I have a 2001 Yamaha 650 V-Star classic. I can’t get it to fire. I have compression, spark, and fuel. When I attempt to start the bike with choke or minimal throttle pull, the bike seems to try to fire and puffs out the the air cleaner like it’s the exhaust and not the air intake.!? Could something be reversed or a vacuum line in the wrong place? I bought this bike none running. I’ve checked all relays, replaced pick up coil, stator coil, plugs/boots, and starter relay. My connections are good, ohm readings are good on everything I can check in manual. Valve clearance good. I am at a loss can you help?

SOURCE: rough idle

make sure the trottle if free of carbon built if is not clean it with toot brush and carburetor cleaner

SOURCE: 200 YAMAHA V-STAR 650 HAS

IT sounds like it is the pickups not working (.telling it to spark) if not then it will be CDI UNIT OR ENGINE GENERATOR COILS

SOURCE: 95 GMC Jimmy 4.3l W vin rough idle

My problem was solved when I repaired my 4 wd activation dash switch. The switch was contacting on 2WD & 4HI at the same time. The front differential activation is vacuum activated possibly creating a tug of war that didn't actually engage it but drained off vacuum from the engine? A theory at best but stumbbled across it because I knew the switch wasn't working properly I repaired it and low and behold rough idle disappeared and all is good for 3 weeks running.

SOURCE: Strange thigs about YAMAHA TW 125

Hi
I have been working on my carb today,the pipe from the bottom of the carb should just run down by the bottom of the swinging arm,there should be another pipe from the pipe on the left side of the carb just above the fuel intake which also runs down to the swinging arm and connect to nothing.
Cheers

SOURCE: 2007 Jeep Wrangler Unlimited Crank-No Start. Replaced FP.

Hey Tim take a look at this, will this help ?
SUBJECT:
No Engine Crank Or No Engine Start Due To Electronic Lockup Of The WCM / SKREEM
OVERVIEW:
This bulletin involves the replacement of the Wireless Control Module (WCM), and if
equipped, the replacement of the Electric Steering Column Lock (ELV). The WCM is also
referred to as the Sentry Key Remote Entry Module (SKREEM).
MODELS:
2007
SYMPTOM/CONDITION:
The customer will experience a no engine crank AND a no engine start condition. Also, the
remote keyless entry (RKE) system will not operate. This condition may be due to an
electrostatic discharge (ESD) from the ignition key into the Wireless Control Module
(WCM), causing the WCM to electronically lockup. This condition may occur more
frequently in dry and/or cold weather conditions where a sufficient electrostatic charge is
more easily produced. This condition is corrected by the replacement of the WCM
DIAGNOSIS:
1. With the condition present (i.e. the vehicle in the no crank / no start condition), connect
the StarSCAN® scan tool to the vehicle.
2. Turn the ignition switch to the “ON” position, and power up the StarSCAN®.
3. If the WCM is electronically locked up, the StarSCAN® will display the WCM as being
“off bus”.
4. If the no crank / no start condition is present, and the WCM is “off bus”, then reset the
WCM by temporarily removing the IOD fuse (with the key out of the ignition switch),
wait for 10 seconds and then reinstall the IOD fuse.
5. With the IOD fuse reset having been performed, verify that the vehicle will now crank,
start, and run.
6. If the condition is temporarily corrected by performing the above steps, and if the part
number of the WCM is earlier than the part number of the WCM listed in the part
reference table in the Service Bulletin Parts Required Section below, then perform the
Repair Procedure.