View Full Version : Proper tuning for a 1986 Yamaha FJ1200...

10-03-2009, 01:34 PM
I have a 1986 Yamaha FJ1200 completely stock except for a Supertrapp 4-1 exhaust and a K&N air filter in the stock air box (Slightly opened up).
Have any of you (Or the moderator) owned or know what the proper jetting (And needle height) should be for my FJ?

Here is the stock jest for my Fj:
Main jet: 112.5
Main air jet: 45
Jet needle: 5FZ72
Jet needle clip position: fixed
Needle jet: Y-2
Pilot jet: 37.5
Starter jet: 30

Chicago, Ill.

10-03-2009, 07:00 PM
That's going to be difficult for you to find, since there's no 'one' answer. The best answer is to tune it yourself for your atmospheric conditions and desired power characteristics. You can either tune by restricting the SuperTrapp or you can open it up and change the main jet and raise the jet needle. Good (sea level) results ballpark on both would be 2-4% richer, i.e. 115-117 mains and raise the jet needle 0.8-1.3mm by placing a washer under it, like so.
http://www.zxforums.com/gallery/data/540/thumbs/cvr-d40w03.jpg (http://www.zxforums.com/gallery/showphoto.php?photo=810)
To finish off your work, have the carburetors synchronized.

10-04-2009, 09:41 PM
Thanks, I will make those changes and see what happens.

10-07-2009, 01:19 AM
Post up your results. I'm sure many others will find your changes helpful.

I just put my bike's settings back to Winter mode, by closing the SuperTrapp up a little (one disc, now 8 of 12 discs) and removing the 0.8mm jet needle shim I had been using. In almost pure stock form the performance is fair, but fully what I expected, when compared to how it was.

I'm afraid of warping a valve in the upcoming frigid weather to come, which is why I remove one disc. Power will be a lot less important as the risk of breaking traction increases as temps plummet. My bike's (http://forums.supertrapp.com/showthread.php?t=434) a/f is sensitive to every minor disc alteration, necessitating the removal of the shim to make it all right again.