Running on 1

[Viseney]

Running on just the one on the right, so #4 I guess.
My 89 (french 100bhp restricted) FJ12 was running OK, but I gave her a full service of Oil, brake lines, air filter, clutch flush,etc, with new tyres and fresh fuel.
She ran OK (in my garage) after but had a slight pop, so I was thinking about checking the shims next, but then one morning she was really tough to start, needed reves to keep turning, and rough as 80 grit sandpaper  .
A check showed the 3 pipes on the left are cold and she's only running on number 4.
I pulled the plugs and only number 4 sparks across the gap. 1,2 and 3, will spark from the plug body to the head bolts with 1 and 2 giving log arcs but three not so good.
I don't think it's down to the NGK iridium plugs I have fitted as I don't see a reason for 3 plugs to go down overnight  . I've ordered some standard NGK's just in case.
Thoughts, experiences and advice would much appreciated 
Cheers.

[Pat Conlon]

Hi Doc, welcome to our digital camp fire. Saw your intro. and you have a beautiful '91 pink striper.
A couple of Q's if you don't mind.
How long ago was the bike running right? Does France use ethanol in the fuel?
Since the last time it ran right, other than changing the plugs, did you do anything to the electrical side of the bike? When you spark tested the new plugs, did you try the old plugs to see if things changed?

The reason I asked, the FJ uses a wasted spark design. As you sit on the bike, the left coil provides spark to cylinders #1 and #4 The right side coil provides spark to cylinders #2 and #3. The FJ's firing order is 1-2-4-3.
Please forgive the silly question, did you get the plug wires back on the right plugs?
Sorry Doc, I had to ask. Looking at your projects I can see you know your stuff, but crazy things happen.
If you had a bad coil, or a bad electrical connection to that coil, it would affect cylinders 1/4 or cylinders 2/3.
Never cylinders #1-2-3 with cylinder #4 firing normally.
Perhaps bad plugs...but 3 out of 4 bad? Doubtful. Check the electrical plug connectors to the coils, David R just reported a problem along that line.
http://www.fjowners.com/index.php?topic=17818.0

Because the FJ uses a wasted spark, you can swap #4 plug wire and put it on #1 cylinder and see if #1 starts responding. Same with #2 and #3 this allow you to check the condition of the plug wires and resistor plug caps....see if a problem follows in the cylinder you switch. The FJ plug wires are a stranded stainless steel core wire and have proved to be very very durable...the resistor plug caps have been known to fail....but 3 cap failures at the same time?  Doubtful.

I suspect something fuel related. Bad fuel = dirty carbs (idle circuit) keeping 1-2-3 from lighting off.
I think the "pop" has something to do with it.

We will get to the bottom of it..... We have some very, very smart folks here on the forum and they have taught me a lot about my FJ. That is an understatement.

Again, welcome Doc!

 Cheers Pat

[Viseney]

Hi Pat, and thanks.
You're right in assuming I do know my way round an engine and can strip and rebuild down to the cranks, but electrics are not a strong point with me.
I did a fairings off service, airbox out and took the carbs off to fit some unrestricted inlets. However the French inlet rubbers are bolted on to the heads with "break off" tamper proof bolts, so the originals stayed in.
One (just one) of the airbox to carb rubbers looked a little perished but the cracking didn't go all the way through. So no air leaks there.
Fuel was fresh, but I did add a dose of STP carbon fuel treatment, which I considered might be the cause of the slight popping at revs.
They do put ethanol into the fuel in France, but I use a low eth gas, and have done for the thousands of miles I've ridden around Europe (not even Polish gas upset her).

I'd not considered using the wasted spark to check and will give that a go when the new plugs arrive.
I hadn't taken the plugs off until this problem occurred, and I always mark my leads with different coloured electrical tape (with matching tape on the heads) to avoid mixing them up.
Normally I'd just remove just one lead at a time for that reason
I can get a good 1cm arc from the HT leads to an earth. While I did disconnect the blox under the fairing to inspect them, clean them up with WD40 and blow out with my compressor I've ruled them out as a problem.
Compression is good.
I'm thinking of pulling the carbs off again, but this time dropping off the float bowls and cleaning the jets. However I'm a bit shy of doing so as I can't see how the jets of 3 carbs would block overnight on clean fuel.
The slow running jets might have caught crud, as I did clean the carbs with a carb cleaner spray, and some runoff might have have made its way in there.

That's the mystery. How can it go from 4 running to just 1 just after sitting for a couple of days?

[Motofun]

If you don't run a fuel filter it is possible to block multiple carbs AND with the FJ on the side stand the #4 carb is on the high side.

[fj1289]

...... However the French inlet rubbers are bolted on to the heads with "break off" tamper proof bolts, so the originals stayed in.

Are the French FJ's restricted?  I've haven't heard of tamper proof bolts on the inlets before.   Curious why they would be there?

[ribbert]

...... However the French inlet rubbers are bolted on to the heads with "break off" tamper proof bolts, so the originals stayed in.

Are the French FJ's restricted?  I've haven't heard of tamper proof bolts on the inlets before.   Curious why they would be there?

I can recall this being brought up on the forum previously in the context of how to remove them.

Noel

[fj1289]

I've missed those discussions.  So, restricted models have tamper proof fasteners for the rubber intakes?

Disregard - found the answer - yes, French models were restricted to 100 hp. 

[Viseney]

I've missed those discussions.  So, restricted models have tamper proof fasteners for the rubber intakes?

Disregard - found the answer - yes, French models were restricted to 100 hp. 

Yeppers restricted at around 105hp. I have a little more torque with FJR exhaust mods, and since I now have the carbs out for a cleaning i thought I'd have another look at removing the breakoff bolts to fit some UK inlets I bought.
Not as hard as it first appears. There is a way to spin them back by using an auto center punch on the edge.
Trouble is, that it seems that even with derestricted inlets and jetting the carbs I might then be faced with RPM mapping issues.
Guess I'll just stick to stock and be happy that I get better fuel economy with max torque at lower RPM, and that my clutch and drivetrain are less stressed.

I did after all buy her for touring with some twisties, not for getting my knee down. My main ride is a VZ800 Marauder, so that should tell you my prefered riding style.

[Viseney]

Just a note to say it's running sweet now
No idea what it was as I basically stripped, cleaned and checked everything while I had it apart, but didn't find an obvious cause or fault. Whatever it was I probably missed it while taking her down and fixed it putting her back together.
Problem solved 
mystery, not so much