First ever post 82 XJ750 Maxum

Hey guys,
This is my first time ever going to the web looking for answers on a bike. I use forums alot for my chevelle and it works out well. So I thought I'd give this a shot. My dad bought this 82 XJ750 new. I used to start this bike for my dad and always knew how to choke it and play with the throttle to get it started. I'd always go out to the garage and start it in my youth for him. So I'm pretty familar with the basics. Back around 99 I took the carbs off and cleaned them up a little. I didn't adjust any mixture settings or anything. Well over the past several years the bike has mostly sat. I recently removed the choke cable because it was all bound up. I can easily choke it by hand by actuating the lever while cranking. I have the bike to where it starts fairly easily with the choke and if I keep it barely choked it idles well. But if I take my hand off the lever it stumbes and dies pretty quickly. I saw a set screw on the end of the throttle cable between two carbs. On the "passenger" side right in the valled betweel the two carbs. Its really tricky to get in there, but I thought for sure that looked like the idle location from my knowledge on a car where the idle should be. I turned it clockwise once and it didn't seem to do much. I cranked it two turns and it maybe seemed a little better. Is this really the idle adjust? If it is, I may have an idle circuit or something plugged. The throttle is a bit touchy just off idle (like it wants to die). But once you hit 2K its running strong on all cylinders. Any quick pointers for me?

 

the big screw in the middle of the carbs IS the main idle adjustment screw

 

Sounds like a thorough carb cleaning is in order. RickCoMatic and Chacal both have good posts on here to follow.

Make sure to pay attention to the place in the bowl where the emulsion tube goes as well as the tube itself.

Oh, and also search for the clunk test while you are at it.

 

So what screw have I been jacking with that is one the end of the throttle linkage?

Does myset up similar to this? I was digging a few other places on the net.
http://www.chadrichard.net/nlextremez/v ... &view=next

 

The screw you've been turning is the #4 carburetor sync screw.

Sounds like a good carb cleaning is in order. Since you apparently have virgin carburetors count how many turns to bottom on each mixture screw and put it back there after cleaning. Should minimize the amount of mixture tweaking you have to do.

Your carburetor rack is very similar to the pic you linked to. The rack you showed has a cable adjust idle stop. On yours you'll find a big knurled screw between carbs 2 and 3 right where that black cable is in the pic.

 

Oh crap. I've been playing with the sync? Gez, I'm an idiot. I have no idea how many times I turned that thing.
I really have no desire to rebuild the carbs right now. I've got a chevelle that I need to get back on the road. No time for two toys. Looks like I'm going to try to turn the sync back roughly where I had it. Then try to change the read idle screw.

 

I believe that the enrichment circuit is working fine if it idles properly with the choke on. I think that the pistons could use a good polishing as well as their shafts with some 1000 + grit wet sandpaper. If those are sticking, then lacking strong vacuum (Idle speed), they probably sit closed. This means that the only fuel the engine is getting is that from the enrichment circuit.

It could be other things as well, but that is where I would start.
Once you have done that, perform a bench sync. You sould only need to adjust carb #4 as it was working before.

 

Is there a preset turn for these syncs? I doubt they have ever been touched before. I just want to put my #4 back to where it was at. I turned it clockwise about 2 1/2-3 turns (I know its alot, but thinking it was the idle screw for all 4 I kept thinking at some point it was going to fixt the idle). I have a vac guage for my chevelle, but reading a touch on here that doesn't seem like that will be all that helpful.

 

Dauber,
there is no preset sync.

Putting # 4 back where it was ... you can get fairly close if you remove the carbs and perform a bench sync. You'll have to do an on the bike sync to get it perfect.

Search here for "manometer" and you'll see some threads with design info to make your own on the cheap. Your gauge for the chevelle might work - you need 2, preferably 4, gauges, one for each carb, or if only two, one that stays on the # 3 carb and the other to move around to the other carbs one at a time to tune to #3.

You will also need the YICS tool to do the sync.