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'02 Vulcan 750, 27k
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11 Posts
Discussion Starter #1
I posted this in my newbie check-in, but realized it'll probably get more thoughts here.

I initially thought this might be related to a fuel filter or sediment in the tank - but I'm increasing thinking it's carb or cam related.

I have an intermittent (though growing more frequent) loss of engine power. It just drops for half a second - just long enough to be noticeable. I haven't noticed a corresponding drop in RPM, but that might be due to the tach's stalk shaking around alot, making it difficult to do a fine reading while I'm riding.

When idling, the RPMs bounce around a bit (~200ish range). Not sure if that's related or normal.

What I did think was related - and made me think of a fuel filter - the engine starts to act like it's running out of gas after using only 2.5 gal. It'll even sputter to a stop. I realized a couple days ago that I didn't test it for the phantom-out-of-gas condition... It also will sometimes die when the engine is still cold. Fully open choke helps prevent this - but does not completely eliminate it.

Alternately, someone mentioned that they heard cam chain noise and that I needed to replace the chain/tensioners. Could that be the cause instead? I don't really know what to listen for, so I can't validate that it was cam chain noise.
 

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Super Moderator
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2,569 Posts
a few things to look at..

for the 'out of gas' feel after a partial tank.. look into POOGS. usually the tank vent or the vent in the gas cap is plugged.

are you saying your idling at 200? or that the idle varies by 200 or so?

My bike will occasionally 'sneeze' after running at a steady throttle position (usually barely off the idle stop, with rpms below 2k or so) for a couple of minutes. and it only does it when warm (I drive thru same school zone once in morning when bike is not fully warm, and in afternoon when it is fully warm, and that's where it does it). My tach don't change when it sneezes, its like one cylinder does it one time.
 

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I realized a couple days ago that I didn't test it for the phantom-out-of-gas condition... It also will sometimes die when the engine is still cold. Fully open choke helps prevent this - but does not completely eliminate it.

Alternately, someone mentioned that they heard cam chain noise and that I needed to replace the chain/tensioners. Could that be the cause instead? I don't really know what to listen for, so I can't validate that it was cam chain noise.
These bikes are notoriously cold blooded, they really like to be warm before they will even out, the choke thing in the AM is completely normal.
Once the bike is fully warmed up the idle should not bounce around, if it does start looking for air leaks/bad air filters etc....

As for the Cam chain tensioners, the Automatic ones that came with this bike were kinda suspect. Most of us here have replaced them with manual ones(Wolfie makes a fantastic set). The sound your listening for if they are going bad/maladjusted is a clicking-ish noise from the engine almost like a sewing machine... but not quite.
The manual ones take all the guess work out of it remove the automatic ones one at a time. Replace with the manual ones and turn the screw in until feel tension in screw. Start the bike and continue SLOWLY tightening until the click stops and the bike does not bog down. If the engine starts to bog you went to far back the screw out in small increments until it starts running normal then set the locknut. Repeat the steps on the other ACCT and your done.
 

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If you want to be sure, record a video on your phone or something and post it to youtube, and paste the link here... we'll listen to it and can help tell you what it is... :)
 

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'02 Vulcan 750, 27k
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11 Posts
Discussion Starter #5
are you saying your idling at 200? or that the idle varies by 200 or so?

My bike will occasionally 'sneeze' after running at a steady throttle position (usually barely off the idle stop, with rpms below 2k or so) for a couple of minutes. and it only does it when warm (I drive thru same school zone once in morning when bike is not fully warm, and in afternoon when it is fully warm, and that's where it does it). My tach don't change when it sneezes, its like one cylinder does it one time.
It varies by 200 or so. A little more stable when warm, but not perfectly steady.

The power drop that I'm talking about has no sound associated with it that I can tell - it's almost like the bike gets hit by a big blast of wind; but I've noticed it happening at anywhere from 20-80 MPH, and doesn't get hit by a corresponding blast. Wind blasts also push the bike from the front, whereas this... The bike just bogs down for half a second. Worse, it's been getting more frequent recently. :(


As for the Cam chain tensioners, the Automatic ones that came with this bike were kinda suspect. Most of us here have replaced them with manual ones(Wolfie makes a fantastic set). The sound your listening for if they are going bad/maladjusted is a clicking-ish noise from the engine almost like a sewing machine... but not quite.
I went ahead and ordered a pair from TOC on Monday. Not sure when they might arrive though, I haven't heard anything. I'm looking forward to putting them in!

If you want to be sure, record a video on your phone or something and post it to youtube, and paste the link here... we'll listen to it and can help tell you what it is...
I'll definitely record it this weekend! Thanks for the offer. :)

Cheers
 

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2014 KLR 650!
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3,361 Posts
Have you ear shaved? That vent hose has to be in dead air (See the ear shave procedure post). POOGS is a definite place to start. clicking is most likely your tension er like jj said.
 

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Super Moderator
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Have you ear shaved? That vent hose has to be in dead air (See the ear shave procedure post). POOGS is a definite place to start. clicking is most likely your tension er like jj said.
and if your not earshaved, make sure the carb vent hose that goes to the right ear isn't bottoming out (cut a 45 degree angle on the end to prevent that)
 

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'02 Vulcan 750, 27k
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11 Posts
Discussion Starter #8
I haven't ear shaved yet. I really like the look of the ear-shave, but I'm hesitant to do it because fuel economy is pretty important to me (commuter bike) and it looks like it goes down after a shave.

I'll definitely take a look at that vent hose though.
 

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'02 Vulcan 750, 27k
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11 Posts
Discussion Starter #10
No? The ear-shave procedure post says that if you change the airflow, then you have to rejet. The ear shave doesn't actually change the airflow?
 
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