85 xj700 idle problem

Greetings,

I recently bought an 85 maxim xj700 which had been sitting for four years without having been prepared to sit. I cleaned the carbs pretty well I think and replaced the tank/petcock which were well rusted. I noticed one of the float valve needles had a damaged rubber tip (seat?) but not having a spare I cleaned it well and put it back into the carb. A few doses of seafoam and she was running and idling well with very little hunting. I put about 150 miles on the bike and it suddenly started to die at idle, not all the time but enough to be a nuisance, (at stop signs I have to rev the engine). Most times I can put the choke half on or so and it will idle better but eventually it will bog out and die just the same. All four of my plugs are white indicating a lean mixture. Wouldn't a stuck float needle cause atleast one carb to run rich? The bike is less likely to stall at a high idle and I found some success by lessening the slack at the adjuster near the throttle grip but this I suspect is not really addressing the problem and causes the throttle to race. I've pretty much resolved to go at the carbs again and bench sync etc... But why, if a sync is needed, would this problem suddenly rear it's head instead of being a problem from the outset? Sorry, lots of questions. Last few..., I purchased a replacement valve needle from cycle recycle online which is supposed to fit the bike. However it looks different than I remember the brass ones on the bike. The new one has what I would describe as "ribs" on the edges and also looks a little smaller. I know I have Hitachi carbs and I want to be sure this is the right part before I remove the carbs again. Could this all be a clogged jet issue? Will the RPMs race when the idle screw is set too far in or is that a stiction issue?

Note: Although this is the first time I have asked a specific question on XJBikes, all the terminology that I am hopefully using correctly I learned on this site before I joined. It has been a great resource and I feel as though I am painfully close to having the bike running well. Any help would be greatly appreciated.

-Marshall Chapman

 

Marshall,

I was having weird problems like you, and I just decided to put a few days aside and do a proper rebuild of the air/fuel system up to the point where it goes into the cylinder. From reading this list a lot, it seems that the petcock fails sometimes, the rubber boots that connect the carbs to the cylinder head get cracked, and of course the carbs need rebuilt due to dirty clogs. In most cases, a basic rebuild without rejetting is sufficient, or a sync.

You will be able to actually see the clog in the jet.

 

thanks jtalafous, I know that was long-winded.

Marshall

 

When you have a situation like yours ... where opening the Enrichment Circuit is necessary to keep the bike running ... the problem is most certainly related to Fuel delivery ... namely, ... the Carbs.

Bikes that aren't laid-up right ... ( and even some that are!) ... have the Jets and Passages get clogged-up with residue.
Cleaning it all out will be necessary to bring the bike back into tune.

 

Thanks Rick,

Your advice is much appreciated. I have read most of your posts and they all tell me what I need to hear but often don't want to hear. I'll tear 'em out agin.

I wonder if you wouldn't mind reviewing my post entitled 'pictures needed' and let me know what you think about my fuel/oil paranoia.

Thanks again.
Marshall Chapman
Bodymore, Murdaland, USA