Coil #2 not working when instruments are plugged in

[Troyskie]

G'day fellas,

Top of the season to everyone!

Now I've a little time off and the roads are full (I don't bother riding for pleasure during the silly season) it is time to sort out some issues with Bendy the Big Bore 1100 (supposedly a 1250, but we'll see).

A little background. This bike has pretty butchered wiring. PO or PO's 'mechanic' have left me a riddle in so many places.

Yesterday I removed the gauges to replace the busted speedo, and also the tacho as it was waving around and didn't seem very good. I also fixed numerous broken connections and removed 30 years of WD40 from the connections.

The bike was intermittently breaking down and at low revs would only run on 1 & 4, suspect is coil #2. That coil was changed. No difference, still not running on 2 & 3.

I put the bike on the hoist, took everything off, attached the workshop fuel & flashed it up. Running on all cylinders. I then started pushing an pulling the wiring & bingo she shuts down, blows fuses, goes schizo.

Three sections of the loom give me grief at this point (plenty of others down stream I've already remedied).

First is the starter switch block. It had evidence of repair on the loom midway to the plug. I did a complete disassembly and found the kill switch had been fiddled with as the wires inside the block were interfering with how it sits on the bar. The previous repair put so much pressure on the wires they were almost snapped off the solder connections to the kills switch. Fine, replace that with a known good one.

Next was the loom from the gauges to the main harness. Loads of gunk on every connector and the park light connection & assembly were a mess. I cleaned it out and plugged everything back together, test fit on the bike, all good.

Third was the cable ties attached in the wrong places putting tension where it shouldn't, and even worse, cinched so tight I'm concerned wire might be crushed.

I took the opportunity to do some other needed maintenance, replace many bolts, many many bolts. So many bolts. Often in places where they were missing, such as only one on the alternator!!!!

All globes were replaced as I had the gauges out.

I then test everything on the bike before putting it back together.

Once she's all dressed up I flash her up.

Nooooooooooooo

She's not running on 2 & 3 again.

I disconnect the instruments & woo hoo, she's running on all 4 cylinders. I plug it back together & I lose 2 & 3 again. WTF??

At least it ran & I went for a test ride. This bike does have some beans!!!! I may have a little pilot jetting to fool with, but all good mechanically. Speedo is working again, tacho was working when plugged in, but 2 & 3 wouldn't fire.

What in the instrument loom could be cancelling #2 coil? Should I put the old tacho back in?

[T Legg]

the orange wire from the tci goes to the left coil and the tachometer and serves sparkplugs 1& 4 so i would think the tach would not affect 2&3

[T Legg]

my loaner fj1100 i just bought was supposed to have an extra set of carburetors but the extra set were not the correct carburetors for the 84 fj1100 and they were missing one slide and the top and spring,when i pulled the carbs on the bike i found the missing slide and top,they installed them on one of the correct carbs.now i have no carburetors for it.buyer beware .

[Troyskie]

Bugger about the carbies mate.

I've narrowed it down to the 9 pin connection.

[Troyskie]

I've swapped relays just to try and still no go.

It is definitely related to the 9 pin connection to the instruments. I unplug that and the bike runs well. I plug it back and 2 & 3 stop firing.

[T Legg]

i checked the compression on the bike and it was much lower than i would like but it was stone cold and i havent checked the valve clearances yet so i am still hopeful in the mean time  Ive ordered a throttle assembly for mikuni rs-36 flatslides  and when it gets here i will try the carbs off my other bike. if it runs ok i will order a set of flatslides for it

[Troyskie]

one of my 11's has low compression and uses a lot of oil. Good for around town and trips to work, but annoying on a long ride.

[T Legg]

i got lucky with my first fj great compression after market rear shock flatslide carbs corbin seat and other upgrades i had no idea the bike wasnt stock when i bought it for 980.00 us.this one will take several thousand to get in that shape before doing the top end.but it will be worth it to have a spare and a loaner.   i looked at my yamaha manual at the ignition circuit it is to bad they dont show the connectors on the diaghram it would make it easier to trace out your ignition problem.

[Bones]

Troy, Mr Blackstock had the same problem years ago, here's what he wrote.

http://www.fjowners.com/index.php?topic=11067.msg108902#msg108902

[Sparky84]

You are correct, 2/3 go to Tacho if you follow grey wire.
So maybe shorting at tacho.

Get Urban to Look at it 

[Troyskie]

Thanks fellas,

Al how do I set the multimeter to check the grey circuits in the loom?

I have this multimeter...

[T Legg]

I forgot you guys have the UK bikes with different wiring colors and the tach runs off of 2,3 instead of 1,4

[ribbert]

......checked the compression .... it was stone cold and i havent checked the valve clearances yet.....

What you describe is not a compression check.

Noel

[T Legg]

......checked the compression .... it was stone cold and i havent checked the valve clearances yet.....

What you describe is not a compression check.

Noel  

That's true that is no way do a proper compression check,I should have at least adjusted the valves but with no working carbs for the bike I was deciding whether to order a new set of carbs for the bike and wanted some idea the shape of the top end.After getting readings between 102 and 118 (I am also at 5000 ft of altitude) I took the decision to hold off spending 800.00 on flatslide carbs until I have adjusted the valves and tried the carbs off my other bike on it first.

[Troyskie]

Eureka (I think).

I caused this problem when I replaced the tacho....