Idle adjustment screw is missing

I've had my 82 xj550 for about a month now and have been fixing the small things--mostly exhaust and wiring that the previous owner attempted to fix. Bike is running much better than before.

The idle was normally staying high (around 2800 rpms) but I could put it in 1st, hold the brake and slowly release the clutch. Once the rpms reached 1300 I would squeeze the clutch again and it would stay there. Now I am looking to fix the idle problem and find that there is no adjustment screw where there should be! Does anyone sell these things separately? Is it possible to fabricate one?

Thanks
John

 

What exactly is missing?

XJ4Ever has a lot of used parts available, as do a lot of members.

Chances are, it's going to take more than replacing a missing idle adjuster to fix your high idle. A hanging idle generally indicates an out-of-sync condition, improper float levels, a vacuum leak or a combination of any of the three. You'll need to do a basic carb service, set float levels and bench sync, get your valves in spec, and then get everything sync'ed and adjusted.

 

I had a feeling that I would be servicing the carbs soon. I need to do the brakes first (this weekend after seeing the post on the delamination of the rear brakes) and then the carbs are next. I was just hoping to get a little improvement before then. Ah well. I'll see if I can get a picture to post after I get home from work.

Thanks
John

 

Well, at 50K if nobody ever touched the valves, it probably wouldn't run.

That being said, your symptoms usually indicate the problems I alluded to, but you will need to check your valve clearances before the final vacuum sync.

Unfortunately, carburetors usually hold the key to getting these things running right.

Here's an exploded Mikuni so you'll get an idea of what's what: http://xjbikes.com/Forums/viewtopic/t=31061.html

 

is there a hole with no screw in it or do you still have the factory plugs that haven't been removed?

 

I took the tank off and got some pictures. The vacuum hose going to the petcock crumbled when I tried to take it off. Luckily I had some from a previous car repair and fixed it. I am always amazed when I have the material to fix things at the house!

Back to the idle screw.... Shouldn't it be there in the round opening?

 

2nd pic

 

3rd pic

 

4th

 

last

 

In your first pic. move the yellow arrow to between the carb, and the airbox boots. then move directly to the bottom of the carb rack between cylinders #2, and #3. Diagonaly opposite from the throttle cable in the pics.

That hole you have pictured is nothing more than a weight reduction hole in the bracket that holds the throttle cable.

Ghost

 

Just when I think I might have it figured out...(palm to forehead)

OK so, the adjustment screw is towards the rear of the bike, correct...

I'll give it another go tomorrow.

I greatly appreciate everyone helping out the newbie!

John

 

HOW TO: Bench-synch your carbs The 8th picture will show the idle adjust screw.

Ghost

 

Vacuum leaks were mentioned...
Pictures 3 and 4 show some pretty good cracking in your intake boots. Picture 4 looks bad aroung that rubber line. That may be part of your problem right there.
I had to edit my post... looking at picture 1, that looks like a pretty substantial crack in the rubber boot by your yellow arrow. Those look like they need replacing.

 

Only maybe. Mine looked pretty horrible too, you have to see if they go all the way through or not. If they don't go all the way through, you can pack the cracks with black adhesive RTV and call it a day.

That IS NOT where the idle knob is, that's just a hole in the bracket.

Idle knob is underneath, facing downward/rearward, in between #2 and #3 carbs.

You did use actual VACUUM line for the petcock, not just "hose" right? Has to be vacuum line or it may collapse in on itself when hot.

Idle knob:

 

Thank you for the pics of the idle adjuster. I still don't think I have one there, but I will check.

I did use actual vacuum hose for the percock repair. I recently had a leaking vacuum hose on my 96 Volvo and decided to replace all the vacuum hoses since I was already in there. I still have about 5 feet of it left so it was perfect. And my wife gets on me about hoarding parts and tools!

I had been worrying about the cracks in the boots from the carb to the engine. The cracks don't appear to go all the way through so I will pick up some of the adhesive rtv and fix them up. Looking online the boots seem to run about $20 each. This seem right? I also assume the boots are different from the airbox to the carbs.

Thanks
John

 

The boots that run $20 each ARE the airbox-to-carb boots. The intake manifolds usually run around $85, if you're lucky.

The only way to be sure about the cracks is to flex the manifolds from INSIDE with your finger once the carbs are off.

For parts, look no further than our resident parts guru, chacal. Proprietor of XJ4Ever.com, source for CORRECT parts at very reasonable prices. Click the logo/link in the site banner for his catalog forum, or send him a PM.

Check my gallery for a glimpse of what's possible.

 

They are all really nice bikes! My favorite it the white 81 Seca. Sweet!!!

 

OK. I checked in the correct place this time and I do not have an idle adjustment screw. It looks like the entire assembly is missing, screw and bracket.

Don't think it is critical at the moment since I am idling high, but I will need one as soon as I'm ready for the carb clean (church of clean) and sync. At that point I will also check the interior of the carb to engine boots for cracks and probably be back on here with a horror story or two, pleading for help.

Thanks for all the help and guidance!

John

 

Hey bigfitz52, that Norton looks awesome! I like the others, but the Norton is sweet!

John

 

Thanks, John. I'm the original owner; every single mile is mine. It's still an incredible bike, even by todays' standards.

Be sure to check your valves before you try to tune the carbs.