Got my XJ 750 Maxim X today !!!

OK..SO IM OFFICALLY AN OWNER OF A 2 WHEELED BOTTOMLESS MONEY PIT JUST LIKE THE REST OF YOU ! LOL

Its ALL original, nice shape, 10k miles, I puttered around the yard on it today,
most everything seems to work ok on it.... BUT....

IT HAS A SPOT IN THE RPM RANGE WHERE IT ACTS LIKE A PLUG IS MISFIRING OR IGNITION CUTTING OUT, PERHAPS THEIR IS A CYLINDER NOT FIRING OR FIRING RIGHT ...


ITS WORSE TILL THE ENGINE WARMS UP... THEN ITS ABOUT HALF AS ROUGH AS WAS COLD...

NEW PLUGS... STILL SAME...

SO WHERE DO I START TO DIAGNOSE THIS ?

AT THIS POINT, I DONT KNOW IF ITS FUEL RELATED, OR ELECTRICAL..

IT RUNS NICE, BUT THEIR IS A MISS OR SOMETING ...

THANKS IN ADVANCE.

OH..ITS MADE IN LATE 85

 

can you identify the cylinder that is missfiring, what color was the plug you took out? it could be as simple as you need to slightly enrich the mixture on that one carb.

 

WIZ,

THE PO CHANGED THE PLUGS , OIL BEFORE HE DROPPED IT OFF.. IT HAD BEEN SITTING UNDER A TARP FOR FEW YEARS. YEA I CHECKED FOR A MOUSE DOWN THE AIR PASSAGE...LOL.... IM WONDERING SINCE THE BIKE IS 22 YEARS OLD, PERHAPS THE PLUG WIRES ARE NOT SO GREAT... IM GOING TO PULL THEM OFF THE PLUGS AN CHECK FOR CORROSION...

IT RUNS SMOOTH BUT YOU CAN TELL THEIR IS A MISS OR ROUGHNESS
IN THERE....IT REVS UP AND DOWN OK OTHERWISE.

TOMMROW, IM GOING TO GET SOME GAS AND FUEL LINE CLEANER AND
SOME GOOD, HIGH OCTANE GAS, AND DUMP IT ALL IN THE TANK AND SEE IF THAT DOESNT HELP SOME....

 

better still, drain that old fuel, clean out the tank & filters, don't forget the beanie filters in the carbs, I recon you will end up pulling the rack & doing a propper clean.

 

WIZ,

HI.. What ive found out is that the miss is noticiable when the engine is cold, but after about 10 mins idiling and its warmed up good, the mis is
very small... get good revs, settles down to idle good, but you can tell there is a stutter in there somewhere....up and down the range.

I guess I have to wonder if the po actually changed all the plugs as he said, those inner ones look really hard to get to...LOL

I put a new gallon of hi octane , and a quarter bottle ( an ounce or so) of
liquid carb cleaner in the tank, maby ill add a bit more carb cleaner and
keep starting it up and getting it to running temp....

also am goin to pull each plug and check them... ( make sure they were
actually changed ) and check the wire ends to make sure the clip for the plug isnt corroded.

( I read on this GREAT WEBSITE AT GEOCITIES WHERE THIS GUY IS AN
XJ ELECTRICAL GENIUS... AND HAS ALL TESTS, TEST SPECS, PROCEDURES FOR TROUBLESHOOTING ELECTRICAL..ECT..FOR XJ'S )
that you SHOULD NEVER run an XJ with a plug wired detached as it CAN
DAMAGE THE SECONDARY COILS... just a FYI for you guys...


COULD BE WIZ THAT IF THIS CANT BE NAILED DOWN TO A BAD PLUG
WIRE OR SOMETHING MINOR OF IGNITION, THAT ILL HAVE TO DO THE
CARB RACK...


IVE HEARD YOU GUYS TALK ABOUT THESE BIKES THE TIMING CHAIN ADJUSTERS WEAR OUT QUICKLY...

HOW DOES ONE TELL IF THAT IS THE CASE ? IS IT NOISY ? OR MAKE THE BIKE NOT RUN JUST RIGHT ???

 

beanie filters in the carbs

WIZ.. CAN YOU DESCRIBE WHERE OR HOW ONE GETS TO THESE
BEANIE FILTERS... THANKS...SB

 

caps lock ftw
sry couldn't resist lol

 

yea my keyboard could use an overhaul, I HAVE A TENDANCY TO PICK IT UP AND POUND IT ON THE DESK WHEN THE PC ACTS KRAZIE...

 

If, as you say, the Bike has been sitting under a Tarp for some time ... it would be a wise choice to remove the Carbs and give them a well-needed cleaning.

Putting an ounce or two of solvent in with the gas is a waste of time.
What you need to do is remove the Carbs and get their individual components all cleaned and totally free of any foreign matter.

You can't really tune-up the bike without KNOWING that the Carbs are perfectly cleaned.
New Plugs won't cure anything.
Tweaking unclean Carbs will just make the situation worse.

There are some pretty-good articles on Carb Cleaning in our archives along with testimonials from those who have successfully cleaned-up their Carbs and got their bikes running tip-top.

You can too!

 

Hi sagebrush, I can't find a 1985 maxim 750, you sure it's not 700.
BTW Rick will tell you where the beanie filters are.

 

Wiz...

tons of guys on this forum have 85/86 750 Maxim X ..... it was simply not imported into the U.S.A. that year as there was a prohibition agianst any bike over 700 that year. Mine is from Hawaii, they were imported there, and then shipped to Canada and the rest of the world. They were made in late 85, as my frame indicates, and they are titled as 85 or 86 models depending on what country and time of original sale. Mine is an 86.

and your right...YOU CANT FIND THEM 99% OF THE TIME IN ANY BOOK FOR PARTS AT MOST CYCLE DEALERS OR REPAIR SHOPS... it DRIVES ME NUTTS.... I went to the largest cycle dealer in the largest city in Colorado and asked for a set of tires... oh they FLAT OUT TOLD ME I WAS
NUTTS.. THERE WAS NO SUCH BIKE.... I SAID OK, ILL BET YOU THAT SET OF NEW TIRES YOUR WRONG... MR SMARTY PANTS SAID OK... YOUR ON...
I SAID..WELL.. ITS PARKED OUTSIDE RIGHT NOW...AND HERE IS THE TITLE... LOOK...WEEP...AND THANKS FOR THE NEW TIRES....

WELL HE STOMPED OUTSIDE, LOOKED IT OVER REAL HARD, LOOKED THE TITLE OVER..COMPAIRED THEM....CAME BACK IN..GOT ON THE INTERNET..HUMMED AROUND THERE FOR A BIT... THEN SAID... OH HELL..
ITS REAL....

I THINK HIS BOSS WAS NOT HAPPY WITH HIM....

 

Beenie Filters?

The Beenie Filters are Screened Plastic Caps which are attached to the INSIDE of the Float Valve Bodys. They are supposed to be the last line of defense for keeping-out Foreign Matter from entering the Fuel Bowls.

They also act to allow the Fuel Supply Gallery to fill and uniformly allow the Fuel Bowls to refill rather than having the supply be unshared in volume as the supply passes-over opened valves when the engine is at cruising speed.

 

Beenie Filters-R-Us!:

fnv2) OEM and aftermarket Mikuni float needle valve SEAT FILTER SCREEN. These small domed mesh screen filters snap onto the top of the float needle valve seat and help to keep crud, junk, and other kinds of cosmic debris out of the carbs. These filter screens are included in the replacement float needle valve assemblies and lower end rebuild kits listed above; but, if you want to re-use your original valve seats, we still recommend the replacement of these screens. Fits all XJ550, XJ650 Turbo, XJ700-X and XJ750-X models, XJ900RK, and XJ1100 models.


HCP5193 OEM Mikuni float valve needle SEAT FILTER SCREEN, use one per carb, each:
$ 8.50

HCP5193SET4 OEM Mikuni float valve needle SEAT FILTER SCREEN, use one per carb, set of 4:
$ 32.00



HCP2735 Aftermarket Mikuni float valve needle SEAT FILTER SCREEN, use one per carb, each:
$ 8.00

HCP2735SET4 Aftermarket Mikuni float valve needle SEAT FILTER SCREEN, use one per carb, set of 4:
$ 28.00

 

I would do a Seafoam dose before diving into carbs. To clean the carbs and retune you need to invest in some special tools or attend a carb clinic. If the carbs are only a little gummy the Seafoam will sometimes clear it on out and make tuning worthwhile.