Carb synch problem

[mralex714]

I have an 89 VR I have been trying to get running. I am have trouble getting the carbs synched. I can get them all the same, but only 4-5 inches of vacuum running smooth, but poor throttle response, or one side at 10 inches but zero on the other side,with smooth idle but usually dies with throttle movement. If I nudge the choke just a hair I can get all 4 to 10 inches with good throttle response. If I release that small amount of choke the idle slows and it stalls. Any insights on what to check.

BTW good gas, new fuel pump and filter, new plugs,air filter, carbs cleaned and new battery.

[garyS-NJ]

Look for an air leak. Verify your mix screws 2 & 1/2 turns out. Check spark on all four cylinders. Suspect carb cleaning, did you do it or a qualified mechanic?

 

Sent from my VS987 using Tapatalk

[yamagrl]

I have an 89 VR I have been trying to get running. I am have trouble getting the carbs synched. I can get them all the same, but only 4-5 inches of vacuum running smooth, but poor throttle response, or one side at 10 inches but zero on the other side,with smooth idle but usually dies with throttle movement. If I nudge the choke just a hair I can get all 4 to 10 inches with good throttle response. If I release that small amount of choke the idle slows and it stalls. Any insights on what to check.

BTW good gas, new fuel pump and filter, new plugs,air filter, carbs cleaned and new battery.

 

Are you using Carbtune or something else?

 

Want some help? We live only 20 minutes from Crestview. I'm not doing much these days... broken wrist.

[Marcarl]

Sounds to me that you need to start from scratch. Start with #2 cylinder, which is the one that your throttle cable is hooked to and make sure the butterfly closes all the way. You'll have to look down into the carb and move the slider to see this. It will only close with adjustment from the idle screw, and if the other carbs are not holding it open. Once you have it closed properly, then do the others. When that is complete, adjust the idle screw so it will run on it's own and then do a sync.

The idle screw is a thumb nut, located between the two carbs, left side of bank, under the joining bar. You can't see it unless you look from the bottom up, but you can feel it and it usually takes two fingers to turn it, one from the one hand and one from the other.

[yamagrl]

Sounds to me that you need to start from scratch. Start with #2 cylinder, which is the one that your throttle cable is hooked to and make sure the butterfly closes all the way. You'll have to look down into the carb and move the slider to see this. It will only close with adjustment from the idle screw, and if the other carbs are not holding it open. Once you have it closed properly, then do the others. When that is complete, adjust the idle screw so it will run on it's own and then do a sync.

The idle screw is a thumb nut, located between the two carbs, left side of bank, under the joining bar. You can't see it unless you look from the bottom up, but you can feel it and it usually takes two fingers to turn it, one from the one hand and one from the other.

 

 

That's kinda what I was thinking but didn't know how to explain it.

[mralex714]

Look for an air leak. Verify your mix screws 2 & 1/2 turns out. Check spark on all four cylinders. Suspect carb cleaning, did you do it or a qualified mechanic?

 

Sent from my VS987 using Tapatalk

 

I did the carb clean myself, all 4 cylinders are firing. Mix screws are at 2&1/2 but it smells rich.

[mralex714]

Are you using Carbtune or something else?

 

Want some help? We live only 20 minutes from Crestview. I'm not doing much these days... broken wrist.

 

I'm using vacuum gauges. Thanks for the offer I'll let you know.

[mralex714]

Sounds to me that you need to start from scratch. Start with #2 cylinder, which is the one that your throttle cable is hooked to and make sure the butterfly closes all the way. You'll have to look down into the carb and move the slider to see this. It will only close with adjustment from the idle screw, and if the other carbs are not holding it open. Once you have it closed properly, then do the others. When that is complete, adjust the idle screw so it will run on it's own and then do a sync.

The idle screw is a thumb nut, located between the two carbs, left side of bank, under the joining bar. You can't see it unless you look from the bottom up, but you can feel it and it usually takes two fingers to turn it, one from the one hand and one from the other.

 

I'll give this a try.

 

Thanks

[MiCarl]

If you get them synchronized at 4-5" it's not running right for some reason. It should sync at about 10".

 

I'd go after it in the following order:

 

1) Check the air cleaner.

2) Compression test. Spec is somewhere in the range of 170 but if they're above 120 you probably have another problem.

3) Check for vacuum leaks.

4) Re-do the carbs or have someone that knows how do them.\

5) 2 1/2 turns is probably too lean. You need to sync, adjust mixtures, set idle, sync, adjust mixtures, set idle several times to tune it properly.

 

This list assumes you are correct that the ignition system is functioning properly.

 

In my experience the falling down when you give throttle is either low air flow (low compression, vacuum leak) or lean (carbs).

[BlueSky]

In the Yamaha video, I think the guy recommended 2 1/2 turns out on the mixture screws as a starting point. Turning in leans and turning out richens. My stupid bike is set on 1 turn out???? It was set like that when I bought it. It ran decent like that for a while but not now. I'm pretty sure I have dirty ignition contacts. I clipped 3/4" on one spark plug wire and rescrewed it into the plug cap and that cylinder exhaust is much hotter than the other 3. I got busy with other stuff and it has been sitting for quite a while. One of these days......

 

But you have to get it running right before balancing. I would set them all the same until I got it running right and then balance and adjust the mixture screws like the video instructs.

[mralex714]

This is what I did today. I started the bike (no choke) it idled at 1k and had 4 inches vacuum. The fuel gauge was flicking between 1 and 2 bars. I didn't want to shut it off and it not restart so I put gas into the tank while it was running and as I did the RPMs increased to 2500. I turned the idle screw down to 1000 rpms and got just under 10 inches vacuum and good throttle response. So I'm guessing the screens on the petcock are dirty. To be sure I am going to let it run down again and see what happens.

[snyper316]

If its on the side stand most of the gas is on the wrong side. Mine hates one bar. And it has new petcock in it.

 

Living life one curve after the other. Vroom scooting, thru the countryside.

[Karaboo]

If your RPM's increased with the gas cap off, maybe the vent line is plugged?

[mralex714]

If its on the side stand most of the gas is on the wrong side. Mine hates one bar. And it has new petcock in it.

 

Living life one curve after the other. Vroom scooting, thru the countryside.

 

It's on the center stand.

[snyper316]

Old gas in bottom?

 

Living life one curve after the other. Vroom scooting, thru the countryside.

[mralex714]

If your RPM's increased with the gas cap off, maybe the vent line is plugged?

 

The neck of the tank is damaged from when the cap wouldn't come off, so the cap just sits atop the opening to keep things out. Changing the tank is on the list of things I need to do, but if the petcock or trash in the tank is my issue I guess I'll do it sooner.

[mralex714]

My problem seems to be an ignition issue. I start out with all 4 cylinders firing, but sometime while I'm trying to sync the carbs 2 quit firing and it's never the same 2. But so far the right front one hasn't been one in fact the temp I get is usually 250-300 degrees. Have tried 5 yes 5 different TCI's including the one from my daily driver and an igntech one all with the same results. I am lost at what to do next. Any thoughts.

 

Thanks

[snyper316]

My problem seems to be an ignition issue. I start out with all 4 cylinders firing, but sometime while I'm trying to sync the carbs 2 quit firing and it's never the same 2. But so far the right front one hasn't been one in fact the temp I get is usually 250-300 degrees. Have tried 5 yes 5 different TCI's including the one from my daily driver and an igntech one all with the same results. I am lost at what to do next. Any thoughts.

 

Thanks

 

Replace the Caps, I guess the resister in them will get loose as they warm up, I would also replace the coil wires. I had the same problem a couple months back and was chasing that damn miss for 3 or so months.

[Marcarl]

Still sounds like it could be a sync problem. Keep in mind that if the fuel mixture isn't right the cylinder will only fire haphazardly or not at all. Either condition, too rich or too lean can have this effect. If the problem seems to be transient then it could very well be a sync issue.

[Marcarl]

If you can identify a cylinder that is missing, spray some carb cleaner or even WD40 into that carb. If the cylinder recovers, then you most likely have a fuel issue, if it does nothing, then it would be an ignition problem, if it tries to kill the engine, then I would suggest everything is working alright in that one because you have flooded the cylinder.

[bongobobny]

Well, if not the TCI, then as suggested replace the plug caps, or for that matter all the wires and caps! I would also look at the coil secondary inside where the plug wire inserts for the dreaded green crud!! Also, when you replace the plug wires after looking do not forget to cut off about a 1/4" so the tang in the coil makes a good connection with the wire and make sure you have the rubber o ring on the coil wire as well so the wire will not vibrate out...

[mralex714]

Got another issue. The tach, temp and volt gauges all quit working. Where is their common failure point?

[snyper316]

Mostly likey any failures i have ran into are within the plugs. If you can pull a single wire with the plug one at a time and clean them up real good. If you can't do that get yourself a can of CRC electronics cleaner and wire brush set and clean them that way.

[camos]

Got another issue. The tach, temp and volt gauges all quit working. Where is their common failure point?

There seems to be a variety of possibly electrical issues here. Assuming the battery is in good condition, have you recently cleaned the terminals, checked the fuse holder and cleaned the several ground connections to the frame?

[mraf]

Got another issue. The tach, temp and volt gauges all quit working. Where is their common failure point?

 

There is a ground wire up in the dash area. I added another in this area just to be sure of a issue I was having one time with something {my senior moment}. Don't ask what it was, I can't remember.