Topic: Bizarr Issue long read please help!

[veloracermike]

So a couple weeks back I took my 350F out and had an weird issue with what seemed like the bike was running out of gas.  It had been sitting for about 4 days.  It started fine and ran great, I had to run up to the north part of town so I took the freeway.  About 8 miles into a 10 mile trip the bike began to miss at anything past 3/8 throttle.  I got off the freeway and made the rest of the trip on surface streets nursing it along.  I arrived and was at the place for about 20min.  Came out and the bike fired right up.  Rode it about two blocks revving it with full throttle and it was fine.  Came to a stop light where it idled perfectly.  I revved to to leave the light and it just fell on it's face.   I couldn't get it past 1/4 throttle. I was around the corner from the shop I use so I nursed to the shop.  We tinkered with it for about an hour and at that point I just left it at the shop (while I was there we put in line and took out the inline filter/checked the breather/checked the flow out of the tank all were good).  Three days later he called and told me that A) my floats were adjusted to the wrong amount (too little flow) and that one of my exhaust valves was nearly closed (I really don't undersand how).  Now the last time I had rode the bike (4 days earlier all was fine).  He said that he took the bike out for several hard runs and it was perfect.  I was away on business so I picked it up yesterday and this is what happened.

The shop is about 4 mi from the freeway.  The bike started from dead cold easily and idled like a clock.  I let it warm up and instantly noticed that the bike was running better than ever.  Perfect throttle response in all rpm ranges and just nice smooth delivery.  It's the best it's ran since I got it...just perfect.  I get on the freeway and just nail it through the gears and get it up to 70 and hold it there for the next 8 mi.  I come up on some traffic and roll off the throttle and then back on, when I get back the bike kinda hiccups then clears out for about a mile then it starts to sputter again and right back to where it was when it ended up in the shop.  I call him and tells me to let it cool off over night and try riding it again this time with the gas cap open.  So this morning I do that.  Bike fires right up, let it warm up, roll out of the neighborhood and again just brilliant. Bike is like a swiss watch.  Get out on the highway and for about 5 miles the bike is just awesome then it starts to sputter and runs like crap again so I limp it home and in the garage it sits.  I'm calling my mechanic in the morning but I'd like to get some feedback before I do...any thoughts?

[nancy]

Putting aside the carb issues - which may very well be at the root of this still - I would also suspect ignition coil and possible failure being imminent of one of them. Symptoms of ONE of mine failing - starts and idles OK, but any throttle opening sees it go no faster- bogs down and will not suddenly "come right" if you screw open the throttle. With mine..I forced the throttle wide open and held it there 3-4 secs...no response - it felt like 2 cylinders. It was as it happened. Stopped..started off again, same symptoms. Next thing - BANG from front of engine followed by very bad and noxious smell. Oh oh. Pushed it home. Coil melted.
Also check HT leads and plug caps for bad connections. Check for size, shape and brightness of sparks when plugs out with caps on and plugged earthed to motor - push starter. Weak or dying coil may show weaker sparks on those 2 plugs.
Mark

[veloracermike]

Thanks Mark I'll check the coils. The weird thing is how it runs fine for 15-20 min then it goes off   I should add that it has a Pamco ignition

My inclination is electrical I was thinking low voltage but the electric starter is fine and the battery is fully charged/charging


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[veloracermike]

Okay just pulled the plugs, all were a very good color of brown and pretty even across the cylinder's.   I'd have to guess if the coils were failing I'd see some black wet plugs no?

[Retro Rocket]

Coils or condensers, i have had coils fail on me only when they are hot, same with condensers ,  its not that uncommon a problem...

Its an easy job to swap in another set of either just to eliminate them as a possible problem...

[Stev-o]

Do you have electronic ignition? If yes, it may be getting hot and causing the issue?

[veloracermike]

The coil theme is beginning to take shape  Just got to get my hands on some extra coils.  Pamco ignition so no condenser.


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[bjbuchanan]

Its a bike not a car but if it was a car that would be the exact symptoms of a bad coil. Good and crisp til it gets warm the blah, death. You have 2 coils so the effect is minimized and you can still actually ride. My theory atleast

[Duke McDukiedook]

Your pamco could be failing when it gets hot or the coils. Check your gas cap vent and blow it out with compressed air.
If your tank is clean get rid of the inline filter, it will just cause you fuel problems and not help anything, all it does is restrict fuel flow.

[veloracermike]

Your pamco could be failing when it gets hot or the coils. Check your gas cap vent and blow it out with compressed air.
If your tank is clean get rid of the inline filter, it will just cause you fuel problems and not help anything, all it does is restrict fuel flow.

Checked the cap and that's definitely not it. Tanks is near spotless and no inline filter. 

If it is the ignition or the coils shouldn't I be seeing one or more plugs looking black and wet?  All four off my plugs are near perfect in color with number one slightly lean.

[veloracermike]

Well kids I think I found the issue.  It was the coils but not overheating or a coil going bad.  I tried a few things this morning and did some runs with no change in symptoms.  I decided just for the hell of it I'd check all the connections.  The bike has a custom wiring harness so it's pretty straight forward.   I unplugged and plugged everything ignition related and took it out for several high speed runs. Zero sputtering.  Then I took it out for about 45min for around town riding and the bike runs just great.  So it was coil related  in the end.  Really appreciate all the help, the coil direction was a big help.

[lucky]

Okay just pulled the plugs, all were a very good color of brown and pretty even across the cylinder's.   I'd have to guess if the coils were failing I'd see some black wet plugs no?

Coils almost NEVER fail.
Connections to them can be poor.

[sniper1]

I just had the same issue with '75 550, I replaced the coils with Dynateck and problem solved. I tought it was the condensors also, but nope, definetly the coils.

[Duke McDukiedook]

Your pamco could be failing when it gets hot or the coils. Check your gas cap vent and blow it out with compressed air.
If your tank is clean get rid of the inline filter, it will just cause you fuel problems and not help anything, all it does is restrict fuel flow.

Checked the cap and that's definitely not it. Tanks is near spotless and no inline filter. 

If it is the ignition or the coils shouldn't I be seeing one or more plugs looking black and wet?  All four off my plugs are near perfect in color with number one slightly lean.

You said inline filter, did you mean the tank filter? Big difference between the two.

[City Boy]

Hey.Good news that you found the problem.I was taught a good line to remember when chasing electric gremlins.In order of likely suspect  1-connections 2-wires 3-components.   Congrats and Rock On

[Retro Rocket]

Okay just pulled the plugs, all were a very good color of brown and pretty even across the cylinder's.   I'd have to guess if the coils were failing I'd see some black wet plugs no?

Coils almost NEVER fail.

Lucky, the simple fact is that they do fail, i have had them fail and they have done on this forum previously and i have no doubt they will again, try being a little more helpful....

[Duke McDukiedook]

Okay just pulled the plugs, all were a very good color of brown and pretty even across the cylinder's.   I'd have to guess if the coils were failing I'd see some black wet plugs no?

Coils almost NEVER fail.

Lucky, the simple fact is that they do fail, i have had them fail and they have done on this forum previously and i have no doubt they will again, try being a little more helpful....

Same here, I have also had a a bad new coil I bought, it was Taiwainese crap so I got what I paid for but it was NEW and BAD.

[veloracermike]

Well regardless of the rate of failure had you guys not pointed me in that direction I'd still be chasing non-existent carb issues. So thanks again!


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[ADW]

Coils or condensers, i have had coils fail on me only when they are hot, same with condensers ,  its not that uncommon a problem...

Its an easy job to swap in another set of either just to eliminate them as a possible problem...

I'd agree with RetroRocket. I've had condensers cause exactly the same problem before, the bike idles nicely but won't take any throttle. Replaced the condenser and everything was fine again. And condensers are certainly much cheaper than coils, so worth trying that first.

[veloracermike]

Coils or condensers, i have had coils fail on me only when they are hot, same with condensers ,  its not that uncommon a problem...

Its an easy job to swap in another set of either just to eliminate them as a possible problem...

I'd agree with RetroRocket. I've had condensers cause exactly the same problem before, the bike idles nicely but won't take any throttle. Replaced the condenser and everything was fine again. And condensers are certainly much cheaper than coils, so worth trying that first.

Funny thing, I was just reading through the lastest issue of Motorcycle Classics magazine and in a carb rebuilt article they say "99% of carburator issues are electrical"