Cold start issues

[Fj.itis]

Here goes,

Bike fj1100 very hard to start when cold, never used to be only a recent thing.

Carbs are super duper clean just went threw them on weekend to be sure. Compression is 160 across the 4 and have 40 pilots. Battery is fully charged but coils are out of spec, one being 3.7 and one being 3.8 on primary.

Warm and hot starts are fine, kicks over first go but when cold i find that when choke is on and starter pressed it will crank but doesn't fire, fuel seems to be there cause i can smell it and see black smoke from exhaust so its fueling up just not firing which makes me think coils but not sure.

Let us know what you think? Its seems to fire much quicker if i have jumper leads hooked up to the car.

Thanks

[JMR]

Check your valve lash clearances.

[ribbert]

Here goes,

Bike fj1100 very hard to start when cold, never used to be only a recent thing.

Carbs are super duper clean just went threw them on weekend to be sure. Compression is 160 across the 4 and have 40 pilots. Battery is fully charged but coils are out of spec, one being 3.7 and one being 3.8 on primary.

Warm and hot starts are fine, kicks over first go but when cold i find that when choke is on and starter pressed it will crank but doesn't fire, fuel seems to be there cause i can smell it and see black smoke from exhaust so its fueling up just not firing which makes me think coils but not sure.

Let us know what you think? Its seems to fire much quicker if i have jumper leads hooked up to the car.

Thanks

If you've got black smoke and petrol smell, something is burning, just not enough to start it and it sounds like classic flooding symptoms. Were the jet changes recent?
A low resting voltage in the battery and a further drop across the loom can leave you with a good cranking speed but not enough at the ignition.

If you have good compressions, the valves clearances will not be an issue, given the readings are taken at cranking speed.

Don't necessarily be fooled by the jumper leads starting it, you are also resting it while you hook them up which could also have some bearing on it.

We have some whizzo electrical guys here that will no doubt have a view that may solve your problem.


Try starting it on half choke and see what happens.

Good luck

Noel

[jscgdunn]

Fuel fouled plugs....when were they last replaced?

Jeff

[FJ_Hooligan]

Did you clean the tiny orifices in the float bowls?  The choke circuit get it's fuel from these ports.

If they are clogged/blocked then using the choke will only make cold starting problems worse.

[Fj.itis]

Valve clearance done less than 2500 ago, jets have always been there, float bowl jets clear and i have been using half choke sometimes less. The waiting thing doesn't change things as I've given it time to rest but still wont start on its own when cold.

Plugs are unknown so that is my next point of call, seems unlikely because they operate fine when warm but who knows.

[FJ_Hooligan]

Just to be clear.  It's not a jet.  It's a pressed in fixed orifice in the port at the bottom of the float bowl.

It is tiny and easly obstructed by debris.

Also, do you still have the 4 hoses that connect to the carbs just above the float bowl?

[Fj.itis]

Yeah all those pressed passages in the float bowl are clear, i checked 2 days ago now.

No all the hoses are gone but i have no leaks or overflow to speak of. Everything has been going great until now for about 2500 km.

Cheers

[Fj.itis]

Update:

12.4 volts going into coil, just put in new plugs and still no start. Pulled out plug and attached it to lead and grounded it on head bolt now i have no visible spark, yesterday i could see some random spark but nothing after new plug change.

Im starting to think coils are shot, what are your thoughts?

[oldktmdude]

Update:

12.4 volts going into coil, just put in new plugs and still no start.

Is this the voltage while starter is cranking or at rest? If at rest, check whilst cranking. Might be time for the coil relay mod?  Pete.

[movenon]

Update:

12.4 volts going into coil, just put in new plugs and still no start. Pulled out plug and attached it to lead and grounded it on head bolt now i have no visible spark, yesterday i could see some random spark but nothing after new plug change.

Im starting to think coils are shot, what are your thoughts?

It could be the plug cap on the no spark issue.  It is a resistor cap. Try one of your other caps.  The wires are solid core.

The resistance between the 2 plug wires from the coil should read around 12K  +- 20%.  That is just the wires without the caps on.
George

[FJ_Hooligan]

So the coils work okay when hot but not when cold.  For an electrical problem, I would expect the opposite.

Still smells like a choke circuit issue to me

[Fj.itis]

Ok, checked the voltage while at rest, will check again under cranking conditions.
I havent started it today to find out if i can start it but it looks like ive got no spark at all now.
Will do some more testing and ill let you know.
As far as the choke circuit goes, ive cleaned the carbs to within an inch of their life and have clearance through all passages, other then that i dont know what else to do with choke circuit.

[Fj.itis]

Pickup coils 160 ohms manual says 132 max

Plug caps resistance 5k ohms manual says 1k max

Coils primary 3.8 and secondary 13k ohms . Manual says 3.2 max for primary, secondarys in spec.


Now when i test for spark im getting some spark from right coil but none from left. So i switched the inputs and put the right input on the left coil and got some spark also. Doesnt seem like much though.

Now cranking voltage at coil inputs is 10 volts on both inputs when going from positive to a ground, but if i go between the two input pins on the right coil i get a voltage whilst cranking but no voltage between two pins on left coil, not sure if that is normal?

Anyone got ideas where to go from here based on this info?

[Fj.itis]

Got it started from dead cold on its own but with great amount of fiddling around with choke on until it sounded flooded then choke off and it eventually cranked over with choke off.

So heres my theory, there is spark there obviously, but not visable to me on one coil only. This could be weak spark i dont know but i think across the board the spark is just lame due to out of spec ignition and pickup coils and also huge plug cap resistance . So enough spark when warm due to fuel vapourizing better but not enough when cold, hence having to adjust the amount of fuel in the the pots with choke on and off when cold.

Could be wrong but its the only thing i can think of, because it runs and starts fine when hot.