One probelm fixed, another started - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
Carbs and Fuel System
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post #1 of 8 (permalink) Old 10-08-2011, 08:21 PM Thread Starter
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One probelm fixed, another started

Hello all, just have a question that i want to run by y'all, I think i have an idea of the problem, but i am no mechanic, so was reaching out for some help.

I picked up a 2002, with 3500 miles on it about a month ago. When i got it it was running on one cylinder at idle and when it passed about 3500 rpms it would take off. It was very slow on the lower end of the power band, sooooo, i took the bike to a local shop (trusted mechanic i know), and had them do a carb job for me.

Well with my pockets a little lighter, i got the bike back and was impress with the smooth acceleration in all rpms, and it really is running nice now. So onto the problem.... Prior to having the carbs gone through, the bike started like a dream, pull the "choke" on an the engine would turn over 2-3 times and spring to life. well now, after having the carb work done, i cannot get the bike to start without using throttle and full choke (regardless of temperature and if the bike has been running recently or not). Once the engine takes off, i do not have to keep the throttle on, it will keep going on its own, but also seems to take significantly longer to warm up.

Onto the bike, it is stone cold stock. Things that are going to be done to it include spark plugs per this sites recs, new battery (when my wet cell one craps out- PO put a brand new one in prior to selling).

The bike itself it running fine, there is no popping on decel, the plugs look good when i pulled them last night. It also appears that the plunders for the enrichment circuit are coming out when choke is applied and going back in when taken off.

So what do you think would make this change in starting the bike? Is there something simple that i am overlooking? I just dont understand why it was fine before and now, not so much? Thankyou in advance.

Kevin
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post #2 of 8 (permalink) Old 10-08-2011, 08:44 PM
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WOW this one gives me goose bumps... ponders...... have ya checked to make sure all the vacuum lines are back on correct after the carb job? You say the plugs look good, so theres no problem there. You might check for fuel flow, could be that a fuel line is pinched off or nearly pinched off. Never heard of a bike starting with FULL choke and FULL throttle, sounds almost as if its not getting fuel,, but,, those are just my thoughts. Possible that the idle mixture screws are into far, this would cause a lean mixuture on start up. My Vulcan is pure stock and i have the mixture idle needles at 1 1/2 turns out for front and rear carbs, she loves them set like that. Im sure others will chime in with their thoughts also.... Good Luck


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post #3 of 8 (permalink) Old 10-08-2011, 09:09 PM Thread Starter
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Old Hip WesTex,

Funny you should mention the vacuum lines, there was one off, but put that back on correctly. With no aide to my problem.

I dont have to use full throttle to get her going, more just crack it when the engine starts to catch. I will double check the fuel lines, and i have not mucked with the `a/f screws yet, but will see what everyone says is a good starting point. Thanks for the thoughts.

Kevin
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post #4 of 8 (permalink) Old 10-09-2011, 10:25 AM
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This is a somewhat random thought, but I'm wondering if whatever was going on was there before you had the carbs cleaned and it's just presenting now. I don't know what the temps have been like in Jacksonville the past week or so, but here in MD they've dropped a lot (for overnight temps, anyway). Definitely changes how the bike starts, warms up, etc. Hopefully someone else can chime in, but I'm just wondering if it's a cold start issue (with "cold" referring to air temp) and if iridium plugs would help with that.

C
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post #5 of 8 (permalink) Old 10-09-2011, 11:15 AM Thread Starter
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crobins365,

nighttime lows since carbs have been gone through in the mid to upper 50's. it was colder than that prior to the carb job and started fine then. Today plan to take the tank off and make sure all hoses not kinked and put on correctly. Also when i finally have a chace to get some of my tools out of storage, will do vacuum test to make sure carbs still sync'd well. Also get plugs one of these days...

Any one have ideas where a/f screws should be out at sea level. i have seen 2.5 - 3 out from fully in a few times that still good advice?


Kevin
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post #6 of 8 (permalink) Old 10-09-2011, 01:47 PM
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doc, I live in Southern Illinois, approx 500 feet above sea level, have my a/f screws turned out about 2 1/4 turns and she runs like a dream.

2000 VN 750
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post #7 of 8 (permalink) Old 10-09-2011, 03:05 PM Thread Starter
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was looking for the correct placement of the vacuum lines. this is a pic for the one vacuum port that is visable on the right side of the bike. the hose goes from the thing in the pic (metal, located under the seat, and has gold caps on both ends). is this right? to folllow will be the pic from the left side of the bike off the fuel valve.

https://www.vn750.com/photopost/showp...o=3508&cat=500

https://www.vn750.com/photopost/showp...o=3509&cat=500

thanks
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post #8 of 8 (permalink) Old 10-10-2011, 03:09 PM Thread Starter
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Well, I am not sure exactly what helped, but had a ray of hope this afternoon. Last night pulled the seat and tank, checked all the hoses. Pulled the plugs ( PO had iridium ngk's in it) and also fount they had an interstate sealed battery). Everything appeared fine. So I went to play with the air/fuel screws. (the cap for the rear carb was off and the cap for the front was still on ????) anyway took it off, put the screws all they way in and backed off 2.5 turns. Today cleaned the connections for the battery, applied d/e grease and put everything back together and tried starting. Engine cycled twice and fired up with just choke. So we will see how she does , wish I could take it out for a ride an see how she runs, but weather is not allowing me at this time.

I think with the shop cleaning the carbs and the a/f screws at factory settings, there was not enough fuel to get her to go. I will post back in a few days when I try it out, and please let me know if there are any more thoughts. Thank you!

Kevin
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