Take a look at these carb needles

[TheRadBaron]

Here's a picture of one of the new needles (on the left) that I just got from Randy compared to one of the old adjustable needles that I took out of the carbs.  
I haven't ridden the bike, but I bought it off a friend that told me it ran great before developing a valve problem.  I'm thinking that the bike has some aftermarket carb parts installed.  The main jets are #122 and they're not Mikuni.
Why do you think that the old needles are so much shorter than the new ones?  It seems like the short needles out make the midrange very rich.

[Harvy]

Here's a picture of one of the new needles (on the left) that I just got from Randy compared to one of the old adjustable needles that I took out of the carbs.  
I haven't ridden the bike, but I bought it off a friend that told me it ran great before developing a valve problem.  I'm thinking that the bike has some aftermarket carb parts installed.  The main jets are #122 and they're not Mikuni.
Why do you think that the old needles are so much shorter than the new ones?  It seems like the short needles out make the midrange very rich.

If I recall correctly, #122 is a Dyne Jet jet.
I can't even guess at the origin of the needle....... I have used DJ needles myself...... they have 5 grooves, but they are the same length as the OEM needles. I currently have Factory Pro needles and emulsion tubes.........but the needle looks nothing like that one.

Harvy

[andyb]

Dynojet jets would be marked 122.  Mikuni jets would be marked 122.5.

With that needle, I'd wonder if it had somehow restricted movement in the slides to prevent full lift, or it'd go rich just before the transition to the mains.

"Running great" doesn't mean running well, just means it'd pull through the revs, it's a big enough engine that it'll pull nicely even when filthy rich, and the FJ is pretty unfussy for jetting.  I think you're going to be finding quite a lot of power soon...

[TheRadBaron]

Yeah, I think so too    I never got to ride the bike before I bought it, but even if I did I wouldn't have experience with anything like it for a reference.  The most powerful bike that I've ridden up to this point is my XS650.
The guy I bought the bike off of is a good friend and I trust him completely.  However, if he thought that it was running great with extremely low and inconsistent compression due to valve problems, and nasty, corroded, too-short needles in the carbs, I'm sure he'll be impressed when I let him ride it again in the spring once I've corrected all these issues (plus made a bunch more improvements).

[pdxfj]

I believe the needle on the right (shorter one) is out of the DJ kit for the 1100's. 

When I was returning the '86 I sold to stock exhaust, jetting, etc I accidentally installed the needles for an 1100.  Bike damn near died at 5-6k then would catch itself and take off like a rocket.

I discovered the correct needles for the 1200 were longer than the 1100 needles.  Once the correct needles were installed it ran perfectly (go figure).

[Copterdriver]

Isn't it interesting what you find in the carbs when you take them apart. The stock FJ1100 I recently bought was running very lean in the idle to 2500 rpm range. There were no vacuum leaks so I synced the carbs and turned the mixture screws out to 3.5 turns and it runs much better between idle and 2500, but it's rich at idle. I believe the leaness is because the float levels are low (5-7mm depending on the carb, 2-4mm is recommended). In the troubleshooting process I also pulled the tops of the carbs and checked to see where the needles were set and found FJ1200 needles (5FZ72) and needle jets, but that shouldn't make it run lean at the low RPM range... should it?

Mike