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Dogg
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« on: August 29, 2021, 02:28:16 PM » |
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98 valk. interstate tank. cobra 6x6 no baffles. .38x108 jets. rode 65 miles and used 4.9 gallons of fuel. it isnt jetted wrong. it runs great. above 4500 rpm it feels sluggish and the surges. does this over and over. i have 4 bikes running same setup. this one is being uncooperative.
i check fuel enricheners, they are closing all the way. fuel doesnt leak anywhere. oil is clean. its all going out the tailpipe.
no negative commments please. just suggestions on where to start.
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3W-lonerider
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« Reply #1 on: August 29, 2021, 03:53:20 PM » |
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just a suggestion. if it has a K&N air filter, maybe its over oiled. i ran a K&N once and over oiled it. ran like it didn't have any power anything over 3 grand.
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98valk
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« Reply #2 on: August 29, 2021, 04:01:24 PM » |
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at 13 mpg it is jetted incorrectly. it will run better if leaned out.
every engine is different, its always what it wants and not what we think it wants.
have u checked or rebuilt the petcock?
with that jetting u run have u had it on a dyno with a four gas analyzer to verify the air fuel ratios?
running too rich will boost the low end torque but kill top end HP.
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« Last Edit: August 29, 2021, 04:17:59 PM by 98valk »
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1998 Std/Tourer, 2007 DR200SE, 1981 CB900C 10speed
1973 Duster 340 4-speed rare A/C, 2001 F250 4x4 7.3L, 6sp
"Our Constitution was made only for a Moral and Religious people. It is wholly inadequate to the goverment of any other."
John Adams 10/11/1798
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pancho
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« Reply #3 on: August 29, 2021, 04:07:01 PM » |
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I'd certainly start by looking at the airbox and filter, something restricting the air flow.
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The most expensive things you will purchase, are those things you would not have needed if you had listened and obeyed.
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f-Stop
Member
Posts: 1810
'98 Standard named Hildr
Driftwood, Texas
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« Reply #4 on: August 29, 2021, 04:44:57 PM » |
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Are you running with the OEM petcock? If so, you may need a new cover set.
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  Had my blinker on across three states! |
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Bagger John - #3785
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« Reply #5 on: August 29, 2021, 05:09:41 PM » |
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Lose the 6x6s, stock exhaust, stock air filter. Some run 38s, some 35s (stock pilot jets). My I/S likes the latter while my Tourer likes the former.
I can easily get 40MPG or higher with the Tourer if ridden at 65MPH; about 35 with the I/S at similar speeds.
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Warlock
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« Reply #6 on: August 29, 2021, 05:11:03 PM » |
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98 valk. interstate tank. cobra 6x6 no baffles. .38x108 jets. rode 65 miles and used 4.9 gallons of fuel. it isnt jetted wrong. it runs great. above 4500 rpm it feels sluggish and the surges. does this over and over. i have 4 bikes running same setup. this one is being uncooperative.
i check fuel enricheners, they are closing all the way. fuel doesnt leak anywhere. oil is clean. its all going out the tailpipe.
no negative commments please. just suggestions on where to start.
I would check all vacuum for leaks. Also check sank and color tune the carbs David |
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 I don't want to hear the labor pains, I just want to see the baby |
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Steel cowboy
Member
Posts: 1284
Moving ahead so life won’t pass me by.
Spring Hill, Fl.
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« Reply #7 on: August 30, 2021, 05:45:53 AM » |
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If the diaphragm in the petcock has a tear on the vacuum side, 2 things can happen. One the vacuum created could be sucking fuel into number 6 intake or were ever the vacuum hose it going too. Two if the vacuum side of the petcock is damaged the flow of fuel could be restricted since vacuum opens the device to allows the flow of fuel.
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2001 black interstate
2003 Jupiter Orange wing
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gordonv
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Posts: 5760
VRCC # 31419
Richmond BC
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« Reply #8 on: August 30, 2021, 11:07:45 AM » |
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98 valk. interstate tank. cobra 6x6 no baffles. .38x108 jets. rode 65 miles and used 4.9 gallons of fuel. it isnt jetted wrong. it runs great. above 4500 rpm it feels sluggish and the surges.
I've taken my 99' IS and rode it HARD, and was on reserve at 125 miles. Usually hit it at 190 miles. You say you drove 65 miles and used 5 gal. How did you ride it, speed/RPM. My best mpg was Hwy at 55 mph, and worst anything above 70 mph. 3200 or < rpm. You mentioned 4500 rpm, so I figure you would have only said that if you have been riding it very hard. Try another tank, but drive it below 3K rpm and down a Hwy, for comparison. |
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1999 Black with custom paint IS   |
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Dogg
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« Reply #9 on: August 31, 2021, 02:51:50 PM » |
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I appriciate all the suggestions. I have 3 bikes all running the same jet set and no issues. This one was a friends bike. I just got done doing a few things and he brings it back telling me about this.
From what he told me, he took the filter out of the box and just put it in the bike. The filter was saturated with oil creating a vacuum in the airbox which pulled the slides up wide open just about the whole time he rode it dumping fuel through the main. above 4k or so, it would slow, the go, like a surge. because of the excess in vacuum, hence, the surge.
Once he cleaned the filter and reinstalled it, bike ran like a raped ape. now, he is happy. just an fyi in case someone runs into this in the future.
just to say, bike has a pingle and been desmogged. all vacuum nipples are capped. I just replaced intake orings when i did the float valves. no vacuum leaks at all. what got me believing this was the problem, at 4000 rpm, sitting still, the hose from the airbox to the vacuum canister collapsed. once i let off the throttle, it went back to its normal shape.
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