Carb synching and more - confused

[noobie]

After a long time I'm back.

I'm sure this has already been discussed, but after checking the first 7 pages of this section I didn't find any existing thread, so I hope you'll forgive me for starting a new one.

Okay, here's the situation.

1978 GS1000EC, lovingly rebuilt into original condition. The carbs are VM26SS.

I'm by now thoroughly confused by how to synch carbs.

The synchronizer I'm using:

First question is: where should the needles on this synchronizer be when the carbs are snyched correctly? If it's needed I'll make better pictures of the syncher tomorrow.

On one side I'm being told that when plugging in the synch tester, that all needles should be on the same level and other sources say that needles #1 and #4 should be the same and #2 and #3 the same, but differently than 1 and 4.

Also, am I right that when checking the carbs with the synchronizer the bike should be running at 2500-3000 RPM? Does that mean to set the idle to that high or just open the throttle manually?

Also, just out of curiosity: how hard is it to put a 1100 or 1150cc engine on a 1000?

The bike in question (and my Fulmer helmet ... for some reason I always forget something on a bike when I want to take a picture of it).

 

[terrylee]

Should be a great detailed instructions on Basscliffs' site on how to sync., I do believe your right needs to be done at 2500 rpms. Do you have a fourth gauge if not it will be tough to get all 4 carbs. set right, when you change one all the other will be effected. If you have a cross over piece on your exhaust you will need to set 2 and 3 the same and 1 and 4 a little higher (see instructions). Hope this helps. terrylee

 

[bwringer]

Make sure you calibrate those gauges each time you use them. This should be in the instructions that came with the gauges. They're not as accurate as a Morgan Carbtune, but they'll do.

Anyway, the actual readings don't matter. They just need to be the same. On shafties and possibly a few other models, you're supposed to set 2 & 3 to slightly lower readings, but I've never bothered.

The problem is that Suzuki never specified exactly how much lower, other than "1/2 ball" on their goofy proprietary sync gauge. I don't think anyone's ever seen one of these in real life and compared it to a real gauge.

 

[twr1776]

Brian (as usual) is correct. The 1/2 ball noted in the Suzuki manual is I believe for pipes with a crossover in between them. For a 4-1 pipe the readings are supposed to be all the same. I have done it both ways and the difference is very small and I'm not sure even noticeable, post 8 here is of a Carbtune which I use and with the crossover I try to go 2 less for the inner cylinders on the guage but that is my best guess on what Suzuki called for. I have never gotten them perfect since the Carbtune is more accurate than I am but I'm still trying.

http://www.thegsresources.com/_forum/showthread.php?t=165739

 

[noobie]

Tried to synch the carbs today with my father (who knows a LOT more about mechanics than I do). This is what we managed to achieve (it's in two pictures):

Carbs #1 (left) and #2 (right)

And carbs #3 (left) and #4 (right)

-------------------

Now the big question I'm here to ask you nice folks is where exactly should the needles be.

Can they be where-ever on the clocks, as long as they're set 1=4 and 2=3; or should they all be in the specific areas of the clocks. For example, should they all be within the green, NORMAL areas?

Also, carb #3 has been pretty mutinous and refuses to cooperate, no matter how we set it, it never stays that way, even though we tighten the bolt firmly. And sometimes it seems to mess up the rest of the settings, since #1 was set correctly before we tried to reset #3... you can see where #1 is now...

Btw., this is the setting we got by screwing around with fuel screws.

We'll be trying again tomorrow, but by then I wanted to have a better idea of how it should be.

Tnx

 

[Steve]

Tried to synch the carbs today with my father (who knows a LOT more about mechanics than I do). This is what we managed to achieve ...

Now the big question I'm here to ask you nice folks is where exactly should the needles be.

Can they be where-ever on the clocks, as long as they're set 1=4 and 2=3; or should they all be in the specific areas of the clocks. For example, should they all be within the green, NORMAL areas?

Also, carb #3 has been pretty mutinous and refuses to cooperate, no matter how we set it, it never stays that way, even though we tighten the bolt firmly. And sometimes it seems to mess up the rest of the settings, since #1 was set correctly before we tried to reset #3... you can see where #1 is now...

Btw., this is the setting we got by screwing around with fuel screws.

We'll be trying again tomorrow, but by then I wanted to have a better idea of how it should be.

Tnx

Several things going on here.

Did you read posts 3 and 4, from bwringer and twr1776? They would answer a couple of your questions.
Do you have a crossover in the exhaust between pipes 2&3? I don't think you do. Therefore, ALL VACUUM READINGS SHOULD BE EQUAL.

Remember that the actual numbers don't matter. In fact, the best of the gauges don't even have numbers on them, you are looking for balance from one cylinder to the others.

The GREEN ZONE is "normal" for something other than our bikes.
(The WHITE zone is for loading and unloading only.)

You talk about #3 being "mutinous", but the pictures show that #4 is the one that is out of line. Of course, this assumes that you have connected the gauges left to right. With the readings you are showing, I would tweak #4 so it is right about the "9" with the rest of them. While perfectly equal is highly desirable, +/- 1 is good on the gauges you have. #1&2 appear to be right at 9, #3 appears to be about 8.5, that is fine. Just get #4 to agree with the others.

One final thing, YOU DON'T ADJUST THE SYNC WITH THE FUEL SCREWS.
The fuel screws (which are the ones on the bottom of the carbs) and the air screws (which are the ones on the side of the carbs) have NOTHING to do with synchronizing the opening of the throttle slides. They are, amazingly enough, for adjusting the fuel mixture at idle and low-throttle openings. The SYNC adjusters are at the top of the carb, under that cap that is held on by three screws. Loosen the locknut, tweak the adjuster, tighten the locknut.

Other points were brought up in previous posts that need some explaining. Before you check anything on your bike, you need to connect all four gauges to a manifold that should have been included with your gauges, then all of them connected to the same vacuum source (one of your vacuum ports) so they are all reading the same vacuum at the same time. Check your gauges to assure that they are all reading the same. If not, make adjustments to that gauge(s) so it does. You need to do this every time you use those dial-type gauges. (That is one reason so few of us use them.)

Speed: Suzuki manuals call for an operating speed of 1750 +/-250 rpm during carb sync. Not sure just why, as the sync process is to co-ordinate when the throttles open. I prefer to do mine right at idle speed or just a bit higher, but no more than 1200. I'm not saying that's the best way to do it, but it works well for my bikes.

.

 

[tkent02]

The fuel screws (which are the ones on the bottom of the carbs) and the air screws (which are the ones on the side of the carbs) have NOTHING to do with synchronizing the opening of the throttle slides. They are, amazingly enough, for adjusting the fuel mixture at idle and low-throttle openings. The SYNC adjusters are at the top of the carb, under that cap that is held on by three screws. Loosen the locknut, tweak the adjuster, tighten the locknut.

.

The air screws or mixture screws don't directly affect the the opening of the throttle slides, but they do have an effect on the vacuum reading. If you tweak all the screws, changing the vacuum reading a little bit, then reset the SYNC adjuster to make the vacuum even again, the screws have indirectly altered the sync adjustment.

It's all interrelated.


And for your other question, an 1100G top end will bolt right on your engine.

 

[Steve]

OK, so maybe I shouldn't have said they have NO affect, but it still remains ...

You don't adjust the sync by "screwing aroung with the fuel screws", as he has admitted.

.

 

[noobie]

Forgot to explain: my setup is stock. 4 headers out of which comes two end-pipes (one on each side of the bike), with #2 and #3 connected with a cross-pipe.

You talk about #3 being "mutinous", but the pictures show that #4 is the one that is out of line.

That situation was after the last time we tried for the day... all other times it was #3 that was problematic and #4 was as it should be. Then suddenly #4 didn't want to play along anymore. And then of course there also had to be a thunderstorm, even though the forecast was for dry weather, which stopped our meddling about.

Of course, this assumes that you have connected the gauges left to right. With the readings you are showing, I would tweak #4 so it is right about the "9" with the rest of them. While perfectly equal is highly desirable, +/- 1 is good on the gauges you have. #1&2 appear to be right at 9, #3 appears to be about 8.5, that is fine. Just get #4 to agree with the others.

And since my #2 and #3 pipes are connected that means the desirable situation would be #1 and #4 at 9 and #2 and #3 at 8?

One final thing, YOU DON'T ADJUST THE SYNC WITH THE FUEL SCREWS.
The fuel screws (which are the ones on the bottom of the carbs) and the air screws (which are the ones on the side of the carbs) have NOTHING to do with synchronizing the opening of the throttle slides. They are, amazingly enough, for adjusting the fuel mixture at idle and low-throttle openings. The SYNC adjusters are at the top of the carb, under that cap that is held on by three screws. Loosen the locknut, tweak the adjuster, tighten the locknut.

Sorry, problem with communicating. Though I've been speaking English for a while now, specialty English phrases still give me problems sometimes as I'm sometimes guessing the correct phrases.

The Sync adjusters is what I meant that we adjusted after having set the screws that are on the side of the carbs, because we removed a cover on top of the carbs, that was fastened by the three screws.

Other points were brought up in previous posts that need some explaining. (snipped)

We did all that.

Speed: Suzuki manuals call for an operating speed of 1750 +/-250 rpm during carb sync. Not sure just why, as the sync process is to co-ordinate when the throttles open. I prefer to do mine right at idle speed or just a bit higher, but no more than 1200. I'm not saying that's the best way to do it, but it works well for my bikes.

That low? Hmm, maybe I'm wrong, but I'm sure I saw 2500-3000 mentioned somewhere on BassCliff's page or on a page he linked to.

Thanks for your help!

 

[apogeecustom]

Those gauges are terrible. Don't waste you're time with them. When you calibrate them to one carb, you have to manually move the need as an adjustment. This has no reliable accuracy because the internal mechanics are so cheap. There is a circular bent brass tube that due to its shape will compress/expand when vacuum is applied and this in turn rotates some gears which then turn the needle. The parts are flimsy, the tubes are hand made (soldered) and you'd be better off just bench syncing. My two cents.

 

[noobie]

Okay, managed to synch the bastards and it runs a lot better now. Will re-check the carbs next week to fine-tune them if necessary.

Thanks for the help guys!