New Coils, no spark at 1 and 4. Narrowed down to CDI (maybe?)

[Tashields21]

EDIT: replaced ignition with Dynatek S, now have spark at all 4 plugs. Shifting focus to figure out why fuel isn't making it to the plugs, I will crank the motor several times and plugs are dry.

New to the GS scene! or 80's bikes in general for that matter. I'm sure this post will reflect that though . I bought a 1982 GS850G about 2 months ago and have been chasing issues since day 2 or 3. I don't have a natural mechanically inclined brain but I like to learn, can use a search bar and never need told twice. My skills are minimal, basic car maintenance is no issue, I have basic tools and a multi-meter. My day to day revolves around residential construction. I did own a 2008 yamaha r6 years back but never had to mess with it outside of cosmetics. Anyway I spent most the of the afternoon on this forum seeing if I can solve my issue through someone else's misfortune but I am throwing in the towel and asking for help. But first a little (actually alot) of how I got to this point.

I bought this bike on marketplace, the previous owner started the build from a box of parts during Covid and finished it this past winter and from what I understand he barely rode it before I got it. This was a custom cafe style build. Very little original wiring remains. It was fitted with a Moto-Gaget m-unit blue with a minimalistic wiring setup, headlight, speedo, turn signals, brake light, plate light. He me he never opened the motor. New battery and regulator/rectifier (i think), new ignition coils. CDI is original or at least OEM. Push button start using phones Bluetooth. Mikuni CV rebuilt carbs jetted for pods. Hopefully that's all the relevant stuff...

So I ride the bike before buying and its real snappy, has great pull. I remember being impressed for a 40+ year old bike, but hell I have no other reference. After 40-50 miles I realize the 40 amp circuit breaker was shorting out, looked like a cheapy from amazon. I went to the local auto parts store and replaced it with a 30 amp fuse, during all that I notice the wiring wasn't to the m-unit specs so I moved a few things around to make it right. Bike fired up after that.

Went to go for a spin but the bike would die when put into gear with clutch lever pulled, also would not roll in gear with clutch lever pulled and motor off. After a little research the clutch cable needed adjusted. Did that, no big deal. Went to ride again and made 1/2 mile away and ran out of gas... I coasted down the hill back to my house (thank god I went that way!) After getting gas I realized the fuel filter was dirty, I'm guessing from the vacuum of me attempting to start it without gas. Back to the store, new filter, flushed the tank as best I could (didn't look rusty) and put it back together.

Another attempt at riding this thing. At this point it started just fine but ran absolutely terrible. High idling and surging at no recognizable pattern. rpms would hang when revved. Bike wanted to die at low rpm when on the throttle, throttle response was terrible and there was maybe half the power output there should have been. It felt like there was a heavy load on the whole system. Automatically I assumed gunk got in the carbs from when I ran out of gas. By this time I had realized the pod filters on there were absolutely terrible, at one point one fell off when I was pulling it out of the garage. Plus I learned those cheap filters blocked critical ports in the cv style carb. So instead of spending the money on nice filters I went straight to upgrading the carbs to Mikuni round slides from Murray's. Looking back, yes I was going to get the round slides eventually but I don't think that issue was carb related.

The carbs come in, I install them and the throttle cable everything went pretty smooth with the exception of my friend arcing the carb body with something else hot on the bike (stupid me for not removing) but I could not tell what it arced with and everything looked normal in that area. Everything installed, the bike cranks but no start. After multiple attempts I crack one of the bowl drain plugs and gas started trickling out so I tightened it back up. At this point I am feeling pretty defeated and give it a rest. Last week I go out and check for spark. 2 and 3 have spark but 1 and 4 do not. I remove the coils from the bike to inspect and the one feeding 1 and 4 has a good size split in the body and some other cracking going on. Without testing anything I just assumed that was it. Off to the parts store I go. 2 new coils, same ngk plug boots. Even with them being new I tested for resistance, both primaries were 4.2 Ohms and the secondary's were 22.6-24.2 Ohms (two different sets of plug boots) Go to start it, still just cranking and still no spark at 1 and 4. Oh, and all the spark plugs are good. I swapped them and same issue. More research, I check the resistance of the pickup coil witch is .31 @20k Ohms which from what I read somewhere else is in spec?

Damn that felt like alot! But I figure more info is better than less. Anyway, what would be some next steps or tests for me to run? Everything I am reading is pointing to the CDI but I have learned relatively quickly that things are not always as they seem, especially with my current knowledge base. Bike will not start at all, even with spark at 2 and 3.

Thanks in advance guys. I look forward to learning!

[ukjules]

That's a few issues !!!
Ill have to think on this as have had similar impossible issues in the past.

Seems a shame you have bought new carbs when you could have stripped and cleaned the standard originals ? I prob would not have done that.

But issue at hand is no spark - that's to fix first (while you are stripping and cleaning the original carbs)
Pickups all way to coils to check then.

Can't remember the coil checks but you say the test ok .

I am sure someone else will jump in on this but I will have a think.
Pick up test ok ?
Swapping coils make any difference?

[tom203]

Well, you said it rode nicely before your purchase, so what happened later?
while we contemplate this, tell us what ignition system this bike has….there seems to be two OEMs.
Remove the signal generator cover, and see if you have a mechanical advancer setup or….

[Tashields21]

EDIT: Tom, I have a mechanical.advance setup.

I'm still at work and not familiar with the different ignition systems, until i learn here is a picture of the signal generator (I think? If it's the same as the pick up/pulse coil) Screenshot_20240528_165511_Gallery.jpg

[chuck hahn]

Put a dynatek ignition on and be done with those pickups and the igniter box.

[ukjules]

I think we need a status check in snappy readable form as your initial manuscript is so long I cant keep going back.

When was last time.bike was fine ? Think was fine until you ride it 2 days after buying ?
Compression ? Can you check ? Useful to know anyway
Petrol getting through on all cylinders ?
Spark ? 1&4 no spark you say
Carbs setting ? (Clean those original carbs !) Mad to buy new carbs at this stage but I don't understand the type you bought .
Do you have original air filter for original carbs ?
What filters do you have on new carbs ?

- what's this :
Push button start using phones Bluetooth.

- test pickups
- when the coils failed did you swap them over to see if the other plug sparked? Or just buy new ones after bench testing ?

[tom203]

Ignition coils are tough…..not sure why it cracked but since it’s connected to the ignitor box - a very weak item- the 1&4 part of ignitor would likely be gone.
Do you have the stock fuse setup ….or did this get replaced with the 40/30 fuse setup ?
Since you have the mechanical advancer setup, I’d probably do what chuckhahn said , to simplify things.
used eBay ignitor boxes are very suspect.

[Tashields21]

It started to run bad after the clutch cable adjustment/running out of gas and swapping fuel filter (all same day). That was a week or so after I bought it. Before that, it ran good minus the issues i had with the short in circuit breaker that I swapped for a fuse. Here is my description from my original post on how it road. "High idling and surging at no recognizable pattern. rpms would hang when revved. Bike wanted to die at low rpm when on the throttle, throttle response was terrible and there was maybe half the power output there should have been. It felt like there was a heavy load on the whole system."

I do not know if there is compression or if gas is getting to all cylinders. I will look into those!

At this point I don't plant on going back to original carbs. I will post a picture of the new setup.

as far as the start button, there is no keyed ignition. Instead the electrical systems control unit (m-unit blue) that the previous owner installed has a feature where you have an app on your smart phone and when the bluetooth on the phone is turned on, the phone must be within a certain distance for the start button to work.

pickups had a restance of .31 with multi-meter set at 20k ohm setting. I read in another forum this is correct but I need to reference a service manual to know for sure.

I did not swap coils when the one failed, just bench tested.

Screenshot_20240529_083326_Chrome.jpg

[tom203]

good pickups and good ignition coil won’t help a smoked ignitor. Remember the ignitor just duplicates what a point/condenser setup does …..breaks the connection to coil at proper time to get spark.

[Tashields21]

I dont have the original fuse setup.I appreciate everyone's input. I'll look into getting the dynatek setup. Is it odd that engine won't fire on 2 and 3 since they do have spark? When it cranks it doesn't sound remotely close to firing. I only ask because I have a read alot about bikes only having 2 cylinders go out and it still starts /runs.

[ukjules]

I have a Newtronic Piranha setup that works fine. Elecs not.my thing but been reliable. Cheaper I think.
Dynatek I am told is the best mind.

I can't to be honest think of anything more likely to throw you down a rabbit hole as buying new non standard carbs for the bike .... Adding another expanse of unknowns to an already non working bike. Sure you'll get them to work but makes it hard when you seem to have so many other starting issues.

- get them old carbs out.on the dining room table and clean em up while mulling over these issues !

Compression - must be fine surely as it ran fine at some.point weeks ago. I would have bought a compression testir instead of new carbs ...

Spark - only on 2. Think it's as guys on here say and buy new ignition ....
Edit - but continue to get from plugs backwards ....

Petrol to plugs. It did run and now doesn't. Are plugs soaked in petrol after turning over ? They must be unless your new carbs are not working right.

No reason it won't run on two cylinders !

[gtem]

Those Murray carbs are for the birds IMO. People give up on the stock CVs *way* too easily and buy those bastardized Murrays 4-2 things that will never perform as well as a set of clean/stock/tuned stock Mikuni CVs running through an airbox. If you look inside a stock airbox you'll see the stock setup includes some very nice bellmouths inside the box. Going to pod filters you're losing bottom/mid range, and more often than not not gaining a thing up top either.

Seems that the bike ran well originally when purchased, and now a whole slew of other variables have been introduced. Your job now is to methodically work through and focus on/change only one variable at a time then confirm whether that changed anything, and in what way. Your Murray carbs are simply introducing yet *another* variable on top of whatever the initial problem was.

I'd confirm by swapping the original set of coils that the original did infact fail as suspected. Get some measurements off the originals. What sort of plugs and wires are you running now with the aftermarket coils? If you have suppression/silicone core wires paired with resistor plugs, that can cause issues with weak/intermittent spark in my experience just a few weeks ago on my XS1100.

[Grimly]

Imo, the Murray's carb set is probably worth getting IF the original OEM setup is really well worn-out with time and mileage.
Those were the reasons I fitted SUs to mine - hundreds of thousands of vibe-inducing motorway miles that rattled the guts of the carbs to bits and back then, the spares simply weren't available, even for the rubber bits, at a sensible price.
A factor nowadays, is the selection of good used low-mileage carbs seems to be getting in shorter supply, so makes the Murray's kit look better.
Having said all that, there's no way a twin-carb will flow as much at the top end as four singles, so top speed and flexibility at the top end will be affected adversely.
Mid-range torque might be ok with them, I don't know for sure. I can say with certainty that low and mid-range torque with the big single SU took some finding again, but it's back.
Once you depart from the way of Madame Suzuki, you have to feel your way along.
Also, the Murray conversion brings with it the joy of re-balancing the throttle cables, and that's a pain in the arse.

[Tashields21]

Seems that the bike ran well originally when purchased, and now a whole slew of other variables have been introduced. Your job now is to methodically work through and focus on/change only one variable at a time then confirm whether that changed anything, and in what way. Your Murray carbs are simply introducing yet *another* variable on top of whatever the initial problem was.

I'd confirm by swapping the original set of coils that the original did infact fail as suspected. Get some measurements off the originals. What sort of plugs and wires are you running now with the aftermarket coils? If you have suppression/silicone core wires paired with resistor plugs, that can cause issues with weak/intermittent spark in my experience just a few weeks ago on my XS1100.

This is true. At the time I thought the carbs were the problem, but I should have done testing to know forsure. Looking back I dont think they were ever the problem, just didn't want to spend $65 per pod when I knew I wanted the vm carbs in the long run. But, that could have waited. Lesson learned that's forsure, ill be the first to admit I an not the most patient person.

I chucked the coil that was split.

i used ngk plugs that were on the coil wires when i bought it, they were in good shape. I do believe the after market coils i bought are a silicone core with the copper wires in the middle that the plugs thread into. When all put together the resistance from coul to the plug is where it should be.

I ordered a dynatek ignition. I should have spark on all 4 after that. I'm still thinking fuel isn't making it to any of the cylinders. I guess I'm just not understanding why since the float bowls are filling with gas when when I crank it. I can actually smell the gas the last time I tried after replacing coils, hopefully that's not bad lol

[ukjules]

When you say 'you are thinking ' that fuel isn't reaching the plugs !
Can you confirm yes or no ? There should be a binary answer here that takes you down to the next path.

I assume the answer is "no"
To sort :
- major carb problem (get old.ones out on the kitchen table )
- spark problem on only 2 cylinders serviced by the one coil . I assume no spark is via the one coil.
Go back from there ......

Prob a good idea to get the dynatech. Think I would have checked a few more steps but hell you need one anyway so nothing lost.

You'll get there I am sure !