1980 GS550E Electronic ignition .... issue

[tatu]

The issue was sudden.
Like ovwrheating I thought. But of course now we know.

I took the carb off yest, I didn't look at the diaphragm but
I didn't really notice anything.
It doesn't soujd like a sudden event ?

What about plug 2 not crackling when Inserted ?
Compression fine

Ok, take the cap off, so that the wire is bare, hold the wire about 4mm off the plug top and start the engine, you will see the spark.

 

[ukjules]

Ok but other three cylinders ok ? And no fuel in vacuum pipe ?
Whatever I'll check again.
Petcoxk is ok doesn't leak. Can't see how I can sort that out
without renewing it

I am taking bike back to only garage that offered to help
to 're check compression .
We must assume it is ok but I will do it one more time.

 

[ukjules]

Ok cap off bare wire - spark jumping across.

 

[tatu]

Ok cap off bare wire - spark jumping across.

Ok, now you have eliminated ignition. That's it and it's conclusive! The engine runs on the other cylinders so it's not a timing issue. the plug is wet, so you have fuel, You know it's not plug because you have swapped/put new.
Check th compression in the way I explained

 

[tatu]

Ok but other three cylinders ok ? And no fuel in vacuum pipe ?
Whatever I'll check again.
Petcoxk is ok doesn't leak. Can't see how I can sort that out
without renewing it

I am taking bike back to only garage that offered to help
to 're check compression .
We must assume it is ok but I will do it one more time.

As an aside, when you check this in the field, unplug the carb end and suck, if you get fuel in yr mouth it's bad, squinting down the pipe from the other end means nothing as it's an open hole

 

[ukjules]

Ok,

I sucked on carb end and I can get petrol in my mouth !

It's on reserve too.mind.

 

[tatu]

on the vacuum tube?

 

[ukjules]

Yes on the vacuum tube , carrb end

 

[tatu]

that is not a problem in itself, But just to eliminate,...You need to block off that pipe, cut it in half and poke a 6mm screw in the two open ends, or cut it short enough to get a screw in to block it off tank end, and then block the piece leading down to the carb. (Leaves you with an option should you wish to change back) from now on you will have to run on the prime position.
Remove the plug from No 2 start the engine long enough to unflood that cylinder, be careful of the spark as it might ignite ejected fuel. swap the recently removed No2 plug with another ,say No1, pet them both back in start up and see what happens.

 

[ukjules]

Ok, there is no prime only on and res.
Can I.work round that ?.tis a standard original.


Where's a 6mm screw when I need one !
Surely not a 10m cycle ....

I'll start now and should find a screwnsomewhere

 

[tatu]

Ok, there is no prime only on and res.
Can I.work round that ?.tis a standard original.


Where's a 6mm screw when I need one !
Surely not a 10m cycle ....

I'll start now and should find a screwnsomewhere

No prime position?
Then don't cut the pipe!

 

[ukjules]

Ok not cutting pipe.
What now ?
Do I still block it tank end ?

1) to get going
2) to fix permanently ?

Should I have a different petcock with prime
for these expeditions ?

 

[tatu]

disconnect it from the tank, do the unflood procedure I explained and swap plugs, see what happens, remember you have only a carbful to accomplish this, if you cant then be prepared to fill the carbs down the tube without using the tank.
TBH I don't think this is it, but it's cheap and easy.
I think you got burnt vlv
But after you've eliminated this you still got the comp test the way I explained

 

[ukjules]

Ok lets stop a minute.
All we have done is dry the plug and chamber a bit
a d swap the plugs.

If I run engine with tank on no petrol will flow
unless I attach vacuum pipe.

If I run engine without tank on same issue as always !

Do I need a pwtxoxk rebuild kit in the Longh run !

 

[ukjules]

Ok,
Plugs swapped and dry now
Unflooded procedure done. Plugs were out in sun for 10 mins

Tank off , vacuum not blocked , only carb fuel.

Same issue , plug 2 when cap pulled no effect
On engine where the other 3 almost stall it when removed

 

[tatu]

ok, from what you say there it's compression. do you block the vacuum tube when you run it with the tank off, with a dry new fresh known working plug?

 

[ukjules]

I do not block vacuum off when I run withiut tank.
At home I do same with external tank hung from ceiling.
Not blocking off vacuum. Runs fine forever

 

[tatu]

send me your, phone no.

 

[ukjules]

If we assume it is compression what does that mean?
Possibilities ?

Valve clearances were spot on when I left.
Head gasket ? Not real leaking ?

 

[tatu]

you will know if the HG was leaking, from sound or mess. maybe vlvs weren't spot on or chipped a vlv who knows? compression test because that's all that's left.