Poor running help

I have just bought this 1982 550 maxim and it runs fantastic with full choke at start up, pulls away with great acceleration but choke in when warm and not great power, feels lumpy, drinking fuel. all points to the carb so checking the plugs 2&4 are really sooty implying too rich, looks as though Im going to have to clean the carbs anyway. it also backfires sometimes, all help appreciated

 

i would most def have the carbs cleaned and sync . replace all plugs , and also check the spark plug boots to make sure they arent grounding anywhere ,

 

Sounds like dirty carbs. Do a search and look for Rick's old school carb cleaning. Follow that and your bike will run like new. But remember to take your time and be careful to look at everthing. If you need parts Len (chacal) has them.

MN

 

The 550s are really sensitive to float level adjustment too; I think a more accurate statement might be Mikunis are really sensitive...

You're describing a classic case of carburetoritis. Complete cleaning, new o-rings as necessary, float levels adjusted correctly, bench sync; you'll fix it. This one's not a "quick fix." An inline fuel filter is also a "must" so you don't re-pollute your clean carbs.

BEFORE ANYTHING ELSE: Check the rear brake for delamination. Too common and potentially very deadly. http://xjbikes.com/Forums/viewtopic/t=15874.html

Also, keep a close eye on the chain. If it's rusted internally it will quickly fail despite being lubed.

 

Can that be the reason why I couldn't brake worth crap?

 

Very possibly. Consider yourself lucky it hasn't caused an unexpected rear wheel LOCKUP.

Read the whole thread; it's happened to a LOT of folks, and a lot of them shared their experiences. A few CLOSE CALLS among them too.