Help! Vstar 250 problem - Star Motorcycle Forums: Star Raider, V-Max, V-Star, Road-Star Forum
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post #1 of 14 (permalink) Old 11-18-2010, 02:22 PM Thread Starter
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Unhappy Help! Vstar 250 problem

On a comfortable (60 degrees) morning ride not long ago, I came into town to the first stoplight and found that my bike would not idle. It worked on one cylinder only unless I kept the revs up. I nursed it to my destination, ran an errand of approx. 10 minutes, came out and started it up to find that now it idled. I've never had any problems with it prior to this.

The next morning, I checked the valves, they were spot on in the middle of their adjustment range just where they had been for the last 11,000 miles. I changed the sparkplugs and went riding. Ran on both cylinders, but I found that the mileage had dropped by about 11-12 miles per gallon. It has stayed that way since that day. For no apparent reason, the mpg has sunk and it will not idle with any vigor although now it does idle. And the power is down needing a bit more throttle than before for the same speed.

It has never been over-heated. It doesn't burn oil. The valves have never been out of adjustment. It has spark, but I cannot tell by looking if it is proper. At idle, if I pull the rear sparkplug wire, it will continue idling at a lower rpm. If I put it back on and then pull the front cylinder plug wire, it will die so it seems that there is some problem with the rear cylinder.

Both cylinders have 160psi pressure when tested cold. I am allergic to messing about with hot engines. If there was a compression problem, there would be a difference hot or cold.

Is it possible for the timing to slip? Individually by cylinder?
Any ideas are appreciated.
I accidentally posted this in general bike forum. Maybe better here?
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post #2 of 14 (permalink) Old 11-18-2010, 02:33 PM
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see your previous post



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post #3 of 14 (permalink) Old 11-18-2010, 03:11 PM Thread Starter
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Quote:
Originally Posted by stratowart View Post
see your previous post
stratowart suggested syncing the carbs, but the 250 has only one carb shared between the two cylinders. Excellent idea but won't work here.

More ideas?
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post #4 of 14 (permalink) Old 11-18-2010, 03:53 PM
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Well then its not the carb. LOL Look for an intake boot to be cracked and leaking if it won't idle but runs fine when throttle applied.

GW
2005 1100 Custom
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ORKed 5/16" Lines
PODs K&N RU-600s W/PCV
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10,000 Monkeys throwing crap at the glass and this one thinks he's Picasso...
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post #5 of 14 (permalink) Old 11-18-2010, 03:59 PM Thread Starter
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All looks good between carb and cylinders. Even though I cannot see a difference, is it possible that the spark is weak on the rear cyinder? Can a coil work but not provide full voltage? I always thought that coils are work/don't work with nothing in between. But I don't know.
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post #6 of 14 (permalink) Old 11-18-2010, 06:23 PM
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Sorry I'm at work and got busy. Get some wd-40 or similar and spray around boot and manifold when you're trying to keep it idling and see if it picks up. It doesn't take much of a leak to make it too lean to run at idle.

GW
2005 1100 Custom
Speedster Slashdowns
ORKed 5/16" Lines
PODs K&N RU-600s W/PCV
PCS XXX/2 cams
Jetted & PMS Tweaked 20.0/152.5 3.0 turns
AIS Removed/Plugged
Wimmer Machine Custom Oil Cooler & Stash Tube
Pro-1 Tach
Dyna 3000 Step 5/ 6500 redline
TPS Connected
6" Fwd Control Extension W/Boards F&R
Memphis Shades Bullet Fairing
Progressive 465 rear
Progressive Springs and GVE front

10,000 Monkeys throwing crap at the glass and this one thinks he's Picasso...
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post #7 of 14 (permalink) Old 11-18-2010, 08:46 PM Thread Starter
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WD-40 it is. I'll give it a try this weekend.
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post #8 of 14 (permalink) Old 11-19-2010, 07:39 AM
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Also check your plugs. What color and any significant color variations? A Coil can go bad and then good again, usually on the route to going bad altogether. Heat related, when they get hot they open and as they cool down the circuit completes again. If you get nothing on these try swapping your coils and see if the problem follows. Do these one at a time so you can find the hard fix.

GW
2005 1100 Custom
Speedster Slashdowns
ORKed 5/16" Lines
PODs K&N RU-600s W/PCV
PCS XXX/2 cams
Jetted & PMS Tweaked 20.0/152.5 3.0 turns
AIS Removed/Plugged
Wimmer Machine Custom Oil Cooler & Stash Tube
Pro-1 Tach
Dyna 3000 Step 5/ 6500 redline
TPS Connected
6" Fwd Control Extension W/Boards F&R
Memphis Shades Bullet Fairing
Progressive 465 rear
Progressive Springs and GVE front

10,000 Monkeys throwing crap at the glass and this one thinks he's Picasso...
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post #9 of 14 (permalink) Old 11-19-2010, 12:27 PM Thread Starter
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Thanks, Fulltilt1. The coil thing, going bad then seeming to revive, is interesting. I'll check when we get a slightly warmer day. No garage, so I work in a carport. Too chilly and dampish for the next few days.

I'll try the wd-40 on the intake manifold bits first. If no change, then I'll get serious about the coils.

The front plug looks perfect. The rear plug looks good but for a dark, carbony area on one side maybe like it's not burning hot enough to keep completely clean. Makes me suspect the coil.
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post #10 of 14 (permalink) Old 11-19-2010, 02:32 PM
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I'd try plugs first, the condition I mentioned for the coils is rare but not unheard of.

GW
2005 1100 Custom
Speedster Slashdowns
ORKed 5/16" Lines
PODs K&N RU-600s W/PCV
PCS XXX/2 cams
Jetted & PMS Tweaked 20.0/152.5 3.0 turns
AIS Removed/Plugged
Wimmer Machine Custom Oil Cooler & Stash Tube
Pro-1 Tach
Dyna 3000 Step 5/ 6500 redline
TPS Connected
6" Fwd Control Extension W/Boards F&R
Memphis Shades Bullet Fairing
Progressive 465 rear
Progressive Springs and GVE front

10,000 Monkeys throwing crap at the glass and this one thinks he's Picasso...
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