Air mod issue - Kawasaki Vulcan Forum : Vulcan Forums
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post #1 of 15 (permalink) Old 08-01-2017, 11:52 AM Thread Starter
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Air mod issue

Hey all, John here. I have a 2002 Vulcan 800. As an attempt to correct a lean condition I was having I decided to perform the grampsize mod that the Russian wolf guy has a guide on. I followed all of his recommendations. Using the OEM needle with a 170 pilot and 52 main jets. I also cleaned the carb while I was at it and checked the float height. All seemed well so I put it all back together with the mix screw 1 and 1/2 out. From then it's been lean, I adjusted the screw (while the bike was running) literally all the way til it fell out. I could barely hear idling difference's while I was adjusting the screw and no matter where the screw was at if I rolled the throttle more than 1/4 way it would die.

What could be the cause of this? I tried putting washers on the needle to see if I needed a shorter needle but that did nothing good, I'm guessing something must be clogged or I have a vacuum leak. I just had it apart, I checked the pilot and main jet for blockage, I checked the line from the petcock and that isn't leaking, I checked the green hose going back below the ignition and that is fine. Is it possible that the rubber boot connecting the carb to the heads is loose or leaking? It feels secure but I hate the clamp that's on it.

All help is appreciated.
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post #2 of 15 (permalink) Old 08-01-2017, 11:20 PM
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I looked up an old post I made about scooterizing my airbox and according to that I used a 170 main jet, and a 48 pilot jet, a dynojet needle and had the idle adjust screw 3 turns out. Considering you used a 52 main jet I am surprised its running lean. If you are 100% certain the carb and jets are spotlessly clean then I would suspect maybe you have a vacuum leak. I was told you can check for vacuum leaks with carb cleaner by spraying around the connections with the bike running. If the idle changes at all then you have a leak. You could also double check that the jets you have installed are in fact the correct size, the teenie numbers they are stamped with are really difficult to read.

Never argue with a fool: onlookers may not be able to tell the difference.
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post #3 of 15 (permalink) Old 08-02-2017, 08:52 AM Thread Starter
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Thank you Beans for your response, I actually did spray carb cleaner on it last night as the sun went down. There's definitely a vacuum leak, I felt like it was certainly the carb boot but I just took it off and inspected it. The boot itself seems fine but I'm not sure if the clamp is working properly. I made sure it was seated correctly and tightened it down as far as I felt necessary and it still seems like it's leaking, is it possible that this clamp is actually creating a leak by tightening it? I ran out of carb spray last night so I'm about to go get some more. If it's not the boot leaking what are the chances that the carb body itself is leaking? The pet cock vacuum line looks secure and in good condition so I don't know what else could be leaking on the motor side of the carb. I'll post in a couple of hours after I get some more spray and try to pin point this leak.

Thanks again.

EDIT: So Vacuum leaks were the issue, the carb boot was loose but wasn't the only issue. A few areas on the carb body seem to be leaking as well so my best guess is these vacuum leaks were present before I started this project and in the process, I made them a lot worse. As soon as these repairs are complete I will post to update the status. Hopefully, there won't be any more surprises.

Last edited by jdh2683; 08-02-2017 at 11:29 AM.
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post #4 of 15 (permalink) Old 08-10-2017, 09:15 AM Thread Starter
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So, I fixed all of my vacuum leaks. There is still an issue that I can't figure out. The bike idle's just fine, but when I roll the throttle it dies. I've noticed that the valve slide kind of sputters if I jump the throttle to about 1/4 way before it dies. I inspected the diaphragm and it seems fine, I've re-seated it numerous times and every time it's exactly the same. Another test I tried was to lift the slide as I rolled the throttle slowly and this didn't help. I inspected all the jets again (re-cleaned as well) everything looks perfect. I'm not good with floats but I know that the bowl has gas in it when it is off. Is it possible that when running the bowl doesn't have sufficient gas to throttle? Every time I drain the bowl it seems like it has plenty of gas in it.

Could the slide be the issue even with the test I performed? At what throttle should the slide begin lifting?

Any help is very much appreciated.
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post #5 of 15 (permalink) Old 08-10-2017, 09:35 AM
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Did you remove the needle shims? Also, I'm not certain about grampsizing, but with scooterizing the recommended main jet is a 50, I ended up using a 48 and it runs fine. Perhaps your 52 main jet is too big?

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post #6 of 15 (permalink) Old 08-10-2017, 09:46 AM
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Just right after it dies, take out your spark plug (any or both one by one) and inspect it, if it's wet or dry. If it's wet, You have too much fuel and not enough air for that fuel amount.
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post #7 of 15 (permalink) Old 08-10-2017, 10:21 AM Thread Starter
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Beans, I did take the shims off. I thought the main only really came into play with more open throttle? I guess I can try putting the stock back in but I don't think less gas is going to help haha.

Tehnis, I ran your plug test 3 times and they are dry. The jets I have are pretty large is there anything else that could be starving the mixture of gas?
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post #8 of 15 (permalink) Old 08-10-2017, 11:09 AM
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M... Okay... Nothing smart comes in my mind any more.
One more test. Install a bottle of gas directly to Your carb (instead of fuel tank). It should provide more gas than Your petcock. If no luck, then the carb still needs to be checked one more time.
Great resource about adjusting floats on CVK.
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post #9 of 15 (permalink) Old 08-10-2017, 12:18 PM Thread Starter
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Thanks tehnis, I'll give the direct fuel source a try in the morning. I just tried adjusting the float and it didn't help. I reset it to the service manual recommended 17mm. One thing I can't understand is how if I pull the choke it runs fine. I thought the choke just pulled more gas, so if there is gas for the choke shouldn't the rest of the system have plenty of gas? I can pull the choke out and turn the throttle wide open with no hiccups (In neutral, havn't tried riding with the choke on). I think this is the last carbureted bike I ever work on haha.
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post #10 of 15 (permalink) Old 08-11-2017, 12:45 AM
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The choke enriches fuel mix by bypassing almost everything in Your carb. It's hard for me to put together all Your actions but I have two more banal ideas
1) Increase the jet needle height to maximum.
2) Turn out the mixture screw to, let's say, 3 and a half or even 4 turns.
Now it should suck the gas in like crazy

Honestly, the carb bikes are OK until someone starts to mod them and think that he or she is much smarter than advanced stock engineers If nothing helps one more option is to return everything back to stock and start the mod step by step from the beginning.
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