Full Choke - only 1500 RPMS, dies idling - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
Carbs and Fuel System
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post #1 of 23 (permalink) Old 11-05-2009, 01:45 PM Thread Starter
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Full Choke - only 1500 RPMS, dies idling

Hey Guys!

New to the site, just found yesterday. LOVE IT! Wished I would have found when I was struggling to remove the carbs to clean.

I recently got a 94 750 from my boss. He didn't drive it much at all. It probably sat for a year or so. It ran, but not great. Took carbs out, cleaned, new airfilters, plugs, oil change and she ran great! Been riding it for a while now, probably put on a couple hundred miles.

Just 2 days ago it seems like it's gummed up again. It will fire up, rev up to 4000 RPMs on Full choke, turn choke off to idle then die. When start again, full choke will only bring it up to 1500RPMs. I can keep it running and even drive it but, I'm sure it's running lean or something. With choke on, it also smells very gassy, like it's running rich.

I read a bunch of posts on turning idle screw out (cap on it, how do you get that off), but I don't think thats the problem. I'm sure its the jets. I read a post on taking jets out with out taking carbs out, but that looks next to impossible.

I put in gas probably 3 weeks ago, and still have 1/4 tank (live real close to work). Do you think this has something to do with it (bad gas)?

Can I put in new fresh gas, and hope it cleans it out? Or is there something I can add to the gas to help clean? Or do I need to take those things out again and reclean?

Sorry for the long post, just wanted to get the picture across. Thanks for any advice!
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post #2 of 23 (permalink) Old 11-05-2009, 02:56 PM
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The idle screw does not have a cap. Its got a rubbery surface but it should turn freely. It will be located on the clutch side of the bike on the carb. Mine looks like a rubber gear. If you look at the picture, it will be to the RIGHT of the yellow arrows. Its looks like a black gear. If you turn it clockwise, it will decrease IDLE RPM, counter clockwise will increase it (i'm 85% sure but I might have it backwards). It should move freely. Initially, I had to turn mine back and forth a few times to free it up.
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post #3 of 23 (permalink) Old 11-05-2009, 03:19 PM
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Quote:
Originally Posted by 750Brian View Post
Hey Guys!

Just 2 days ago it seems like it's gummed up again. It will fire up, rev up to 4000 RPMs on Full choke, turn choke off to idle then die. When start again, full choke will only bring it up to 1500RPMs. I can keep it running and even drive it but, I'm sure it's running lean or something. With choke on, it also smells very gassy, like it's running rich.

I read a bunch of posts on turning idle screw out (cap on it, how do you get that off), but I don't think thats the problem. I'm sure its the jets. I read a post on taking jets out with out taking carbs out, but that looks next to impossible.

any advice!
next to the vac port on the carb there is a lead circle... to get that cap out just run a drill bit in there and that should break her free if not a pick will allow u to pull her out ... be careful not to go into the mix screw

cleaning the jets without the pull is tricky but all u need is a short or rt angle screwdriver to pull the cap off from there spray carb clen into the jets also take a strand of throttle cable (old bicycle brake cable ) and poke up into the jets

Quote:
Originally Posted by 750Brian View Post
Hey Guys!

I put in gas probably 3 weeks ago, and still have 1/4 tank (live real close to work). Do you think this has something to do with it (bad gas)?

Can I put in new fresh gas, and hope it cleans it out? Or is there something I can add to the gas to help clean? Or do I need to take those things out again and reclean?

Sorry for the long post, just wanted to get the picture across. Thanks for any advice!
bad gas is common did u clean out the tank when u rebuilt the carbs... ?? dump in a few ounces of seafoam into the tank and top her off, install some inline fuel filters to keep more stuff out of the carbs ... may want to pull the petcock and see if its a little gummed up....

Seafoam is great u can put in full strength to eh bowls and let her soak overnight befor doing the other cleaning stuff seafoam has been known to clear up problems just in itself

when this happened to me the it was actually running on one cylinder and rather gutless ... check to see if both exhast pipes are gettin hot .... remember the front one is double insulated so it wont get as hot ...



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post #4 of 23 (permalink) Old 11-05-2009, 06:15 PM
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woah, woah, woah!
So does our carb have 2 different air/fuel mix screws!?!? below is a pic (from CRobin's) of what I thought was the only one! Is the above pic one as well!? If not what's the difference... should the one above be 1 5/8 to 2 1/4 turns out as well?

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post #5 of 23 (permalink) Old 11-05-2009, 06:22 PM
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Quote:
Originally Posted by webby778 View Post
woah, woah, woah!
So does our carb have 2 different air/fuel mix screws!?!? below is a pic (from CRobin's) of what I thought was the only one! Is the above pic one as well!? If not what's the difference... should the one above be 1 5/8 to 2 1/4 turns out as well?

~dw

https://www.vn750.com/photopost/showp...a/f&perpage=12
Only one mixture screw per carb, two carbs per engine one for each cylinder.


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post #6 of 23 (permalink) Old 11-05-2009, 06:25 PM
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Sounds like the pilot jet is clogged.
X2 on what seebeeare said on making sure the tank&petcock are clean and adding filters.
Pull the fuel line off of the carb and let some fuel drain into an empty pop bottle to see if there's any junk commin from the tank. Hopefully you won't have to pull the carbs again.

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post #7 of 23 (permalink) Old 11-05-2009, 06:30 PM Thread Starter
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Thanks guys!

I said that wrong about the idle screw. I know where that is. It was the jet behind the lead cap I was talking about. I'll give the drill a try.

I did not clean the tank. Should have done that.

Seafoam - I'll give that a try first! Thanks!
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post #8 of 23 (permalink) Old 11-05-2009, 06:41 PM Thread Starter
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bad gas is common did u clean out the tank when u rebuilt the carbs... ?? dump in a few ounces of seafoam into the tank and top her off, install some inline fuel filters to keep more stuff out of the carbs ... may want to pull the petcock and see if its a little gummed up....

For the inline fuel filters, do I need 2, one coming out the hoses that point straight back towards the engine?

Seafoam is great u can put in full strength to eh bowls and let her soak overnight befor doing the other cleaning stuff seafoam has been known to clear up problems just in itself

Also, what do I soak? Does this mean running a bit to get into the "system" stop and let it rest over night?

Crap - tried to get the fancy quote boxes in, but didn't work. Again, new to forum. Sorry.
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post #9 of 23 (permalink) Old 11-05-2009, 10:01 PM
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The filters go on the two outer fuel lines coming off the petcock. The center line to the petcock is a vacuum line.

You can drain the gas from the carbs and refill them with straight Seafoam. Let sit for at least 12 hours. The longer the better. Drain the Seafoam and see if she will crank. If yes, add 1/2 can of Seafoam to a full tank of fresh gas and ride it. Repeat once if needed. If that doesn't clean the carb sufficiently, need to pull them and give them a good cleaning. Periodically adding around 3 ounces of Seafoam to a tank of gas is a good way to keep the system clean.

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post #10 of 23 (permalink) Old 11-05-2009, 10:19 PM Thread Starter
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Quote:
Originally Posted by flitecontrol View Post
The filters go on the two outer fuel lines coming off the petcock. The center line to the petcock is a vacuum line.

You can drain the gas from the carbs and refill them with straight Seafoam. Let sit for at least 12 hours. The longer the better. Drain the Seafoam and see if she will crank. If yes, add 1/2 can of Seafoam to a full tank of fresh gas and ride it. Repeat once if needed. If that doesn't clean the carb sufficiently, need to pull them and give them a good cleaning. Periodically adding around 3 ounces of Seafoam to a tank of gas is a good way to keep the system clean.
Thanks for that advice, I'm leaving work right now and going home to try the soak!! What is the best way to fill and drain the carbs? I think to drain, is that allen screw, correct? I unscrewed that once and it came leaking out.
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