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Carburetor Tune - vacuum sync

  • Thread starter Thread starter legaleli
  • Start date Start date
L

legaleli

Guest
I think my next job should be syncing my carburetors. Here are my thoughts and I'd love opinions:

The valves were adjusted and the carburetors were cleaned just before I bought the 1982 GS850 a few months ago (the vendor claimed this was done and there is evidence to suggest this happened - the carburetors seemed very clean on the outside and new boots were installed and correspondence from the mechanic included claims that he had them out and apart). Also there is a new gasket on the valve cover suggesting the cover was off - and again, the mechanic claimed he did have the cover off and the valves shimmed. The plugs and wires are new and properly installed.

Here are the symptoms - the bike has a noticeable vibration when I "rev" the motor. The strange thing is that it does not feel "mechanical" - it is a tight vibration that is uniform throughout the rev range - as if it does not "resonate" at certain RPMs - it does not get worse or better as I rev up. I am thinking that the barbs are out of whack with each other and it is causing the noticeable vibration.

If this is likely - and even if it's not, should I check the sync? If so, I will need to buy the tools and get the job done.

The manual has a decent description of what to do, but I also have replaced the pre-muffler on my bike with straight pipes and I will need to balance the carburetors for that set up.

I went looking for the links that were previously provided to me as to where to buy the tools and perform the operation, and as usual... I suck.

This would also be another cool project for me to photograph from start to finish. HELP!:D
 
Carbs out of sync will definitely create the vibration you described.
 
It's amazing the vibrations the valves can make, I know from experience. Even though the PO said the valves were done it wouldn't hurt to check. Wouldn't hurt to check all your nut's n' bolts since she's new to you either. I would offer to pop over with my carbsynch and colortune since I see you're a fellow Canadian...but you're on the wrong ocean!
 
azr said:
It's amazing the vibrations the valves can make, I know from experience. Even though the PO said the valves were done it wouldn't hurt to check. Wouldn't hurt to check all your nut's n' bolts since she's new to you either. I would offer to pop over with my carbsynch and colortune since I see you're a fellow Canadian...but you're on the wrong ocean!
Click to expand...
Where did you buy your colortune and for how much?
 
legaleli said:
I'm going to buy one - I don't trust myself to be able to build a good one!

I see that Z1 Enterprises has one:

http://www.z1enterprises.com/detail.aspx?ID=1689

Do I need to buy anything else with this (i.e. adapter kits)?
Click to expand...

The Motion Pro comes with the correct adapters...

Although the motion pro does work, I used mine a few times, the Morgan Carb tune....(found here: http://www.carbtune.com/ ), is about the same price and much superior.
I have used both and there is no doubt which is better.

If you get the Morgan, order the correct adapters from Z1, they are much better than the adapters that come with the Morgan.
 
Baatfam said:
The Motion Pro comes with the correct adapters...

Although the motion pro does work, I used mine a few times, the Morgan Carb tune....(found here: http://www.carbtune.com/ ), is about the same price and much superior.
I have used both and there is no doubt which is better.

If you get the Morgan, order the correct adapters from Z1, they are much better than the adapters that come with the Morgan.
Click to expand...

What to do?! I just checked the carbtune.com site and it says:

"STOP PRESS: THERE ARE STILL PROBLEMS WITH THE VOLCANIC ASH THAT HAS GROUNDED ALL FLIGHTS. DELIVERIES TO EUROPE ARE BEING TRANSFERRED TO ROAD AND RAIL. MAIL FOR THE REST OF WORLD IS BEING HELD IN LONDON (orders FROM 14TH APRIL) FOR THE NEXT AVAILABLE FLIGHTS SO THERE WILL BE DELAYS TO R.O.W. DELIVERIES."

I would obviously prefer the better device... stupid volcano.
 
Last edited:
legaleli said:
What to do?! I just checked the carbtune.com site and it says:

"STOP PRESS: THERE ARE STILL PROBLEMS WITH THE VOLCANIC ASH THAT HAS GROUNDED ALL FLIGHTS. DELIVERIES TO EUROPE ARE BEING TRANSFERRED TO ROAD AND RAIL. MAIL FOR THE REST OF WORLD IS BEING HELD IN LONDON (orders FROM 14TH APRIL) FOR THE NEXT AVAILABLE FLIGHTS SO THERE WILL BE DELAYS TO R.O.W. DELIVERIES."

I would obviously prefer the better device... stupid volcano.
Click to expand...
Order it and wait. That Motion Pro is a POS, both on its own and especially in comparison to the Carbtune
 
It's probably hard to tell the difference between the two.
Tight valves can have a "tightness" feeling and the bike can have trouble running at 1100RPM Idle speed, (it'll idle higher), it will also generally run like CRAP. It might feel like the bike is running extremely lean.
(it did this on my bike atleast.)


If the bike is out of Sync, this means the Cylinders are "fighting" each other, and thus.....out of sync.
I "think" the higher RPM's you go, the more vibration you tend to have?
(dunno, remember somebody talking about RPM's being a problem when your out of sync?)

I had both problems on my 650.

--------

The BIGGEST improvement you can LIKELY do, is check those valves clearances!
I have a shim-style valve setup on my 650, and when I checked the valve numbers, YIKES, they were BEYOND tight!
(which is under 0.03)

I got the flowchart from steve, did the math, ordered a couple new shims from Z1, then just happened to be able to swap the rest of the Shims around to get the exact numbers I needed....pretty cool!

Bike ran A THOUSAND times better, and instantly smoother.....

(the "mechanic" who did it, could have been a blundering idiot and probably didn't know what the hell he was doing.......no surprise there.....you would be surprised how many shops "claim" to work on older bikes, but have ZERO clue as to what they are doing.....which is why THIS site is valuable!)

There seems to be a big hate for "mechanic shops" on these forums.
Don't really blame anybody there......i dont trust anybody to work on my vehicles either.

-------

But yeah, order your Sync gauge or whatever setup you're going with.

Then try to get yourself some valve spec gauges.
(which are "usually" just your typical feeler gauges with a buncha thin metal sliders that you stick in the check the valve clearance, but order from Z1 or somewhere that has the EXACT numbers you need.....0.03-0.10 are extremely hard to find! I have like 6 Feeler gauges at my house, and only 1 had barely the sizes that I needed.....I even bought a motorcycle feeler gauge, and it didnt even go down to 0.10! So know the numbers your looking for first!:D)
 
How to determine adapter size?

How to determine adapter size?

Baatfam said:
The Motion Pro comes with the correct adapters...

Although the motion pro does work, I used mine a few times, the Morgan Carb tune....(found here: http://www.carbtune.com/ ), is about the same price and much superior.
I have used both and there is no doubt which is better.

If you get the Morgan, order the correct adapters from Z1, they are much better than the adapters that come with the Morgan.
Click to expand...

Anyone know how I can determine the proper size adapters for my 1978 GS550C? I saw 5mm and 6mm on part websites.

From reading these posts, I decided and have ordered the Morgan Carb tune and color tune. Thanks for all of your opinions!
 
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