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Oils aint Oils .. neither are plug threads..

Discussion in 'Technical and Troubleshooting Torque' started by VCM, Oct 4, 2009.

  1. My Hornet 600 gets a migrane...

    Ahh bike maintenance .. don't you love it!

    Last Tues, on my way to work I noticed a strange deep rattle on deceleration.
    Concerned it may be the chain tensioner I decided to take a look.
    Nope .. tensioner was fine, :confused:
    Oh well, may as well check the timing chain & gears .. and whilst I'm at it check valve clearances.
    On disassembly, I noticed No. 3 plug lead not quite seated down enough over the plug .. strange. After checking the chain/gears for play ( were fine ), I removed both cams, all plugs and proceeded the check valve clearances.
    Anyway .. clearances were not bad, but a little too close to bottom specs. Borrowed a box of shims ( handy having a bike shop 3 doors down ), and set clearances to TOP limit for longevity of service :wink:
    COOL ! time to put my baby back together.
    Cams installed, Valve timing set, tensioner in, rocker cover fitted, now the plugs ...:-s .. No. 3 Plug didn't seem to screw all the way home. WTF?
    Seemed like the thread was damaged.. ok, lets try a little more elbow grease.
    STRIPPED THREAD! :roll: .. SHIT!
    No Biggie .. Just enough room there to fit a hellicoil. Deal with it tomorrow.

    Next day, I wind the hellicoil tap down ( dipped in Petroleum Jelly to catch all the filings ). SWEET ! Wind down the hellicoil ... all's good.
    Back goes the plug.
    :? Plug still not winding in far enough. Remove plug and take a closer look at the problem..:eek:
    Take a guess

    Attached Files:

  2. Re: My Hornet 600 gets a migrane...

    I assumed the plug was threaded all the way up to the sealing washer, so I fitted the hellicoil just flush with the head. The shoulder on the plug ( 1st pic ), is meant to be positioned down the plug hole ..ie thread is meant to start aprox 8mm down the thread in order to accommodate the shoulder.:facepalm:
    DAMN! what now ?? remove the head. ( ie cams, exhaust, radiator, carbs etc. )
    As luck would have it, and with help from the guys at the bike shop, we managed to dislodge the start of the hellicoil and pull it through.
    2nd hellicoil fitted, THIS time further down, Spark Plug fitted PERFECTLY!!
    A lesson learned.

    Well at least I now know where that noise was coming from .. compression leak from the spark plug.
    Bike went back together fine, Carbs sync done, mixtures done.
    Runs alot smoother now .. EXCEPT I'm now getting a bad misfire at low loads .. just off idle. I suspect it's the HT Lead.... more likely No. 3 cyl.

    So here I am with the hornet ALMOST running perfectly again.
    I learned an invaluable lesson .. never assume!

    Here is where I need to ask a question ...
    (a) Are after-market performance leads avail for bikes? if so where?
    (b) CB600F specific : Do leads come as one piece ( ie attached to the cap ), or does the lead come separate?

    Ohh a little TIP for H6, and I guess CBR600F owners. The Chain tensioner can be modified very cheaply, ( under 5 bucks ), to stop that dreaded chain noise on start-up and also prevent the tensioner from being thrown back when they fail, ( happens apparently ).
  3. Well done Vinnie. Goes to show even the mechanically minded amongst us have an oopps moment occasionally. Well done on the "recovery" mate.
  4. Thanks mate. Still have this damn 'misfire' at idle/low revs. Checked Coils, HT Leads, Plugs..all ok.
    Wondering if it's fuel based now ?? Might play with mixture settings. Damn there is something to be said for EFI systems, setting carbs are a pain in the ass.
  5. UPDATE:
    Def running on 3 Cyls. The ride home ( I left early ), was awful. Sounds like an egg-beater and runs even worse. Tomorrow I'll check compressions. I suspect that the 'tang' from the first hellicoil has lodged itself in between valve and valve seat. :facepalm:
    That'll mean the Cylinder head is coming off... translation > no bike for at least 1-2 weeks :eek:
  6. least it isn't a big end! :|

    i still think it's electrical, but you'll know tomorrow when the comp test results are in.
  7. 165 165 155 165

    Still no wiser.
  8. Could it be the end bit of the Helicoil poking down into the combustion chamber causing predetonation of the fuel air/mixture due to a localised hotspot?

    Compression numbers seem okay?

    A V8 supercar mechanic I know is very careful when using Helicoils in cylinder heads because of this reason. Anyway, just a suggestion and good luck with the investigation.
  9. Anything's possible I guess.
    Anyway, I was putting it back together, fitted the spark plugs, didn't like the feel of No.3 .. yep damn thing stripped!
    The Cylinder head is now off and on the bench ... :( Hellicoil screwed itself out with the plug
    The plan is to machine a bush to fit into the head ( threaded internally for the spark plug, remove the PAIR valve system, machine the head a tad, replace HT leads re-assemble the bike and hope for the best.
  10. might be worth a few phone calls in the morning and see if you can source another cylinder head, just as a back up plan.

    i like the idea of a bush pressed into the head, but my only concern is the cylinder pressure hammering the bush out of the head... unless it's pressed in from the combustion chamber side.

    anywho, you're the cylinder head guru, will be interested in how u go about solving this (liked the idea of shaving the head).
  11. If I had the head off, I would take it too some pros to get the hole rewelded, tapped and a new seat for the spark plug machined. There are places that can do this, but I have no idea of the costs involved.

    Good luck with it VCM. Sounds like a bugger of a problem.
  12. I have no problem welding the plug location etc, however that would involve machining all valves & seats due to the heat involved... something I don't wanna have to do, seeing as all valves are seating fine and clearances have been set.
    I will, however, remove the valves on No. 3 Cyl .. just to check.

    Attached Files:

  13. So glad this is you and not me! Sorry to see her in bits mate. You may pick up a few more neddies when she's all back together.
  14. I used to work with a guy who caused pre-ignition in one cyclinder of his bike by using a helicoil in the plug thread, after he stripped it. He struggled with it for ages, and didn't get the bike to run right until he changed the head.

    EDIT: OKay. That was strange. I responded to VtrElmarco's post, which was the last and said it was fromToday, although at 3:48pm, and when I posted additional posts appeared, time stamped yesterday. Some post sequencing problem. Anyway, carry on Vinnie. I see you are beyond Helicoils now.
  15. Yep.. way beyond using a hellicoil now mate.
    Looking at something similar to this:
    Not sure If I'm permitted to post many pics in the same thread. Was going to post pics of various stages of repair, including removing the PAIR emission system & blocking the feed ports in the head, thread repair & head surface milling etc .. if any one is interested.


    Attached Files:

  16. 8 images per post. (hasn't made it into the T&C's yet)
  17. Thanks Rob .. per post then, not per thread .. cool !:p
    I've ordered the insert, seems it may take a few days as 10X1 is not a popular size. I removed honda's PAIR system today ( cause it's bullshit and a waste of valuable engine vacuum ). Rather than fit blanking plates to block those little ports, I used an alloy crack repair plug. Looks neat & does the trick.
    Left to Right.
    Pic1: PAIR system.
    Pic2: Exhaust feed ports in Cyl head
    Pic3: Tapping for allow plugs

    Attached Files:

  18. Pic1: The Plug used ( Alloy )
    Pic2: Installed Plug ( with loctite ) breaks flush with head.
    Pic3: Peened over .. finished product Exhaust tight seal.

    Attached Files:

  19. Hmm, a stainless steel insert in an aluminium head. I guess it would be okay, since a spark plug is a different metal anyway. Not completely sure though. At least Hellicoils wouldn't have a different expansion rate like that unit would.

    Post up the repair. I'd be interested to see how it goes.
  20. Seems that insert is now not available in my suppliers warehouse, and it could take over a week to ship in.:evil:

    I've now given the head to a colleague, a bit of a wiz with intricate machining.
    He's gonna make up a bronze bush, fit and tap to suit.
    Hoping to have it back tommorrow.