Lean issues

[Thmsdoyle]

My 84 FJ flutters / hesitates around 2200 rpm up to 3500 rpm. If I'm riding at a steady speed for a spell then open the throttle it will also do it. Off idle it is responsive and once past the rpm range it has great power at full throttle. I have adjusted the slide/needle jet with out helping the problem. The needle jet is set at second notch from the bottom (pointy end). I can open the choke just a very small bit and it does go away (so i know I'm lean). But is this a pilot jet issues or am i looking at a larger main jet? With my full throttle response and good power i'm skeptical if the main is the issue. As i'm writing this, this thought came to mind about a possible air leak? any one else experience this. Stock 84 with air pods on it. Can't tell you the jet sizes as I have not been in the bottom of the carbs yet. 

[Yamifj1200]

Sounds to me your problem is there is something plugging up the carb somewhere. Time to do a complete carb clean. There is a great write up here on the site that will tell you everything you will need to do to properly clean your carbs..
http://www.fjowners.com/index.php?topic=655.0
You may also have a vacuum leak at the intakes of the o-rings that seal the intakes to the head. Let us know what you find..

Eric M

[fj1289]

Welcome!

Going to need a bit more info to provide any assistance.  Things like: How are your carbs set up now?  Stock Yamaha jetting?  Carb kit?  If so what make?  Owner rejetted?

What is your pilot jet?  and pilot air jet?  

Also, can almost guarantee that pulling and cleaning the carbs would be a good start and let you get into them and see how they are jetted.  

There is a lot of good info also in the files section for carbs.  Read through some of that info and ask whatever questions you have - lots of knowledge avaialble here!

Cheers,
Chris W.

[SlowOldGuy]

If you've got the needle pulled up that far and it's not making any difference then you might want to consider trying something else.  Sounds a lot like your idle jets are clogged up.

Opening the choke will tell you NOTHING about how your carbs are set up.  The choke (enrichener) circuit is a sort of mini-carb in that it supplies a richer air/fuel mixture instead of just adding extra fuel.  As such, when you barely apply the choke, you may just be letting in extra air.

But, starting with a clean set of carbs is an excellent idea.

DavidR.

[yamaha fj rider]

Thmsdolye time to bite the bullet and tear down those carbs. Clean them and find out what jets are in there. Check the o rings between intake boots and cylinder head.  After sync the carbs. Hope this helps.

Kurt