Carb sync problems

[SVS140]

I took off the rear carb off my bike and gave it a good clean as the bike was running rough and backfiring. No wonder really, pilot jet was blocked....it's not backfiring anymore.

When I put the carb back on, I checked the sync also since I had removed the sync cable (and the throttle and the choke cables) when I took off the carb. The carbs are way out of sync and I suspect I've had the carbs out of sync also before I took off the carb.

I am now struggling to sync them up. I start by setting the revs to around 1000 rpm with the idle screw. The I start adjusting the sync through the rearmost adjuster on the front carb. The carbs sync quite close to each other (but not exact) however as I turn the sync adjuster, the bike all revs up to around 2000 rpm. Turning down the idle screw doesn't seem to help to bring the revs back down . I also notice that when I turn down the idle screw, the "arm" which it pushes up when you turn it in doesn't go back down, is this expected ??

Please enlighten me, what am I doing wrong??

[navigator]

Start by introducing plenty of slack at the adjuster at the grip.
perform your sync, then when done, adjust at the grip until you have 1/8" of play before the throttle engages.

[sgtcall]

Well lucky for you Q87 just sent me some good information from the purple board about carb tune. You can find it in the IA dropbox under Other Information.

https://www.dropbox.com/preview/Intrude ... e=personal

[navigator]

Well lucky for you Q87 just sent me some good information from the purple board about carb tune. You can find it in the IA dropbox under Other Information.

https://www.dropbox.com/preview/Intrude ... e=personal

How and why do I need to sign in to dropbox?

[hillsy v2]

Says the folder doesn't exist?

[sgtcall]

Says the folder doesn't exist?

Try going in from here. viewtopic.php?f=19&t=14168

You shouldn't have to sign in. Let me know how it goes.

[sgtcall]

And try this out.

http://web.archive.org/web/201512052215 ... alert.com/

[hillsy v2]

And try this out.

http://web.archive.org/web/201512052215 ... alert.com/

yeah that one works

[sgtcall]

And try this out.

http://web.archive.org/web/201512052215 ... alert.com/

yeah that one works

Did the drop box work too?

[hillsy v2]

And try this out.

http://web.archive.org/web/201512052215 ... alert.com/

yeah that one works

Did the drop box work too?

Sorry - I got that a bit wrong. This link goes to the way back time machine....but the link in the other thread (Intruder Manuals and Information) goes to the dropbox.

[sgtcall]

Sorry - I got that a bit wrong. This link goes to the way back time machine....but the link in the other thread (Intruder Manuals and Information) goes to the dropbox.

[SVS140]

Start by introducing plenty of slack at the adjuster at the grip.
perform your sync, then when done, adjust at the grip until you have 1/8" of play before the throttle engages.

Hi Navigator.

I tried this out - admittedly, I don't have much slack at the grip as I was already near the limit - could this be related I did turn it a couple of turns though and it feels a bit more slack.....

However the problem persists. I could raise the rear cylinder (left gauge) vacuum as high as the image below however it was running at around 1300rpm at that point.



Another question I have, is it expected to move down that arm on top of the idle screw by hand rather than turning the idle screw out? I can turn the screw in and it pushes the arm up increasing the idling speed but when I hit the 1300rpm with the sync cable adjustment, I can't turn out the idle screw as the arm stays up and I have to manually push it back down and lose all sync settings in the process.

In the image below, you can see the idle screw turned down but the arm does not retract down with it - is this normal??



Thanks in advance for any help.

[navigator]

Start by introducing plenty of slack at the adjuster at the grip.
perform your sync, then when done, adjust at the grip until you have 1/8" of play before the throttle engages.

Hi Navigator.

I tried this out - admittedly, I don't have much slack at the grip as I was already near the limit - could this be related I did turn it a couple of turns though and it feels a bit more slack.....

However the problem persists. I could raise the rear cylinder (left gauge) vacuum as high as the image below however it was running at around 1300rpm at that point.



Another question I have, is it expected to move down that arm on top of the idle screw by hand rather than turning the idle screw out? I can turn the screw in and it pushes the arm up increasing the idling speed but when I hit the 1300rpm with the sync cable adjustment, I can't turn out the idle screw as the arm stays up and I have to manually push it back down and lose all sync settings in the process.

In the image below, you can see the idle screw turned down but the arm does not retract down with it - is this normal??



Thanks in advance for any help.

It appears to be a mechanical issue.
Since it appears there is no slack in the cable above the adjuster in your 2nd picture, that cable is holding the throttle open. The return spring on the butterfly of the rear carb should be strong enough to close the throttle. if you can close it by hand, something is hung up.
Get as much slack at the grip as you can, to be sure the grip is not opening the butterflies.
Check your cables to be sure they operate freely. The cable splitter under the tank is another place to check for problems.
In a static position, each carbs butterfly linkage should snap back to the closed position with the aid of the return springs.
If all that checks out, start by adjusting the cables so that each carbs linkage starts to open at exactly the same time.

The carb sync adjustments are very finite, a small turn goes a long way.
The idea is not to get as high a vacuum as possible, but to have the vacuum equal on both carbs.

[Lechy]

Have a look here for more info: viewtopic.php?f=32&t=4139

[SVS140]

Start by introducing plenty of slack at the adjuster at the grip.
perform your sync, then when done, adjust at the grip until you have 1/8" of play before the throttle engages.

Hi Navigator.

I tried this out - admittedly, I don't have much slack at the grip as I was already near the limit - could this be related I did turn it a couple of turns though and it feels a bit more slack.....

However the problem persists. I could raise the rear cylinder (left gauge) vacuum as high as the image below however it was running at around 1300rpm at that point.



Another question I have, is it expected to move down that arm on top of the idle screw by hand rather than turning the idle screw out? I can turn the screw in and it pushes the arm up increasing the idling speed but when I hit the 1300rpm with the sync cable adjustment, I can't turn out the idle screw as the arm stays up and I have to manually push it back down and lose all sync settings in the process.

In the image below, you can see the idle screw turned down but the arm does not retract down with it - is this normal??



Thanks in advance for any help.

It appears to be a mechanical issue.
Since it appears there is no slack in the cable above the adjuster in your 2nd picture, that cable is holding the throttle open. The return spring on the butterfly of the rear carb should be strong enough to close the throttle. if you can close it by hand, something is hung up.
Get as much slack at the grip as you can, to be sure the grip is not opening the butterflies.
Check your cables to be sure they operate freely. The cable splitter under the tank is another place to check for problems.
In a static position, each carbs butterfly linkage should snap back to the closed position with the aid of the return springs.
If all that checks out, start by adjusting the cables so that each carbs linkage starts to open at exactly the same time.

The carb sync adjustments are very finite, a small turn goes a long way.
The idea is not to get as high a vacuum as possible, but to have the vacuum equal on both carbs.

Hmm...ok will check.

I'm aware the vacuum shouldn't be as high as possible but rather equal however in my case, possibly since there's some mechanical issue as you point out, the vacuum of the front cylinder is not changing at all.