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JackDG |
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JackDG Renault 5 Driver
Joined: 23 Apr 2013 Karma :
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stinkwheel |
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stinkwheel Bovine Proctologist
Joined: 12 Jul 2004 Karma :
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Posted: 22:09 - 26 Jul 2021 Post subject: |
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The threads in the head have partially stripped, you can see the bits of aluminium stuck in the sparkplug threads. It'll need driling out and an insert fitting.
The top is chewed up by the spring steel in the coil cap, probably because it's been rattling about and partly because it may have been arcing as it rattled and nibbling away at it.
There are many things you need to take care about when stripping a head off. This is not an exhaustive list:
Number 1 is not snapping the waisted exhaust studs when you remove the headers.
Take lots of digital photos so you remember the routing of pipes and cables.
Don't get bits mixed up, get a trav with 16 compartments so you can put them back where you found them.
Measure your valve clearances before you take the head off in case you want to re-shim while you're in there. If you are going to re-shim, you will need a micrometer.
Back-off cam caps a little at a time, make sure they are coming up smoothly and symmetrically.
Check you can actually get the head off with the engine in frame. Mrs stinkwheel has an alloy frame CBR6 and damn it's tight in there!
You will spend more time scraping off old gasket materiel than anything else.
Be ultra paranoid about dropping anything down the open camchain tunnel, pack them with rags. Make sure the rags are removed fully after (mate blew his blueprinted and race tuned katana motor on lap 2 of a race just last weekend due to a 1" square scrap of j-cloth in the engine! Also dumped a full engine of royal purple XPR oil at £35/litre all over the track!).
On reassembly, check the timing, check twice then check again.
Calibrate your torque wrench. Ensure it clicks after every adjustment to the settings before using it on the bike.
Just buy an OEM head gasket. This is not somewhere to cheap out. ____________________ “Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles. |
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JackDG |
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JackDG Renault 5 Driver
Joined: 23 Apr 2013 Karma :
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jeffyjeff |
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jeffyjeff World Chat Champion
Joined: 02 May 2020 Karma :
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Islander |
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Islander World Chat Champion
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JackDG |
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JackDG Renault 5 Driver
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A100man |
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A100man World Chat Champion
Joined: 19 Aug 2013 Karma :
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Posted: 11:23 - 27 Jul 2021 Post subject: |
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JackDG wrote: |
The reason against that makes sense to me is that its an extra layer of material that will thermally expand at a different rate to the head / spark plug, potentially causing leakage.
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Never heard that about helicoil- sounds like pub blather to me. ____________________ Now: A100, GT250A, XJ598, FZ750
Then: Fizz, RS200, KL250, XJ550, Laverda Alpina, XJ600, FZS600 |
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JackDG |
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JackDG Renault 5 Driver
Joined: 23 Apr 2013 Karma :
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xX-Alex-Xx |
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xX-Alex-Xx World Chat Champion
Joined: 12 Sep 2019 Karma :
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JackDG |
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JackDG Renault 5 Driver
Joined: 23 Apr 2013 Karma :
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Posted: 22:45 - 27 Jul 2021 Post subject: |
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Pulled the exhaust, rad, fuel tank and airbox today. Fortunately I changed the studs and bolts about 2 years ago and they came off super easy
got the spark plugs out, in order as they are on the bike. far right is the one that was ejected.
Looks like 1 & 4 have some dirt / burning on the ceramic and the middle 2 look fine. Any opinions?
https://imgur.com/JW8Xa0d.jpg ____________________ 1992 GPZ 500 |
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jeffyjeff |
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jeffyjeff World Chat Champion
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Easy-X |
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Easy-X Super Spammer
Joined: 08 Mar 2019 Karma :
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Robby |
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Robby Dirty Old Man
Joined: 16 May 2002 Karma :
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A100man |
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A100man World Chat Champion
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stinkwheel |
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stinkwheel Bovine Proctologist
Joined: 12 Jul 2004 Karma :
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Posted: 17:17 - 28 Jul 2021 Post subject: |
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I seriously doubt if you could get a tap down there and started reliably enough with the head in-situ on an early alloy frame CBR6. it took me all my time to get the plugs in and out of Mrs stinkwheels, I had to drop the plug down then the socket then short sections of extension bar one at a time. ____________________ “Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles. |
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JackDG |
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JackDG Renault 5 Driver
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Islander |
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Islander World Chat Champion
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stinkwheel |
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stinkwheel Bovine Proctologist
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Islander |
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Islander World Chat Champion
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Pete. |
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Pete. Super Spammer
Joined: 22 Aug 2006 Karma :
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Posted: 20:46 - 28 Jul 2021 Post subject: |
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I'd stick a helicoil in there, and I'd do it in the bike too. Actually I have the kit to do it all in the bike if it's a 10mm thread plug.
There's loads of things you can do to mitigate getting debris in the cylinder ranging from 'don't worry about it' to cramming the hole with greased paper or even using a hoover and thin pipe. Personally I tend to not worry about it, aluminium melts at about 600degC whereas combustion chambers run at 900. Any bits of swarf will melt away into nothing. In fact, anyone who has removed a plug without first blowing the crap out of the plug well has probably done much worse than drop swarf in the hole. ____________________ a.k.a 'Geri'
132.9mph off and walked away. Gear is good, gear is good, gear is very very good |
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Nobby the Bastard |
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Nobby the Bastard Harley Gaydar
Joined: 16 Aug 2013 Karma :
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JackDG |
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JackDG Renault 5 Driver
Joined: 23 Apr 2013 Karma :
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Posted: 16:15 - 15 Aug 2021 Post subject: |
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measured valves and removed the head, went amazingly drama free.
all the exhausts were pretty much the same, 0.27mm (nominal 0.28 +/- 0.03)
Intakes varied from 0.2 down to 0.15 (nominal 0.2 +/- 0.03). Most were 0.16/0.15 so I'm guessing these could do with shimming?
So, the thread on the one that popped off is unexpectedly buggered! you can place the spark plug deep enough so that the tip would be in the cylinder without even threading it!
The cylinder 1 that somone mentioned to take a close look at also isn't as pretty as the middle 2 cylinders.
So, gonna cost up getting the tools to thread insert 1 & 4 (maybe phone a garage as well), and shop around for a new head and see what the prices would be like.
Links to pics of the thread; although its hard to get a good idea from a photo.
https://imgur.com/a/HeLHlqy
Anything else worth checking out while the bike is apart?
Thanks all for your continued pointers on this! ____________________ 1992 GPZ 500 |
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photoman |
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photoman Two Stroke Sniffer
Joined: 07 Aug 2021 Karma :
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JackDG |
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JackDG Renault 5 Driver
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doggone |
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doggone World Chat Champion
Joined: 20 May 2004 Karma :
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Old Thread Alert!
The last post was made 2 years, 253 days ago. Instead of replying here, would creating a new thread be more useful? |
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