1990 Yamaha FJ1200 dies when throttle is turned. .

SOURCE: Won't idle without choke

The pilot jet controls the air/gas fuel mix at idle . If the jet gets plugged up not enough gas gets to the emgine at idle. You will need to remove the carbs and float bowls and clean them, paying special attention to the pilot valve. Count the number of turns to remove the pilot screw and replace the same number of turns then turn counter clockwise 1/2 turn.

A “very helpful” rating for this answer? Thanks!

rtpflh

• 546 Answers
• Posted on Sep 26, 2009

SOURCE: I think someone hooked up fuel lines wrong. The

not that familiar w/Yamaha,but disconnected vacuum hoses may connect to fuel petcock at tank.I know Honda uses a system that only allows fuel to flow when vacuum is supplied.

SOURCE: 81 Suzuki gs650 #2 carb floods gas out after start

The float is stuck open in the leaking carb. Remove the float bowl and clean the carb after removing the pin holding the float in place. While the float is out, shake it to see if gas has gotten inside it. If so, you will need a new float or will need to drain the float then re-solder it to seal it up again. To drain the float chances are you will need to drill a vent hole in it to allow the gas to drain. Just solder the vent closed when done.

SOURCE: Idling engine dies with even slight throttle twist.

Check float height in carbs.Thanks for asking and I hope this helps out.Please leave me 4 thumbs up.

SOURCE: My 2002 V-Star 1100 Classic

G'day.
I can't solve this(there are litaraly hundreds of things it could be) BUT I can give you a way to narrow it down a bit.
I'm thinking it may not be running on all cylinders and an easy way to check is to start the bike from cold(do this test in the first few seconds after starting from cold DONT BURN YOURELF),put a bit of spit on your fingers and quickly touch each exhaust header in turn, to see that they are all warming up equally together.This will narrow down if your problem is related to one or more cylinders.
If one or more of the pipes is cold/er than the others then you know which cylinders are causing the problem.
If you find that this is the case- one or more of the headers are cold then.
Remove the spark plugs-Keep in order.Examine the plugs-used plugs tell a story.How do they look?clean?black & sooty?Are they all the same colour?
Re-fit plugs to caps,sit plugs on metal of rocker cover,press starter - cheack for spark on all plugs.DO NOT HOLD OR TOUCH PLUG/CAPS WHILST CRANKING-WARNING - HIGH VOLTAGE- CAN KILL.
I can also suggest a few common problems that bothered the v-stars/viragos.
They were notorious for open circuiting their spark plug caps on either cylinder.Having the coils tested will confirm this. If you have a multi meter let me know & i'll guide you through testing them.

Air leaking at the inlet manifolds-where they bolt to the cylinder-test this by spraying with wd type spray with engine running-if engine revs change-has air leaks(sucking in wd & affecting mixture.)
They even pop the carbies out at the front some times & **** air there.
The inlet manifolds also have hoses & plugs on them(for checking the carbie balance/vacume fuel tap)Check all these for splits & tears-common depending on the condition of the bike/milage/fuel used.
This will not solve your problem but may help you to isolate where your issue lies.


I hope this is somewhat helpful & I'm happy to help if you need after following these suggestions
Kind regards Andrew Porrelli











I hope that this is in some way helpfull.

Testimonial: "Thanks very much for that information. I plan to continue working on it this weekend, and I'll definitely use these ideas. Take care...Danny O."