Coil issues with my 82 GS1000S Katana

[roy826]

She was running very good after the carb rebuild and tuning. Then all of a sudden last weekend it fired up cold like it was missing a cyl. I revved it once or twice and it cleared up. Passed it off as cold weather and a 40 year old carb motorcycle. Fast forward to yesterday here in the low 60's. It cranked and same thing missing a few cyls it sounded like. Number 2 and 3 pipe barely warm and 1 and 4 hot. Stupid me thought oh great my carbs have clogged up. So I pulled them, nope they were fine a little sediment out of the bowls on draining but nothing significant considering the original tank in still in good shape on the inside and I rode it 25 miles so far after sitting for 13 years. I do run a brass type in line filter. Gas was all new and non ethanol 87. Blew through all passages and nope not the carbs. Focus shifted to spark or fire. So I tested the coils with my limited youtube training on a multimeter and it appears if I am doing this right coil for #2 and 3 is not good. Coil for #1 and 4 marginal at best. Both are 40 year old oem coils. All of the wires have green stuff at their connections to the plug caps which are aftermarket NGKs. Oem caps gave up the ghost many many years ago and the NGKs have been rock solid to date. I also discovered the petcock was leaking a little with gas in on position which it is not suppose to so a diaphragm rebuild kit ordered for that. I honestly think the dark colored small sediment I saw in the float bowls was from the diaphragm disintegrating after the first gas flow from 13 years sitting. Nothing visible in the fuel filter housing of course. Don't even think it works.

So do I go back with Suzuki coils for $145 a piece and wait a month to get them or is there an alternative that easily bolts on and comes with the wires?

 

[Redman]

Good that you are aware of the plug caps.
you say they are solid, you measure ohms?
you say green stuff on wires at the caps, you try cutting off about 1/4 or 3/8 inch, and see if symptoms clear?

 

[Nessism]

Agree with Redman; snip off that green stuff and screw the caps back on. Better yet, replace the wires. It takes a little work, but you can pull them out of the coils. Maybe try sticking in a pick tool, along the edge of the wire and coil. Down about 1 cm. With the pick in, squirt some WD-40 alongside and wiggle the pick around. Then pull out the pick and do that 2-3 more times around the wire. Once you work a little WD-40 in there the wire should pull out. Be aware that there is a spike down into the recess so don't mess that up. Come time to replace the wires, get 7mm copper core wire. Not supressor core wire, because that stuff has resistance in it.

Good luck

 

[roy826]

Good that you are aware of the plug caps.
you say they are solid, you measure ohms?
you say green stuff on wires at the caps, you try cutting off about 1/4 or 3/8 inch, and see if symptoms clear?

Yes measuring ohms and I did cut off some wire on the worst one on #3 and it was still green stuff. #2 and 3 are the worst wires of the 4 at the ends with corrosion. Have not tested the caps them selves yet will do that. The rest is failing every test.

I suspected something was just not right when I first got it running back end of Dec it just felt flat and I thought it sounded like it was missing under acceleration but just could not remember that far back how it ran. It idled fine with the sync done to carbs and just purred sitting there and would blip the throttle nice just didn't feel right under a load going. It has been over 13 years since I last rode it and all my bikes now are high revving new bikes 2020 and 2021 models.

 

[roy826]

My coils are not passing the primary side test post to post before I even do the secondary testing into the wire end.

 

[roy826]

Plug caps range from 5.5, 5,6 4.5 and 4.7 lowest being the ones that were on coil for #2 and 3 cyl. Cut some more wire off wire ends and got to bare metal but I am still not getting a reading from the coil. The primary reading only flashes on the meter briefly and goes to zero on both of them highest reading I saw doing that was 2.36 meter set to 20k when I set to 200k I get nothing at the wire ends.

 

[Grimly]

Get a pair of Honda MT-08 coils. They were fitted to dozens of Honda models over the years and are pretty bulletproof. They have a primary resistance of 3ohms, so suit the GS and the bonus is they have totally replaceable HT leads, with a removeable cap on each lead. I've been running a pair from a CBR1000 for the best part of 30 years (came off a fairly new broken bike) and trouble-free.
My preferred source nowadays is Gold Wing GL1500 - wait for ebay to bring up a triple set for $25 or so.

 

[Cipher]

Plug caps range from 5.5, 5,6 4.5 and 4.7 lowest being the ones that were on coil for #2 and 3 cyl. Cut some more wire off wire ends and got to bare metal but I am still not getting a reading from the coil. The primary reading only flashes on the meter briefly and goes to zero on both of them highest reading I saw doing that was 2.36 meter set to 20k when I set to 200k I get nothing at the wire ends.

Its odd that both coils would be dead.
Are you doing the secondary with the caps off?

from you post the bikes is running yes? so the readings your getting on the coils must be wrong
change the meter battery maybe?

you should also check the output from the harness to the coils
pulsar coils go wonky too

 

[roy826]

Coils are off the bike. Yes secondary was with plug caps off. I have two meters both are in good shape with battery's and same results. Both coils had some greasy grimy crap come out of them at some point and it has hardened to the casing.

I gave up on the whole idea of checking the coils and ordered new oem $uzuki coils for it from my local dealer which come with the wires already attached and were in stock in the Cali and Penn. warehouses so a couple of days to me. Should have them by next week. My NGK plug caps seem fine I'll reuse them on the new wires. I am pretty certain the one coil for #2 and 3 cyl was dead the other was not far behind. Bike was only running on the #1 and 4 cyl. and that happened all of a sudden then cleared briefly then back to running on 2 cyl for good.

One other thing I'll add, the tach quit working completely when it started to run on 2 cyls. The tach on the 1000 Katana is not driven off a cable through the valve cover it is triggered through the wiring electronically.

 

[roy826]

Got my new Suzuki coils in yesterday. Made in Japan by Denso and very nice quality complete with metal mounting hardware. Weird part is the plug wires are like 2' long each so I guess I have to cut to proper length. Local dealer did both coils for $285 OTD. Not to bad.

 

[Redman]

I see you got new coils, so we need not discuss about coils.

about the caps: I would not be concerned about the slightly low readings, that is still about 5k.

my experince is that thier failure mode is to go higher resistance, like 20k and then 50k (weak spark) and then full open (infinite resistance, no spark) with age and use.

 

[roy826]

I see you got new coils, so we need not discuss about coils.

about the caps: I would not be concerned about the slightly low readings, that is still about 5k.

my experince is that thier failure mode is to go higher resistance, like 20k and then 50k (weak spark) and then full open (infinite resistance, no spark) with age and use.

Thanks for advice about the caps. I cleaned them up a little and plan to reuse them. I have not cut the plug wires to fit yet. I did get the coils installed and marked my cut lines on the wires. I plan to finish it up tonight hopefully. Fingers crossed it cranks up and runs on all 4 cylinders.

 

[Cipher]

Got my new Suzuki coils in yesterday. Made in Japan by Denso and very nice quality complete with metal mounting hardware. Weird part is the plug wires are like 2' long each so I guess I have to cut to proper length. Local dealer did both coils for $285 OTD. Not to bad.

Fast turnaround Denso is OEM supplier iirc.
The extra length is for wider applicability and that seems a decent price for two.
I assume your keeping it stock for a good reason.

 

[roy826]

Fast turnaround Denso is OEM supplier iirc.
The extra length is for wider applicability and that seems a decent price for two.
I assume your keeping it stock for a good reason.

Yes keeping it stock because it is 100% stock right now with only a Yosh full exhaust system on it. I have the original 4 into 2 black chrome exhaust but it is showing pit rust in the bends at 40 years old. The Yosh system has been on it 20+ years now and it is surprisingly in good shape overall. The bike has been kept stock its entire time. I did trim off the back fender 20 years ago and wish I had not now. I'll stay with oem parts until the day comes I cannot buy them anymore.

 

[roy826]

Coils were the ticket! Bike fired up and ran great even sounds meaner out the exhaust and the crappy tachometer is back working. Slight ticking noise coming from the tank but that may have been there all along. I only put a gallon of gas in it to get it fired up since I plan to have the gas tank repainted soon. Could the ticking noise be the new coils being picked up by the hollow almost empty gas tank sitting right on top of them? All of the spark plug caps screwed into the plug wire leads very tight and are in fully I made sure to get that right by taping off the depth needed. .Left myself plenty of future wire ends to snip off if and when I change out plug caps ever again. No more spitting and sputting when revved up she just screams up top now. Bad coils were killing the motor on this thing. I knew it felt kinda weak but being I had not rode it in 20+ years just couldn't put my finger on it. Still not 100% satisfied with the carb tune seems a tad rich at idle with the stock filter in it verses the old K&N drop in I had in it that fell apart cleaning it recently. So I went back to a paper stock element. May just be the air screw off a bit but I am pretty sure I have them all at 2 1/2 out now. Anything else in and I get a hanging idle after a blip. Currently it is fine on a one two blip but idle falls down a little then picks back up slowly. I'll work on that later once the weather warms here in 2-3 months time.