Popping, RPM's drop slow, lack of power - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 7 (permalink) Old 12-03-2011, 05:52 PM Thread Starter
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Red face Popping, RPM's drop slow, lack of power

This bike has been coastered for years and ran great. Then life got in the way and the poor thing sat in a garage for many months. Had some seafoam in there but failed to run it as often as I should have. Long story short I just got done cleaning and re-installing the carbs.

She now runs well but there's a slight lack of power on hard acceleration.
Idle is around 9000 RPM's when it used to be around 1100 RPM's.
The RPM's drop a bit slow.
There's popping on deceleration but not when using the choke.

I've re-tightened the boots between the carbs and the cylinders and all the hoses. I also put a new cap on the rear carb's nipple (that used to connect to the emissions junk).
Battery connections are good and the spark plugs are new and gaped.
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post #2 of 7 (permalink) Old 12-03-2011, 06:23 PM
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Originally Posted by Bean View Post
This bike has been coastered for years and ran great. Then life got in the way and the poor thing sat in a garage for many months. Had some seafoam in there but failed to run it as often as I should have. Long story short I just got done cleaning and re-installing the carbs.

She now runs well but there's a slight lack of power on hard acceleration.
Idle is around 9000 RPM's when it used to be around 1100 RPM's.
The RPM's drop a bit slow.
There's popping on deceleration but not when using the choke.

I've re-tightened the boots between the carbs and the cylinders and all the hoses. I also put a new cap on the rear carb's nipple (that used to connect to the emissions junk).
Battery connections are good and the spark plugs are new and gaped.
I`m sure you mean 900 rpm idle.
Have you turned out the air/fuel mixture screws to richen the mix and eliminate the popping?
Are the throttle cables sliding freely inside their sheaths.

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post #3 of 7 (permalink) Old 12-03-2011, 08:59 PM Thread Starter
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Woops! Yeah 900RPM's! Which seems well enough but I know that's below normal.

I have messed with the air/fuel screws but I believe those only effect idle? I've got em at 3 turns at the moment. More then that seems to have no effect. Less turns just makes her run even slower.
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post #4 of 7 (permalink) Old 12-03-2011, 11:10 PM
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Sat for months? I'd fill the carbs with SeaFoam and/or spray them with carb cleaner. How old is your gas?

You likely just have some goo in the carb(s) that needs to get flushed out. It's lower idle means it's not getting the same amount of fuel as before....symptom of a semi clogged jet.

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post #5 of 7 (permalink) Old 12-04-2011, 12:49 AM Thread Starter
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There was indeed clogged jets, hence why I removed the carbs in the first place.
The tank has also been drained, cleaned and reinstalled.

Since then, the symptoms are consistent at all throttle/RPM ranges as far as I can tell. There's no ranges that cause it to sputter or stall. In fact the bike runs pretty good. But I sound like a popcorn machine going down the road and I recall it having a bit more umph then it does now.
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post #6 of 7 (permalink) Old 12-04-2011, 08:16 PM Thread Starter
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This morning I tried to ride it to work and wouldn't you know it the battery was dead! So I'm thinking I've got an electrical problem. Maybe something's grounding out. It would explain a lot of things.
I'll have to wait till I have a day off to poke around. Until then it'll be on a charger. I'm open to any input you guys may have.
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post #7 of 7 (permalink) Old 12-08-2011, 03:04 PM Thread Starter
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With a charged up battery she fired up no problems. Then after some poking around I noticed fuel was leaking from one of the lines running from the petcock to the carbs. Tightened that down as well as it's sister and I'm happy to say she's running pretty good now without any popping.

Throttle cables themselves are fine but it seems like the spring that pulls it back wasn't wound as tight as it should. Which would have been my own fault for taking the spring off in the first place. I'm not going to pull the carbs again just to tighten it though.

The only problem the bike has left is a lack of power above 70mph. I'm hoping it's just some leftovers in the jets that will eventually work it's way out. Seafoam can probably handle that. I'm going to start commuting on the bike again so we'll see how she does with regular rides.
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