (permalink) Old 06-03-2008, 01:51 PM Thread Starter
 
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thanks, i'll try this before my ride home today and see if it works.
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post #4 of 6 (permalink) Old 06-03-2008, 02:52 PM
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Mine did the same thing yours is doing. Tried Seafoam and that didn't work. Cut the vent at 45, didn't work. Took the carbs off and cleaned out the bowls, and that worked. An 86 with only 11k or so on it has sat alot. Depending on if it was garaged or out in the weather and on whether the gas was changed out regularly, which I doubt, I'll bet the carbs are pretty gunked up. Seafoam can work wonders on some bikes but if the gunk problem it too great, it can't do it all by itself.

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 #5 of 6 (permalink) Old 07-29-2008, 11:31 AM
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Hey, just wondering how this worked out? I am experiencing almost exactly the same issue. I've worked out pretty much everything else with the bike. Now that it idles great and has been running like a clock for a few hundred miles, I think I may be riding it a little more 'spirited' than I had been! So I am not sure if the problem existed all along, and I just wasn't noticing it because of everything else, or it is a new issue. I figured it was the vent hose, but I've tried inserting it at different depths (already cut to 45 deg), and I've also tried to let it hang free in the airbox; but no joy. I've backflushed the carbs a few times over the past several weeks while dealing with other stuff, and the solvent always flowed out the vent hose as expected, so I know it is not completely blocked. I'm going to try take the vent hoses off and blow them out with compressed air to clear any junk that might be restricting airflow. I am hoping to avoid pulling the carbs to clean out the bowls. (I also run a few ounces of Seafoam into almost every fill up) So far, I've managed to find and fix all of my issues, even the one I caused , without having to pull the carbs. I have a feeling that that is about to change!

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 #6 of 6 (permalink) Old 07-29-2008, 09:14 PM
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The problem with backflushing and the like is that it only gets into the idle jets and not the main jet. The opening in the main jet is very small and it doesn't take much to restrict its flow. The only thing that worked in my case was biting the bullet and removing and tearing down the carbs. I took the jets out and blew them out with compressed air. That seems to have remedied the problem. Just make sure you really tighten them down, though not too hard as they are brass. The high speed jet on my rear carb vibrated loose and acutally came out of its mount causing the rear cylinder to die at 3500 RPM. Once I put the jet back in, all was well.

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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