1st Gen V-Max Idle rough when hot

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Gianni

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hello everyone, I have a vmax full power 2001. the problem is the following: practically when the bike heats up the idle becomes rough, I mean, the bike runs smoothly at 1000 rpm, then when the temperature increases, it starts working the fan, idle becomes irregular and the bike turns off. I have checked the electrical system and it works well, there is no leakage of electricity up to the cylinders and the battery is charged regularly. I also did the carburetor alignment. sorry for my english and thanks to whoever will answer me
 

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Screwloose

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hello everyone, I have a vmax full power 2001. the problem is the following: practically when the bike heats up the idle becomes rough, I mean, the bike runs smoothly at 1000 rpm, then when the temperature increases, it starts working the fan, idle becomes irregular and the bike turns off. I have checked the electrical system and it works well, there is no leakage of electricity up to the cylinders and the battery is charged regularly. I also did the carburetor alignment. sorry for my english and thanks to whoever will answer me
I had similar problems on my 1999 and found a few things. The electrics checked out ok, but the plug caps were the originals, so I changed them and the leads, but would go for COPS the next time if doing the job again. Then I found one of the rubber boots below a carb had split behind the clamp, where the rubber softens with more heat, then draws air. You can spray oil on them when hot to see if that is the case. Also check your fuel heights in the carbs when the engine is at running temp.
Hopefully that helps.
 

caseyjones955

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I went to COPS on my Venture and Vmax. It's a very small investment if your handy with a soldering iron. I got a slightly cleaner idle/off idle and it was easier to tune. Anything that is cheap, makes the bike lighter, more reliable and more ridable, I'm in.

I dont mean to suggest that I'm sure your issue would be resolved by converting to COPS, I didn't get a great feel for what the cause may be. There is a good write-up here somewhere about cleaning and testing the coils as well as the spark plug caps.

Are you smelling raw fuel when this is happening?
Is ethanol in the fuel an issue where you are?
 

Smithjs35

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I have the same issue with my 2000 Carbon, found out there was a significant drop in voltage when the fan started. Changed regulator and voltage came up but I still have the issue. Now have the idle up to 1250 to keep the stall at bay. Thanks to caseyjones955 I will check the leads and caps as they are originals. Also, would like to give a set of COPS a try too. The one thing that keeps hanging around in my head is it all started shortly after installing LED head and taillights. Will keep you posted.
 

Gianni

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I think my recharge system have problem , 12.3 at 1000 rpm, 12,6 at 2000 Rpm, shoud be what?
 

VMAXXIMUM

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More than that. That is your problem. Fan kicking on and your charging system can’t keep up. Search the forum for the crimp fix, and have your battery load tested. You should be better than 13.5 off idle. You should check your grounds as well.
 

Gianni

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More than that. That is your problem. Fan kicking on and your charging system can’t keep up. Search the forum for the crimp fix, and have your battery load tested. You should be better than 13.5 off idle. You should check your grounds as well.
Crimp fix i did, should be the r/r?
 

Gianni

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So i got the the new RR.
Bike cold and off 12,6v
Bike cold and engine on , light on ad
1000rpm 13,1v
Bike Whit trottle 14.3v
Bike when fun kick in 12.3v - 12.7v
The problem still
Stator test : 0.5,0.5,0.5 and no short and Whit trottle i got on every 3 legs 70v in AV
Sad :(
 

Martin Kestle

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Hey Gianni, I'm no expert but had the exact same symptoms on my 2003 and it drove me crazy for a year. What cured it for me was setting the plug gaps to spec (improved the condition but not fully fixed) and recently doing the very painful valve lash adjustment. Quite a few of the valves were out of spec but since adjusting them the bike idles fine when hot. Good luck!
 

JMax92

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Hi Gianni,
If you have run out of ideas, I would try stripping the carburetors down and thoroughly cleaning them out, replacing any bad parts. I would especially look at your adjustable pilot screws and small diaphragm set (on my ‘92 this is #5). I did them on my 1992 recently and they were filthy, as well as all 4 pilot screws were totally wrecked by whoever installed them. After that my bike has been running super smooth.
Good luck
 

Denci

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So i got the the new RR.
Bike cold and off 12,6vt
Bike cold and engine on , light on ad
1000rpm 13,1v
Bike Whit trottle 14.3v
Bike when fun kick in 12.3v - 12.7v
The problem still
Stator test : 0.5,0.5,0.5 and no short and Whit trottle i got on every 3 legs 70v in AV
Sad :(
Something that I havent seen mentioned in this thread was to check the fan itself, just because it is coming on doesn't mean it is performing properly. I would perform an amp draw test. Sounds to me it is pulling too many! If you have access to one to swap and test great but if not you will need to get the specs for the fan and test it.
 

sparky4123

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I had a similar problem on a different model where the coil would fail when it got hot. Let it cool of and the bike would run properly again. As mentioned previously the carbs will likely need a going over as well. I have had more than one bike run well cold then not good when hot. Would be in the idle circuit.
 

Fire-medic

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when the temperature increases, it starts working the fan, idle becomes irregular and the bike turns off.
If the bike engine stops once the bike is hot, likely your pick-up coil is bad. The symptom you described is common for a bad ignition pick-up coil. The bike will-not start hot. Once it cools, it will re-start.

Take a resistance reading on it when the bike's engine cuts-out/stops. You will probably discover an open circuit (no continuity) for the pick-up coil. Below is the value it should have for ohms/resistance, whether the engine is cold or hot. The pick-up coil should read between 94-127 ohms.

VMax electrical resistance data enlarged.pngVMax electrical resistance data.png
 

Gianni

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If the bike engine stops once the bike is hot, likely your pick-up coil is bad. The symptom you described is common for a bad ignition pick-up coil. The bike will-not start hot. Once it cools, it will re-start.

Take a resistance reading on it when the bike's engine cuts-out/stops. You will probably discover an open circuit (no continuity) for the pick-up coil. Below is the value it should have for ohms/resistance, whether the engine is cold or hot. The pick-up coil should read between 94-127 ohms.

View attachment 84704View attachment 84705
My bike start Always. For me Is mistery
 
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