xj rpm issues

[mav2]

hey all had the xj out for her first run today, have a small problem, the bike has an xs1100 engine in it, po of engine said the problem he had with it was 2 cyls cutting in and out on it, i had it out today, and travelling up the street in 3rd gear and all of a sudden no power at all, kinda like a flat spot, if i drop it 1 gear it will cut back in and go ok for a minute then same thing again..anyone have any ideas?

all the electrics have been changed, only thing the same as it was in the xs is the engine and carbs, the xs vacum advance is gone and the xj electronics installed..

could it be the carbs out of sync? had the carbs back off of it yesterday to repair air leaks on the carb mounts to engine(i forgot to install gaskets.lol)
new plugs installed, new plug caps.

[DGXSER]

ITs carbs somewhere. What RPM range does it occurr in? Is it consistantly in an RPM range?

The enginge itself is a pump, what gear or what RPM does not effect if it works or not. The fuel and the spark are what change RPM. If your certain spark is good, then I'd look at carbs for sure. Other option is pick up coil wires. Does it happen when you are changing RPM, adding or removing throttle?

[dbeardslee]

With two cylinders cutting in and out I'd check the pickup coil wires first. Resistance at the 4-prong TCI connector should be 720 ohms plus or minus 20%. Put a DMM on it at the connector, and jiggle the wires at the pickup coils. If the readings on the DMM change, check the wires for breaks. Might want to check the pickup coil gap as well. Spec is .7mm, but I have mine set at .56mm as the magnets are 30 years old. Of course that assumes the XJ electronics are the same as the XS.

[mav2]

cutting out problem,

was checking the tci unit, removed the cover and found a coupleof cold solder joints in there, one in paticular is the red/wht wire going to the tci, that one is definately a cold joint, and there are a couple more there that are likely suspects, so i guess i will sit down later tonite and rework the entire board..will keep you posted..

[trbig]

Of course that assumes the XJ electronics are the same as the XS.

Gonna have to rethink Guru status for you, my friend. After all this time on the board, we'll hear no excuses.

XJ electronics are a totally different critter. The pickups are solid mounted. Any advance or retard in timing is done electronically in the TCI from input recieved from a vaccum line attached to a boost sensor.

Now.. here's your hat. Go sit in the corner.


Tod

[trbig]

That is something worth checking.. that the vaccum line runs from your #2 carb body.. not the carb boot.. up to the boost sensor and is in good shape.

Tod

[DGXSER]

So the wires to the pickup coils in the XJ do nto get flexed like the XS do. Do they still break open like the XS do, perhps not as frequently though?

I believe the 81 has alot less of this due it having no mech advance, only the vac advance. But it still happens.

[TopCatGr58]

Hey Mav,

As has been "discovered", the XJ's ignition parts DON'T MOVE, no flexing of the pickup coil wires. But there's still the possibility of intermittent cutting out of 2 cylinders which could be caused by an actual bad PU coil, or cold solder joints on the TCI, OR a high tension coil going bad...like when it heats up, breaking continuity, etc.!?

But could also be fuel related. Do you still have the OCTY, vacuum lines to it could be cracked and leaking, and so when under low load, minimal suction to OCTY so not opening all the way restricting fuel flow. OR the OCTY itself could be fautly, stuck, etc. again restricting fuel flow. When it happens, you could try turning the petcocks to PRIME and see if the problem goes away!?
T.C.

[mav2]

vacum lines

That is something worth checking.. that the vaccum line runs from your #2 carb body.. not the carb boot.. up to the boost sensor and is in good shape.


is this the way it is supposed to be?, i know on my bike i have the vacum line from the #2 carb going to the octy, and the boost sensor is on #4 carb boot.could this be part of my problem??

[petejw]

Hi Mav,
yep, that could be causing you problems, connect the
boost sensor hose to the no;2 carb body, and the occy hose
to no4 on the carb boot nipple.

[mav2]

vacum

ok, will try that and post how it works..

[dbeardslee]

Tod - How long do I have to stay in this d@@@ corner, anyway?

[DGXSER]

Tod - How long do I have to stay in this d@@@ corner, anyway?

Yeah right.....like anything would get you to sit still longer than a second anyway.

[mav2]

coils

hey again, i just ordered new coils yesterday, the ones i ordered were DYNA
green which have a 3ohm primary,andi believe it was a 11 k secondary, will these work on my engine?xj1100?

[bikerphil]

3 ohm coils will work fine.