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Author Topic: Bike running rough  (Read 1375 times)
studlly 64
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*****
Posts: 52


Norwood, Mass


« on: October 15, 2021, 12:49:14 PM »

Hello everyone,
early this year I took the carburetors off for a deep cleaning after it sat for a couple years.
now the bike runs rough, cylinder 1 & 3 seems not responding when I pull the spark plug out for both, all other cylinders drop rpm when I pull the spark wire out.
#1 & 3 spark is as good as the others.
also I changed vacuum lines and the small plugs on all intakes except number 6, when I change gears e.g 3rd to 4th the rpm jumps up. I do have a little backfiring, I tightened the muffler bolts as well!
any suggestions will be greatly appreciate it
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1998 ST
Bagger John - #3785
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Posts: 1952



« Reply #1 on: October 15, 2021, 12:59:50 PM »

Check all vacuum hoses and caps?

Replace the intake runner O rings when the carbs were taken off?
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Mooskee
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Posts: 559


Southport NC


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« Reply #2 on: October 15, 2021, 01:05:28 PM »

Make sure you put the spark plug wires back on the correct cylinders.
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Valkyrie Carbs and Custom www.valkyriecarbsandcustom.com
studlly 64
Member
*****
Posts: 52


Norwood, Mass


« Reply #3 on: October 15, 2021, 02:47:46 PM »

O-rings were changed, spark plug wires are in the correct order. I did open the carb drain and fuel is coming out on both!!
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1998 ST
studlly 64
Member
*****
Posts: 52


Norwood, Mass


« Reply #4 on: October 15, 2021, 02:49:16 PM »

Check all vacuum hoses and caps?

Replace the intake runner O rings when the carbs were taken off?
is there any other vacuum hoses I need to check. I replaced all but #6!
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1998 ST
Mooskee
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Posts: 559


Southport NC


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« Reply #5 on: October 15, 2021, 05:37:41 PM »

How did you do the deep cleaning? Carb cleaner, ultrasonic?

Are you sure the slow jets are clear on 1& 3?

Did you remove the pilot screws? Where are they set?

It sounds like you have no fire in #1&3.

Even if you had vacuum leaks you would still have combustion in #1&3.

Possible fuel delivery issue at idle.  Slow Jets may be clogged or pilot screws all the way in.
or passages in carb for slow ckt plugged on 1&3.

Start it, run throttle up to 3000 RPM and remove #1 and then #3 plug wire to see if you get RPM drops. Running  it at 3000 is fast enough to get into the main jets. If you have fire then, you'll know it is a slow fuel delivery issue.
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Valkyrie Carbs and Custom www.valkyriecarbsandcustom.com
WintrSol
Member
*****
Posts: leet


Florissant, MO


« Reply #6 on: October 15, 2021, 05:57:14 PM »

In addition to the above, did you check and reset the sync? If some are far enough out, it will be uneven enough to be running rough.
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98 Honda Valkyrie GL1500CT Tourer
Photo of my FIL Jack, in honor of his WWII service
Madmike
Member
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Posts: 837


Campbell River BC, Canada


« Reply #7 on: October 16, 2021, 03:47:19 PM »

Check the orings on teh tubes into the heads on the cylinders that aren't firing, popping could be a vacuum leak.  You can use a prudent amount of starting fluid around the joint to see if it is sucking air.
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studlly 64
Member
*****
Posts: 52


Norwood, Mass


« Reply #8 on: October 18, 2021, 02:20:17 PM »

How did you do the deep cleaning? Carb cleaner, ultrasonic?

Are you sure the slow jets are clear on 1& 3?

Did you remove the pilot screws? Where are they set?

It sounds like you have no fire in #1&3.

Even if you had vacuum leaks you would still have combustion in #1&3.

Possible fuel delivery issue at idle.  Slow Jets may be clogged or pilot screws all the way in.
or passages in carb for slow ckt plugged on 1&3.

Start it, run throttle up to 3000 RPM and remove #1 and then #3 plug wire to see if you get RPM drops. Running  it at 3000 is fast enough to get into the main jets. If you have fire then, you'll know it is a slow fuel delivery issue.

thanks Mooskee for the tip.
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1998 ST
studlly 64
Member
*****
Posts: 52


Norwood, Mass


« Reply #9 on: October 18, 2021, 02:23:00 PM »

How did you do the deep cleaning? Carb cleaner, ultrasonic?

Are you sure the slow jets are clear on 1& 3?

Did you remove the pilot screws? Where are they set?

It sounds like you have no fire in #1&3.

Even if you had vacuum leaks you would still have combustion in #1&3.

Possible fuel delivery issue at idle.  Slow Jets may be clogged or pilot screws all the way in.
or passages in carb for slow ckt plugged on 1&3.

Start it, run throttle up to 3000 RPM and remove #1 and then #3 plug wire to see if you get RPM drops. Running  it at 3000 is fast enough to get into the main jets. If you have fire then, you'll know it is a slow fuel delivery issue.
thanks for the tip Mooskee. i did fire it up to 300rpm and pulled 1 & 3 spark plug one at a time, the rpm drops a little. I think the slow jets are clogged put half a bottle of berruman B-12 will see how that goes!

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1998 ST
studlly 64
Member
*****
Posts: 52


Norwood, Mass


« Reply #10 on: October 18, 2021, 02:24:32 PM »

In addition to the above, did you check and reset the sync? If some are far enough out, it will be uneven enough to be running rough.
WintrSol,
how do I reset the sync? ?
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1998 ST
WintrSol
Member
*****
Posts: leet


Florissant, MO


« Reply #11 on: October 18, 2021, 08:26:30 PM »

In addition to the above, did you check and reset the sync? If some are far enough out, it will be uneven enough to be running rough.

WintrSol,
how do I reset the sync? ?


There is a screw on each of the throttle linkages on the port (left) side, and the for and aft ones on the starboard side - #3 is the reference, so doesn't have one. You would connect to each of the vacuum ports and adjust the screw for each carb to match the vacuum of #3. Easiest to do if you are desmogged, and have a DigiSync tool, so you can connect all six at the same time. The service manual has the procedure when you only have two matched vacuum gauges; in any case, it shows where the adjustment screws are. If you are still using the vacuum operated petcock, you need to apply a small vacuum to it to keep the fuel flowing. There used to be a section with illustrated repairs, but I don't remember where to find it, and some have gone away.

EDIT: you may find what you need here: http://www.valkyrieriders.com/shoptalk/
« Last Edit: October 18, 2021, 08:28:15 PM by WintrSol » Logged

98 Honda Valkyrie GL1500CT Tourer
Photo of my FIL Jack, in honor of his WWII service
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