Can I adjust mixture after Syncing?

[Skyboy8950]

82 GS650GL

So I just had my carbs synced. Man, it runs like a champ now. Before I got them synced, I adjusted the mixture by adjusting the screws until I got maximum RPMs out of each one as I have read to do on the forums. Now I am double guessing myself and may want to play with the mixture screws some more but am wondering if doing so will change the sync at all? Thanks in advance for the help.

PS. I was getting 45mpg with me and my lady going 65mph. Is this on par for gas milage? Thanks.

[duaneage]

If it idles smooth without issues I would leave it alone, Too much repair can ruin things.

45 mpg with a passenger sounds about right. I got 52 at 60 mph by myself. Terrain and wind matter, uphill into headwinds gives you worse mileage.

[chef1366]

Fix it till it's broke.:shock:

[earlfor]

NO! Or in other words.......... NO NO NO NO!!!!!! BACK AWAY from those mixture screws and keep your hands in your pockets. :-)

E.


[quote=Skyboy8950;629111]82 GS650GL

So I just had my carbs synced. Man, it runs like a champ now. Before I got them synced, I adjusted the mixture by adjusting the screws until I got maximum RPMs out of each one as I have read to do on the forums. Now I am double guessing myself and may want to play with the mixture screws some more but am wondering if doing so will change the sync at all? Thanks in advance for the help.

[Skyboy8950]

I get the picture. Thanks guys.

[Steve]

Personally, I will check each of them twice when the gauges are still attached.

If you had the carbs synched by somebody else, then played with the mixture screws, it probably did not change much, if any, so it's probably not worth the effort to hook everything back up.

Whatever you do, no NOT take Earl's suggestion. :shock:

Do NOT keep your hands in your pockets.

Put them on the grips, keep twisting the right one. \\/

Enjoy the ride. :-D


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[Skyboy8950]

Well, luckily, I haven't messed with them since the sync (yes, someone did it for me as I do not have a manometer). It is running pretty well, so I will just keep riding. Thanks.

[t3rmin]

Actually I think (theoretically) you should be able to adjust the mixture screws after syncing the carbs. The sync process gets the throttle plates/vacuum even; messing with the mixture screws won't change that AFAIK. In fact I've done it myself many times to no ill effect.

[Steve]

I have thought that way as well, T3, but I figure that if the mixture screw is off a bit and it changes how that cylinder is pulling, it might change the sync just a bit. That is why (as mentioned above) I sync, adjust mixture, sync again, then try to fine-tune the mixture. Works best when done all at one time, to minimize other vairables.


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[t3rmin]

Well at any rate I wouldn't adjust one with the other being way off. Best, as you said, to make sure they're all in the ballpark, even if that means doing each a few times. But I wouldn't give a second thought to "tweaking" the mixture screws after a sync.

[chef1366]

I've messed with mine after a sync but if you have a steady idle and no stumble on take-off I wouldn't mess with them.

[earlfor]

Since the reason to adjust the mixture screws is to find the optimum idle speed and intake volume is a function of rpm, then any mixture adjustment is going to "pull" the synch curve. It would not be much, but I dont see any way the synch could remain as good as it was previous to "tampering" with the mixture screws. This is assuming the synch was balanced to begin with. If it wasnt, who knows? LOL
E.

Actually I think (theoretically) you should be able to adjust the mixture screws after syncing the carbs. The sync process gets the throttle plates/vacuum even; messing with the mixture screws won't change that AFAIK. In fact I've done it myself many times to no ill effect.

[t3rmin]

Since the reason to adjust the mixture screws is to find the optimum idle speed and intake volume is a function of rpm.

(Just for the sake of discussion... :-D )

Yeah, but RPM between cyls is always equal. Adjusting the mixture screws may change the RPMs, but that's for the whole motor. The RPM/vacuum relationship between the cyls shouldn't really be changing. You might alter your idle speed, but that doesn't really affect sync either and you just adjust it back down/up with the knob as part of your mixture screw adjustment process anyway.

I've radically changed my mixture screw settings between syncs and the second sync didn't show any differences.

[earlfor]

Unfortunately, I can see no way to refute that rpm between cylinders is always equal, so I guess I'll have to let that one go. LOL
I understand what youre saying and it makes sense. However, have you had occasion to tweak a mixture screw and find after tweaking, the cylinder ran stronger? The rpm will come up a touch and the vacuum balance/relationships will change slightly.
(at least it does whenever I have tried it) I would agree with you and assume the synch changed due to the rpm increase, but adjusting the idle knob to the previous rpm level does not return the vacuum levels to the same relationship they had with each other. So my conclusion is it is the mixture that causes the change. As I said, its not a huge change. In theory and as you said, there should be no difference, but in practice and observation, I find there is. Its certainly possible and would not be the first time I have misinterpreted something observed. LOL Just the other day, the wife had the dog in one hand and was opening the dishwasher with the other and I...................... :-)

E.

(Just for the sake of discussion... :-D )

Yeah, but RPM between cyls is always equal. Adjusting the mixture screws may change the RPMs, but that's for the whole motor. The RPM/vacuum relationship between the cyls shouldn't really be changing. You might alter your idle speed, but that doesn't really affect sync either and you just adjust it back down/up with the knob as part of your mixture screw adjustment process anyway.

I've radically changed my mixture screw settings between syncs and the second sync didn't show any differences.

[t3rmin]

However, have you had occasion to tweak a mixture screw and find after tweaking, the cylinder ran stronger?

Never could avoid a good friendly discussion, so... :-D

Well... adjust the mixture screw and you are changing the mixture all through the RPM range (even if only slightly, by percentage, at more-than-idle speeds), so I'd say it's definitely possible to have a cyl run stronger after adjusting the mixture screw. Especially at idle and off-idle I think there could be a noticeable difference in running after properly adjusting the mixture screws.

I really don't think you affect inter-carb vacuum relationships ("carb sync") with the mixture screws, though. Of course you also want the carbs/cyls on the same page as far as A/F ratio, which is controlled somewhat by those screws, so in that respect you're affecting sync, just not in a way that'd be reflected on your manometer. Just IMHO and AFAICT of course! ;-)