Smithers XS650 Bobber

[Hans]

Bad spark plug?  Unlikely but known to happen.

[Dennis]

An advantage of a vertical twin with ignition that fires both plugs at the same time is easy diagnosis.  Paul and I switched both the leads and the plugs and still the left side would not fire. 

Guy came by last night and we switched the carbs.  Still not firing.  That left only something in the cylinder.  Paul and I confirmed that I had good compression.  Guy suggested it could only be the valve adjustment.  I assured him I had done it correctly when assembling the engine, but all of the above tests left nothing else.

I let the engine cool down and re-checked the valves.  The left inlet was way too tight.  At 11:30 I had back together and gave a quick blip of the electric starter and it started right up and purred like a kitten.  It did let go a pretty big Bang when all the un burnt gas in the exhaust went off.

I just have to install the gas tank and fuel lines, and check for all the un-tightened fasteners.  I have a plate and valid insurance (since last Friday).   I may even get out for ride night tonight.

Peace & Grease, Dennis

[stikman]

Good to hear.

[Hans]

Yay, pay no attention to the rain, it's gonna blow over.

[Dennis]

Saga continues.

In preparation for Ride Night, and having experienced about 3 seconds of the bike running perfect at 11:30 the night before, I plumbed up the tank and tightened all the loose bits.  Fired her up and ... back to one cylinder.

I limped down to the Dub and met the group.  Consensus was that if a little loosening of the valves made it run (even for only a few seconds), loosen some more and see if it helps.  I loosened only the left intake.  I loosened it .05 mm looser than the loosest factory spec for an exhaust valve (this is an inlet valve) so it would be nice 'n sloppy.  Still not working.

I am going to put the adjustment back to where it should be, .1 mm.  I am going to re-do the previous diagnostic tests; including switching the carbs again.  I may even see if a set of stock carbs I have fit in the new rubber manifolds and try them.

I stared at the bike for an hour just trying to think of something I missed.  I am really stumped.  One observation I made which may be a factor is the spark does not seem to be the nice bright blue "snap" that one wants when testing for spark.  There is definitely spark in both cylinders, and it is enough to light up the right side, but maybe I just need a bit more zap.  I don't want to chase good money after bad, but the only thing not new in the entire electrical system are the coils and wires.  I can get a new hotter coil and new wires. 

Other than the above, I am at a loss.

Peace & Grease, Dennis

[Qball]

It was sugested above, but try buying brand new plugs (even if you have new plugs ). Its a long shot but a cheap 15$ fix if it works.  Plugs coluld have just rolled out of the factory not quite right.  Ive only had it once but was hell figuring it out.  Plugs out of cylender would give spark, then put them in and they wouldnt.   Replaced them after a small fortune of other crap and she ran like a dream.  It was on my old xs400 i think.  Worth a shot anyways

[stikman]

I'd definitely want to try a set of good used coils that someone else either has kicking around or, preferably, off a running bike, not just buy a new set without a definite diagnosis.  Would also want to try another complete set of running carbs; new doesn't mean it ain't broke.  And the fact that someone has had their grubbies in that 'new' carb doesn't bode well.

I'd start with setting the valve lash back to what it should normally be, test ride to be sure, move on with troubleshooting.

Well known but oft not followed advice:  Only change one thing at a time.

Keep us posted on the progress.

[Dennis]

Q-Ball re: spark plugs.  I have tried new and new again.  However, I did read on-line that the next hotter plug is recommended by Pamco Pete, the maker of the electronic ignition.

Stikman: I will probably try my extra set of stock carbs if they fit the manifolds.  The XS650s had two different sizes over the years, and the set I have are the smaller ones used during the last few years.  I think my manifolds are for the larger ones.  I am not going to change the manifolds again.  Done it twice, after I could not get the new ones tight with the cheapo "factory" clamps.  I bought some better quality line clamps and they work great.

I can't just plug in a different coil.  When I wired the bike, I did not use snap in, snap out connectors.  I would have to cut and reconnect the wiring.

I will likely order up the new hotter coil in any event; simply because the one I have in it came with the bike, is 33 years old, and is the only used part in my entire electrical system.

Peace & Grease, Dennis

[Qball]

Ill run out to the shop here denis and see what i have, but i had a xs given to me last year.  Call my cell today (250)615-7789 im in town lat tonight so just call any time.  We will see if i can supply what you need for time being

[Dennis]

I'm pretty sure the problem is solved.  After much farting around and replacing the coil, still no firing on the left cylinder. 

I joined up with the Club at the BX Pub on Tuesday and relayed all of the latest saga.  With so much knowledge in one place, the general consensus was timing. "But it can't be" says me.  "Its a brand new electronic ignition timed with a timing light." 

While most present will want to take credit, it was Hans who had the Eureka moment, and figured the magnets in the new electronic ignition system must be in the wrong position.  Back at the garage with a case of beer and helpful friends, one of the two magnets was drilled out and moved to a different position.  After re-installing, the bike fired up and the left side worked.

Not quite the end of the story.  I followed up with an email discussion to Pamco Pete, the manufacturer.  He is great to deal with and answered my email to him within an hour.  The short version; the rotor is defective.  It is supposed to have  four magnets 90 degrees apart.   There are four holes, but there were only two magnets.  They are supposed to be north - south - north - south.  90 degrees of dwell, spark fires, 90 degrees nothing, 90 degrees of dwell, spark fires, 90 degrees of nothing .... repeat.

Pamco Pete has sent me a new (and improved) rotor.  Dwell is limited to 60 degrees to keep the coil from over charging. 

In his last email he figured my bike should not be running the way it is set up now.  Who knew?  In any event, I have the Ebay Bobber with a new electronic ignition and coils to install while waiting for my replacement rotor from Pamco Pete.

Peace & points, Dennis

[Donovan]

That's great news.  Who would have thought that the electronic ignition was at fault.  Too bad we could not have figured that out earlier as that would have saved you a lot of time and frustration.