82 GS450 Loses spark after about 15 minutes

[Guest]

Hi all, ive been scouring the internet, manuals, etc for a possible cause to my issue. the bike starts up great, has new battery, runs great, and then will seemingly randomly lose spark when riding. it cuts out completely, backfires, and wont start for a minute or 2. it will crank, but not fire. looking for a direction to go in as far as checking components with a meter. i dont know if thi could be a R/R or stator issue, i dont see how they'd be related, but i'm not an expert. any help would be greatly appreciated. also, if anyone has any methods on testing the ignitor, i'd welcome it.


thank you

[Nessism]

R/R and stator is for the charging system, not for spark unless your battery is dead. Check the charging system for proper voltage but that's unlikely to be the problem.

Most likely your ignitor is bad. That is a common problem for the 450. Tons of discussion threads about that exact topic sitting in the archives.

[hillsy]

Could also be a coil breaking down as it gets hot.

[tom203]

Do posplayr's quick test and post results- your charging system might be interfering : best to rule it out.

http://www.thegsresources.com/_forum/showthread.php?164993-Charging-System-QUICK-TEST/page2&p=1272192#post1272192

[Gorminrider]

maybe

http://members.dslextreme.com/users/storagecliff/images/electrical_odd-n-ends.html#A11

Your shop manual may have a test for these too. PLUS, I do believe you and I share the same TCI "igniter". You will find tests for this igniter in the manual for "GS250T-300L '82 Service manual (70mb) here

http://members.dslextreme.com/users/bikecliff

[electronaut21]

quick charg test results:

battery - 12.8
battery with key - 12.5
idle - 13.1
2500 rpm - 13.7
4500rpm - 14.2
key off - 12.9

resistance in coils was within spec, before starting and after it died. resistance in pickup coils also in spec. wiring harness has no visible shorts, all connectors have been cleaned and checked for continuity(had one defective connector behind headlight, replaced). Im going to guess the igniter(ignitor?) is to blame here. i cant test it per the factory manual because it works as it should 95 percent of the time, and it isnt "broken" long enough for me to test properly.

being that i dont want to try and source a known good igniter, i've got a dyna ds3-3c on order. i understand theres some modification in order to get it to work. i'll run the coil relay mod with it, and hopefully this should solve the issue.

[hillsy]

Are you positive it's a spark issue and not a fuel starvation problem? Could be a blocked fuel tank vent.

[Gorminrider]

um. I'm not happy either, because symptoms do not neccessarily mean "ignitor" in my own limited experiences... I was merely trying to help per specific question and hoping it would pass it. but whatever,
Report back if the new thing fixes it.

[Nessism]

The 450 and 2nd generation 550's are both prone to ignitor failures. If this issue was occurring on a different model bike I'd suggest looking elsewhere but on a 450...

Incidentally, my first GS bike was a 450 and it had this same issue. Random spark dropping. Unplugging the ignitor and replugging it back in would typically get the bike running again. Never did solve the issue; the bike was wrecked shortly after going back into service when a left turner got me. At any rate, buying a Dyna S is money well spent in my opinion.

[electronaut21]

Are you positive it's a spark issue and not a fuel starvation problem? Could be a blocked fuel tank vent.

I've disassembled the gas cap, I didn't see any build up or anything. Also there's no hissing when I remove the cap after it runs for a bit. I think it's unlikely that there is a fuel issue, as I've rebuilt and synced the carbs, and replaced the petcock. Also when I try to start it immediately after it dies, there's popping from fuel entering the exhaust. It also backfires extremely loud if it cuts out when you're getting on the throttle.

[Gorminrider]

Well, ignition sounds more likely given a reputation for failing but while you are waiting on the Dyna...
Here's something maybe...inspect the pickups (under the small right hand cover). I recently found one in my spares that came unstuck. I could flip it up on it's side away from the trigger magnet. I epoxied it back to position.
Also, while you are there, inspect the wires where they go into the casing. Member UKJules had an "Intermittent issue" (But without the backfiring I think) and went through many hoops until discovering a chafed wire where it went through.
and maybe Advance weights? anything hindering them twisting the trigger magnet ahead? perhaps a wire in there is interfering...

I know, it's old ground well trampled by you, but I'm thinking simple things to narrow it down. Even the ability to make it worse is a big clue.. smells gassy? New Petcock? stock with the vacuum operation? Even if new, doublecheck and see if any gas is coming down that vacuum tube (by disconnecting it). You could also plug that hose with a dowel or something and then run the bike with petcock on "prime"(vacuum disabled=full flow).

If it gets worse, that'd indicate float needles are not sealing or vice-versa-(and less likely)stuck.