CARBURETOR PROBLE, WITH 45 Hg vacuum? HELP!!

[hilliss]

1999 RSV - 32k miles.... already ran my SeaFoam through for 2008.

Was synching the carbs, and the front left (if sitting on the bike) is going nuts. Havent fouled a plug... but, all the other carbs are balanced to each other at 25 Hg, and front left swings to 45-50 and will not come back down.

 

Any thoughts before I pull the carbs off the bike for a thorough cleaning only to potentially discover it might be something simple I am overlooking?

 

Thanks all for any input.

[gibvel]

What kind of sync tool are you using? Does is seem to be running alright? Wonder if your guage is lying to you, did you switch hoses around?

[hilliss]

Good suggestion. I have a Motion Pro 4 Channel. I had swapped lines on it just in case if was an issue with my dials (a couple times actually)... but nope - the guages are in sync and correct.

 

I had actually quoted the cm of Hg, not the inches. I am running 10 inch on 3 cylinders, and 19 inch on the front left cylinder.... I am baffled.

[Johnh]

I ran into the same problem a couple years ago. If you synched it using the factory shop manual, it shows the wrong screws for the carbs you are trying to synch. It sounds like you have the left front throttle plate completely closed. There is a post on here someplace on which screws to adjust in the proper sequence.

[Marcarl]

The front left is your #2 carb. The only way to adjust it is with the idle adjusting screw. So you adjust # 2 first, then the one behind it which is #1, then you go to the other side and forget about #'s 2&1 and set # 3 to #4, now you adjust #4 to #2 and you should be done. Hope this helps.

[Marcarl]

Posted before I re read it. #2 is adjusted for idle first, then you have your base vaccum number. Also keep your RPMs around the 900 mark by adjusting the idle screw \ thumbwheel.

[gibvel]

Yeah, wondered if you had the dial guages and wondered if one of them could be giving the wrong numbers. I'm assuming this isn't the first time you've synced or is it?

 

Johnh is correct. The screw to sync #2 to #1 has to be reached from the right hand side of the bike (Left and right are sitting on the bike as if riding) THROUGH the carbs with a very long phillips screw driver. For syncing #3 to #4 the screw is a phillips on the right hand side of the carbs. To sync #1 & #2 to #3 & #4 the screw is a flat head screw on the left hand side of the carbs just above the choke knob, kind of hidden a bit.

 

As Carl said, the way to tell adjust the #2 cylinder is with the throttle (idle screw). Since these don't have a tach it may be that your throttle is set a little high.

 

Here's a how to by Don with pictures of screw locations.

 

http://www.venturerider.org/forum/showthread.php?t=258

 

Sorry if you know how to do this already and this is all redundant to you. Just wanted to cover all the bases and, if these things weren't the problem, maybe someone else can jump in and give there about something else.

[hilliss]

Thanks - Hopefully this will do it.

 

I kept trying to understand how the vacuum would be so high in cylinder two, while perfectly on point with 1,3 and 4. But a closed throttle plate would certainly make sense.

 

To adjust the engine idle then, the screw on the left side of the bike (when sitting on it) first?

[hilliss]

Alright - still need help.

 

Went back out and walked through everything again. Idle is right on the money. Went to sync #1 and #2 (as it is #2 that has high vacuum)..... used the correct sync screws from the right side of the bike as I had before. I cannot get #2 to come back down in vacuum. But 1, 3, and 4 are all sync'd.

 

If I have a throttle plate that is closed..... how do I adjust that on just 1 carb?

 

Thanks!

[MiCarl]

Ok, I've not synced a 2nd gen., but the principal is the same on all machines.

 

You have 4 carburetors, and 3 sync screws to adjust the relative butterfly opening between them.

 

One of the carbs has the idle stop screw on it. In principal you match the other 3 to this one. From what was posted earlier it seems that the idle stop screw is on #2, so you can't reduce it's vacuum (or more properly, increase it's pressure).

 

What you need to do is reduce the pressure (increase vacuum) in the other 3 until they match #2. You adjust the sync screws to close those butterflies down. As you do this your idle speed will come down, you'll compensate by turning in the idle stop screw which will increase the pressure (reduce vacuum) in number 2.

 

Eventually you'll get the pressure up in #2, and down in the other three until they all balance. Then you're synchronized.

[Neil86]

Maybe this will help....engine off....observe the linkage for #1 and #2 carbs....roll open the throttle to make sure both carbs (#1 & #2) linkages move. If everything is okay there.....then it sounds like the idle stop screw is backed out so the other 3 carbs are synched open further to keep your idle speed up. You may have to increase the idle speed stop screw, which opens #2 throttle, drops its vacuum then synchronize the others to it, then lower the idle speed now all 4 are in synch.

You didn't mention having the 4 carbs bank apart...thats the only other thing I can imagine might foul things up if the linkages got misaligned when reassembling.

[Johnh]

if you synch with the idle too slow and follow the factory manual, the screw they tell you to turn to synch # 1 and 2 is actually the one for 3 to 2 and the screw they show for 3 to 2 is acually the one for 1 to 2. This will cause exactly the condition you are describing.

I literally pulled my hair out for 2 days until some kind soul on this site clued me in on Yamahas misprint.

[hilliss]

Sometimes.... simplicity is the answer!

 

Thank you Johnh, McCarl, Gibvel and Neil86... it was that idle screw. It had backed out and I was synching at too low an RPM....

 

As I turned the idle screw (which directly effects carb #2), the idle raced, and then I synched #1 and #2 which brought the idle right back down, and the vacuum balanced right up.

 

Then went back to 3 and 4 (still fine) so synched 3 and 4 to 1 and 2.... idle was still a little high for my liking, so with the carb tuner still on, I played another couple seconds with it and then off I went!!

 

Thank you again.... nothing like knowing it isnt supposed to be this hard, but your mind not allowing you to solve it because of frustration! And I would be pulling the hair out.... but none left to pull!!

 

If any of you are ever through Kentucky, shoot me a note... I owe you each lunch!