'80 SG driveability issues, want your thoughts...

[Bonz]

TomRodgers,

Maybe some debris or other such stuff that was in the enricher circuit (XS adds fuel via the enricher circuit as opposed to a true choke that limits air, so the net effect is a rich mixture to start) broke free and clogged something up. That's my first and best guess, but only a guess.

Other thoughts?

[TomRodgers]

I was kinda thinking carb issue......maybe one or two of the pilots is clogged..but fuel filters show good...but it makes sense that one or two pilots clogged and when shifts over to mains, it runs balls out....

[Bonz]

On my 80 SG that was the reason for starting this thread, I did a quick carb sync when I got home last night with my homemade manometer (sync gauge) while the bike was totally warm (HOT!). Put a big fan out in the driveway for airflow, did 3&4, then 1&2, and man, that bike smoothed out in terms of taking the edge off of what I would have thought was just normal vibration of the bike. It's now noticeably smoother at idle and all engine cruising speeds and in between. Still has that flatness where I have to clutch it and re-engage to make go away that comes in right at the transition from light throttle to no throttle when I'm putt-putting along, so I promise my fellow XS brothers I will check the pick up wires. Just keep finding other stuff to do that makes improvements in other areas to do as well.

Question... I just did each pair, and did not do each pair to the other pair. My homemade sync gauge was made for my V Strom 1000 (V twin) so I have but two lines. Do I now hook carb 1 or 2 to carb 3 or 4 to do the sync between the two pairs, or should I really have a sync tool that does 4 cylinders in order to sync the pairs to eachother? Make sense?

If 1 & 2 are good relative to eachother, and 3 & 4 are good relative to eachother, then picking one from each pair should do the trick to sync them all, eh?

Thanks in advance!

[Larrym]

Theoretical versus Applied Science

If 1 & 2 are good relative to eachother, and 3 & 4 are good relative to eachother, then picking one from each pair should do the trick to sync them all, eh?

Thanks in advance!

hbonser,

Theoretically you're right. The two pairs(1+2) and (3+4) do need to be synchronized to match the other pair. In practice though, all carbs have to be sync'ed to carb #3 because it is the "non-adjustable" one. Carb 4 gets sync'ed to #3, then 1+2 get sync'ed to each other, and then finally 1+2 get matched to 3+4.

May I suggest that you place the two available Sync lines to the intake boot "nipples" of carbs 2 and 3 then adjust the screw between 2 +3?

As far as needing 4 separate lines and 4 vacuum indicators it's more of an efficiency/expediency thing. The process can be done with only one gauge/line but that means pulling off/re-positioning the one available vacuum line.

"Learn by doing".

HTH

[Bonz]

Larrym,

Thanks for the post. That's good info to know, esp that #3 is the baseline, so to speak.

I'll put the lines on 2 and 3 tonight, and see how it goes. The bike responded so well with just getting the pairs matched up, that I'm pretty happy already.

Have a good one!

[crazy steve]

To be honest Cy, I have not worked on the earlier models in the timing area yet. So I will take your word on that.

I know that alot of the long time member gurus always have stated that the 81 model does not experience the issue as much as the earlier models due to no mech advance. And I do KNOW that I have worked on three 81 models that have never needed the pickup wires repaired.

Cy is correct; the mechanical advance rotates the ignition rotor, the vacuum moves the pickup plate. So the presence or lack of mechanical advance has no bearing on how long/well the wires hold up.

And maybe by '81 Yamaha had found a better quality wire....

[natemoen]

And maybe by '81 Yamaha had found a better quality wire....

Anyone got a good set of '81 pickups

[Poprock]

Maybe time for a carb cleaning. Not many veriables left.

[Bonz]

Hey TomRodgers,

Another thing that you could check is to see if something went haywire with the enricher external hardware. Like something got stuck, or came apart that would mechanically make it hard to move the enricher lever. Make sense?

If something externally got messed up, then you could have the thing running rich and it won't take off until it can actually use that fuel at higher rpm and load. I would still run rich, but it might cover up that fact to a large degree at higher speeds.

[DGXSER]

Anyone got a good set of '81 pickups

Actually.......I still have the complete timing assembly from an 81 that is un spoken for.

[latexeses]

hbonser

When you checked the petcock filter did you confirm that fuel flows through the filter or did it just looked clean?
On my Standard tank the petcocks looked clean but they had a light and very clear coating of laquer on them and you could not blow air through them anywhere except right at the top of the filter.

Cut an aerosol can of Gumout loose on those filters and see what happens. I'll bet you a cold soda that they have a coat of laquer on the screen.

[natemoen]

When you checked the petcock filter did you confirm that fuel flows through the filter or did it just looked clean?
On my Standard tank the petcocks looked clean but they had a light and very clear coating of laquer on them and you could not blow air through them anywhere except right at the top of the filter.

Cut an aerosol can of Gumout loose on those filters and see what happens. I'll bet you a cold soda that they have a coat of laquer on the screen.

I will have to remember this come winter when things come apart. Never even thought about it.

[Ken Talbot]

And maybe by '81 Yamaha had found a better
quality wire....

Could be, but I've had to do the pick-up coil wire repair on Tsunami and Purple Reign - both 'H models. Heck, I even wrote it up in a little tech repair article a few years back.

[natemoen]

Could be, but I've had to do the pick-up coil wire repair on Tsunami and Purple Reign - both 'H models. Heck, I even wrote it up in a little tech repair article a few years back.

Oh the plot of the '81 pickups thickens!