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Addicted to Projects
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Discussion Starter #1
I've been away for a few years. Had a slip on ice going to work and back surgery/recovery. I'm trying to get my 85 vn700 back up and running after sitting. I've done all the routine stuff and some of the real fun stuff. Found out stater wasn't doing its thing so engine pulled and stater replaced.
But I'm still unable to ride her. In the last month I've pulled the carbs more times than I can count. The bike will idol beautifully but as I turn the throttle it bogs down about 4000 rpm. If I gently nurse the throttle I've gotten it up to around 6000 rpm. I can't ride gently nursing the throttle. I have inline fuel filters that I can see have fuel running through them but it's almost like the bike is running out of fuel.
I'm just stumped.
Any ideas from all you gurus?
 

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NewB to Vulcans
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220 Posts
I added an inch of fuel hose to make tank removal easier. Then my bike had the same issues, would run fine at small throttle openings . Turns out the hose was kinked and restricting flow to one cylinder. Took away the extra inch and its just fine. Maybe your addition of the fuel filters is restricting flow?
 

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FREEBIRDS MC CENTRAL NY
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16,076 Posts
Mine did not like in line filters either

Sent from my Z899VL using Tapatalk
 

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Yup, some have had problems using fuel filters, others say their's are working fine.

Make sure all the lines are at least running level to downward, none running uphill. With no filters, upward sloping hoses won't flow well.

Carb vents routed correctly? Problem would show up while moving only.
 

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2014 KLR 650!
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3,361 Posts
Most dramatic fix for my bike was the tw200 petcock mod. Just rode way better when I did that. It's been a while and I could be dreaming but I sold that bike knowing it was working perfect.
 

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Addicted to Projects
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Discussion Starter #6
I guess I'll get some more new fuel line and give that a try. Thanks all.
 

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Addicted to Projects
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Discussion Starter #7
Removing the inline fuel filters was the ticket. I never thought that would be the case because I simply replaced the old and put new ones on. I was able to get out and put about 30 miles on the bike, the first time in several years. Thanks again.
 

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Those fuel filters build up a clear varnish-like coating over time. Particularly on long idle bikes. Same with petcock. Hot storage locations (outside?) profuce similar conditions.
 

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Addicted to Projects
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Discussion Starter #9
Well I didn't have any issues with the other inline fuel filters. They had the goldish colored granular looking filter. The brand new ones I replaced them with were a plastic with a plastic membrane as the substrate. They were positioned identical, very close to straight up and down. The fuel lines were dropping from the petcock through the filters into the carbs. The vulc would still bog down as the rpms went up around 4000. If I nursed it carefully I could work it up to around 6500, but it took some time. It wasn't going to make it for even a quick ride around the block.
After I took the inline filters off, she ran like a dream. It revved up great. I've finally been able to get back into the wind.
I can't explain how or why but without the inline filters it runs great.
 
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I have noticed that the plastic fuel filters are 6mm dia but you need 8mm dia to run these bikes same as fuel lines.
 
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