An Alaska fishing trip is at stake....

One of my coworkers has a 1982 XJ550 Maxim, with 20,000 miles, that he has attempted to tune with little success. He approached me at first with a load of questions about tuning the bike and related topics. Frustrated, with no quick results, the bike was dropped off by him at my shop last week with a note on it. The note read: if you can get this thing running as good as yours it worth a five day deep sea fishing trip in Alaska this coming September.
Fish on, baby!
On to the tuning of the bike and what I'm experiencing.
First and formost, I have the valves in spec, no vacuum leaks, good spark on the plugs (on the lean side colorwise) and the carbs were serviced by the local dealership.
~When attempting to vacuum sync the carbs I'm noticing that the idle never really finds a consistent spot to return to. I balance the carb levels between 1500 -1800 rpm no problem. Then back the idle to 1100 rpm and the bike idles solid. Then I blip the throttle and the idle attempts to regain its setpoint but it's either hanging high or struggling
below 1000. This occurs with and without the YICS tool.
~ Color tuning was done to adjust for lean condition as per spark plug color.
Same "no return to idle" situation. I wasn't expecting much of a change.
~Additionally, I experimented and helped the bike back to idle by blipping the throttle and applying a little pressure on the sync screw upon its return. This provided a consistant return to to solid idle.

What my thoughts are in rectifying the idle problem:
~binding or incorrectly reassembled linkages between carbs.
~carb return springs incorrectly reassembled
~butterfly valve(s) hanging up
~perforated diapram (maybe)
-incorrect or dirty idle jets
~incorrect float level
I'm pulling the carbs to check them out for float levels, clean idle circuits, jet sizes, alignment of components, and blah X 3. By experience I don't trust anyones carb work but my own.
Thoughts, suggestions or guidance regarding this matter are welcomed.

 

Looks like you have most possibilities listed - shaft seals changed?

 

One thing to check ( at least how I do it) take 2 business cards cut in two , slide under all 4 butterfly plates turn synch screws till you get a slight drag on one card and check next carb . I'f one plate is slightly off this is the one you may have to lossen and reposition. Hold carb rack up to the light and see if you have only a slight view of light that is where you want to be . ( oh just realized 550 have Mikuni butterfly screws are peened in place unless they have been replaced. ) still the same way of doing bench synch though.

 

With regard to the shafts seals, I leaning towards: probably not. I do know that the rack was broken apart for ultrasonic cleaning.
The butterfly alignment will be looked into today. It was a issue for me when I changed my shaft seals. I like your method of checking them and will use it to verify even clearance amounts.
Thanks to both of you.

 

One of my pet peeves is working on other peoples machines and not knowing 100% what has been done to it, mechanically. I have all the cool gadgets to make tuning happen but without a comprehensive maintenance history it can be a hassle.

Any tuning suggestions related to this problem are appreciated.

I'll be sure to follow-up with my findings for someone else's benefit.

 

Assume that no work was done, and that any work that was done was done incorretly. This will establish a baseline that ensures you don't miss anything.

 

⤴verbatim, you read my mind.
Does the "K" in your name stand for "Kreskin"?

 

While you have the carbs off, you might as well do a compression test..........

 

Excellent call.
I wasn't even thinking along those lines, just focusing on the carbs. Tunnel vison.
After dissecting the carbs thats a logical next step.

 

With the carbs removed I found that two of the throttle valve butterflies had been installed backwards, with the stamped numbers up.At least its certain that the throttle shaft seals where replaced.
On this bike, I also found that with the sync screw springs there was three that were thicker gauged than the others. It was assembled with the thinner gauged springs below the actual sync screws so I swapped them. Is this common with Maxims? I don't recall my 550 Seca having different springs.
Another issue was the float levels were incorrect, they ranged from shy to way-off.
The worst part was that I found 5 of the 8 lower screws on the alignment rail had little to no threads left. I suspect the use of a electric impact gun to be at fault here. I used threaded inserts to fix this issue and they worked great.
After syncing / color tuning, the bike now returns to idle as normal. It synced very easily. I put about 40 miles on it making sure that everything was spot on. Mission accomplished.
I rode the bike to work and had the forklift operator help me load it in the back of his truck without saying anything to him. I left him a note that said "FISH ON!"
Obviously, I got a call that evening and an email with my flight confirmation number to Alaska shortly after that.
In light of the above discrepant items the bike owner decided to skip the compression test. I mentioned that he might want to choose a different repair shop next time because of the simple mistakes made when reassembling the carbs. He agreed with me and mentioned that being I'll be retiring soon (and early) that I was going to be his new mechanic.
I don't think so.

 

Good work. Another xj back on the road

 

For the sync screws-- you should have the heavier springs on top, with the sync screw. The lighter-weight springs go on the sliding barrel underneath the plate.

Easy way to remember (Matti.....remember this--).......think "TOP-HEAVY".

Dave

 

I like top heavy, but a heavy bottom doesn't hurt either

 

When you go to Alaska fishing:
Try to book the night trips; you can get a bag limit for day one... then past midnight you get another. At least that is what a co-worker told me as he handed me some halibut steaks. Mmmmmm

 

But then the next days limit has already been caught. If you abide by the rules, then you're not about to take anything more til the beginning of day 3........so just get your first days' limit before day one is over.

 

Thank you for confirming this, I guess.
I hate to mess with it since its running just fine and he's been riding the hell out of the thing since I returned it to him, but
I'm going to loose sleep about this unless its addressed.
I gotta do the right thing and try to explain to him whats up and I'll leave it up to him if he wants me to fix it or not.