Linear Control Valve (LCV) Cleaning, bypass and info - Road Star Warrior Forum : Yamaha Star Warrior Forums

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Old 10-29-2019, 03:04 AM   #1 (permalink)
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Default Linear Control Valve (LCV) Cleaning, bypass and info

The linear control valve (LCV) is sort of like a choke but for fuel injected engines.
The linear control valve supplies air to the throttle bodies when starting or during engine warm up and causes higher idle Rpm's.
The intake air volume determines the basic injection duration. As the intake air increases through the linear control valve, the intake air volume corrects the basic injection duration.
The correction volume changes according to the position of the valve at starting and when the valve position changes to accommodate the engine temperature and engine oil temperature as the intake air volume increases.
When the engine oil temperature reaches 80 įC (176 įF) or higher, the linear control valve fully
closes to stop the air volume from increasing and control returns to basic injection control.

Now, this part can cause some issues if the pintle seat (see pic) or the tapered pintle (see pic) develops build up to prevent the valve to fully close and let surfaces to seal.
It can also possibly develop a vac leak between the O-ring on the valve motor and the passage housing(see pic).
The motor can also fail all together and not function or properly function.

Either way these can cause a vac leak that can cause some issues you will chase and chase and may not find.

A way to quickly eliminate the LCV being the issue to vac leak symptoms is to remove the 2 smaller hoses off the LCV and plug them good making sure no air gets past. Make sure you see no cracks in the 2 hoses going to your throttle bodies before running the motor. If your symptoms go away or reduce you have a few options.
If you do not get a diag code-

1. Leave the LCV blocked off as testing by plugging the 2 hoses from the LCV.
2. Pull the 2 hoses off the throttle bodies and cap the nipples(with time the caps can crack and you'll develop a vac leak.

NOTE FOR THE 2 OPTIONS ABOVE.
You will now have to give some throttle while starting especially in colder weather and you'll have to hold the throttle to warm the engine up to keep it running. Keep in mind that if you go and try to sell your bike this new starting prosses may sway potential buyers away as it will look like the bike has issues.


3. You can set the hoses back on the LCV and spray throttle body cleaner through the inlet hose while first start/starting for a few seconds. The valve closes so you will have to repeat over and over unless you do have a bad vac leak through the valve then keep spraying a few seconds stop the repeat. The engine may be hard to run at first as that's what the cleaner will do so give it some throttle. This may/may not help.
4. Remove the LCV and clean by hand with throttle body cleaner. The O-ring may need a bit of silicon to help seal a vac leak so apply a thin coat and let dry while assembled.

((If anyone has anything to add or any input feel free to mention it and I'll adjust the posting))
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Old 10-29-2019, 03:05 AM   #2 (permalink)
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Old 10-29-2019, 08:48 AM   #3 (permalink)
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Great write-up! The only thing I'd suggest is maybe pointing out where exactly it is on the bike.



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Old 10-29-2019, 09:19 AM   #4 (permalink)
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Quote:
Originally Posted by Sandytows View Post
The only thing I'd suggest is maybe pointing out where exactly it is on the bike.
He has already done it. In the last image, everything is schematically visible.
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Old 10-29-2019, 10:26 AM   #5 (permalink)
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Good write up on the LCV cages call it IAC (Idle Air Control)

I absolutely hated that friggin thing from the get go the higher rpm to base idle rpm hot engine restarts were really annoying. Shelved it in 2002 its still on the shelf.

Use a fat "O" ring of the correct inside diameter that fits snugly between the throttle grip flange & switch box. Loop a small zip tie loosely through the "O" ring that's your "handle". Insert for cold start up you can adjust the throttle as desired when inserted it will stay where you put it..
Beside cold start & warm up you now have an easily adjustable cruise control without levers / clamps etc. Grab the zip tie to pop it out & leave it on the grip. If you need to buy this stuff the cost may be about .25 can't say for sure I had the stuff in my shop.
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Last edited by Churchkey; 10-29-2019 at 10:32 AM.
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Old 10-29-2019, 12:00 PM   #6 (permalink)
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A month ago, went with friends, we closed the motorcycle season. We thought we will so. It was cold, about 3-5 degrees Celsius. My motorcycle behaved strangely when it speeded up to the about 120 km/h and twitched. It looked like I was briefly and abruptly twisting the throttle grip to maximum. Upon arrival at the intermediate point, I checked the contacts of the ignition coils. I thought it was because of them. At the same time, I recorded the readings in the diagnostic mode and the parameter d1: 10 showed 165 degrees Fahrenheit. This means that the valve was hesitated close to complete closure and its operation was felt on the go. Another version to that trip.

PS
I rode on the previous Warrior without this LCV for a couple of months. You can live without him. Only in the cold do you need to hold the gas handle ajar at the start.
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Old 10-29-2019, 01:22 PM   #7 (permalink)
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I took mine off my Raider, it was acting up and I’d get the dreaded hi idle low idle syndrome. I just use my go cruise to set the idle when it’s cold.
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Last edited by LeaderDuece; 10-29-2019 at 11:14 PM.
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Old 10-29-2019, 07:17 PM   #8 (permalink)
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Quote:
Originally Posted by Churchkey View Post
Good write up on the LCV cages call it IAC (Idle Air Control)

I absolutely hated that friggin thing from the get go the higher rpm to base idle rpm hot engine restarts were really annoying. Shelved it in 2002 its still on the shelf.

Use a fat "O" ring of the correct inside diameter that fits snugly between the throttle grip flange & switch box. Loop a small zip tie loosely through the "O" ring that's your "handle". Insert for cold start up you can adjust the throttle as desired when inserted it will stay where you put it..
Beside cold start & warm up you now have an easily adjustable cruise control without levers / clamps etc. Grab the zip tie to pop it out & leave it on the grip. If you need to buy this stuff the cost may be about .25 can't say for sure I had the stuff in my shop.
I hate that high idle also haha. Probably half of us all do ha.
But I remember that little trick as I did it for a while. Pretty cool.


Quote:
Originally Posted by freeezzzz View Post
A month ago, went with friends, we closed the motorcycle season. We thought we will so. It was cold, about 3-5 degrees Celsius. My motorcycle behaved strangely when it speeded up to the about 120 km/h and twitched. It looked like I was briefly and abruptly twisting the throttle grip to maximum. Upon arrival at the intermediate point, I checked the contacts of the ignition coils. I thought it was because of them. At the same time, I recorded the readings in the diagnostic mode and the parameter d1: 10 showed 165 degrees Fahrenheit. This means that the valve was hesitated close to complete closure and its operation was felt on the go. Another version to that trip.

PS
I rode on the previous Warrior without this LCV for a couple of months. You can live without him. Only in the cold do you need to hold the gas handle ajar at the start.
Sound like it didn't know what to do with that low temperature haha. Atleast you knew what to check out before pulling things apart trying to fine the issue haha.


Quote:
Originally Posted by LeaderDuece View Post
I took mine of my Raider, it was acting up and Iíd get the dreaded hi idle low idle syndrome. I just use my go cruise to set the idle when itís cold.
Wow, you actually removed it. I wanted to but didn't wanna dig up into the frame neck. I ended up using the seafoam spray to clean mine out and it smooth down the idle fluctuation pretty good.
How's your idle now and at Start up?
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Old 10-29-2019, 11:16 PM   #9 (permalink)
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Originally Posted by rij1 View Post
I hate that high idle also haha. Probably half of us all do ha.
But I remember that little trick as I did it for a while. Pretty cool.




Sound like it didn't know what to do with that low temperature haha. Atleast you knew what to check out before pulling things apart trying to fine the issue haha.




Wow, you actually removed it. I wanted to but didn't wanna dig up into the frame neck. I ended up using the seafoam spray to clean mine out and it smooth down the idle fluctuation pretty good.
How's your idle now and at Start up?
Itís low on a cold day. It wonít stay running unless I give it some throttle. But thatís only for about 30 seconds or less. Iím not sure the D&D style forced intake stacks would look good with it still under the neck. I didnít know about cleaning it, and I was just tired of it alternating hi and low idles.
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Old 10-30-2019, 12:00 AM   #10 (permalink)
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Mine's long gone also. Just takes a little crack of the throttle to start and then 10 to 60 Seconds holding minimal throttle while it warms up with 15 being on a warm day and 60 being on a very cold day.
Here it is on a day of about 50. I don't normally have to rev it so hard to get it to stay running, I made that video mostly for the exhaust sound but it captures the behavior without the lcv also

https://youtu.be/6DrHfzWlJPQ

With the coils relocated under the tank and the LCV gone it really opens up the view of the front rocker cover.

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