misfire/stuttering and popping

Hi chaps new member here, recently bought an 81 xj 650 I live in the UK the bike is an import however not sure from where, I am planning a rebuild of the bike cosmetically. I have tried cleaning the carbs(very nasty) they have been stripped 100% and soaked for 1 week in cleaner, blew out with compressor, reassembled carbs checked float levels and refitted carbs. Bike ran but rough and very uneven on all pots. I have used a digi carb balance gauge at work to sync carbs, they are all now reading even, however there is running probs with bike. At idle it starts sweet and revs freely but with a slight mis and some popping after throttle returns, revs take some time to return to idle now and then. Under load the bike had no power under 3500rpm - spluttering and popping off throttle, talked to a friend that said lift the needles so I've popped some 1mm washers under the needles and it gained some power but the problem moved to the 4000-5500rpm range, plugs showed a number of different colours from jet black and sooty to bone white, drilled out the brass tacks from fuel/air mixture screws and found the no.4 was set to fully in,2-3 were set at 1/14 and 1 was set to 3 turns out, I have reset all screws to 2 turns out and rechecked the carb sync - all A ok but still runs badly, any help very welcome, main jet sizes 110 pilot 60 standard air box and a 4 into 1 micron with sports tail pipe. :roll:

 

-check your valve clearances and adjust if needed. This should have been done before the sync, and I see no mention. Beaucoup important.

-HOW did you "check" the float levels? If it wasn't by using fuel and clear tubing, (wet setting) then check the float levels.

-How "100%" did the carbs come apart? Butterflies and throttle shafts? Emulsion tubes? Enrichment plungers? Needle seats? If you didn't "uncap" the primary mixture screws until afterward, the carbs AREN'T clean. There're passages under those screws, plus they have tiny o-rings on them that probably need to be replaced.

-if you soaked assembled carbs in carb cleaner for a week, it's highly likely that you've horribly damaged the (trapped) throttle shaft seals.

-Is the airbox "connected" (are the airbox boots in place?)

-Does this bike have any mods to the exhaust or intake?

Or it could be ignition related but until all of the above has been confirmed it won't help.

 

airbox connected, micron 4 into 1 sports exhaust, trapped throttle seals? - bad with continental terminology but if you mean the vacum rubbers on the slides then they were removed, all jets removed, butterflies left in, bowls and floats washed and float needles washed seperatly. all passages blasted with air.

 

I had the same model a few years back so still have a set of coils will try and find them to fit, possible coil issue but more likely carb based.

 

Having similar issue with my bike, plus a runaway idle.

Looking like I have a vacuum leak with the throttle shaft seals (the shaft that the butterflies are in...one on the left and one of the right of the butterfly...seals the "rod" that holds the butterfly to the throttle linkage. 8 of these in total.). Just ordered my replacements. If you didn't remove them before the carb dip for a week, they are toast and will need to be replaced...along with any other rubber seal/o-ring that was left on.

You DID take out the mixture screws, right? (small screws on top of the carb bodies, on the same side as fuel enrichment and throttle. Intake side.)

Inside under those screws is a spring, washer, and TINY o ring, the size of the O on the computer screen. If that wasn't taken out, you will need 4 of those as well.

Better head to the church of clean. http://www.xjbikes.com/Forums/viewtopic/t=14692.html

 

found problem, the emulsification jet was buggerd in one carbs, now runs a treat, played with jet sizes alittle and she seems happy with 120 main and 45 side with 1mm lift to the needles goes well now, but I'm never happy so next week there is a ported 750 head going on along with some 750 barrels should go well.