Carb sync

[Rumble]

There's a post down the list a bit, (http://www.intruders-alert.com/viewtopic.php?f=10&t=147), that's locked for comments. Just wanted to throw my two pennies in and share that I've had great success with the Twinmax carb synchronizer. This video: https://www.youtube.com/watch?v=zdzQUUhp2l4 shows basic operation. I only use it for idle sync. Maybe this fellas beemer requires a different method. Dunno.
I've also used it to get my GV1200GL (V4) straightened out but that's a different write-up for a different forum.

There's an upside to the drought - check it out!

[YoDude]

Nice! Thanks for sharing.

Yo-

[NE_FL]

Good info.

[Fred]

I don't use them. From my apprenticeship we never had them on the late 60's even a flat V12 with 6 double down draft Webers was done by ear.

The intruder is not difficult but then not so forgiving as there is no balancer in the inlet manifold and each carb individual.

Ive had a thread locked over on the purple because some one thinks they know more than I do. You can do it by just feeling the pulses of gasses coming from the exhaust . This is quite accurate if you have 2 singles.

The other way of course is just a simple water hose pipe about 1 meter long and listen to the hissing from the carbs --easy.

You may find that even when its set by whatever the tuning devise of you choice it does not run perfectly,-- adjustment by ear may improve it because you are setting it to the engines moods and swings rather than just purely on air intake.

[wj_hurd]

I don't use them. From my apprenticeship we never had them on the late 60's even a flat V12 with 6 double down draft Webers was done by ear.

The intruder is not difficult but then not so forgiving as there is no balancer in the inlet manifold and each carb individual.

I've had a thread locked over on the purple because some one thinks they know more than I do. You can do it by just feeling the pulses of gasses coming from the exhaust . This is quite accurate if you have 2 singles.

The other way of course is just a simple water hose pipe about 1 meter long and listen to the hissing from the carbs --easy.

You may find that even when its set by whatever the tuning devise of you choice it does not run perfectly,-- adjustment by ear may improve it because you are setting it to the engines moods and swings rather than just purely on air intake.

I'm so lost with this Fred... I would love a little more detail on how to do this.
I would like to get my bike a little more dialed in this season, and this is something I would like to do.
I'm no stranger to a wrench and grease, so I'm not afraid to dive in. However I'am afraid of messing up.

All I have is opened up A/F screws on my bike, no carb mods have been done. I tinkered with them some last year, but I have lots of popping when she is cold and I think that the carbs could use a closer dial in.

I was actually looking at a mercury vacuum gauge to dial them in better.
http://www.revzilla.com/product/motion- ... aQodRCkA5Q
Willing to drop the coin on the tool if needed. But if you have a good way of doing this... I'm all ears!

[Fred]

Sorry im 3 months behind, ive not been around. You still there, you still wanna discus.

[jonnycando]

I paid the dealer to sync me this year...and after I put fresh plugs in reckoned he did a decent job. Recently I put new used HD Softail mufflers on, and that eliminated the crossover pipe of the factory setup. I put in new header gaskets...the front one was burnt to a crisp for some reason. Leakage probably...Now, you would think with fouled plugs and a header that leaked at least some would throw off a sync job. At least you'd be syncing to that condition, and on correcting it you would mess it up. Well....if I go totally by feel, the pulse coming out of the pipes is the same both sides now....and the engine runs smoother and quieter....is it in sync or not? Who knows...but it runs well.

[YoDude]

If it doesn't start vibrating on you until you hit about 90, you're doing pretty good. Before I did the last sync on mine, it would start vibrating at about 70 and got worse going faster. After the last sync I did, it is better up until about 80 now, but that's only tuning by ear. I have a sync tool (morgan carbtune) but I've never used it. I imagine a real fine tune job should produce a much smoother ride.

Yo-

[Fred]

I paid the dealer to sync me this year...and after I put fresh plugs in reckoned he did a decent job. Recently I put new used HD Softail mufflers on, and that eliminated the crossover pipe of the factory setup. I put in new header gaskets...the front one was burnt to a crisp for some reason. Leakage probably...Now, you would think with fouled plugs and a header that leaked at least some would throw off a sync job. At least you'd be syncing to that condition, and on correcting it you would mess it up. Well....if I go totally by feel, the pulse coming out of the pipes is the same both sides now....and the engine runs smoother and quieter....is it in sync or not? Who knows...but it runs well.

Well done John, thats what its about , take a deap breath relax and become one with the engine. You have how synced the idle as the engine wants not to the simple balance of air intake.

My next sync would be to put my finger on the front cable quadrant and very slowly crack the throttle while looking the the rear cable quadrant --if your finger and eye sees no difference in opening your done. You further check this to the engine by just cracking the throttle while running. Each cylinder should start to pull the same time.

Forget full throttle sinc it is impossible to achieve.

[Lechy]

All I use is a "U" tube manometer, about 12' of 4mm clear plastic hose tied to a broomstick with about 12" of 2 stroke oil. I made some adapters out of 5mmx1mm long bolts with the heads cut off. I do the first stage rough balance by Fred's method then fine tune with the "U" tube. I get a sympathetic vibration in the mirrors at about 4000 rpm but that clears at around 4500 rpm and then all is smooth up to 7000 rpm I could probably take it up to 7500 + but the power curve has pretty much flattened out at 7000 rpm.
I also balance my CB 750 inline 4 with this set up, if you understand how the carbs are linked it is easy on the 4 all that is needed is a fast idle synch.
[emoji41]

[scootermcq]

I made some adapters out of 5mmx1mm long bolts with the heads cut off.

How does that work? Are they hollow bolts or how do you measure the vacuum?

[Lechy]

I had a local machine shop drill them through, you don't measure the vacuum, you make a comparison of the vacuum being pulled by the cylinders. When you start, one side will probably be high and the other low, adjust until they are the same level and both cylinders are pulling the same vacuum, ergo balanced.
Remember, no amount of balancing will work if the valves are burned or the rings are broken, then it is time for a compression check.
[emoji41]

[Fred]

Just use stainless cheese head screws --drill it out and solder on some brass nipples.

Just tighten with a small driver in the nipple --they don't need to be tight.

If you are paranoid about leakage just use heavy grease on the threads --I dint bother. Its only a 5 minute attachment

[EstIntruder]

Interesting reading, I just want to sync my intruder, but I never done this before so I have few questions what I could not get a answer from internet.

Why I want to sync is because I reckon rear carby is running rich, beacuse if I turn AF screw in then idle goes higher and if out then there comes bit some out when revving.

1. How to you know that your bike is running at 1000RPM ?
2. How to set it at 1000rpm? From main idle screw what is under the rear carby?
3. If my rear carby pilot jet is too rich or lean, how do adjust it? any factory settings?
4. How carbys vacum system is working? The more butterfly valve is open then then more vacum it's creating and that's how main jet is pulled up?

I have not repaired carburetors before, so sorry if questions might seem bit foolish. Also english is not my first language, it's estonian language.

[WintrSol]

Interesting reading, I just want to sync my intruder, but I never done this before so I have few questions what I could not get a answer from internet.

Why I want to sync is because I reckon rear carby is running rich, beacuse if I turn AF screw in then idle goes higher and if out then there comes bit some out when revving.

1. How to you know that your bike is running at 1000RPM ?

Get a small tach, or a hand-held one; I have one of these: There are also simple tachs available many places, that cost even less than that one.

2. How to set it at 1000rpm? From main idle screw what is under the rear carby?

Yes, that sets the idle for the rear carb, and pulls the sync cable that sets the idle for the front. BTW, that cable is what you adjust for idle sync.

3. If my rear carby pilot jet is too rich or lean, how do adjust it? any factory settings?

There is an adjustment for the idle, called the pilot screw; these are covered with a brass plug from the factory, which is easily removed, if yours haven't been.

4. How carbys vacum system is working? The more butterfly valve is open then then more vacum it's creating and that's how main jet is pulled up?

Vacuum is created by the engine pulling air through the carburetor; at idle, the vacuum is usually highest, and it drops as the throttle butterfly is opened. If you open the throttle quickly, vacuum drops a lot, then increases as the engine rpm catches up. As you close the throttle, vacuum rises, until the engine rpm slows. What a good sync does is make sure both throttle butterfly valves open and close at the same time, so that power is the same from both cylinders; measuring that the vacuum is the same as you open and close the throttle ensures this.

[EstIntruder]

Thanks for your time, I understand it much better now.

At the moment it is running like this: Sync hoses connected and bike running and if I dissconnect rear vacuum hose so it can such extra air- it starts to work better as the idle speed goes up. Rear mixture screw it just about half turn out what puts me thinking that is it getting extra fuel because the float is not closing well?

Another thing, If I play with the front mixture screw and turn it out 3 turns the idle goes high as well, but how many turn can I turn the screw out?

How I'm thinking:
1. I want to find a sweet spot for both carbys by turning mixture screw.
2. Then I put rear carby running at 1000RPM
3. Then I sync Idle cable?

Is that the right order?

[WintrSol]

You will find that the mixture screws will work much better after the idle sync.
Removing a vacuum line increases the amount of air, and leans the mixture; that cylinder should start to stumble when that happens. Since yours speed up, I would guess you have a very rich mixture, for some reason; you can verify this by looking at the spark plugs. Since the pilot screw is so far in, you could have too much fuel in the bowl of the carburetor; you should check the fill level. Easily done with a thin clear tube connected to the drain, and turn up alongside the carb in a 'U'; when you then open the drain, the fuel will rise in the tube, and indicate how high the level is in the bowl. If you have a copy of the manual, it will say what it should be, but, for the VS800, it should be 7.0mm below the line where the bowl meets the carb body; I expect it is about the same for the VS1400. The reference for the front carb is harder to spot, but the level should be near 17mm above where the bottom of the bowl seals against the body on the inside; that number is also for the VS800, so consult the manual to confirm it for the VS1400. Here is a photo of the VS800 carb, showing the reference marks (the VS1400 carb is nearly the same):

[WintrSol]

How I'm thinking:
1. I want to find a sweet spot for both carbys by turning mixture screw.
2. Then I put rear carby running at 1000RPM
3. Then I sync Idle cable?

Is that the right order?

Start with a sync of the idle cable at 1000 to 1200 rpm, so both carbs match at idle, adjusting the idle each time it changes.
Then, aim the exhaust at a wall, or something that will reflect the sound, and adjust the pilot screws. While you should not keep it this low, the adjustment is more sensitive at about 900 rpm. Pick one carb, and turn it clockwise until you hear a stumble in the exhaust, and note the position of the screw. Then turn it counter-clockwise, until you hear a slight roughness; now turn the screw so it is about half way between those two positions. Repeat on the other carb. Adjust the rpm as needed, then try it again, until you are satisfied it is running at its peak; for starting in cooler weather, and reduced pops in the exhaust, I usually turn them both counter-clockwise about as much as the slot in the screw is wide. Then set the idle at 1000 to 1200 rpm, to make sure you get plenty of oil pressure; I prefer 1200rpm on my twins. Recheck the sync, but is probably hasn't changed.

[EstIntruder]

Is there a chance that rear intake valves need to adjusted? For example, maybe it pushes air back to the carby (mixed air ) and thats why the mixture is so rich, because it is like double amount what is going back to cilinder again?

[jonnycando]

We have hydraulic valve lifters ( actually lash adjusters) so nothing to adjust with regard to the valves.