Nothing like a nice carb sync...ahhhh


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WingAdmin
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Nothing like a nice carb sync...ahhhh

Postby WingAdmin » Sat Sep 24, 2011 9:14 pm



My bike has been running rougher and rougher lately, it's kind of gradually gotten worse. It's been creeping up to the point where I took it out for a couple hours today, and it just wasn't enjoyable, because I wasn't liking how "rough" the engine felt, particularly on accelerating.

So after I got home, I sat down and did a long-overdue carb sync. The #2 and #4 carbs were WAY out, and the left/right balance wasn't great either. Now that they're all balanced, it's as smooth as butter, a million percent better. Smiles all around.

Carb syncs are SO worth the time taken to do them....



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Steve F
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Re: Nothing like a nice carb sync...ahhhh

Postby Steve F » Sun Sep 25, 2011 8:03 pm

I totally agree with it being worth it, even if it isn't too bad to be a noticable problem. While I have an 1800, and carb syncing isn't required, I do have a '76 CB750 and those things need adjustment at least every 4k miles or so. If I wait any longer, the performance starts to deteriorate at an alarming rate. Tha ol' 750 is a blast to ride, but sometimes you have to do some maintenance.
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Re: Nothing like a nice carb sync...ahhhh

Postby WA9FWT » Mon Sep 26, 2011 8:10 pm

If I remember it wasn't to long ago you did a carb sync to your unit.But of coarse time flies....
If not that many miles, what do you think cause's it to go out of sink ? ... age, fuel, additives.

Just my thinking that one should get abt 5K before sync again.

WA9FWT Phil

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Re: Nothing like a nice carb sync...ahhhh

Postby HyperPete » Tue Sep 27, 2011 8:07 am

My new to me '82 Aspencade has a tough time exceeding 80 MPH, and the idle "lopes" a bit. I'm guessing that these are both symptoms of needing a carb synch.
Some scientists claim that hydrogen, because it is so plentiful, is the basic building block of the universe. I dispute that. I say there is more stupidity than hydrogen, and that is the basic building block of the universe.
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Re: Nothing like a nice carb sync...ahhhh

Postby WingAdmin » Tue Sep 27, 2011 9:39 am

WA9FWT wrote:If I remember it wasn't to long ago you did a carb sync to your unit.But of coarse time flies....
If not that many miles, what do you think cause's it to go out of sink ? ... age, fuel, additives.

Just my thinking that one should get abt 5K before sync again.

WA9FWT Phil


According to my records, it was 16 months and 7,500 miles since my last carb sync. So within the realm of possibility, anyway.

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Re: Nothing like a nice carb sync...ahhhh

Postby thrasherg » Tue Sep 27, 2011 2:44 pm

HyperPete wrote:My new to me '82 Aspencade has a tough time exceeding 80 MPH, and the idle "lopes" a bit. I'm guessing that these are both symptoms of needing a carb synch.


A carb sync will only smooth the idle, it will have no effect on top speed, if you can't exceed 80mph, you have another problem (not sync related!).

Gary

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Re: Nothing like a nice carb sync...ahhhh

Postby WingAdmin » Tue Sep 27, 2011 4:28 pm

thrasherg wrote:A carb sync will only smooth the idle, it will have no effect on top speed, if you can't exceed 80mph, you have another problem (not sync related!).

Gary


Well...it won't affect top speed, but it will have a bit of effect on low-engine RPM as well as idle, i.e. pulling away from a stop, when the sliders are ALMOST closed. The wider the slides open, the larger the open area in the throttles for them to let air through, and the smaller the percentage the sync adjustment, and the less effect the carb sync has.

Put it this way - let's say the area of the opening inside the throttles that is restricted by the slides at idle should be 0.25 square inches (not saying it is, just made that number up). If one of the carbs is out of sync so that it is open to 0.35 square inches instead of 0.25 square inches, that's a large percentage: it's out by 40%.

Now open the throttle a bit, so the opening should be 0.75 square inches. The unbalanced carb is still unbalanced by +0.1 square inches, as before, so it is now open to 0.85 square inches instead of 0.75 square inches. That's a lesser percentage - only 13% of the overall opening. As you continue to open the throttle, the ratio of the unbalanced carb's offset to the overall throttle opening continues to decrease, to a point where the effect is no longer distinguishable.

The end result is, all else being equal (i.e. meaning the carbs are otherwise healthy and operating properly), an engine with unbalanced carbs will be roughest at idle, and will get progressively smoother as the throttle is opened more and more.

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Re: Nothing like a nice carb sync...ahhhh

Postby thrasherg » Tue Sep 27, 2011 4:43 pm

Agreed WingAdmin, but at full throttle any inbalance in the carb sync will have <1% effect on max power (All carbs will be fully open or so close to fully open that the engine will make almost full power) so I stand by my statement, that carb sync has no bearing on his bike's inability to exceed 80MPH!! :D

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Re: Nothing like a nice carb sync...ahhhh

Postby HyperPete » Tue Sep 27, 2011 5:00 pm

I guess I'll start with the Seafoam and go from there... The synch should at least help the uneven idle. If issues persist I'll start a thread rather than hijacking this one.
Some scientists claim that hydrogen, because it is so plentiful, is the basic building block of the universe. I dispute that. I say there is more stupidity than hydrogen, and that is the basic building block of the universe.
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Re: Nothing like a nice carb sync...ahhhh

Postby WA9FWT » Tue Sep 27, 2011 5:28 pm

HyperPete wrote:My new to me '82 Aspencade has a tough time exceeding 80 MPH, and the idle "lopes" a bit. I'm guessing that these are both symptoms of needing a carb synch.


Well just to day a fellow was having the same problem as you (750 Honda ), no speed because of the engine missing at higher speeds. Seems ok at idle, but not all the time.
This afternoon we installed a timing lite to watch the ignition as we went through the gears.At times we thought it was ignition, or was it the carbs ?. He had it at another dealer and told us it had the carbs rebuilt Ect. Lets give this a try, and removed the air filter. That was it, the thing just needed more air.
$$$$$ Later and all it was to fix the problem was replacing with a new air filter.
Some times we make Moutains out of mole hills, I guess... :)
WA9FWT Phil

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Re: Nothing like a nice carb sync...ahhhh

Postby Steve F » Tue Sep 27, 2011 9:38 pm

HyperPete wrote:My new to me '82 Aspencade has a tough time exceeding 80 MPH, and the idle "lopes" a bit. I'm guessing that these are both symptoms of needing a carb synch.
The "loping" is either a synch or idle mixture problem, or a combination. Try doing this in sequence....engine COLD, adjust valve clearance. start engine, and once warmed up, adjust the idle mixture and set idle speed according to spec. Next, do a timing check/adjust and finally, do a carb synch. Be sure your timing advancers are working, and not stuck. Also, a new set of plugs can't hurt.
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Re: Nothing like a nice carb sync...ahhhh

Postby HyperPete » Wed Sep 28, 2011 7:27 am

Thanks for the responses and suggestions everyone. I'll try what has been suggested, but I feel badly in having hijacked this thread. After checking everything out this weekend, if the problem persists, I'll post a new thread and solicit further advice.
Some scientists claim that hydrogen, because it is so plentiful, is the basic building block of the universe. I dispute that. I say there is more stupidity than hydrogen, and that is the basic building block of the universe.
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Re: Nothing like a nice carb sync...ahhhh

Postby thrasherg » Wed Sep 28, 2011 9:13 am

HyperPete wrote:Thanks for the responses and suggestions everyone. I'll try what has been suggested, but I feel badly in having hijacked this thread. After checking everything out this weekend, if the problem persists, I'll post a new thread and solicit further advice.


I wouldn't worry about it, Wingadmin is a big boy and he's the Admin so he could have wiped your account if he was upset with the hijack!! :D
It is always better to start your own thread.. Fingers crossed you find the cause of your problem this weekend, but we are all here to help/confuse the situation!! :twisted:

Gary

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Re: Nothing like a nice carb sync...ahhhh

Postby littlebeaver » Thu Sep 29, 2011 5:22 pm

Wingadmin. Did you do the sycn. using all four gauges or did you use just one gauge? How do you go back and check everything with just one gauge? Is it a pain, is the four gauge way easier? After you showed how to make one [four gauge] I needed one but I just bought a set, the next thing I know your going to a single carb method...Why I oughta :lol: ...No... I wish to understand this better, is the single way better? If any of you guy's have not sync. the carb's you will need to as soon as you can, it makes a huge difference in how the bike accellerates... :D I do mine with the four gauges and it seems to be pretty good..

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Re: Nothing like a nice carb sync...ahhhh

Postby WingAdmin » Thu Sep 29, 2011 9:09 pm

littlebeaver wrote:Wingadmin. Did you do the sycn. using all four gauges or did you use just one gauge? How do you go back and check everything with just one gauge? Is it a pain, is the four gauge way easier? After you showed how to make one [four gauge] I needed one but I just bought a set, the next thing I know your going to a single carb method...Why I oughta :lol: ...No... I wish to understand this better, is the single way better? If any of you guy's have not sync. the carb's you will need to as soon as you can, it makes a huge difference in how the bike accellerates... :D I do mine with the four gauges and it seems to be pretty good..


I did neither. :)

The problem with the four gauge method I used, is that the four gauges I got from Harbor Freight were not calibrated to one another.

The problem with the single gauge method is that it's really tough to remember exactly what the first one was reading while you rush to swap it to the second.

So what I did was take a tube with a T-junction, and connect it to two gauges. I then sucked on the end of the tube and watched what the gauges indicated. Luckily, I had two that read exactly the same - the other two were way out. I marked those two as "do not use" and took the two good ones.

I then used those two gauges at the same time. First, I put one on cylinder 1 and one on cylinder 3, and balanced them. Then I did the same to 2 and 4. Then I did the left to right on 3 and 4. Quick and easy, and it works great. So I'm going to recommend the two-gauge method. Unless you happen to have four well-calibrated gauges, that's still really the easiest way! :)

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Re: Nothing like a nice carb sync...ahhhh

Postby littlebeaver » Thu Sep 29, 2011 11:11 pm

Well, if that doesn't just beat all, now I'm chasing my tail trying to keep up with all of your changes, ha ha, I like that you have figured out the different ways of doing it though, I feel the gauges I got do a good job, I'm pretty picky about that kinda stuff too.. My friend has a set that is really nice, very costly I'm sure...The main thing is you got it done and it's smooth again.. :D I'm glad your a good sport.... :lol:




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