Pick-up vacuum line

[oldyam80sg]

A while ago i rerouted the vacuum line that goes from the pick-up coil to the carb body as per the thread.Today, when i went for a ride the bike felt like it was backfiring alot and at slow speeds i had to keep the revs up to make it to my destination.When i had the bike tuned years ago the vacuum line went from the pickup coil to the 2nd carb body looking at the bike from the left side.I switched this a while ago and have not had the chance to really test it out.The vacuum line had a reducer in between it and with that in between, the noise from the pick up coil is deadened.My mechanic said that last year he took my bike for a 30 mile ride and had no problems.Please explain.

[79XS11F]

I'm not real sure what your saying in your description of what you changed? If you moved the advance hose to the carb body from the boot then re-sync the carbs. Also check the pickup coil wires
Rob

[AlanB]

Hi OldYam,

Did you cap off the nipple on the boot where the line came off? The carb nipple is also smaller than the boot nipple, so you may have a vac leak there.

If you do not have a vac. leak, the problem is probably unrelated- These bikes run OK without the vac advance connected, so long as there are no vac leaks!

You can test by swapping the line back to where it was; should only take a second.

AlanB

[TopCatGr58]

Hey OldYam,

I think you mistyped something there. I think you meant to say that the vacuum line was on the #2 carb boot/synch port and that it had a restrictor in line to stop pulsing that would normally occur when connected to the boot?!

Now, you say that you put it on the proper #2 carb body port! Did you remove the inline reducer?

Now on a recent run, you had to give it more throttle to keep it running! You'll want to check to make sure all 4 pipes are getting hot! Let the bike cool, and then restart and test the pipes. IF you get/find some cool ones, then let the troubleshooting begin. Depending on how many and which ones are cold will determine where you look next. 1-2 or 3-4, most likely carbs/fuel delivery!

1-4 or 2-3, ignition circuit, either PU coils, Ignition coils, TCI, etc.!

Good Luck!
T.C.

[oldyam80sg]

Top Cat I will explain what i did because i think you are not understanding what i am saying.For years my SG ran with the vacuum line from the pick-up coil area to the carb boot closest to the advancer unit.It made some noise and it was suggested to me from someone a long time ago, that i put in a tee- fitting to quiet that noise.It ran like that good for approxiametly 16 years.I read a thread and someone said that line in question goes to the 2 nd carb body looking in from the clutch side.So i hooked up that line to the carb boot and i took the cap and put it on the carb boot closest to the clutch side.I believe this is #1 carb.Well the bike ran like crap when i changed it as per the thread.I switched everything back to the way i had it and so far no problems.

[pggg]

No2 carb, has this port for the vac hose

[TopCatGr58]

Well,

If it ain't broke, don't fix it!

HOWEVER, it should NOT be connected to either carb BOOT, but to the metal port on the #2 carb body! IF it has a restrictor tube INLINE, it needs to be removed because the #2 carb body has a much smaller port hole size than the carb boot and doesn't need the extra restriction! And the carb boot ports need to be capped off.

Also, as Rob stated, you would probably need to resynch the carbs since you have upset the vacuum balance on #1 by removing the vac. adv. hose from the boot.

BUT as long as you're happy with how it runs being connected to the #1 BOOT with a restrictor inline, then so be it! RIDE ON!
T.C.

[oldyam80sg]

TopCat - I took the vacuum line coming out of the advancer unit and attached it to the #2 carb body-not the boot.Line coming out of octy goes to #2 boot and #1 gets capped off right? Now the cap that goes to #1 -can they be purchased as mine has a slight crack in it? Also i probably do need to re-sync everything to get it running right.Would the sync issue cause the backfiring on decel?Also i have no body that will look at the bike because they all say that if they break something they dont want parts problems.Sorry i dont want it to sound like i'm questioning your advice.I value your input and wisdom.

[TopCatGr58]

Hey Yam,

Yes, you can go to your local auto store and get rubber vacuum caps to fit the port, and it cracked and leaking could be what is causing it to pop on decel and poor performance, running lean vs. the other carbs. Once you cap it off properly, you may find that it is running okay, and can then schedule the synch for a more opportune time!?

In your reply 2 replies before this last one, you had said you put the vacuum line on the #2 carb boot...that's why I was re-inquiring about what you had said and done, that's all!
T.C.

[oldyam80sg]

Thank you TopCat .I will check my auto parts store.Sometimes it gets frustrating knowing you are so close to running then something else goes wrong.Dont mean to sound hard-headed I appreciate the knowledge that i lack!

[scalded dog]

Hello TC, hadn't been on here much lately, as I have learned most things that I need to know, but have recently started having problems, when I really open it up for quick quater mile, I think it may be the vac-advance, the problem is it will bog for a few seconds then spit out a ton of black smoke, and then take off like a bat out of...., has anyone had problems with the vac-box, tube or whatever it is called, LOL. TIA. Later 'Dog

[DiverRay]

'Dog,
It seems you are RICH at low end!! Black smoke is unburned fuel, and the bogging tells me you need to look at the pilot circuit. Once you start the transition to the mains, at about 3K, it cleans up and runs. I would start with adjusting the mixture screws, per the tech tip, and then go from there.

[scalded dog]

Thanks, DRay. Will check that. Later 'Dog

[petejw]

hey yam,
was just curious if u have checked
the vac advance 4 leaks/holes, suck
on the rubber hose which will raise
the vac advance unit, stick ur tongue
over the hose, vacuum should hold if it doesnt
that could cause a lean mixture in the 2nd cylinder,
ive noticed on a cpl of these bikes lately the vac advance
units are buggered. hope it helps.

[scalded dog]

Forgot that one, will also try that. Thanks, Later 'Dog