A follow-up to a question I had earlier... - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 26 (permalink) Old 06-18-2015, 12:58 AM Thread Starter
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A follow-up to a question I had earlier...

Got pretty much all the bugs worked out of my '02 VN750. I had asked a previous question regarding how the bike feels in 5th gear, at higher speeds. It seemed to hesitate when I was cruising around 60-65 mph.

I took it back into the shop, and they took it for a ride. They told me something that explained it, but I'm paraphrasing here. Want to see if anyone else has heard such a thing. They said that because the bike is carburated and not fuel injected, there are certain RPMs where, basically, the jets have to kick in where something else isn't, and there can be a slight lag while the bike is deciding which way it wants to go. (I wish I could remember exactly what he said) But, apparently, I should adjust speed to slightly above or below where that's happening, and that's supposed to "fix" the issue.

Does any of this make sense? Does anyone else experience this?

Mike's Moving
Orlando, Florida

2002 VN750

Need to know the part number to a confirmed 18mm Deep Well socket bit to change your VN750's spark plugs?

Craftsman Part Number 50728
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post #2 of 26 (permalink) Old 06-18-2015, 01:03 AM
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Were any mods done to bike?

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post #3 of 26 (permalink) Old 06-18-2015, 01:27 AM Thread Starter
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Originally Posted by OleDirtyDoc View Post
Were any mods done to bike?
No. Bike is pretty stock. No ear shaves, or any other mod that I'm aware of. I just had the carbs cleaned, new float bowl and needles.

Mike's Moving
Orlando, Florida

2002 VN750

Need to know the part number to a confirmed 18mm Deep Well socket bit to change your VN750's spark plugs?

Craftsman Part Number 50728
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post #4 of 26 (permalink) Old 06-18-2015, 09:13 AM
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Does it do it when you are just cruising at a steady speed or is it when you try to quickly accelerate at that speed? And have you noticed if a gust of wind can make it happen at that speed?

The reason I ask is if the carb vent hose isn't stuck in the slotted hole in the back of one of the ears (air filter box) it can behave like that with a gust of wind or accelerating. The best way to make sure that isnt a problem is to cut the end of the carb vent hose at a 45 degree angle and stick it in that hole. Then it shouldn't cause any issues.

As far as what the shop told you...maybe. But I would think that would definitely only happen on really quick acceleration and only if there is something else causing a brief lack of fuel. I never had any trouble with my vn accelerating quickly or hesitating except when the carb vent hose fell out of the hole.

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post #5 of 26 (permalink) Old 06-18-2015, 09:15 AM
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Quote:
Originally Posted by OrlandoVulcan View Post
Got pretty much all the bugs worked out of my '02 VN750. I had asked a previous question regarding how the bike feels in 5th gear, at higher speeds. It seemed to hesitate when I was cruising around 60-65 mph.

I took it back into the shop, and they took it for a ride. They told me something that explained it, but I'm paraphrasing here. Want to see if anyone else has heard such a thing. They said that because the bike is carburated and not fuel injected, there are certain RPMs where, basically, the jets have to kick in where something else isn't, and there can be a slight lag while the bike is deciding which way it wants to go. (I wish I could remember exactly what he said) But, apparently, I should adjust speed to slightly above or below where that's happening, and that's supposed to "fix" the issue.

Does any of this make sense? Does anyone else experience this?
NO, not right. At 60 you are doing around 4000 rpms. After 2800 rpms the carb is already running on both the pilot and main jets. The problem is either a fuel delivery issue, an ignition issue, or as simple as a carb vent issue.

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post #6 of 26 (permalink) Old 06-18-2015, 09:18 AM
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I'm with Deviate. You aren't going from pilot to main jet or anything.

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post #7 of 26 (permalink) Old 06-18-2015, 10:44 AM Thread Starter
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Quote:
Originally Posted by Deviate View Post
Does it do it when you are just cruising at a steady speed or is it when you try to quickly accelerate at that speed? And have you noticed if a gust of wind can make it happen at that speed?

The reason I ask is if the carb vent hose isn't stuck in the slotted hole in the back of one of the ears (air filter box) it can behave like that with a gust of wind or accelerating. The best way to make sure that isnt a problem is to cut the end of the carb vent hose at a 45 degree angle and stick it in that hole. Then it shouldn't cause any issues.

As far as what the shop told you...maybe. But I would think that would definitely only happen on really quick acceleration and only if there is something else causing a brief lack of fuel. I never had any trouble with my vn accelerating quickly or hesitating except when the carb vent hose fell out of the hole.
It seems to accelerate (and decelerate) just fine. It's when I'm "cruising" that I sometimes seem to get it. When I first noticed it happening, I actually assumed that it WAS wind causing it, and I still think I get a little of that. But, when I'm cruising, trying to hold the throttle at a constant speed in that range, that seems to be when it happens.

Mike's Moving
Orlando, Florida

2002 VN750

Need to know the part number to a confirmed 18mm Deep Well socket bit to change your VN750's spark plugs?

Craftsman Part Number 50728
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post #8 of 26 (permalink) Old 06-18-2015, 10:48 AM Thread Starter
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Quote:
Originally Posted by JM2001 View Post
NO, not right. At 60 you are doing around 4000 rpms. After 2800 rpms the carb is already running on both the pilot and main jets. The problem is either a fuel delivery issue, an ignition issue, or as simple as a carb vent issue.
Now, when I had the carbs cleaned, this reminded me, I had the...crap..now I'm trying to think of the damn word....the little thing on the left side of the bike that turns the fuel on and off replaced.

Even with dirty carbs, I don't recall the bike doing this before when I was cruising. I figured that since this was the first time I rode with the carbs cleaned, that his explanation was reasonable.

I'll check the vents, and I'll see if I can look at the fuel lines, but why would ignition cause this? Do you mean the plugs?

Mike's Moving
Orlando, Florida

2002 VN750

Need to know the part number to a confirmed 18mm Deep Well socket bit to change your VN750's spark plugs?

Craftsman Part Number 50728
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post #9 of 26 (permalink) Old 06-18-2015, 01:10 PM
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I've seen 4 cylinder cars do this exact thing when the plugs and wires need replacing. Accelerate and everything just fine, but would sort of lose power, or hesitate at cruising speed. A "mechanic" told me that the insulation on the wire loses resistance after awhile, but couldn't explain why it would only affect performance at specific speeds.

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post #10 of 26 (permalink) Old 06-18-2015, 01:21 PM
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Quote:
Originally Posted by JM2001 View Post
NO, not right. At 60 you are doing around 4000 rpms. After 2800 rpms the carb is already running on both the pilot and main jets. The problem is either a fuel delivery issue, an ignition issue, or as simple as a carb vent issue.
Jets work according to throttle, not rpm.

At 2800rpm in fifth, I'm definitely under 25% throttle. That said, main won't kick in til somewhere after 35, and needle not til 50% throttle. You can have 2800rpm at full throttle too, and at all positions between, while accelerating.
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