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Spark Plug Popped Out - CBR 600 F4i

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stinkwheel
Bovine Proctologist



Joined: 12 Jul 2004
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PostPosted: 11:39 - 16 Aug 2021    Post subject: Reply with quote

There are places that will fit them for you. It's an easy job if the head is off.

At the end of the day, you'd then have a known good head with known good cams and followers that go with it. I'd go so far as to say a head with plug inserts is better than one without in many ways.

I've seen me fit inserts to brand new parts for my Enfield, pre-empting the alloy stripping out (they have oddball fine threads which aren't well suited to alloy).

While the head is off, worth measuring the camchain to check it's within spec. Have a good look at the coolant hoses while you have the bodywork off and access to them. Likewise fuel lines and control cables. Make sure the exhaust studs are all in good order.

Maybe do the valve stem oil seals? The seals themselves are cheap.
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JackDG
Renault 5 Driver



Joined: 23 Apr 2013
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PostPosted: 11:08 - 20 Aug 2021    Post subject: Reply with quote

good tips stinky I'll look over those.

The other day browsing fleabay I did buy a head that was going for £75... (weak impulse control)

Just arrived and looks much cleaner / less used than my current head.

All the threads (including exhaust studs) look good, and it came populated with spark plugs, valves, buckets and shims.

Think I'll still get the original one repaired and maybe sell on or keep and sell the ebay one. no strong feelings either way

Question for the new head - the bucket and shims were all over the place from shipping so don't know which shim is for which valve. What's the process here? randomly assign them, install, measure clearance then re-arrange the shims / replace shims as necessary? Cheers!
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Nobby the Bastard
Harley Gaydar



Joined: 16 Aug 2013
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PostPosted: 11:15 - 20 Aug 2021    Post subject: Reply with quote

JackDG wrote:


Question for the new head - the bucket and shims were all over the place from shipping so don't know which shim is for which valve. What's the process here? randomly assign them, install, measure clearance then re-arrange the shims / replace shims as necessary? Cheers!



Oh dear. Thats not good.

Yes as you say, stick them in and measure the gaps. Reshim as required. Once you've measured gaps don't move the buckets around....
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JackDG
Renault 5 Driver



Joined: 23 Apr 2013
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PostPosted: 11:23 - 20 Aug 2021    Post subject: Reply with quote

Perfect, thanks for the confirmation. Gonna be an expert at shimming Rolling Eyes

oh and I dont need to worry about anything with putting the cam shafts onto a new head?
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Nobby the Bastard
Harley Gaydar



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PostPosted: 11:28 - 20 Aug 2021    Post subject: Reply with quote

So it didn't come with the cams? Thats also not good. Generally you aren't supposed to use cams from different engines.

I've heard of people doing it but it's generally best practice not to swap cams around. You should ideally also not move cam caps around even within the same engine.
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JackDG
Renault 5 Driver



Joined: 23 Apr 2013
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PostPosted: 19:56 - 09 Sep 2021    Post subject: Reply with quote

Got the thread inserts done, no. 1&4. full inserts as opposed to the helicoil. Measured all the shims from the other head and it works out that I can use these in the original head to get back to factory clearance without needing to buy any extras.

You were correct about spending most of my time removing gasket material. These lines left behind are a pain! Done the outside of the cam tunnel and starting on the upper right of far right cylinder.

Currently using a razor blade + carb clean. Any tips or just persistance?
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stinkwheel
Bovine Proctologist



Joined: 12 Jul 2004
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PostPosted: 20:18 - 09 Sep 2021    Post subject: Reply with quote

I've heard of people hammering the end of a piece of copper pipe flat and using that as a scraper but I always land up going back to a stanley knife blade with a bit of tape along the back to protect my fingers.

Th etip is if you feel like you are rushing, take a break and do something else for a bit before you gouge lumps out of the alloy.
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“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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A100man
World Chat Champion



Joined: 19 Aug 2013
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PostPosted: 11:12 - 10 Sep 2021    Post subject: Reply with quote

If you round the corners of your tool you lessen the chance of digging a corner in. I have a well worn decorators scraper for this kind of work.
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JackDG
Renault 5 Driver



Joined: 23 Apr 2013
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PostPosted: 17:59 - 28 Sep 2021    Post subject: Reply with quote

Finally got it back together - decided to replace a few sundries along the way (thermostat rubber, thermostat gasket, camcover o-rings etc.) so had to wait for the shipping.

It appears after having 1 & 4 thread insert, the plugs are sitting ever so slighty higher than 2&3 (maybe 2mm max).

But it starts up and seems to run fine! Just need to find some petrol to put some miles on it and build the confidence in the mechanics of it up again!

many thanks for everyones input on this, much appreciated!
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A100man
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PostPosted: 18:26 - 28 Sep 2021    Post subject: Reply with quote

Good result Thumbs Up
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sickpup
Old Timer



Joined: 21 Apr 2004
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PostPosted: 10:52 - 04 Oct 2021    Post subject: Reply with quote

JackDG wrote:
It appears after having 1 & 4 thread insert, the plugs are sitting ever so slighty higher than 2&3 (maybe 2mm max)


This means they likely used Timeserts and didn't recess them into the head as they should, they have a lip on them. Could be they didn't do this due to space limitations.
This may cause an incomplete combustion problem and carbon forming on the thread in the head locking the plug in place

The comment about Timeserts being superior to Helicoils is wrong, each has it's place. In this case I have seen Helicoils fail as they let combustion pressure through being a spring so a Timesert is better in this application but I have also seen old Timeserts wind out which tends not to happen with Helicoils.
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JackDG
Renault 5 Driver



Joined: 23 Apr 2013
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PostPosted: 15:39 - 04 Oct 2021    Post subject: Reply with quote

Yeah they used timeserts sickpup.

I'll be keeping a close eye and will update here if anything arises.
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Pete.
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PostPosted: 16:37 - 04 Oct 2021    Post subject: Reply with quote

Helicoils should not let combustion gases past because it's not the helicoil or plug thread that does the sealing, it's the sealing washer on the plug.
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sickpup
Old Timer



Joined: 21 Apr 2004
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PostPosted: 16:51 - 04 Oct 2021    Post subject: Reply with quote

Pete. wrote:
Helicoils should not let combustion gases past because it's not the helicoil or plug thread that does the sealing, it's the sealing washer on the plug.


That's the word, shouldn't.

Problem is when people reuse sparks plugs and the washer is already compressed so doesn't make a good seal.
I've seen it on sump bolt repairs where people reuse the washer and the oil leaks from the outer side of the helicoil, never seen it with a timesert.

It shouldn't matter but sometimes it does.

I should add in general i prefer Helicoils.
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Jim Mc
Nearly there...



Joined: 28 Dec 2010
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PostPosted: 10:57 - 01 Nov 2021    Post subject: Reply with quote

I'd have bought a new head personally.
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c_dug
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PostPosted: 11:17 - 01 Nov 2021    Post subject: Reply with quote

Pete. wrote:
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.


Bit late to the party, but for those in doubt, Pete. did this to my bike at the side of the road (well, work car park) a few years back and it ran absolutely fine for a good many miles until it was stolen and burned by scumbags. I reckon a solid 10,000 miles post-helicoil with no issues at all.
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