Topic: Update 03/28/10 Stripped cylinder head threads, Please Help-photos attached

[Slams77]

I recently pulled both plugs from my CB450 and on the way out either cross threaded or stripped the last 3 or 4 threads of each cylinder.  I am not sure which term to use being that the threads aren’t completely gone but rather spaced out now? The attached photos of my left and right cylinder might give a better idea of what’s going on with the threads.  My question though is, Can I chase the threads with a tap or will I have to run helicoils to repair the threads?  

[City Boy]

Hi.Try the tap first.Nothing to lose and may avoid a coil.

[Zig]

there is a tool available that will chase thread from the inside,out ie: good thread to bad.

[Slams77]

Thanks, I found internal spark plug thread chasers for about $50.00, and they work from the inside threads out.  Does anyone have experience using these?  Will this repair the top threads that look to be crossed?

[mystic_1]

The top threads are probably history at this point, but it looks to me like you've got plenty of good thread left in the holes.  Chasing with a tap will probably result in the distorted threads breaking off, they're compromised now anyway.  Clean and de-burr the holes and threads well after you chase the thread, and you shouldn't have a problem imho.  Use care when installing plugs from here on out since it may be easier to cross-thread them in the future.

mystic_1

[steam-powered man]

would a neversieze-type product be helpful in preventing this?  (dissimilar materials).
bobp   

[bucky katt]

anytime i put dissimilar metals threaded together i use anti sieze. case bolts, engine cover bolts, spark plugs. cheap insurance. i think if it were mine i'd bite the bullet and heli-coil both spark plug holes, but thats me.

[Slams77]

Thanks, I’ll chase the threads first to see how it comes out then use anti seize when I reinstall the plugs.  This will most likely be a temporary fix so I can get the bike started (been sitting for 20 plus years) then I’ll do a complete disassemble of the bike at which point I’ll do the helicoils.

[bjb87gta]

If you must replace the threads, find someone to install a Timesert instead of a Helicoil. The Timesert withstands vibration far better than anything else, and is a widely approved and used repair method in the automotive world. You can go to their website at timesert.com to see why they will do a nicer job to repair any stripped out thread. If you need to do two, you might as well have them do all four. There is also a chance they can be replaced without removing the head from the motor, but it would be best to have it off. Good luck

[Slams77]

I had seen this kit on their website but at around $150.00 it’s kinda steep right now.  There is a local shop that will do a helicoil, and if I end up having to go that route, I’ll ask them what type they do.  Keeping my fingers crossed that I’ll only have to chase the threads.

[Slams77]

FYI in case anyone runs in to the same problem I did and would like to try and do the repair themselves.  On the suggestions of other members, I picked up an internal thread chaser from my local auto store and ran it through a couple of times and it worked.  I was able to insert the spark plugs without any problems, and the best part about it is that I got it for $20.00 on clearance.  Now I can finally work on getting it running again.

[City Boy]

Congrats, make your day?  Rock On

[Slams77]

Totally…especially being that I only paid $20.00 instead of $50.00 for the tool or having to pay for a helicoil without knowing if it runs first.

[camelman]

Glad it worked out.  I wouldn't worry too much about those upper threads either.  You never need as many threads for full load as are present on spark plugs/bolts.  You need more with aluminum than with steel, but you still only need full engagement with 6 or so threads.

Camelman

[Porscheguy912]

would a neversieze-type product be helpful in preventing this?  (dissimilar materials).
bobp   

Be careful using the the Neversieze stuff on spark plugs. It can cause the plugs to short (not spark) if not carefully applied.
dont just goop it on there.