Carb Synching 101

[ESJr1642]

Very nice write up sir, thank you!

[TheRev]

I know this is a stupid question but do you place the vacuum lines from your sync tool on the actual carbs or the carb manifold boots? Also, when done with the sync do you cap the vacuum port that isn't being used by the vacuum advance and the petcocks? Thanks

[BA80]

Use the prime position on your petcocks when syncing and then hook everything back up the way it's supposed to be when your done..........

The vacuum advance DOES NOT GET DISCONNECTED.

[donebysunday]

Use the prime position on your petcocks when syncing and then hook everything back up the way it's supposed to be when your done..........

The vacuum advance DOES NOT GET DISCONNECTED.

The vacuum for the octi does get disconnected, that is why you need to switch to prime. Put the caps back or hook the octi back up on the carbs your not/done syncing.
Has anyone used this tool, just got it and was wanting one since my first 4 cyl SF11 ?


Thanks, Done

[IanDMacDonald]

Use the prime position on your petcocks when syncing and then hook everything back up the way it's supposed to be when your done..........

The vacuum advance DOES NOT GET DISCONNECTED.

Hi Done- I believe you read that wrong, as Greg stated the VACUUM ADVANCE tube connected to the #3 carb stays connected. It's the intake manifold vacuum hoses that should be disconnected to allow for the sync gauge lines to be installed.

[donebysunday]

As you said.
It's the intake manifold vacuum hoses that should be disconnected to allow for the sync gauge lines to be installed.

I agree, the intake manifold caps/plugs and the octi. vac. hose need to be put back on when your done syncing that side, the vacuum advance is not touched, it's left connected to #3 carb.
Sorry for my confusing the issue.
Been wondering if I screwed up my brain in that crash. Seems most everyone I know is taking offense at something I said, losing friends and relatives left and right.

Has anyone used this tool, just got it and was wanting one since my first SF11 in 79 ?



Thanks, Done

[IanDMacDonald]

Yes, I have one, and another more expensive MP 90 degree. Very useful tool, but the cheaper one only has a Phillips bit if I recall.

[BA80]

I have one very similar. It's an old Snap On carb adjusting tool for QuadraJet carbs. The bits are interchangeable. It's 1/4" drive and you can put any bit or socket on it.

[TADracer]

Yes, this is a very well written post.

Only thing I would say is about technique and not the order of things. That would be DO NOT GET IMPATIENT AND RUSH! It takes a few minutes to get a good sync so set up a fan to cool your motor.

Each adjustment should be very small in fact just, resting a screwdriver on the sync screws can show a change the vacuum reading for that cylinder. So make small adjustments one at a time and then let the motor idle for about a minute to give all the carbs a chance to even out. Remember an adjustment on one carb actually affects them all.

[Schming]

Correction if I may . . .

Hi Done- I believe you read that wrong, as Greg stated the VACUUM ADVANCE tube connected to the #3 carb stays connected. It's the intake manifold vacuum hoses that should be disconnected to allow for the sync gauge lines to be installed.

The Vacuum advance hose is connected to the #2 carb, second one in from the left as you sit on the bike.

Your welcome in advance

[IanDMacDonald]

The Vacuum advance hose is connected to the #2 carb, second one in from the left as you sit on the bike.

Your welcome in advance

You may very well indeed Schming, lol. I have mine capped-off, that's why I'm not too familiar with it like everything else.

[dolphans1]

So on the 78-79 carbs, when adjusting the idle screw, that large spindly looking wheel/screw, how do you turn it one why or the other, is there a special tool or does one just use a screw driver. Also, if you adjust this one wheel/ idle screw, I presume it adjusts the idle on all four carbs evenly?

Thanks, nice post.

d-1

[IanDMacDonald]

It has notches 360 on it. Use a flat-blade and push one way or the other.

[donebysunday]

So on the 78-79 carbs, when adjusting the idle screw, that large spindly looking wheel/screw, how do you turn it one why or the other, is there a special tool or does one just use a screw driver. Also, if you adjust this one wheel/ idle screw, I presume it adjusts the idle on all four carbs evenly?

Thanks, nice post.

d-1

Yes using a long flat blade, as long as that screw is movable/not froze up, poke it in the groove CW to increase RPM. CCW to lower RPM.. Yes it controls all the carbs, so you should not need to sync. them again. On the other hand it does not hurt to check sync. anytime your up to it. I had some mercury that I bought in 79 for my SF 8 lb. after my carb styx got messed up I made my own with the last of the mercury I had. But I wanted to try other homemade tools for this. I took 2 cycle oil mixed with fuel, enough to give it color so I could see it and made a equalizer, it works but is very sensitive, you must have the carbs set really close or they will just suck the mix out of the tube, might be good for doing the idle mix screw sync. ?

[dolphans1]

Yes using a long flat blade, as long as that screw is movable/not froze up, poke it in the groove CW to increase RPM. CCW to lower RPM.. Yes it controls all the carbs, so you should not need to sync. them again. On the other hand it does not hurt to check sync. anytime your up to it. I had some mercury that I bought in 79 for my SF 8 lb. after my carb styx got messed up I made my own with the last of the mercury I had. But I wanted to try other homemade tools for this. I took 2 cycle oil mixed with fuel, enough to give it color so I could see it and. made a equalizer, it works but is very sensitive, you must have the carbs set really close or they will just suck the mix out of the tube, might be good for doing the idle mix screw sync. ?

Thanks, I had my carbs checked for sync and they were spot on, once bike was fully warm or hot and choke off, the RPM's would slowly drop below 1000RPMs on idle and stall out, if I rotate throttle the throttle grip just a slight tad, and hold it there, the bike idles just fine.

Can the the throttle cable be adjusted near the the throttle grip near handle bars, where that chrome nut linkage meets the throttle grip? What is that nut for, to remove slack from cable?

Thanks,

d-1