1982 GS450TZ - stalls when hot

[Thumper88]

So I just got my bike in road worthy condition...or so I thought...

Been searching these forums for hours soaking it all in, this is my first bike. I've been to BikeCliff's web site, seen his welcome post a thousand times (so it seems), and have been through this bike literally front to back. Usually work on cars, and pretty good at it. Details are key, and I like to take my time to do it right the first time.

I rewired a lot of the electrical (PO thought he was a master electrician - wire tied and taped up). Installed Blue Seas fuse panel, relays for ignition coils, high beam, and low beam, Shindengen FH010 regulator, ElectroSport stator (wired direct to the stator and to the battery through the fuse panel) new starter relay, 8 gauge wire to starter and engine ground (10 gauge to fuse panel - which powers everything else). All of that installed on custom panels -- hidden behind stock covers.

Cluster bulbs all replaced with LEDs, even the shift indicator. LED front turn signals and rear taillight (made for an RC51). New 7" Xanadu headlight (bigger bucket than stock--nice) with H4 Silverstar bulb.

New EBC pads and shoes, bleed the front brake, drilled front rotor from gs650, new bearings in steering stem and both wheels, new front and rear IRC Durotour tires, new o-ring chain, new sprockets (stock ratio), rebuilt forks with progressive springs.

Rebuilt top end, new head from parts bike--had bad exhaust valves, all new gaskets, new viton valve seals, dropped oil pain to clean it out, adjusted valves, adjusted timing, rebuilt cam tensioner, new NGK B8ES spark plugs and caps, 170 psi compression on both cylinders...

BikeMaster Daytona handle bars, Yamaha R1 grips, new headlight switch, and new levers.

Bike starts up great, has K&N pods and chopped stock pipes (wrapped) with slip-on Emgo mufflers. Jetted the carb (6sigma kit) -- 127.5 main jet, 3.5 turns on both adjustment screws, about half the height of stock spacer for needles (made a huge difference), and cleaned thoroughly. All new O-rings from cycleorings.com and synced them.

The only stock electrical is the ignition....coils, pickups, and ignitor.

Eventually I'll get to paint and details like that...but right now I just want to ride it...been working on it for a solid week...

Took it for its first test ride today (antsy to take a ride with my recently acquired cycle endorsement--bike not registered yet). Ran great until I made it about two blocks away and then it started to sputter and eventually stall.
Hit the ignition cutoff switch for a while, tried again and it fired right up (not until I waited for a while). Got it home and pulled right up to the garage and stalled again. The less time I waited, the faster it would die. Trying to start it right away would just result in some nice loud exhaust pops.

Now I suspected ignition coils, I touched the right side coil and it was scalding hot...
The left side was noticeably cooler....still warm, but not nearly as hot...sorry didn't have my infrared thermometer on hand so no exact measurement.

I think I have a bad coil, only happens when it gets warmed up and I drive it around (higher rpms--coil firing more often )...it will idle all day long (worked fine while syncing carbs). What do you guys think? What are my options as far as coils go? What's the best? I plan to use this during my final semester at the University of Michigan (electrical engineering)...so it needs to be reliable. It's definitely getting fuel, brand new petcock and hoses. Pretty sure the exhaust pop I'm hearing is the result of drawing in fuel and then the coil finally makes a connection and fires.


Here's a few pics of the beast...

[tom203]

Very nice looking. Make sure vent in gas cap area isn't plugged; did you test new petcock for correct operation . Measure primary and secondary resistance of both coils and compare- odd that one is getting so hot so quickly- are you sure that kill switch and key are turning off power to coils?

[Thumper88]

Vent definitely not plugged, gas was leaking out as I was changing out the petcock.

Confirmed petcock operation.

Will have to measure the resistance of the coils and see the results.

Kill switch definitely works, I can hear the relay click on and off.

[pete]

High resistance can definitely cause heat, and Tom's probably onto it there I reckon.

It could be as simple as the plug caps for the spark plugs are old and crappy.

They're cheap to replace with NGK ones, just trim a bit of the spark plug lead and put new plug caps on if that's the case.

Definitely sounds like you've done a good job on the rest!

[Thumper88]

spark caps are brand new, NGK

[tom203]

I missed all the relay stuff. Since you are an EE, why not hot wire the ignition system ( coils to battery direct) to bypass everything and see if problem disappears .

[hjacobmiller]

R/R? any idea of what your system is charging to? With a new stator but a shoddy R/R it might be running too much through it. It'd be worth checking anyways just make sure youre not going to fry anything else up.

[Thumper88]

Got some used coils off of eBay. Installed both of them, started it up and left it running. Got my gear and was walking up to the motorcycle and it stalled out.

Checked the signal generator, both coils ohmed out to be good.

Pulled the plugs out, left side keeps sparking, but the right side doesn't do anything.

Mentioned in my first post that regulator is Shindengen, and it works well.
Coils are getting power direct from battery via relay. Double checked output of relay, and they are getting power.

Have to test it on the bench (with oscilloscope and signal generator), but looks like I will be building an igniter.

Not sure if I mentioned it before, but previous owner experienced the same problem.

[jfman]

Took it for its first test ride today (antsy to take a ride with my recently acquired cycle endorsement--bike not registered yet). Ran great until I made it about two blocks away and then it started to sputter and eventually stall.
Hit the ignition cutoff switch for a while, tried again and it fired right up (not until I waited for a while). Got it home and pulled right up to the garage and stalled again. The less time I waited, the faster it would die. Trying to start it right away would just result in some nice loud exhaust pops.

HA ha! Same exact scenario with my 1983 30 minutes ago. I put a battery in it today, cranked right up. I rode 4-5 blocks then it quit running at idle. Wouldnt start back up.. I let it sit for 5 minutes then let it roll and I bump started it but I had to hit the gas and keep it revving otherwise it will die.

It seem to run great at WOT but as soon as I have to slow down it stalls.

I had to make it home while reving it at 5k the whole way.

I think it's a a carb issue... and I'm def not in a carb pulling kind of mood tonight.

will pull the plugs tomorrow.

I'll keep up posted with info as I fix mine.

[pete]

Got some used coils off of eBay. Installed both of them, started it up and left it running. Got my gear and was walking up to the motorcycle and it stalled out.

Checked the signal generator, both coils ohmed out to be good.

Pulled the plugs out, left side keeps sparking, but the right side doesn't do anything.

Mentioned in my first post that regulator is Shindengen, and it works well.
Coils are getting power direct from battery via relay. Double checked output of relay, and they are getting power.

Have to test it on the bench (with oscilloscope and signal generator), but looks like I will be building an igniter.

Not sure if I mentioned it before, but previous owner experienced the same problem.

I've long suspected that the issue with mine dying was the capacitors drying out after 30 years in addition to the likely overcharging that has gone on at some point as all GS' seem to do that at some point with the original stock R/R's.

My attempts at adapting a pair of GM style HEI module's ended up nowhere and I ended up with a Dynatek DS3-3C kit in there... it's awesome

Good luck!

[pete]

HA ha! Same exact scenario with my 1983 30 minutes ago. I put a battery in it today, cranked right up. I rode 4-5 blocks then it quit running at idle. Wouldnt start back up.. I let it sit for 5 minutes then let it roll and I bump started it but I had to hit the gas and keep it revving otherwise it will die.

It seem to run great at WOT but as soon as I have to slow down it stalls.

I had to make it home while reving it at 5k the whole way.

I think it's a a carb issue... and I'm def not in a carb pulling kind of mood tonight.

will pull the plugs tomorrow.

I'll keep up posted with info as I fix mine.

Try popping the fuel cap next time it happens... if the breather vent is blocked it will starve the carbs of fuel after a while...

[jfman]

removing the fuel cap had no effect...

I pulled the carbs and the pilot jets were clogged. The bike ran on choke because the choke enriches the mictures but whit the choke off the bike was getting no fuel at all unless I gave it throttle.

[pete]

That'll do it every time...

Glad you found it

[Thumper88]

Got the oscilloscope out and hooked it up to the signal generator coils, made sure everything was good there. No loss in signal, so those checked out good.

Then hooked it up to the coil outputs of the igniter. The left coil output stayed strong and steady, but the right coil output started to decrease after a short time...to nothing. Suspicion confirmed, igniter is toast....at least one side of it is.

I happened to have a plate off of a parts bike. Low and behold it had an igniter on it, but all of the wires had been cut...almost flush.

Tested the bad igniter with my 2ch digital signal generator, hooked up to coils and spark plugs. Same results as on bike, although a lot quicker because I was firing them faster.
Tested the "new" igniter, kept sparking away...looking good.

Anyways, I clipped the harness off of my bad igniter and soldered/heatshrinked it to the "new" one. Raining outside and after midnight here, but the bike is running. Have to take a test drive tomorrow (today?), but if bench results say anything, problem fixed.

Still plan to build my own, but this will do for now.

[pete]

Bugger on the ignitor but do a search for Kokar's thread on his ignitor. I believe it's electrically the same as ours but the harness connector is different, so should be a swap in.

I personally went with a Dynatek DS3-3C kit and am very happy with it.