Intermittend starting issue..

Starter motor cranks over, no spark.. My initial suspect was the sidestand relay circuit, bypassed that at the relay (its the one under the cdi right?) still no go
Anybody any ideas? ('82 750 seca)

 

First of all. Is your battery fully charged ? If battery is slow turning the engine over, there is too much current drop and the spark will be too weak.
With multimeter check coil for resistance.

 

First of all, check whether you have 12V on the R/W wire that goes to the coils and to the TCI unit. If not, then your ignition is disabled somewhere (ignition switch, kill switch, ignition fuse or holder, etc).

The other thing to check is whether the B/W wire on the TCI unit is grounded. It shouldn't be... it should be floating normally, but it will be grounded if the sidestand relay is disabling the ignition. (bypassing the side stand relay basically means removing it).

If you do have 12V on the R/W and the B/W is not grounded, does the tach move when you're cranking? The tach is run from the coil drive for the 2/3 coil. If the tach moves then you should also have spark on 2 and 3. If the tach moves, but you don't have spark on 2 and 3 then I would suspect the 2/3 coil, but, the 2/3 coil and its circuit is largely independent from the 1/4 coil and its circuit.

If you got this far, the tach does not move, and you're not getting spark on either 1/4 or 2/3, then I'd say you've got a bad TCI or at least bad connections to the TCI.

 

I had this problem last week...it ended up one of the coils was faulty and only 2 of the 4 sparks were firing so I replaced the faulty coil and now it works like a charm ...starts first go everytime now

 

Firstly, if the motor turns over, it's not any of the cut out circuits, i.e. side stand, kill switch, neutral switch. So, no spark from all 4 plugs? if just 2 maybe coil.

 

Excellent point.

 

Well, the R/W Wire on the TCI is about 8.7V, seems i have a pretty high resistance somewhere (Anybody have an idea how much current the TCI draws?) The bike is coming home on the back of a friend's truck tomorrow so i can work in the comfort of my own garage .

 

There is a cut out system for the TCI separate from the starter, "the black wire" SQLGuy mentions above.. So there can be a problem with a cut out system.

 

Black wire = earth. Please elucidate.

 

I'm not sure which Relay IS the Safety Relay on the 750 Seca.

It's on the Frame Center-tube between the Seat Bolt-down and the Turn Signal Cancel Box on the Maxim's.

But, getting the Bike started not that the cool weather is upon us is an adventure.
My Bike wouldn't go today.
I had to let it sit for 30-Minutes on a Battery Charger and STILL goose-it with Starting Fluid to get it Started.

Once it Started it acted like it didn't need to be coaxed.
Cool-blooded thing!

If you are where it gets chilly at night and you are still riding the bike ... check your tires. When the cool weather arrives ... the tires lose air pressure like somebody sneaks-in and lets it out.

 

B/W,

 

The TCI unit, in total (i.e. through the R/W wire and through the Gray and Orange wires), should probably draw about 5A when the bike's running. If the ignition's on but the engine's not running, it should probably draw less than an amp.

Did you measure that 8.7V during cranking, or just sitting with the ignition on? Even during cranking that's pretty low. First candidates would be a bad ignition switch or bad fuse box.

 

RickCo

How cold was it at your place this morning?

It was below freezing here but mine started right up.
It sat in the unheated, uninsulated garage overnight.
I push it out of the garage and on to the sidewalk before I start it to keep the fumes out of the garage and hence out of the house. Family complains if I start it in the garage.

Rode into work and it was chilly but its only 5 miles. Made sure to look for puddles of frozen water. There were a few off in the gutters.

 

Pretty darn cold.
Cold enough to have to take a scraper to the windshield of the car before she took-off for Boston.
I knew getting the Bike to start was going to be a fight.
I would have won it straight-up if I had enough starting fluid to do the job.
I didn't.

But I'm getting good at hooking-up the cables to the Maxim. I don't even need to remove the Side Cover.
I pull the the Rubber Cable-end Boot off the Hot Wire going to the Solenoid and attach the Red End there and just clip the other end of the charger right to the Block.

A few minutes of juice at 6 Amps.

New Bike.

 

My 1A charger came with a pair of plugs that is supposed to allow the plug to be tucked somewhere other than under the side cover and connected to the battery. I have yet to connect it. I connect the charger once every week or two on general principle.

So far, since cleaning the carbs, the bike has started within a few revolutions and it sits in an uninsulated garage. Adjusting the slack out of the choke cable solved a temporary starting difficulty.

We have had frost on the windshields most mornings the past week.

I have a business associate that lives in Lincoln MA so I know its colder where you are.

I wonder if there is a block heater than can go into your oil fill hole......

 

8.7V Just sitting.. Found one point of high resistance, PO wired in an inline fuseholder by just twisting the wires together.. Soldered and heatshrinked now. Still no go.
My TCI draws 3.5A (through fuseholder), seems excessive can anybody verify?

I just reflowed some joints on the exposed side of the tci, she fires on 2 cylinders now! This seems to confirm i am having some TCI issues.

Thanks everyone for all the input, it has all been really helpfull !