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Discussion Starter #1
So I sent my carbs (not on the bike) out to be cleaned, the float needle wasnt sealing and she would leak gas all over and flood out a cylinder (it took a month!) I got them back last week, put them back on and started her up. The problem no longer exists. I rebuilt the petcock, cleaned out the tank and tried to synch the carbs by sound (no manometer). I have her idling (by sound) better than she ever did in the 8 years we have been together. BUT, she runs like crap on the road unless I rev her waaaay up there. So at 85 MPH she feels smooth and sounds great, but from past idle till 6000 RPM she feels like a slug. She is de-goated, and has HD Dyna pipes....but she ran great with those mods for quite some time before the carbs got gummed up.
The question:
Does this just sound like a typical synch problem that could be fixed with the proper synch tools (manometer etc)
OR
did I get back a dirty carb? I havent had a real ride since May and I am going freakin NUTS!!!!!
I have an appt with the shop on thursday after work for an inspection and a synch... should I keep the appointment?
 

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Someone once told me to sync the carbs by ear, but for the life of me I had no idea what I was listening to. So I built my own manometer and use that now for syncing purposes. Cheaper than a mercury one, cheaper labor (ha!), and if you leave the tubing from one side of the manometer on the exhaust pipe and it melts, it's a $1.00 replacement (not that I've done that or anything...).

Here's the link to the one I built: http://www.powerchutes.com/manometer.asp

Might as well try that yourself before heading back to the shop.
 

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Discussion Starter #3
well, It turns out I synched it by ear quite well. The mechanic told me I was not off by much at all. But she is still running crappy. he did temperature tests on each cylinder, synched them and rode it. It still runs like its not getting enough fuel at mid RPM's.
Since the carbs were professionally cleaned, I figure that it is not the carbs. But of course they could have done a poor job....see my dilemma?
Anyone know what else could cause the bike to run poorly at mid RPM's? and have no power?
 

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Good job on the ear-sync! Yours must be better-trained than mine (I still can't quit my day job! :mad: )

When I was having trouble in the midrange with McKnight, turned out to be my rear coil. Maybe check your ignition coils - make sure the wires are attached properly to the coils themselves, and that the spark plug cap is firmly on each plug. But I found that out by looking for a vacuum leak - reportedly, if you spray WD40 around the carb boots, ducts, etc., if there's a leak, you'll experience an increase in idle. (I just saw sparks by the back of the airbox and realized that the coil was shorting...).

Here's a link to that thread and some of the suggestions. http://www.vn750.com/forum/showthread.php?t=4695
 

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Discussion Starter #5
thank you for the response and the compliment!
Anyway, I think you may be on to something...I will definately check the coils and wiring. I just rode through a tank of gas/seafoam. I went 96 miles till the needle read empty. Now thats some crappy gas mileage!
 

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Wow - that's pretty bad! I haven't checked my mileage since I fixed the coil, but I'm hoping it's better than that.

If you read through that thread, you'll pick up (hopefully) that if you're using a substance to check for a vacuum leak...but you are wondering about an electrical problem...use a non-flammable substance. Someone suggested Windex; I used WD40, which I believe could've left me without eyebrows... :wow:

In addition to checking for a coil short, jsut make sure that the wires to the coils (the red and the green) are actually attached. They're easy to knock loose, and also easy to forget about reattaching after having bits of the engine off.
 

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Discussion Starter #7
no vaccuum leak, and no visible short. All wires are attached and in great shape. I took apart the petcock too and it is working properly (with a new diaphragm).
Tonight I will look at the air filters, maybe they are gooped up, I did have them off when I took off the carbs but I did not look them over.....
if no luck then I will assume the carbs are still junked up and bring it back to the shop. This problem began AFTER I had the carbs cleaned. The carbs used to spill gas which was definately fixed, but now it runs poorly...
 

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no vaccuum leak, and no visible short. All wires are attached and in great shape. I took apart the petcock too and it is working properly (with a new diaphragm).
Tonight I will look at the air filters, maybe they are gooped up, I did have them off when I took off the carbs but I did not look them over.....
if no luck then I will assume the carbs are still junked up and bring it back to the shop. This problem began AFTER I had the carbs cleaned. The carbs used to spill gas which was definately fixed, but now it runs poorly...
Hmmm... definitely check the air filters (folks have found that they've crumbled in situ) and the ducts to the airbox; but unless the shop is willing to take care of your carbs gratis, I'd suggest thinking about cleaning 'em yourself (my motto: If I can mess up for free what I can pay a professional to screw up, I think I'll do it myself...).

Can you give a more detailed description of what "running like crap at mid-range" looks and feels like? Like, can you even take the bike to WOT and have it run?
 

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Discussion Starter #9
running like crap:
It idles like a dream, and even revs nice in the driveway, but put her under a load and I have no power. I can get her up to cruising speed, but it does not have any pull, it kinda "breaks up" and I can tell that it is not running at peak performance. In fact going up a steep hill (that I usually can keep pulling to the top) I cannot even go 55mph! I would not even dream of passing someone on the flats...I worry I wont get around them.
She is in the shop right now waiting for new air filters so they can put her on a dyno.
I just want to ride!!!! this is starting to make me angry.
my wife was riding in a car on the way to drop off the bike, she said my exhaust smelled funny...not like gas from the can but not right.
 

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I was having trouble with McKnight awhile back, and it turned out to be the rear igntiion coil. Changed that out and it was fine. But then I sync'd the carbs and put the engine guard back on last weekend, and it ran like crap - like the kinda crap you're describing - all over again. Changed the plugs, swapped out the coil, still ran like crap (I couldn't even hit 45 mph!). So I pulled the air filter housing units and one of the ducts going to the airbox had come loose at the bottom, in an area where you really can't see it unless you pull the entire housing unit. I'm figuring that duct is perhaps a little "tired" and I probably smacked it a time or two trying to get the engine guard back on. Took it out yesterday, ran great again (65 mph, WOT, no break-up at all).

The thing about vacuum leaks - even small ones - is that it's like trying to drink a Coke with a hole in your straw. Just not enough suction to get fuel into the carbs. Works ok at idle, 'cause there's no airflow, but once you're moving, it gets all messed up. I'm still thinking they did something when they "professionally" cleaned your carbs - either didn't put a gasket in right, or there's a small leak in there somewhere. That's gotta be really frustrating -not just not being able to ride, but having to keep taking the bike in for service. :mad:
 

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Benjammin'
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I'm not a huge wrench, but in my experience, it sounds like you may have a cylinder dropping off. Loss of power in combination with poor gas mileage usally is an indication of one cylinder not firing. Have you pulled your plugs after a ride and looked at them to see if there is a difference between sides?
 

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Discussion Starter #12
I agree especially with the fuel efficiency problem. The rear is definately not keeping up. When my new air filters get here, I they will put her on a dyno and test her out. Then I will know what is up.
and yes, we pulled the plugs and tested the exhaust temp. the front was a little rich but the rear looked fine.
 

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Discussion Starter #13
In case you are wondering what happened...
They need new filters so they can get a true fuel air ratio on the Dyno. I sent away for filters, waited a week, and was told they cannot get them anymore! I am mad! anyway, I bought some K&n's which still are not here from E-bay. Still waiting and have only gone through 2 tanks of gas all summer!
I can only wait...
 

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so did you get things worked out?
 

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Discussion Starter #15
Riding Again (somewhat)

So the K&N's went in the ears, mechanic went for ride...no change. He took off the carbs (again) and adjusted the float height, put them back in and I have my bike back! She runs like a dream! He showed me the dyno runs on the computer (no printout for me to keep) and showed me the horsepower and even compared it to a brand new yamaha 750 side by side. the Vulcan was 9 HP more. In my excitement (that she runs) I cannot remember exactly but I think it read either 49 or 59 HP then it tapered off till the redline. The VN750 spec sheet states that we are riding 52 or 65 depending who you talk to...but anyway, I believe it was just a speck in the carbs, all said and done (not including the air filter) cost me $360 and almost the entire summer in time. You can bet I am going to run seafoam and winterize... But I must say, 360 dollars in 13 years is not bad. As this is the first time I have had her serviced at a shop!
Thanks everyone for your thoughts and ideas. I gotta get some sleep so I can get up early and ride!
BF
 

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and the Adventure Cycle
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Great news, Weasel!!
And like Cindy said, there's still plenty of ridin' time. (Just tell your boss the carbs got fixed, but the steering wouldn't let ya turn around!!) :smiley_th LOL
 

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Yes coils can hurt performance that was a problem with a honda 450 I had was fixing up. since you checked air leaks you found none is another thing. Dirty air cleaners as others have said can cut milage and performance. I had a honda 400 auto that had a hestitation at low rpms and felt it was a carb problem. Try to pull one wire (spark plug)off at a times and see if it dies this will at least tell you if something is wrong on one cylinder. I imagine you already did this.
 
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