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Spark plug caps failing

S

Smartleynz

Tuned and Synch'ed
Joined
Oct 1, 2014
Messages
91
Location
Taranaki New Zealand
Hi, just did my 20,000 service, took of to warm it up, pre oil level final check and it developed a miss, in one cylinder, maybe a dud plug I thought, pulled the plug leads of and found a white burn/ arking out mark, put tape over it took off again, and ......OK , shit hot of to the Burt Munro, so after the earthquake had passed and we finally got a ticket for the cook strait ferry, away I go, 4.5 hrs later get to Wellington and it is doing it again but other pot, ride to Nelson, pop the tops of again and check, yes , 2 more plug caps have ark marks on them, tape and try and has been ok since (4000k) later still good. my mechanic called a dealer in Wellington and they have had problems with them. Has anyone else had the same? They have carbon in them which breaks, apparently the new models have different type plug caps. sounds like a manufacture defect to me.
 
Spell checker is not your friend!

I ask about the gaps you set the spark plugs to, as the NGK recommendation is higher than the Guzzi manual.

Electrode gap 0.6mm - 0.7mm (0.024 - .028in) MG Service Manual
Electrode gap 0.9mm (0.035") as spec'd by NGK

If you are running the larger gap, perhaps this might be contributing to the arcing.
 
I prefer to believe NGK 0.035 as 0.024-0.028 is the standard gap for old style plugs and ignitions. Almost everything these days uses the wider gap. While Guzzi designed the bike NGK designed the plugs. If the caps are arcing I would put on NGK plug caps or similar. Even with the narrower gap there would be a loss of some spark through the leakage. Known problem on a lot of Guzzis. I changed mine out on my Norge for peace of mind.
 
kiwi dave said:
Spell checker is not your friend!

I ask about the gaps you set the spark plugs to, as the NGK recommendation is higher than the Guzzi manual.

Electrode gap 0.6mm - 0.7mm (0.024 - .028in) MG Service Manual
Electrode gap 0.9mm (0.035") as spec'd by NGK

If you are running the larger gap, perhaps this might be contributing to the arcing.
Click to expand...
Guzzi recommended gap, lots spell cheque?
 
kiwi dave said:
Not that simple. The lead has a rubber seal to keep moisture out and oil in. The offset one is a custom shape.

But prove me wrong. I'll all ears.
Click to expand...
I forget what the 1400 caps are like. If they are custom I hope somebody finds a cure. Mine never gave me any trouble on the 1400.
 
I prefer the wire gauges as opposed to the flat feeler gauges for measuring the gap. I use a spark plug tool to bend the outer electrode. Opening the gap with a screwdriver, and reducing the gap by hitting the electrode with the handle of same screwdriver is not recommended (but I've done it often :blush:).
 
kiwi dave said:
I prefer the wire gauges as opposed to the flat feeler gauges for measuring the gap. I use a spark plug tool to bend the outer electrode. Opening the gap with a screwdriver, and reducing the gap by hitting the electrode with the handle of same screwdriver is not recommended (but I've done it often :blush:).
Click to expand...
So no one has had a problem with plug covers/caps arcing out?
 
I've done several services and had to use enough force to pull them from the plug (that like Dave above), had the cap break apart. They are only available as complete wire and cap. Thankfully the NGK SB05E (also used for such issues on the 1200 8V) easily mated up and solved the problem. Not sure why some are so stubbornly seated by Guzzi.
 
My caps have never broken, just parted company with the cable. There is a retainer mechanism built into the cap where the wire end of the cable is forced in and then "retained". Unfortunately, they don't appear to stay put, and fall out again.

Glueing the insulator of the cable to the surface it touches within the cap appears to keep them together (so far).
 
Towards the end of the summer I started getting a VERY intermittent misfire at higher elevations and attributed it to the ECU not keeping up. But as fall came the misfire became more frequent even at home. So it looks like an inspection is in order. Its got 9800 miles on it now.
 
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