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Discussion Starter #1
Hello,
My 2000 vstar 650 is running like ****, seems like front cylinder is not running. The exhaust for front cylinder is popping, throwing flames out of cobra exhaust. When I try full throttle it stars to bog down as if fuel starvation, but new aftermarket fuel filter from oreily shows gas. Removed only front spark plug boot and bike still runs. Removed only rear spark plug boot and bike shuts off. Both spark plugs have spark, I checked. No air leaks, checked by spraying wd40 when at idle. Could it be front carb, maybe needs to be synched, bad gas? I just rebuilt and cleaned both carbs a few months ago and seemed to run fine for a while. I just want bike to run like it used to, like a bat outta hell.
Thanks for reading and any input would be greatly appreciated.
PS Is it normal for bike to still run after pulling spark plug boot from front plug versus bike shutting off when pulling only rear boot?
 

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Super Moderator "Loose Nut"
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When you get a chance, pull the front plug and post picture, this will help see what that cylinder is doing. First guess you are running way rich and plug is fouled. Smell the oil, does it have a gas smell, if it does, do not run the bike anymore. Only a small amount of fuel in oil will dilute the oil and ruin the bearings.
 

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Discussion Starter #4
I pulled both plugs, both looked the same, a little grey. Swapped the rear plug to the front cylinder and vice versa, still same problem. Should I replace plugs even though they are showing spark?
Thanks
 

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2006 Stratoliner, 2014 Triumph Rocket III Touring, '81 XS650SH Project
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Hello @bobby1378 and welcome from Virginia. As for your PS question, many V-Twins rotate with both pistons firing on the same stroke. If yours is like this than yes, unplugging one jug will allow the bike to continue to run. Harley has this feature for stop lights where one cylinder is shut off electronically [no fuel or spark] until the throttle is turned then it comes alive again.
If your bike is engineered tis way, then you have an electrical issue since one jug will run the bike but the other will not. If you haven't changed the plug wires, they are now 20 years old. Replacing them can't hurt at tis age.
 

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Discussion Starter #8
Hello @bobby1378 and welcome from Virginia. As for your PS question, many V-Twins rotate with both pistons firing on the same stroke. If yours is like this than yes, unplugging one jug will allow the bike to continue to run. Harley has this feature for stop lights where one cylinder is shut off electronically [no fuel or spark] until the throttle is turned then it comes alive again.
If your bike is engineered tis way, then you have an electrical issue since one jug will run the bike but the other will not. If you haven't changed the plug wires, they are now 20 years old. Replacing them can't hurt at tis age.
Hey Boog,
But the plug/wire in front cylinder in question shows spark when cranking motor, could it still possibly be the plug wire? Thanks in advance.
 

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Yes it could. Spark will jump to the easiest ground it can find. Here's a thread talking about similar issue. If you use the sites search function using plug wire and boot several good threads come up.

 

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Discussion Starter #10
Yes it could. Spark will jump to the easiest ground it can find. Here's a thread talking about similar issue. If you use the sites search function using plug wire and boot several good threads come up.

Hey Les,
When I unplug the front spark plug boot and leave the rear boot connected, the bike still runs. When I leave front boot connected and disconnect the rear plug boot, the bike turns off. What does that mean?
 

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Are you sure the front is firing. It's easy to think it's firing all the time, but not. How I test, both exhaust should be close in temperatures, a cheap touchless thermometer works great.

99870


The old fashion way, USE CAUTION, wet paper towel, put on pipe, does the water sizzle? Do on both header pipes, do they sizzle the same. I actually lick my finger and touch real quickly, don't recommend, but works well. Guess that's why I don't have much finger prints left, that and all the welding I've done.
 

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Discussion Starter #12
Yes they are both HOT. Front cylinder head and pipe from front head are hot, i checked to make sure it wasnt cold.
Im thinking bad gas or too much air....idk. Maybe PMS screw needs adjusting, synching carbs or rejetting. What do u think?
 

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Doing a lean drop might help.
PREFERRED METHOD - The Lean Drop - If you have a tach, start at 2-1/2 to 3 turns out equally on both carbs with stock screws and then gradually turn each screw in until the idle drops slightly. Then back them out slowly to the point the idle just comes back up. This is called a "lean drop". You may need to make minor adjustments if you still get some backfire on decel.
Then you always sync the carbs anytime you touch them. You could have an intake air leak. Spray some carb or brake fluid around the intake. If RPM increases you have an air leak.
 

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Then you always sync the carbs anytime you touch them.
I've heard this mentioned but have only seen it on a YouTube video. They had some sort of multiple vacuum gauge they were using. Is there a shade tree method? The owners manual recommends it done every 4,000 miles.
 
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I've heard this mentioned but have only seen it on a YouTube video. They had some sort of multiple vacuum gauge they were using. Is there a shade tree method? The owners manual recommends it done every 4,000 miles.
Yep, cost about $5, been using one for years. You are just looking for an even reading, not looking at any numbers.


 

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Discussion Starter #16
So I bought new plugs, and synched carbs. Still having issue. Running like too much air or not enough fuel into cylinder 1/carb 1. So I have pods im going to install. Do I need to rejet with the kit it came with, or take to mechanic to do it, or can I get away with just adjusting the PMS 1 and a 1/2 turns on both carbs?
Thanks again.
 

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I would pull the plugs and see what they look like. If it is lean i would richen it up and try it. With the pods i have no idea but others will.
 

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The jets that come with rhe kits are a very food starting point. For most it works real well.
 

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Usually flames out the exhaust is an ignition timing issue. Since that's all electronically controlled, you could have a failing pickup coil IF there are 2 of them - one for each cylinder (there aren't, usually). Or, there is an ignition problem somewhere up the line from there. Wires, cap, resistor in the cap, coil, primary wires, etc..
 
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