Coil problem or ?

[scarr]

It's 65 degrees here in Missouri and the mud is hardening up, and I want to ride. But my '81 GS650E has a miss (or two). Here's what I did:

I used a timing light to check each cylinder. Results were: plugs 2 and 4 were firing steady at idle and all RPM's -- plugs 1 and 3 were missing at idle and cut out at high RPM's.

I switched the inputs from the left coil to the right coil and vice versa, and the plug wires to correspond. Results were reversed: plugs 1 and 3 were firing steady at idle and all RPM's -- plugs 2 and 4 were missing at idle and cut out at high RPM's.

This doesn't make sense to me because I thought one coil fired 1 and 4, and the other coil fired 2 and 3.

Please help: What's going on?

[duaneage]

First check the plugs, better yet buy new ones because they are cheap and we can eliminate them as a potential problem, just gap them .6 -.7 mm and toss them in.
How are the coil grounds? The coils ground where they are mounted, make sure they are not loose andthat they are not all rusty.

Check the connections on the ignition box to make sure we have a good solid connection there.

Check the 1/4 inch spade terminals that plug onto the coils, replace if fubar.

These are old bikes (i have a 81 650 myself) and we have to be diligent about bad electrical connections before we shop for parts, which are not cheap.

[earlfor]

Re: Coil problem or ?

When sitting on the bike, your cylinders are numbered 1,2 3,4 from left to right. The left coil fires cylinders 1 and 4 using the left pickyup on the end of the crankshaft. The right coil fires cylinders 2 and 3 using the right crankshaft pickup. If you have your coils firing 1,3 on one coil and 2,4 on the other, your problem is you have your spark plug leads on the wrong cylinders.

Earl


[quote="scarr"]It's 65 degrees here in Missouri and the mud is hardening up, and I want to ride. But my '81 GS650E has a miss (or two). Here's what I did:

I used a timing light to check each cylinder. Results were: plugs 2 and 4 were firing steady at idle and all RPM's -- plugs 1 and 3 were missing at idle and cut out at high RPM's.

I switched the inputs from the left coil to the right coil and vice versa, and the plug wires to correspond. Results were reversed: plugs 1 and 3 were firing steady at idle and all RPM's -- plugs 2 and 4 were missing at idle and cut out at high RPM's.

This doesn't make sense to me because I thought one coil fired 1 and 4, and the other coil fired 2 and 3.

Please help: What's going on?[/q


uote]

[duaneage]

Re: Coil problem or ?

When sitting on the bike, your cylinders are numbered 1,2 3,4 from left to right. The left coil fires cylinders 1 and 4 using the left pickyup on the end of the crankshaft. The right coil fires cylinders 2 and 4 using the right crankshaft pickup. If you have your coils firing 1,3 on one coil and 2,4 on the other, your problem is you have your spark plug leads on the wrong cylinders.

Earl

I think Earl means 1, 4 and 2,3 fire in pairs, not 1,4 + 2,4

There might be numbers on the wires, mine has them still.They also are cut to length, 2 won't reach 1 and 3 won't reach 4.

Once you sort it out write a number on each boot with permament marker so you won't get them mixed up.

[earlfor]

Re: Coil problem or ?

Uhhh yeah Duane. :-) I wish I could type and think at the same time. :-)

Earl



I think Earl means 1, 4 and 2,3 fire in pairs, not 1,4 + 2,4

There might be numbers on the wires, mine has them still.They also are cut to length, 2 won't reach 1 and 3 won't reach 4.

Once you sort it out write a number on each boot with permament marker so you won't get them mixed up.[/quote]