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How often do you rebuild/sync carbs

  • Thread starter Thread starter MAJikMARCer
  • Start date Start date
M

MAJikMARCer

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So I'm still waiting to rebuild my carbs, but it got me thinking. How often should carbs be cleaned/rebuilt/synced? Every year? Depends on mileage? Depends on fuel?

What I'm getting as is, as a maintenance issue, not a tuning one. I know they have to be tweaked if you change pipes or go to pods, that's not what I'm really asking about.

Long and short of it is with one bike and no major aspirations to have a stable of GSs, does it make sense to buy all the parts and tools to do it all, including vacuum syncing?
 
MAJikMARCer said:
So I'm still waiting to rebuild my carbs, but it got me thinking. How often should carbs be cleaned/rebuilt/synced? Every year? Depends on mileage? Depends on fuel?

What I'm getting as is, as a maintenance issue, not a tuning one. I know they have to be tweaked if you change pipes or go to pods, that's not what I'm really asking about.

Long and short of it is with one bike and no major aspirations to have a stable of GSs, does it make sense to buy all the parts and tools to do it all, including vacuum syncing?
Click to expand...

One of my GS1100E's had crud in the tank so even with a decent in-line filter installed, small particles would build up in the float bowls.

This became an annual event to pull the carbs onto the bench for cleaning. I'd bench sync them and then sync them in place afterwards.

My other bikes never fell out of sync if I didn't need to remove the carbs.
 
nice tool to have for sure - http://www.carbtune.com/

Look at Spyug, he had to redo his carbs like 4 times already on his bike, one on the 250, and also did mine, his investment has more than paid for itself.

you would need a carb tune, at least I think anytime you tear into the carbs, this could be once a year, if you store your bike and it gets gummed up, or you get crap in them and have to strip em and clean em.

But if the bike is ridden and no changes occur, I don't see a need for this type of work to be done for a long time....

mind you I am no expert, but it's just the way I see it....

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It only makes sense to get the tools if you do your own work. :D

How often do they need to be "rebuilt"? That depends on how well you do it the first time.
If you soak them properly, replace all the o-rings, set the float levels correctly, etc., etc., and then either ride it enough to keep (somewhat) fresh gas in it or winterize it properly, you may not have to "rebuild" them for another 10 years or more. I say that because I did the carbs on my wife's bike seven years ago. Last year, I had to change some gaskets on the engine, and, of course, the job mushroomed into going so far as to change a cylinder liner. :eek: While the engine was apart, I figured "what the heck, I have the o-rings, I'll just do it again." Well, the carbs looked just like they did when I put them together seven years ago. I soaked them anyway (which required re-painting them) and put in new o-rings, even though the ones I took out looked GREAT. Six years, over 20,000 miles, NO problems.

Carb sync is a maintenance item. The vacuum produced by the running engine is a product of the cylinder trying to draw air past an obstruction (the throttle plate). The idea is to synchronize the throttle plates so all the cylinders are able to draw the same amount of air, enabling a smooth-running engine. If you do anything to change how much the engine is able to breathe, you need to compensate. If you ever have to adjust valve clearances, you are changing how much that cylinder can breathe. Now you will need to tweak the carb sync to compensate. Since the valves are supposed to be checked every 3-4000 miles, and the clearances tend to get smaller, there is a decent chance that you will be changing shims, if you ride your bike.

Do you need the tools? If you do your own work, yes. Do you have a friend nearby that has them? Maybe. Is there a shop anywhere nearby that will actually allow your 30-year-old bike through the door and will charge you less than the price of the sync tool (currently $102) to do the job? Do you realize that you might have to pay them again in another 3-4000 miles?

It's up to you, but now you have some insight.
icon_shrug.gif


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I keep track of two things: Fuel mileage (MPG) and Performance.

MPG is sort of a running average for a vehicle, expected to fluctuate by the type of driving (city vs. country, easy rides vs. performance riding), but tends to vary about a general range and is a good indicator of the overall state of tune.

Performance is more subjective, but often highlights a problem early (lack of power, drop-off in some RPM range, etc.). Usually we start looking "right now" when we notice a performance issue.

Unless there is dirt or rust in your fuel, or you let the bike sit for long periods of time, you hardly have to touch your carbs once they are set up correctly. Said another way, you can go years without any adjustments other than seasonal idle speed adjustments needed for an air-cooled motor. Full teardowns are rarely needed unless the bike has sat for a long time and gotten gummed up with varnish or the o-rings are dried out. Once those o-rings are replaced, they should be good for another 10-20 years.
 
This is why I love this site. Great insightful information. Thanks guys. This helps a lot. $100 isn't bad for a sync tool. I'd love to have a local buddy who had one or would go halvesies with me, but I havent met any local GSRs yet. Maybe tomorrow at the local "MetricFest" show and shine. There is going to be a swap meet too. I'll keep my eyes out for a sync tool. Anything special I should watch for, aside that it can accommodate four intakes. ;)
 
MAJikMARCer said:
I'll keep my eyes out for a sync tool. Anything special I should watch for, aside that it can accommodate four intakes. ;)
Click to expand...
I doubt you could find one, but mercury-based gauges are the BEST for accuracy and ease of use. However, that accuracy is offset by the hazardous nature of mercury.

Dial-type gauges are tricky to use and hard to read. They need to be calibrated EVERY TIME YOU USE THEM, so try to avoid them.
Go ahead and get them if they are being given to you, but don't pay anything for them.

Home-made gauges are highly questionable. There might be one out there that actually works, but most of the ones that I have seen are far too cumbersome for the average person (or me) to use.

You are correct in looking for something that handles all four carbs at once. There are some who say you can balance two carbs, then move to the next, but it only takes having them watch one session with all four vacuum levels displayed at the same time for them to see how making one adjustment affects all four readings. Doing that with two at a time will have you chasing your tail all day long.

GateKeeper gave you the link to the one that is generally preferred here. I would have one of them myself, if I didn't already have a nice set of mercury gauges. :D
I have had them for 33 years, I am not about to give them up any time soon. :p

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I had my 650 for 14 years, and never had reason to touch the carbs.

It seems to me that if carbs are syncrhonized with properly adjusted valves, readjusting valves should not require resynchronization. Adjusting valves to get them back in spec should return air flow to what it had been during the preivious synchronization.
 
Well in my experience, its only necessary when performance drops off, mileage goes bad or you introduce crap into them from a dirty "jerry can" as in my present case :).

As some of the guys have mentioned, they can go years if the fuel is kept clean and stabalized and the bike is run regularly. Like most everything else in life, sitting still is death to a bike.

If the bike is running well I'd say leave it alone and yup the Morgan Carbtune can't be beat for ease of use. One of the best tols I've ever bought.

Cheers,
Spyug
 
themess said:
I had my 650 for 14 years, and never had reason to touch the carbs.

It seems to me that if carbs are syncrhonized with properly adjusted valves, readjusting valves should not require resynchronization. Adjusting valves to get them back in spec should return air flow to what it had been during the preivious synchronization.
Click to expand...
This is spot on! Adjust valves first (and set ignition if using points), THEN synch the carbs. If you do it this way, you will probably never need to resynch the carbs for years and years.

But if you synch the carbs first, you'll have to synch them again after you do the valves and ignition. Synching carbs first just compensates for other things that should have been fixed first.
 
During the 32 years I've had my bike, the carbs have been sync once and spray cleaned 3 times or something like that and one set of float needles.. I am doing a complete tear down and dipping of them now. New orings, gaskets, intake boots and the like. I think 32 years is enough don't cha think.
 
Steve said:
I doubt you could find one, but mercury-based gauges are the BEST for accuracy and ease of use. However, that accuracy is offset by the hazardous nature of mercury.

I have a brand new mercury sync gauge I bought from Dennis Kirk sometime ago, There are about to be used for the first time soon.
Click to expand...
 
Rebuild

Rebuild

I would only consider rebuilding the carbs if the bike doesn't run well. For some reason, I had lots of problems with my 750 and rebuilt them about once every 18 months. I've only done it once on my 1100 and it continues to run great....after 4 years. If that continues, I'll never do it again.:-\\\
 
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