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Discussion Starter #1
After cleaning the bike, I wanted to slightly lower the idle speed from about 1100 to 900-950 RPM (=printed on a Yamaha sticker (5PX4 model) on the rear fender under the seat). Turning the well-known brass knob counterclockwise did not work because the screw on the throttle house to which it is connected with the cable appeared to be stuck (dirt or corrosion). I removed the tank, sprayed/cleaned the idle-screw with WD40 and moved it in and out with a tool a couple of times so that the screw now nicely responds from a distance by movements of the cable and brass-knob to which it is connected. However, before starting the work, I forgot to take a picture of the initial position of the idle screw on the throttle house, so I just positioned that screw in the minimum position, just touching the disk to which the gas cables are connected. However, in this minimum position of the engine starts running immediately at a pretty high idle speed of about 1400 RPM, which is probably about normal to warm-up the engine (as it did before), but RPM does not come down, and even increases slightly. This can not be due to the position of the aformentioned idle screw as it is already its minimum position. I thought, well lets take her for a spin and see what will happen. Taking off is o.k. but not smooth as she did before, at higher speeds and RPM's things are o.k., lots of power. However, when I halt at a traffic light, the RPMs drops for a second and increases again to an unacceptable level of 1500-1700 RPM.

The throttle cables move freely. I even increased the slack in the cables considerably to be sure that the throttle-disk to which the cables are connected can move back to the lowest RPM position. I cleaned the upper part of the engine a bit but cannot imagine that I accidently disconnected hoses to the LCV or so. Might it be that, mechanically, the LCV got stuck, because the warrior has not been driven for 3 months? The hoses to the LCV and throttle body seem well connected. Is the position of the idling screw critical, even if positioned at the minimum? An unexpected vacuum leak in the hoses perhaps? I have not touched the PC5 connectors, but to eliminate its workings I will just disable the PC5 by putting the original connectors back to work.

I was thinking about taking the LCV apart and clean it internally (following the very nice write-up about the LCV and ways to test its workings and disabling the LCV). If this does not help I will disable it using the methods described elsewhere on the forum, e.g. rij1 and others), but better to first check with the specialists here. I would highly appreciate some advice/suggestions. Thanks.
 

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It's very easy to disable your LCV to check to see if that's your problem. Just note that when you do your idle will have to be adjusted.
 

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+1 I agree. Only remove the two hoses between the LCV and their intake nipples. specifically, remove both hoses from their intake nipple.

Cap both nipples.

While in there, check the linkage at the actual intake butterfly again.

Start bike and check idle.

If no change then test for a leaking intake gasket while the area is accessible.
 

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The way the idle wants to be high after freeing up the idle screw is a bit weird.
It almost sounds like something is binding slightly holding the throttle wheel/throttle bodies open.

With the engine warmed up I would remove the tank and a filter off a throttle body (if you have a big air kit) and back the idle screw off to where its not contacting the throttle wheel. Look down the throttle body at the valve making sure it's closed all the way.

Start the bike then flick the throttle grip a couple times (turn and release the throttle grip) to see if the idle drops.
If not grab the throttle wheel and turn it towards the closed position.
Let us know what comes out of testing this.

As you mentioned, you know about the write up about the LCV but here's the link again to have it available in your thread.
If the above test doesn't change anything you can block off the 2 hoses as mentioned aswell. Do this while you have the tank off while testing the above.
Linear Control Valve (LCV) Cleaning, bypass and info
If the idle does drop after blocking off the LCV then adjust your throttle screw back up.
If the idle does not lower then you may have a vacuum leak somewhere else and would have to look around for the cause.

NOTE, Do all the above with a hot motor.
Also, you can run the bike safely without the tank on.
 

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Discussion Starter #6
Thank you very much for this advice. I am just starting to dismantantle the tank and OEM airbox (connected to a spike cone airfilter on right side). Will share the results, but will first start working on all this and document experiences. Will start with exporing what I can learn from the on board diagnostics. Thanks againl
 

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Discussion Starter #7
I went through the diagnostics codes. Diag code 01 checks two throttle angles throttle fully closed and fully open. Throttle closed produced the value 14 (should be in 15-20 range) and full throttle produced 86 (should be 95-100). So i turned the brass-knob clockwise to increase idling RPM (engine not running!) and the number increased from 14 to 15 and to 16 (in the 15-20 range). Not clear how to increase the full throttle score in diagnostic mode as I would probably have to fiddle with the butterfly-system. Not for now. The LCV is tested by diagnostic code 54. Difficult to interpret my result. When I turn the kill switch on and off, according to instruction, the engine trouble warning light switches on after 1 second and stays on for 12 seconds. The manual reads (pages 6-16)....."after 1 second has elapsed from the time the engine stop switch has been turned from off to on, it actuates the LCV four times every 5 seconds and illuminates the engine trouble warning light (fully closed 2 seconds, fully open 2 seconds). According to the manual I should 'check the LCV operating sound, 3 times with the engine stop switch on. I don;t know how to interpret my results, the 12 seconds. Could it be the result of 3 times 2*2 seconds for open and close of the lcv?
 

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Discussion Starter #9 (Edited)
I did not disconnect the (two of the three) hoses from the LCV. I thought I need to know first what the diagnostic result is. If its o.k. the LCD should be functioning properly, or...? To get to the LCV and even where the two hoses are connected to the trottle bodies is, so it seems, quite some work, such as removing the OEM air box. Too late in the evening now to start the engine....First want to see what the effect of a now correct position of the idling screw (as it generates code 16, which is now in the correct range). As I blew one or two fuses when replacing the front turning lights, I wonder if the LCV is linked to some fuse?
 

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The TPS can be clocked on its mounts, set it for the correct full throttle reading. The TPS idle reading will vary dependent on the base idle speed this reading is insignificant.

As previously advised: Remove the LCV hoses from the throttle bodies they are the larger hoses & put a cap on each throttle body port. Start the engine, when cold you may need to add a bit of throttle to keep it running. Adjust the base idle for 850 to 900 hot engine.

If the throttle plate balance adjustment has been changed, this is the screw adjustment located between the throttle bodies. Engine off use 2 pieces of wire placed in the throttle bodies with the throttle plates closed on the wires. Pull on the wires they should have the same amount of resistance if not adjust the balance screw to make them the same.

You have an idle air adjustment in the side of each throttle body suggest a sync tool for adjustment.

If the LCV has been blocked & the idle is high regardless of the base idle adjustment adjust the throttle cable tension @ the twist grip it may be to tight.

If you want / need a replacement LCV I have one for sale, PM for info.
Good luck
 

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+1 totally agree with all. The next step is the easy work of capping the lcv nipples and setting warm idle to spec with the lcv air induction source out-of-the-circuit.

Based on results of that, we can help you to understand what is next. I gave you the three next things to do while in there anyway. Church gave you more breadth so your vision widens.

Work the plan and you will gain wider vision and understanding that because this is an injected and sensor-governed bike you cannot always trust a symptom is rooted where it might be if it was an old-tech carburated bike.

Find the actual root cause then you can make decisions between any options that come into view. What you learn here will be in your toolbox into the future.
 

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Discussion Starter #12 (Edited)
Guess I have to do some home work...I'll be back. It bothers me that things were okay before I started replacing the fork seals (had to take the fork-system and handle bar off) and front turn lights, replaced two fuses. These have nothing to do with the problem at hand. Let's try to cap the 2 hoses where they are connected to the throttle-body. First time for me to dive into this matter.
 

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The first time I took the stock airbox off my bike I had a **** of a time getting it back on and when I did the throttle cables were binding a little bit resulting in the throttle not closing completely without assistance. The second time I took the stock airbox off I never put it back on. That thing is a major pain.

Sent from my SAMSUNG-SM-G930A using Tapatalk
 

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Discussion Starter #14
Thank you again. In addition to the above, I also find the advice you gave on 31 may 2015 (LCV????? post) very instructive. I am not living in the desert so there are various shops, but locating the 8mm size caps (5/16) was unsuccesful. I will fabricate something using gasoline tube, two bolds and tie-raps. Will try to do the LCV test as suggested by Churchkey in that message.
 

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Discussion Starter #15 (Edited)
@Sandytows. Thanks for the warning! I am studying how-to dismantle parts in the right sequence. Did not find instructions about how-to precisely, but RS Warrior Bryan's youtube on DIY Vbak does help (i have the same chrome cone spike air intake). Interesting experience anyway. Trick is to document what I am doing. Will first do the capping as suggested. If it works, then I will get the LCV out (if churchkey's test procedure indicates it might be stuck) and clean it internally and test it again. I prefer a working LCV, although, apparently, technically its kind of redundant according to the specialists on the forum.
 

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@Sandytows. Thanks for the warning! I am studying how-to dismantle parts in the right sequence. Did not find instructions about how-to. Interesting experience anyway. Will first do the capping as suggested. If it works, then I will get the LCV out (if churchkey's test procedure indicates it might be stuck) and clean it internally and test it again. I prefer a working LCV, although, apparently, technically its kind of redundant according to the specialists on the forum.
I took mine out and never looked back it's really not an issue even in the real cold

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Did you find the free e-copy of the service manual around here yet?

If not, then click link below my sigpic, scroll down a bit to the group of links and click technical bits. Once there, notice the tabs. Select manuals. Save that url to your home screen.

I have the manual and supplements and other bits as pdf files on my phone for the road and on my desktop pc for big screen at home.

A few things are not perfect but in general its a great resource for troubleshooting, for disassembly reassembly, and for understanding how each system works.
 

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Discussion Starter #18
Arizonawarrior, when I bought the 2003 Warrior of the first owner in 2015 I bought the hardcopy on the internet (Road Star Warrior 2003-2005, service manual, LIT-11616-RS-WO. Then I explored the RSW forum for additional technical docs (pdfs) and downloaded them.

After reading a lot in the manual, and many more posts, I think I will first try to cap the two LCV tubes on the side of the LCV. I know the hoses may even be the cause of the problem and not the LCV, but its better to take that risk first because it probably can be done without all work involved with getting rid of the 'silencer air filter case' (e.g. p. 3-9, 3-10) and cap the throttle body inlets of these two LCV hoses. That I would do if the aforementioned short-cut does not lead to low idle speed, just to rule out the possibity that one or both hoses have air-leaks. That would be a more permanent solution. Correct me if I'am wrong.

I may have overlooked it, but haven't come across instruction=post of how to get to the LCV. I recall also a question "where, precisely, is this LCV located". Well, its stuck in between the two ignition coils (to which the spark plug cables are connected) (p. 2-40, figure A). Removal is very simple. Note that spark plug cables have stickers for left and right side on it (left=while seated on the warrior). The result so far is in the pictures below. I am going to try to release the two hoses on the outside of the LCV and cap them, leaving the center hose installed, and LCV exits to the aforemented two hoses uncapped. Thought I better document it. If this does not work......

250171

250172

250173
 

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Discussion Starter #19
Well, it worked. I capped the two hoses at the LCV side, quickly reinstalled the tank and started the engine. Intially, the engine halted quite quickly but in the second attempt I kept RPMs a bit higher with the wrist. After warm up of about 30 secs, the engine kept running, but at a very low RPM. I increased with the idle screw and settled at 1000 RPM, as she did before. No increase in RPMs anymore, but the engine is not yet idling the way I am used to. If I give full throttle (i am in the backyard, with many neighbours around) **** brakes loose, she reacts very quickly to the throttle, as she used to. I've made a compressed video (4mb), and will see whether i can upload the video. You can listen to the result and see the two capped hoses on the video. Don't want to jump to conclusions, but this suggest that I should at least try to dismount and clean the LCV and try whether this helps after reinstalling the LCV and the three hoses. The LCV is mounted with 2 bolds only to the frame. If the bolds can be released, the third hose can be removed too from the Lcv, and the LCV can be removed from the frame without removing the OEM air filter box and connections. But that;s for tomorrow.
 

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This may seem petty but adjust warm idle to 850~950rpm where it does not drop below 850 even if it goes momentarily above 950 (its a vtwin after all). It may not seem to matter but if you get into decisions based on sensor readings then it could.

In a sentence please describe exactly how it changed. From 'x' it is now 'x'.

I ask these things because you posted this: ". I capped the two hoses at the LCV side."

You need to disconnect the two hoses from the intakes and CAP THE INTAKE NIPPLES on top the motor. Not the hoses. A cut-up-bit of plastic sandwich bag and rubber band is fine. Don't let it melt.

You do NOT need to reinstall the top tank for these several suggested tasks. It will run off the bottom tank exactly the same.

Sorry but this is a tricky issue and want to help not confuse.
 
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