V Star 250 starts and dies immediately after releasing start - Star Motorcycle Forums: Star Raider, V-Max, V-Star, Road-Star Forum
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post #1 of 23 (permalink) Old 07-12-2019, 07:01 PM Thread Starter
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V Star 250 starts and dies immediately after releasing start

Hello,
I just got a Yamaha V Star 250 off of Craigslist. Pretty low miles and in crazy clean condition. It will start up for a second and then die. It does turn over but as soon as I release the start button it dies. The bike does not start if I have the engine kill switch set to off.

Here is a video I made of the start up.

To note what I have done so far:
  • removed and cleaned carbs
  • Drained and added fresh oil and new oil filter
  • new spark plugs
  • fresh gas (no ethanol)
  • tested the sidestand switch
  • tried bypassing sidestand switch
  • tried bypassing kill switch (at handlebar)
  • checked the fuses.
  • Charged the batter and load tested it.

I feel like is something to do with the kill switch or sidestand just because of the way it stop right after turning over, but I don't know. Any ideas on what else to check? I am afraid it might be electrical.

Last edited by CatManFoo; 07-12-2019 at 08:32 PM.
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post #2 of 23 (permalink) Old 07-12-2019, 07:12 PM
KCW
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are you pulling the choke all the way out to start it

and are you sure the choke cable is connected to the carb mechanism?
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post #3 of 23 (permalink) Old 07-12-2019, 07:16 PM Thread Starter
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Quote:
Originally Posted by KCW View Post
are you pulling the choke all the way out to start it

and are you sure the choke cable is connected to the carb mechanism?
Check and check there. It will only turn over if I have the choke all out so I know its working, plus I check to make sure the carb end of the choke was fully seated and screwed in. When I pulled the carbs, I inspected and tested the choke.
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Yamaha V Star XV250
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post #4 of 23 (permalink) Old 07-12-2019, 07:26 PM
KCW
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the thing missing from your did-that list is the fuel pump

these bikes have one because the bottom of the fuel tank is lower than the float bowls, so the bike would run with a full tank of gas, but not all the way to empty

pull the fuel line off the carbs, turn the ignition on, and the fuel pump should run, at least for a few seconds, and spray gasoline out the hose.

If the fuel pump is not working, then unhook the line from the petcock and make sure it letting gas flow when you turn it on, then connect that line directly to the carbs, and if the tank is full, the bike should run.

if the direct connect fuel line does not make the bike run correctly, then I would think the ignition is dropping out when you release the starter button for some odd reason. An inline spark detector would let you see if the plugs stop firing when you release the starter button.
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Last edited by KCW; 07-12-2019 at 07:28 PM.
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post #5 of 23 (permalink) Old 07-12-2019, 07:56 PM Thread Starter
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Quote:
Originally Posted by KCW View Post
the thing missing from your did-that list is the fuel pump
.
Fuel pump works. Forgot to mention that I took it out and cleaned it (it was clean) and I tested it to make sure it was pumping fuel. I don't have a spark detector so I'll have to get one to test that.
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post #6 of 23 (permalink) Old 07-12-2019, 07:57 PM
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It is either fuel, air or spark. Breathers clean? Choke stuck. Manually fill the carb with gas and see if it runs longer. A good squirt of gas in the sparkplug hole will run the engine longer than it is if you have spark.
Not sure the electrical setup but the equivalent of putting 12 volts to the coil should ensure spark.

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post #7 of 23 (permalink) Old 07-12-2019, 08:08 PM Thread Starter
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Originally Posted by Bucfan11 View Post
It is either fuel, air or spark. Breathers clean? Choke stuck. Manually fill the carb with gas and see if it runs longer. A good squirt of gas in the sparkplug hole will run the engine longer than it is if you have spark.
Not sure the electrical setup but the equivalent of putting 12 volts to the coil should ensure spark.
Breathers as in the air intake/airfilter? And by choke stuck do you mean stuck closed or open? I'll go try your suggestions and report back

Edit: Just tested the fuel pump again and yes it is pumping gas to the carb.

Yamaha V Star XV250

Last edited by CatManFoo; 07-12-2019 at 08:31 PM.
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post #8 of 23 (permalink) Old 07-12-2019, 08:44 PM
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the other possibility is you have really bad vacuum leaks, maybe the boots are not sealed to the carbs

if you have a propane torch you could turn it on m(un lit) and direct the gas flow at the base of the carbs, or where the boots connect to the heads - if the bike starts while you are cranking it like this, you have a vacuum leak. Carb cleaner also works, can make a bit of a mess though - but it should evaporate off.

another possibility is the timing is off (someone was messing with the timing chains) or something is wrong with the cams or valve adjustments

the fast way to check for that is to do a compression test on the two cylinders - if the compression is low the bike will stumble and will not run correctly.

Did the previous owner give you any history on the bike? Any previous problems? From the work you already did it sounds like it sat for a long time either with no gas in the tank or the fuel broke down and fouled out the carbs.

Have you looked in the tank with a flashlight, see any rust in there?

if the fuel filter was plugged you would get no flow from the fuel pump.

If the fuel filter is missing, and there is rust in the tank, it will get sucked into your newly cleaned carbs and block the passages again.

one more thing, the carbs should have a throttle position sensor, its used to advance the spark as the throttle is opened - if that is not connected or not reading correctly, the spark timing will be way off.
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Last edited by KCW; 07-12-2019 at 08:47 PM.
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post #9 of 23 (permalink) Old 07-13-2019, 01:26 AM Thread Starter
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Quote:
Originally Posted by KCW View Post
...
1. Checked the boots, both are tight. The top of the top boot doesn't have a clamp or anything but seems tight
2. I did a compression gauge test and as it was cranking about 4 turns got to 30psi.
3. Bike is super clean, always garaged, no rust, inside of tank is clean, 0 rust. Did sit for years without being used. That's why I pulled the carbs.
4. The fuel "filters" in the tank? I didnt see an external filter anywhere.

as far as cams or valve adjustments, I don't know if that is something I can do. Maybe I need to just take this bike to the shop..

Where is the the throttle position sensor on this bike?
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post #10 of 23 (permalink) Old 07-13-2019, 06:00 AM
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the compression on both cylinders is only 30psi after 4 revolutions of the engine?!

it should be 150 to 180 after it stops climbing (might take several revolutions to stop increasing, but the first compression stroke should throw it up to 90psi or more.

30psi is nothing - if you did the compression test correctly you have a serious mechanical failure, like the timing chains both broke or are missing, or completely out of place from where they should be, or your valves are stuck open, or there are no rings on the cylinders....

?!?!!!

Last edited by KCW; 07-13-2019 at 06:12 AM.
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