Honda-SOHC
SOHC.co.uk Forums => CB350/400 => Topic started by: Athame57 on December 28, 2019, 02:40:15 PM
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This morning I washed the bike and it couldn't start....oh well after a while I remove some spark plugs to inspect and clean, and for whatever reason I started the bike again. Alas, not before this ham fisted yokel stripped some of the thread in the right side spark plug hole, only about 30% of the spark plug is screwed in so there won't be any unnecessary riding. Will the workshop be able to retap the thread without pulling the top end off first?
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That can be done with a well greased tap, or you could try cutting some vertical slots in an old spark plug and try to reform the damaged section yourself. Plugs are best fitted by hand to start with so there's less chance of cross threading.
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In the past. I have used a expanding thread tap with great success.
Grease it first. Then insert it into the plug hole. Expand it to suit the remains of the original thread. Then turn the thread tap. Out it comes bringing any debris with it. Because it cuts on the way out. Unlike a conventional thread tap.
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I have just checked.
The tool is a. Reverse action thread tap. From Sealey tools.
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Did the same thing on a car engine 38 years ago and bought this tool to run down and reclaim some thread using plenty of grease to catch any swarf created.
[attachimg=1]
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Any thread repair without removing the head has to be taken as a one stop attempt to reclaim the ally, but it is possible as previously said by others.
I cross-threaded my one of the heads on my CX500 many years ago and the plug literally fired-out when the bike started.
I took a plug and hacksawed a slot down the threaded shank, cleaned all the swarf off and used it to act as a taper-thread, with plenty of grease.
Yes, it worked and I did thousands more miles with that re-cut thread, but I always had to 'oil' the new plug on that head when i replaced plugs at service time.
The thread was 'tight' and I didn't have the funds back then to do the job correctly or worse-pay someone else to (us engineers are generally resourceful but certainly not wealthy)
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Back in the 70's fitted many helicoils without removing heausing well greased drill and tap.
Always gave customer the option of removing engine and head as should be done or cheaper way as described on principle that if any alloy swarf did go in and need clearing out it would not damage anything and cost no more total than having engine out first.
Out of all the ones we did we only had to take one engine out and found that one had shattered the rings anyway
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I find smear of Coppaslip or similar on the threads when refitting plugs helps reduce the chance of thread problems, as does not over tightening. ;)
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I got lucky, the mechanic at the workshop I usually use fixed it for free! :D Maybe he is preserving relations? ;)
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I got lucky, the mechanic at the workshop I usually use fixed it for free! :D Maybe he is preserving relations? ;)
Is his name Norman Bates as he did that as well ;D ;D ;D
;D ;D ;D
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(https://upload.wikimedia.org/wikipedia/en/c/cf/Norman_Bates_in_%22Psycho%22_%281960%29.jpg)
Well...he looked a bit like this with an east european accent!