72 XS2 back fires out the left carb

[Jdove]

HI all,

Bought 1st xs650 trying to get it road ready. It start easily cold (no choke) and idles well 1100 rpms, until warm and then shuts off. When I continue to kick it, it back fires out the left carb and pops the carb out of the boot. This has now happened twice in a row.

Since I got it approx month ago I have put on coil, wires, plugs, pamco ignition, pma, carb boots. I have cleaned the carbs, set float height. I am running pods with straight pipes. Jets are 135 main and 42.5 pilot. Mix screw is 2.5 turns.

I checked/adjusted cam chain, valves, timing, bench synced the cabs with a piece of paper to get it going. Fixed small tear in left diaphram. Checked for air leaks around boots and throttle with quick start, no significant an't change in idle.

Tried to set idle/mix with DCM however it will not run on one cylinder. Also it will not run long or reliably to sync with monometer yet. I am thinking I am running rich (plugs are black). It is running hotter on the right side. I am wondering what to change/check next.

Any advise would be appreciated.

ThanKS
JDove

 

[figure8]

I'm a little lost. You said one cylinder isn't firing but then said one cylinder is running hotter than the other.

My mistake, dcm meaning dead cylinder method. Try swapping the spark plugs wires to see if anything changes?

 

[Jdove]

Both are firing, however the right cylinder is hotter (approx 30 degrees). Took temp with infrared temp gun below plug. The bike runs good from cold for 5 to 10 minutes, then dies out.

If I try to to restart hot, it back fires out the left carb and pops the carb out of the boot.

 

[TwoManyXS1Bs]

Welcome to the forum, jdove.

...Mix screw is 2.5 turns...

If you indeed have '72 carbs, that's quite rich. Normal starting point for '72 carbs is 3/4 turn out.
No wonder it starts without choke.

Download the carb guide from this thread, and double-check your carb settings.

http://www.xs650.com/threads/carbs-carburetors.43/

 

[Jdove]

I turned the screws to one turn only. It started with choke and ran well for about 5 min and shut off.

I checked spark - OK, plugs black but not wet. After a break and a few kicks it started and ran OK.

No backfire, and carbs still on bike.

I am using a temp gas tank (metal water bottle), hanging off the handle bars. I think adequate fuel flow may be part of my issue as well.

Next I am going to take a stab at syncing the carbs with a manometer.

Thank you for the advice.

JDove

 

[Orion61]

Your points need to be set on your left lung, A good rule of thumb is backfires out of exhaust= retarded timing, pop out of Carb = too far advanced timing. I idles fine until it is warm, that is where everything tightens up seats and those backfires are enough to interrupt the Right cyl keeping the bike running! another 2 things it could be, COIL getting bad, if a coil is getting bad sometime they will fire until they get hot. Also your left condenser could be bad. It sounds like you are new to the XS/TX650, you know where the points are located? (under the chrome cap upper left cyl) sorry if you knew but just trying to help...
1st thing, check Gap and timing, 2nd swap coils and/or condensers....
Of course your carbs can make a difference and you said you had some damage to the diaphragm, a lean running carb will also cause carb pops..
Good luck,
Cousin Larry