Running hot then dying

[Beardy]

I have a 1982 xs650 Heritage Special and am having great difficulty getting it running properly.
1. It will start on the button but only with the choke closed, which is very unusual as it has always needed the choke fully open in order to get it started.
2. Engine runs perfectly at idle for about five minutes before it begins to stutter and backfire. When the revs are increased the backfiring gets worse until it eventually stops running and will not start again until it has completely cooled down.
3. When it is running it gets very hot in a short space of time even with a fan blowing at the engine.
Boyer ignition system getting signal from original pick-ups. New battery. Charging system OK. Good coil. Timing checked with strobe light and is OK. Wiring all checked and in good condition. Carbs spotless with 132.5 main jet and 42.5 pilot, mixture screw 3 turns out,diaphragms perfect, new boots installed. Tank cap venting OK. New petcock (non vacuum type).

Any help much appreciated.

 

[Paulrxs650]

Hi,

When you say it has always need the choke, what has changed since then. What have you done to the bike?
When you say Boyer is getting pick up from the original pick ups, what do you mean? The Boyer should use its own pickup plate installed in the left hand points hosing and it's own rod through the cam.
Is the intake exhaust system stock?
Have you changed the plug leads? They can degrade over time causing spark "leakage" when the engine warms up and eventually stop the spark.

 

[Beardy]

Thanks for the reply.

Everything on the bike is stock except for the Boyer. Pickup was fitted as per instructions but when the white dot was lined up with the hole the bike would not start however when the plate was rotated quite a bit it started but still had the symptoms as outlined previously. A "mechanic" connected the pickups on the stator to the Boyer in an attempt to get it running. New plugs, leads and caps fitted. Bike has not been used for about eight years.

 

[RcRider89]

run it till it stops and check for spark.

Comp check wouldn't hurt either. You say it's been sitting 8 years. How long has it run since?

 

[Paulrxs650]

Just to check, your timing too.
With the left hand side (sitting on the bike) cylinder on its compression stroke. The engine should be set to full advance - 40 degrees before top dead centre, then the white dot on the rod aligned with the hole in the pick up plate.
Can you explain a little more about A "mechanic" connected the pickups on the stator to the Boyer in an attempt to get it running.
As RcRiders says, when it stops a good check is to take the two wires that run from the Boyer to the pick up plate and with the ignition on, strike them together. This should make the Boyer spark.
Also check - are you charging the battery? check the voltage at the battery when running it should be 13 - 14v and rise when you blip the throttle.

 

[Beardy]

Thanks for the help.
New rotor, re-set ignition timing and voilà she is running beautifully.