High RPM ldle when warm

[Robi]

Hi Guys

I have a 2005 Yamaha Rage RS90. Starts easy and idols fine and when I turn off the choke it idols at around 1000rpm. If I slightly touch the throttle and let got engine rpm’s are high at 3000rpm and won’t come down unless I pull the choke and turn off. Then the same thing will happen again. Any hints to what this would be caused from? I’ve checked the throttle cable that seems fine, and have ran some sea foam thru and no difference. I woii you pd attach a video but it never works.

Thanks for your help in advance.

 

[steiner]

When is the last time you cleaned the carbs. Sounds like a lean condition at hot idle

 

[maim]

no vac leaks?

 

[Robi]

I just bought it this season so not sure last time carbs were cleaned. How would I check for vac leaks?

 

[maim]

with it all together, spray all the carbs connections with flamable brake cleaner or quick start while it is idling. if idle goes up, usually indicates a leak.

 

[RobX-1]

If you just purchased it, I would definitely go through the carbs. Unless it has high mileage, a thorough cleaning (ie. not just adding seafoam but removing jets, needle valves which have tiny screens under them, spraying/soaking parts, etc) and a carb sync could be all that is needed. Now, after 11,000 miles on my 03 RX-1 and performing this process yearly, I went and rebuilt the carbs and ordered new jets, needle valves, and o-rings as I was never able to get the carbs to sync like I had.

 

[74Nitro]

Make sure pilots are clean and then do a carb sync.

 

[RobX-1]

X2 as I probably could have gotten by with just replacing those tiny pilot jets, but with the mileage and knowing I was keeping it, I opted to replace all. Those pilot jets are notorious for getting clogged and being the root cause of many non-EFI owners' carb issues.

 

[74Nitro]

X2 as I probably could have gotten by with just replacing those tiny pilot jets, but with the mileage and knowing I was keeping it, I opted to replace all. Those pilot jets are notorious for getting clogged and being the root cause of many non-EFI owners' carb issues.

Absolutely, and all too often someone turns one of those screws in between the carbs as well. If the sync on these carbs gets out of whack, idle is all over the place.
Also check the carb boots, I had a badly corroded vector here last week, and the aluminum separated from the rubber.

 

[Robi]

Thanks for the great reply’s guys!

 

[Robi]

Does anyone know if there is a post in here on how to sync the carbs?

Thanks

 

[steiner]

Using the Search Tab. Typed in Sync Carbs and then search in This Forum

Search results for query: sync carbs

ty4stroke.com

 

[RobX-1]

Here's my notes taken from Freddie Klies (RIP) of ECP. I still reference this when sync'ing my RX-1. The only thing I do differently since I have a 4 tube manometer, is I bought two plastic T's for the two hoses going off the #1 and #4 intake manifold rather than connect them together. By using the T's to connect the two hoses of the manometers to each of those black hoses and then connect to the intake manifolds, you still supply vacuum to the fuel pumps and won't run out of fuel when syncing the carbs:

Warm the engine up good before connecting the manometer. Make sure the engine idle speed once warmed up is between 1200 and 1450 RPM's. If it is not raise or lower the idle to this specification. Shut engine off when it is good and warm, then disconnect the 2 black hoses going to the #1 and #4 intake manifold. Connect these 2 hoses together as this is what operates your fuel pump. A small piece of tubing of some kind works nicely for this. This will prevent the pumps from going airbound thereby giving you a little more time to run the engine off of what is in the float bowls only. The other alternative would be to hang an auxiliary fuel tank up and use this as your fuel source by connecting these 2 hoses via a "T" to the auxiliary fuel source. If you are reasonably efficient, you can usually get the carbs sync'd before running the float bowls dry. Okay, so now the #1 and the #4 hoses are connected from the manometer to the intake manifolds spigots located at the top of each manifold directly in front of the valve cover. Next, remove the black rubber plugs on the #2 and the #3 intake manifolds and connect the remaining 2 lines from the manometer to these. Note that the manometer (If you bought it from me anyways) is numbered. You should put the cylinders corresponding to the number for each number on the manometer. Start the engine and let it idle. if all 4 mercury tubes are even within a small amount or very close there is no need to adjust anything. Start by adjusting the # 2 carb to the #3 carb. The adjusting screws are located between each carburetor and are a Philips head screwdriver configuration. There are 3 Philips head screws for doing this. One is between carb 1 and 2 one is between carb 2 and 3 and another between carb 3 and 4. The reason there is only 3 on a 4 cylinder engine is due to the fact that when you make an adjustment, you are adjusting one carb up and one carb down. Perform the same procedure for the #3 and the #4 carbs. These Philips head screws can be seen by looking straight down between each carburetor. If a cylinder is showing high on the manometer, adjust the screw counterclockwise. Note that you will not only be lowering that carb but also raising the one next to it so slight movements are only necessary. If it is low try moving the adjusting screw clockwise. Give then engine a few "raps" of the throttle between each adjustment to allow the engine to "stabilize" to the new setting. High revs are not required so be very careful not to allow the clutch to engage. A quick tip too...when you press down on the screwdriver to adjust each carb, you will actually change the sync due to the fact that you are pressing on the adjustor. Don't let this fool you. Make a small adjustment and remove the screwdriver pressure from the adjusting screw and give it a moment to respond to the new setting. Reconnect all your hoses to their appropriate locations and reinstall the plugs for the to #3 and #4 manifolds. You are done.

All you are doing is matching the other three carbs to the base carb. Base carb is # 3 in an RX-1. You do not need to worry about setting all the carbs to a specific setting. It is very helpful to have a 4 tube manometer because all the carbs interact and the mercury is bouncing around to much to get a specific reading. You just want all 4 tubes equal. The throttle cable is connected to Carb #3. The bolt to adjust #2 is right next to the throttle cable. That makes #1 on the PTO side and #4 on the mag side.

 

[Robi]

Hi took off the float bowl tonight and cleaned the main jet and pilot jet. Was wondering what this brass circle is beside the main jet? I seen a video on YouTube from an RX1 that had 3 jets but is it possible this carb only has 2? Thanks

 

[radianguy]

First when I bought my Vector new in 08 I had the same issue, it took a bit of time adjusting the ideal screw and testing. After a bit of adjustment it idled perfect and did not creep up after I stopped riding.