It's been a while since I posted in this part of the forum!

But then the bike has run like a treat until now...

On a track day yesterday it misfired often whilst on the power, more so when moving up through the rev range than sitting at WOT down the huge main straight.

Earlier I got the coil packs off and the plugs out to have a look.

The plugs are all a good colour and the gaps are correct.

The primary sides both read 3.3 with the multimeter set at 200ohms.

The secondary sides read 14.3 and 14.6 (front and rear) with the multimeter set at 200Kohms.

Going by the specs both the secondary sides are out. Plus after taking out the ht leads to do the test I found that one of the spikes on the rear coil had a fair amount of corrosion on it. A clean and squirt with contact cleaner didn't help though.

I'll test the pulse coil later too just to rule that out, and do a full inspection of the wiring loom too.

But I'm thinking it might be time just to bite the bullet and get two new coil packs?

They are one of the very few functional bits I haven't replaced yet!





EDIT: The pulse coil was very slightly out of spec at 400ohms not 450-550, and the wiring loom checked out fine. My finger is pointing to the coil pack(s). Anyone any ideas?

Where the plug caps fitted when you measured the secondary resistance? Have you checked the battery voltage?

I removed the plug caps and ht leads for the test.

Tested them separately and they all came in around 500ohms.

I hadn't thought to check the battery, I'll do that tonight along with the rest of the charging system.

What resistance are the plug caps? Ignition coil and pickup resistances are not significantly out of spec and may be even closer after correction for ambient temperature if it was not the 20 degrees referenced in the spec.

Plug caps were still fitted to the leads when tested, so 500ohms.

It probably was 20 degrees yesterday, it's hot here at the moment, so no need to correct

Battery voltage is 12.8V

Resistance between the alternator windings is 0.5 on the 200ohm setting.

Re-measured the coils, it is exactly 20 degrees today, and they both came in at 14.5 on the 200K ohm setting.

Ht lead and plug cap
1 = 481 on the 2K ohm
2 = 468
3 = 541
4 = 554

I can't remember when I changed the spark plugs but they are no older than 5 years old.

It was a hot day on Sunday and subsequently the bike ran hot, which it generally does anyway.

Do you think the coil packs would be showing early signs of failure when hot?

I could always take them over to the club building and get a heat gun on them

EDIT: Took them to the club and got the heat gun on them.

Heated them to what I thought operating temperature would be whilst on a hot bike under high load. Both primary sides went up to 4.0 on the 200ohm scale, and both secondary sides went up to 16.6 on the 200K ohms scale.

I wasn't able to get measurements as they heated up as I don't have Croc clips or anything, but I'm still not sure what that'd mean.

HT lead and cap figures on 500 ohms is odd. Would expect 0 ohms or if resistive caps, 5000 ohms or 10000 ohms. Are they solid or carbon centred leads? Resistance changes with temp hence the resistance spec has a 20 degree reference. The true performance of the coils, and many other electrical parts, can only be guaranteed by a measurement when running or substitution, resistance is only good for identifying a significant failure. The ignition unit may be an issue unless you have already done a substitution.

Was not running so hot that the jetting was a little off?

Ht leads are silicon cased with what seems a white fibre core and very difficult to get a reading off

I haven't managed to substitute anything as I have no spares.

I wouldn't think it was fuelling as the misfires were very violent and the bike still pulled well reaching top speed easily.

I'd like to sub out the coils, ignition box etc but I'd need the parts and half a day on a dyno really. So not practical...

Sounds like carbon cored leads, you could try replacing leads only. Carbon core can burn through adversely affecting spark power.

Thinking about that, one of the leads did look like it had a blackened core...

I'll double check later