Vacuum lines way off.. help please - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 9 (permalink) Old 07-24-2011, 09:05 PM Thread Starter
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Vacuum lines way off.. help please

Hey guys,

I have been searching and reading and as usual, there is nothing short of great info here.
Well you guys fixed my idle problem about 6 months ago, but now I have a new problem.
while running at 55 or 60 constant, I have a fairly annoying surge.
I searched and found that my carb vent lines with the T fitting were not going to the right ear, but to the back of my fuel tank. Yesterday I moved the Vent line to the right ear " which there is no place to stick the line so its just laying inside the filter..
So now while riding, if I go to accelerate with half throttle or more, the bike will sputter badly. But if I take off very slowly and short shift its ok.
so... Where exactly do you put the vent line on the right ear? There is no vent peg there..
And second, why after taking the vent line off of the back of the tank would I now not be able to accelerate?

I do have jardine pipes, but everything else is stock..

Also has been running great besides the 55-60 surge..

Thanks guys
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post #2 of 9 (permalink) Old 07-24-2011, 09:39 PM
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I think the earliest model years had the vent hose mounted on the bottom of the tank.
If your bike was running well with it mounted there, put it back.

If the vent hose has high speed air passing over the end of it, the pressure in the carb bowl fluctuates and will cause the surging you are experiencing.

The slotted hole in this picture of the right ear is where most of the vent hoses are located.
http://www.flickr.com/photos/leekayd...7600772238066/
If you relocate the vent hose to the ear, cut the end off at a 45* angle facing the slot to prevent plugging the hole if the hose gets pushed to the bottom.

If you earshave the bike, you can tie the hose so it faces the back of the bike to prevent vacuum/pressure fluctuations, or put a filter on it.

Gordon

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Last edited by OlHossCanada; 07-24-2011 at 09:44 PM.
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post #3 of 9 (permalink) Old 07-24-2011, 09:40 PM
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There's a little notch in the plastic back of the air filter box into which you should be able to press the vent line - it's along the top of the box, about an inch or two from the back.

The issue with a vent line facing forward is that it puts back-pressure on the carbs - they're trying to vent, and they've got all this air pressing right back into them. Kinda like yawning into a fan. :

C
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post #4 of 9 (permalink) Old 07-24-2011, 09:46 PM Thread Starter
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I hate to put it back if its not where its supposed to go. Seems to me like thats just a bandade...
Thats a great pic, I will see if I can get that line installed in that slot..

I just adjusted the air/fuel screws, no change to my mid range problem, but idle and low end is fantastic. No pop at all thru the exaust now either..

Just dont see how moving that vent line can cause this problem even at slow speeds..
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post #5 of 9 (permalink) Old 07-24-2011, 10:05 PM
If only it had 6th gear..
 
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Quote:
Originally Posted by RoachHotel View Post
I hate to put it back if its not where its supposed to go. Seems to me like thats just a bandade...
Thats a great pic, I will see if I can get that line installed in that slot..

I just adjusted the air/fuel screws, no change to my mid range problem, but idle and low end is fantastic. No pop at all thru the exaust now either..

Just dont see how moving that vent line can cause this problem even at slow speeds..
If you don't have the spot on the right ear to connect it then it is supposed to go under the tank so no worries there. So are you saying that you have to nurse the bike up to speed because if you try to accelerate quickly it bogs? It may be your low speed jets are dirty. They're active till around 2200 rpm (I think, somewhere around there). Could be just one carb doing it too (sputtering) and dropping a cylinder intermittently thus losing half your power. The surging could be another symptom of the carbs needing to be cleaned. When your cruising at 55 60 and it surges, does the
engine tone/rhythm (dropping a cylinder) change or is it more like if you flexed the throttle as you
go? Also what type of plugs are you running and have you popped them to check the condition?

Last edited by DavesVulster; 07-24-2011 at 10:07 PM.
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post #6 of 9 (permalink) Old 07-24-2011, 10:18 PM Thread Starter
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Ok well to throw a wrench in it. I put the line back on the tank and ofcourse it runs like a raped ape.
I didnt have a chance to hit the highway, but I will give more info tomm after my ride to work and back.

And I have crappy autolite plugs.

And yes when cruising at 55 the engine tone does change like its dropping a cylinder. But doesnt do it all the time, and I can always ride thru it. As in, hit the throttle and go 65.. Ride great for a few, then surges.. Go back down to 55 great for a min or 2 then surges. So its a constant speed, at or above 55 usually..

Also I would go with the carb cleaning, but I did all that bigtime a few months ago, had the tank relined, carbs fully gone thru. And it doesnt do the surging all the time.. Almost seems to be worse when its warmer outside. Could be my imagination, but afternoon ride home always seems more so then morning ride to work..

Good stuff tho, thanks.
More info tomm after ride to work.
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post #7 of 9 (permalink) Old 07-24-2011, 10:33 PM
If only it had 6th gear..
 
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Hmm.... you may find it's the plugs. I have the autolites in mine as well. They're ok but yeah nothing great for sure. Going with iridium later. Side note- I will never use champion plugs in any engine that is in my family. Had a set that would give up the ghost under a load dropping half my cylinders (460 v8 Lincoln land-ark) but would idle like it was new. Have known others who have had problems with them also. Anyway, my point is that if you've done the carbs you may be dealing with more of and electrical issue than fuel. Just a thought. I'd probably throw in a set or iridiums, and even if you've got to look further into this, you'll have the plugs everyone is raving about and maybe you'll get lucky and the problem will vanish. I hope that for you. Good luck,
Dave.
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post #8 of 9 (permalink) Old 07-24-2011, 10:40 PM
If only it had 6th gear..
 
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LOL, I was just thinking about problems during driving/riding. An engine will always screw up at the most common speed it's owner likes to drive at, making his life miserable. The 1st scratch in your windshield will always be directly in your line of sight, and the wiper that streaks or the washer nozzle that stops working...will always be on the drivers side! :/. Let us know how the ride is tomorrow. Peace.
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post #9 of 9 (permalink) Old 07-24-2011, 11:46 PM
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You may have a restrickted fuel tank vent at the gas cap.

02 honda sabre 1100
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