Cutting out at 50 and heavier throttle - Star Motorcycle Forums: Star Raider, V-Max, V-Star, Road-Star Forum
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post #1 of 21 (permalink) Old 07-24-2018, 10:27 AM Thread Starter
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Cutting out at 50 and heavier throttle

Sometime last summer, my 2002 V Star 650 started cutting out at anything but light acceleration as well as anything over 50 mph.
Just pulled the plugs and they are carbon fouled.
Never winterized it last winter. Started it up every month. Ran some seafood through it.
Planning on pulling the sides of the carbs off and cleanings jets. Also will replace fuel filter.
Am I looking in the right direction?
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post #2 of 21 (permalink) Old 07-24-2018, 11:09 AM
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usually when the carbs are gunked up it runs lean and burns the plugs.

If the plugs are black, your choke could be sticking on, or your float bowls might be hanging open and flooding the engine. That would usually pour gas out the overflow tube on the right side, between the cylinders, right on top of the engine case.

A really dirty air filter will make the engine run rich, could also be oil blow by from worn rings. If your air filter is not white like paper then replace it.

How many miles are on the engine?

Does it use any oil between 4000 mile oil changes?

the only other maintenance thing I can think of is, when was the last time the valves were checked/adjusted?
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post #3 of 21 (permalink) Old 07-24-2018, 12:56 PM Thread Starter
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Air filter is clean. Doesn't use any oil. 26,000 km on engine (16,000 miles). I'll check for gas overflow (I haven't smelled any). How would I dislodge a float? Gonna pull the tank and at least change the fuel filter. I'll be able to have a better look with the tank off, too.

I don't believe the valves were ever adjusted. The only Yamaha bike shop here in town don't even know how to adjust the valves! How do you like that?
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post #4 of 21 (permalink) Old 07-24-2018, 01:03 PM
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Quote:
Originally Posted by csonni View Post
Sometime last summer, my 2002 V Star 650 started cutting out at anything but light acceleration as well as anything over 50 mph.
Just pulled the plugs and they are carbon fouled.
Never winterized it last winter. Started it up every month. Ran some SEAFOOD through it.
Planning on pulling the sides of the carbs off and cleanings jets. Also will replace fuel filter.
Am I looking in the right direction?
WELL, I’d start looking first at what you’re FEEDING your bike. Never tried “SEAFOOD” before. Are you using shellfish or certain varieties of crustaceans??
🤣🤣
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post #5 of 21 (permalink) Old 07-24-2018, 01:09 PM Thread Starter
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Originally Posted by ChiefGunner View Post
WELL, Iíd start looking first at what youíre FEEDING your bike. Never tried ďSEAFOODĒ before. Are you using shellfish or certain varieties of crustaceans??
🤣🤣
Haha!!! I never saw that. Crazy spell correct. That was intended to be Seafoam.
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post #6 of 21 (permalink) Old 07-24-2018, 01:15 PM
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If you know the valves have never been checked or adjusted that is something to look into. Its all simple wrench and screwdriver work but you have to pull the carbs off the intake manifold (tubes) to get the cylinder head plastic covers off, to get the covers off the tappets to check them. Its about a 2 to 3 hour job if you have never done it before.

Checking them is easy - you turn the engine over with a socket wrench on the crankshaft (little quarter size cover on the left side) till each piston is at top dead center, then you push feeler gauges between the tappet and the end of the valve, and see which one fits. If the valves are too tight or too loose, you back off the locking nut and adjust the screw till its correct, then carefully tighten the locking nut down again.

The service manual is available on line in a pdf format for free for the 650. It has the procedure for the valve check. There are probably youtube videos too.

Having said all that, I dont think a tight valve would make the engine run rich.. but you should still check them at some point. If they are too tight the valve cannot close all the way and the sealing surface starts to burn away.

with only 16k miles on the bike there is no way your rings are worn out and blowing oil into the combustion chamber.

I forgot to ask the obvious: has the bike been modified? Aftermarket exhaust or intake filter pods? Has the bike been re-jetted or adjusted on the PMscrews to run 'better' ?
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post #7 of 21 (permalink) Old 07-24-2018, 02:19 PM Thread Starter
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As far as the valves, if anything, they need tightening up. There is a clatter. Maybe that's normal.
No mods that I'm aware of (I got it 2nd hand with 18,000 km on it).
Got the tank off. Found what was rattling away inside. One of the bolts had come loose from the gas cap (gold bolt) and fallen down in. Got that out with a magnet.
I should probably consider pulling the carbs since I have the tank off. This vid demonstrates how to do some cleaning by just pulling off the covers of the carbs. He does stress not to upset the floats as they are difficult to adjust.
My fuel filter seems quite clean. I replaced it anyways.
I didn't see any sign off fuel coming out the overfill tube at all. So, I suppose all I can do is pull those jets shown in the vid and blow them out.
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post #8 of 21 (permalink) Old 07-24-2018, 02:35 PM
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You said you pulled the plugs and they were fouled out with carbon. Did you replace them and see if the bike runs any better?

Something running rich (like the choke stuck on) would make the plugs carbon up.

Once the plugs get fouled to a certain point the bike will not run well, like you said - stalling out under power.

I know a lot of people tear into their carbs and clean them, but if the bike is properly stored over the winter that should never be necessary.

I assume you put 4 ounces of seafoam in the gas and ran that thru the bike, or is it not running well enough to drive off 4 gallons of gas? If the bike wont run well enough to ride it, then yes you need to clean your carbs, there is no other way to do it if the gas wont flow thru them.
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post #9 of 21 (permalink) Old 07-24-2018, 02:55 PM Thread Starter
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I didnít yet replace the plugs. The electrodes appear clean. Itís just sooty black around the rim and insulator. The bike actually runs fine at light throttle. I took it out in the open and couldnít get past 50 mph without sputtering. Just cruising below 50 is fine. Iíve gone through 4-5 tanks with it running like this. Strangely, the first time I remember it cutting out was when I got caught in the rain. I figured water might have gotten into the wires coming out of that box mounted on the frame near the horn in the front. Maybe thatís a hint to something other than the carbs?
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post #10 of 21 (permalink) Old 07-24-2018, 03:42 PM
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Pictures help when describing things. Such as how "carbon fouled" your plugs are and the "wires coming out of that box mounted on the frame near the horn in the front." By the way, that does not sound good.

No matter what you ride. Just ride!
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