XJ650 Maxim Running Issues.

Hi

I have an 82 XJ650 Maxim 44,000 miles. The bike starts great, first time every time but doesn't idle correctly, it hunts/stumbles. This is very noticeable while trying to slow ride, it feels like its missing, coughing, stumbling etc. Doesn't stall, just frustrating while riding slow or approaching junctions for example. However, once you get past around 2500rpm its like a different bike, it takes off and pulls all the way as it should. It really does go!

We've taken off the carbs, disassembled them, (didn't break the rack, left together) and throughly cleaned. Left over night in carb cleaner too. We set the screws to 3 turns out and bench synced.

The valves were also checked and adjusted and brought back within spec. New oil, New plugs, New coils. Sprayed wd40 and butane gas around the boots, no air leaks. YICS tool installed to block off ports and vacuum synced.

The bike wouldn't start at 3 turns out, we can get the bike to start at 4 turns out but was running lean (idle hunt). We used the colortune tool and set the mixture according to the instructions (blue, all the way to yellow then backed off until turned blue). This made no difference, we then tried the mixture set so there was a slight yellow tint, still no difference (idle hunting). (This was around 5.5 turns)

However at 5.75 the flame turns yellow, the idle revs do drop slightly but it smooths out and the revs are stable, the rev counter needle doesn't move up or down, no bouncing at all, its just stable. So we adjusted the idle back to spec 1050rpm and it did run great, but now it just randomly stalls / cuts out while slow riding. No missing or stumbling, just cut out. And you can smell and feel it burning your eyes if it was left idling in the garage. Too rich i presume? My concern is that should the mixture screw be wound out this far, is this normal?

Stock air filter, stock exhaust 4 into 2. Stock bike. Am i missing something? Any help or advice would be appreciated. One thing I have missed out is float levels. The previous owner had rounded the screws in the bowl and we are unable to remove them. These are untested. Could incorrect float levels cause the issues described?

Thanks.

James

 

Yes.

 

Ok. I see one major issue with what you had done to the carbs. Dipping them in carb cleaner without a full disassemble. Those shaft seals, if they wern't leaking air before, I'm sure they are now.

Everything you have done, turning idle mix out to 5+ turns, with stock intake and exhaust, tells me one of two things could be wrong. Shaft seals are bad. Or your boots beteen the carbs and head may be leaking. Either way, you are overcompensating fuel enrichment for a volume of air that should not be going into the motor.

Sounds like a vacuum leak issue to me.

 

What exactly did you dip the carbs in?
Did you check the throttle shaft seals following the dip?

 

Hi

Thanks for the replies,

Sorry no I left the rack, I did spray some carb cleaner through it and wipe clean, I left the jets and internals to soak overnight in carb cleaner.

So throttle shaft seals possible leaking, maybe before the clean and having sprayed some carb cleaner through most definitely will leak now?

The intake boots are ok, these do not leak.

 

I see a clue (maybe). When you put the jets back in did you follow the manual? The reason I ask is because some of the jet positions are mis-identified in the shop manual.

Quoting Rick since he says it better than I.

And re-check your float levels (wet).

 

Hi

Yes the jets are all in their correct places. I'll take the advice given and set the floats, just need to work out how to remove the screws, they appeared to have been rounded.

Also, where can I buy the throttle shaft seals, I am unable to find these online.

Thanks again

James

 

Send a PM to Chacal.