81 xj650 ycis missing or acting like hitting a rmp limiter

Hi
Ive got a 81 xj650 ycis with 63000km. I bought it and the last ower had pod filters on it. It seemed to miss at 3500-4000 rpm 5000-5500 rpm and 6500-7000 rpm. I removed the carbs, cleaned the jets and elmulson tubes which did not remidy the problem.

After seeing so many horror stories of the air Pods I ordered a used air box and installed it tonight. After a test drive the problem is still there. I pulled the plugs 1 and 4 have some what white tips and 2 and 3 are black.. 3 being the worst. I can get pictures If you guys think it would help.

The bike starts and idles fire. runs smooth when not acting up. :cry:

 

have you done checked your valve clearances, running synced the carbs, and colortuned it yet.

 

No not yet. I was kind of betting it was the pods causing the problems.

 

valves should be done every 5k miles and they often are left untouched so its a good thing to do on any new bike. If 2 plugs are whitish and 2 are dark your going to need to play with your mixture settings and get them all nice and medium brown. Also if you didn't do a complete job on the cards you might as well pull them an look up the whole 9 yards, the church of clean, and your carbs need to go clunk. Get them done the right way or they can give you a lot of trouble and of course after playing with the other adjustments you need to do a running sync. Get all that done and see where your at. Its a good idea to do a compression test and make sure you pull your rear wheel and check your brakes for delamination.

 

Don't remember the 81 being a YICS engine............

Dave F

 

I kind of thought the valves would have been done not too long ago. not 100% sure but the old man who had it said he always had regular maintance done. BUT I should check them to be sure.

As for the YICS, The production date is 7/81 my papers say its also a 81. The motor says YICS. It also has front air adjustable shocks too

 

I can get pics if you would like

 

production 7/81 is going to be a 82 model year check your 17 digit vin's 10th digit A = 1980, B = 1981, C = 1982, D = 1983, E = 1984, F = 1985, G = 1986.

you can decode your vin here http://xjbikes.com/Forums/viewtopic/t=14577.html

 

weird mines only 9 digit's long. 5N9 yep looks like its actually a 82 Thanks. BTW is there any common electrical problems that could cause my symptoms that you know off?

 

The 17 digit VIN did not go into full effect until the 83 model year. Most if not all 80-82 models will still have the shorty 9 digit VIN.

A production date of 7/81 could be an end of run 81 model. If the engine numbers match the frame. That could account for a YICS engine in an 81 model. If the engine numbers do not match the frame. The engine was replaced at some time.

Ghost

 

Ya 81 production could still have the short vin. Most electrical problems would either be more intermittent or more persistent across all rpms. these bikes do tend to have a week fuse box, a lot of us replace them with an atc fuse box.

 

If your bike had pods, check the jet #'s, it's possible he rejetted for the pods, so switching back to the airbox won't resolve that until the jet #'s are correct.

 

I know that the mains are 118's. i cant read the pilots. does any one know what sizes they should be?

 

And would it make a difference were i have a canadian bike?

 

pretty sure on these. the canadian/european bikes bike used a #112 and US bikes used a #110 main. Canadian used a #43 pilot and US used a #40.

so your bike appears to have been rejeted for the pods

 

well i think i will order some up monday. them and an sync and valve check are in order

 

Ok.
Check valve clearences, carbs go clunk, synced ( tho not a good one) and replaced the jets to stock jetting.

Still at 7000-9000 there is somtimes a "miss". Riders behind me say they will see puffs of Black smoke.

Im wondering if It could be a coil acting up?

 

oh and the fuse box has been replaced with inline fuses

 

Have you done a carb sync?

 

Black smoke is indicative of a rich fuel mixture. Since the po had pods, and jetted the carbs, it is highly possible that the holes in the diaphragm pistons were drilled, and/or the main jet needle changed.