1981 XJ 550 Maxim Start and Run issues

I bought my Maxim about a month and a half ago, here is the story. So I bought this bike from a back woods guy who ran a home business and it seemed on the up and up. It ran fine at his place although my friend says "He drove it like he stole it," I disagree with this, but I would hate to misrepresent the situation by accident. The bike had old gas in it and while putting it on my truck, the little that was left ran out. At this point I will say that before this we started it several times and never had a problem. However when I get the bike home and it wont start without starter fluid. Once running I could drive it around no problem, but still I needed the fluid. So I assumed that I was having a vapor-lock or plugged carb problem. So I:

Replaced battery
Oil Change
Tightened and oiled chain
Cleaned and polished up carbs
cleaned air filter
Made sure I had spark on all cylinders

So I put the carb back in, and some level of success, it now starts but not reliably and only with the choke. It will also only run with the choke open, and only above 2000 rpm. I cant for the life of me get it to idle lower or to start reliably. Is it that I missed something in the carb cleaning?

Do you guys have any suggestions. I am trying to keep my eye out for any advice on similar bikes, and have learned a lot already. Thank you, I am really excited to start showing you guys pictures of it running... when that happens

 

Wow! Almost like deja vu! Welcome to XJBikes Straitwalker <--nice handle.

As crazy as it sounds I swear XJ's all require extra love after escaping a jerk-off PO (previous owner)-they only run well at the sale because they desperately want to escape their current owner-your 550 experience is similar to mine but the problems cropped up a few more miles down the road. Ok so zen stuff out of the way.

Sounds like you have a good start on making this 550 come back to life. Your symptoms point directly at the carbs, but valves are also a concern as they set the whole thing in motion. When you say 'cleaned and polished' the carbs, does that include every passage clear, every jet clean, 'clunk test,' wet set float levels, and bench synch followed by vacuum synch? Did you remove the pilot screws, clean those passages, and replace any worn rubber? If any answer to the above is 'no' then you're going back in. But check and adjust your valves prior to that so your vacuum synch will be meaningful.

Not idling is an indication that 'off' throttle your pilot or mixture circuit isn't supplying 'pilot' or idling mixture-hence the need to engage the enrichment plungers (choke) which make up for it. Do a search on here for 'church of clean' and 'Mikunis' to get a complete idea of what is needed.

When they are running right these half-liter bikes are amazingly fun and fast-so keep up the efforts and keep asking questions and you'll get there. I haven't found a better forum with better advice than this one. Virtually everyone on here is honestly trying to help and has great ideas. Enjoy your new obsession. :wink:

 

Thank you MercuryMan (my handle involves my name). Well of course, the ONLY thing I did not touch in the carb was the Pilot jet, which it sounds like is the problem. I did however throw some carb cleaner through them and it seemed to flow through. But it sounds like I should pull them out... a little scared. I have a few snowmobiles and rebuild those carbs but rarely touch the pilot because I am afraid to do more damage than good.

I really fell in love with the bike, immediately. I saw through the oil and dust to the beauty of the bike itself. I am really excited to get out there and ride, only been out twice it was AWESOME. (this is my first bike) and really want to get back out there.

 

had a very similar experience with my recent xj550 purchase, ran excellent the two times i test drove it, and then died as soon as i got it into my garage. now i have done so much too it now and its still not quite there. but its super close.

 

So sorry its been a while. I got my bike all back together and realized I had misplaced the keys..... Kinda Stupid. But anyways, so I have been putting it all back together today. It starts right up, and idles around 1200 rpm.... for the first few seconds, after about half a minute it revs WAY up to around 4000 rpm. Does anyone have some idea what could be causing this? I keep moving the idle knob out. I am not revving or anything like that, and I am not using the choke at all.

 

It works! I played with it for a few... hours... and now it works!

 

StraitWalker - welcome to the forums! I've only been on it myself for a few months but I can tell you the amount of great info on here is endless.

I hope you got everything squared away! It sounds like you were experiencing the result of carbs that were out of synch. Did you end up doing a dynamic synch? If not, I would highly recommend it!