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Honda ST1300 Section => Honda ST1300 General Questions => Topic started by: Jardast on September 22, 2019, 08:47:04 AM
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Hi all, I was riding home last night after 10 hours in the saddle when I lost power and a loud noise started coming from the right side of the motor. I pulled over and checked the bike over. Nothing noticeable, no change in temperature, oil looked fine, cylinder heads not leaking. Tried to start and it would idle. I managed to get the bike home just putting along. On inspection this morning, No.2 spark plug was completely removed and had the ground electrode pushed against the centre electrode. No oil or burning on the plug. The tread looked to be OK so I assumed I must not have tightened it enough during service and it somehow worked its way loose. I tried to put it back in only to find it will not screw in. I am assuming the plug was forced out through pressure though there was no obvious signs. I can't image it vibrating loose but this may be the case. If so, I assume I will need to re-thread the seat to put in a new plug. Any help or advice would be greatly appreciated.
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Hi,
This may turn out to be an expensive repair if the thread is damaged.
To fix the issue it will probably mean that the cylinder head will need to be removed to prevent any metal getting into the cylinder.
I'd imagine a Helical thread insert might fix it but that's only a guess.
Hopefully someone with better knowledge can assist with a suitable fix.
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How on earth can the ground electrode be deformed except by the piston or a foreign object striking it?
Since a plug really can't work loose because of its long thread (assuming a moderate amount of tightening), this really is a mystery.
It appears you putted home on 3 cylinders, and I'm not optimistic about the health of the dud cylinder.
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Get a tap the correct thread of the plug and with plenty of grease see if you can re-thread the hole and fit a new plug.
If something has gotten inside the engine enough to drive the plug out of the thread then it will be head off to find out why.
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Only way for the plug to hit a piston, is if it is too long. Was the correct type of plug used.
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Thanks Alan, I was thinking the same.
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Biggles I have been thinking about that. I’m guessing when the plug became loose it just bounced up and down the shaft from the compression. The plug itself isn’t that badly damaged. I changed all the plugs about 15k ago. I bought them from the Honda shop so they are the right plug. I did only nip them up though. Better than hand tight but I didn’t lean on the wrench.
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Stevo can’t imagine anything getting into the cylinder unless something broke off from the inside. No banging or real rattling beforehand though.
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Brock, definitely the right plug.
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If the plug worked loose the noise may have been the essentially un muffled exhaust from the combustion stage. I guess you would also have had some combustion in the recess the plug fits in. Its possible the plug was bashed around when nearly out by the repeated pressure/vacuum generated by the piston.
Try one of the undamaged plugs in the spot where the plug came out.