Resend my activation email : Register : Log in 
BCF: Bike Chat Forums


Spark Plug Popped Out - CBR 600 F4i

Reply to topic
Bike Chat Forums Index -> The Workshop Goto page 1, 2  Next
View previous topic : View next topic  
Author Message

JackDG
Renault 5 Driver



Joined: 23 Apr 2013
Karma :

PostPosted: 21:50 - 26 Jul 2021    Post subject: Spark Plug Popped Out - CBR 600 F4i Reply with quote

Hello,

I had a spark plug pop out of the cylinder. Bike was running on 3 cylinders while I finished lap and returned to pit.

This happened once before about 18months ago - it seemed to thread in fine so I put it down to incorrect torque but now its happened again I'm going to pull the head and have a proper look.

I noticed the spark plug also had damage to the top that connects to the coil, anyone know what would cause this?

The condition and the plug also makes me think it was blowing past the threads at least for a short while.


Never pulled a head before, what kind of things should I be looking for to find the issue with the cylinder / plug? damaged threads etc.?
____________________
1992 GPZ 500
 Back to top
View user's profile Send private message You must be logged in to rate posts

stinkwheel
Bovine Proctologist



Joined: 12 Jul 2004
Karma :

PostPosted: 22:09 - 26 Jul 2021    Post subject: Reply with quote

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.
 Back to top
View user's profile Send private message You must be logged in to rate posts

JackDG
Renault 5 Driver



Joined: 23 Apr 2013
Karma :

PostPosted: 09:46 - 27 Jul 2021    Post subject: Reply with quote

Stinkwheel,many thanks for that informative post!

I think I'm gonna pull the head, the service manual shows it done in frame. Gonna take advantage and do the valves as well.

Being a 40,000 mile engine now is there anything else I should do while I'm replacing the head?

Does anyone know a ballpark price for a used head? The standard f4 head is significantly cheaper than my F4i head - I can't find a concrete answer for if they are interchangeable

Many thanks,

Jack
____________________
1992 GPZ 500
 Back to top
View user's profile Send private message You must be logged in to rate posts

jeffyjeff
World Chat Champion



Joined: 02 May 2020
Karma :

PostPosted: 10:21 - 27 Jul 2021    Post subject: Reply with quote

You don't need a different head. Repair the original one with a thread insert. If you replace the head, the valve lash clearances you measure before disassembly will no longer be usable. You will then have to measure and adjust your clearances from scratch (necessitating cam removal and reinstallation).
____________________
History shows again and again how nature points out the folly of men - BOC
 Back to top
View user's profile Send private message Send e-mail You must be logged in to rate posts

Islander
World Chat Champion



Joined: 05 Aug 2012
Karma :

PostPosted: 10:38 - 27 Jul 2021    Post subject: Reply with quote

jeffyjeff wrote:
You don't need a different head. Repair the original one with a thread insert. If you replace the head, the valve lash clearances you measure before disassembly will no longer be usable. You will then have to measure and adjust your clearances from scratch (necessitating cam removal and reinstallation).


^^ That.

If you're not confident to repair the thread yourself then find a local engineering firm to do it for you. If you go down that road then ask if they use Timesert inserts - it's a superior repair to the usual helicoil.
 Back to top
View user's profile Send private message You must be logged in to rate posts

JackDG
Renault 5 Driver



Joined: 23 Apr 2013
Karma :

PostPosted: 10:54 - 27 Jul 2021    Post subject: Reply with quote

I'm very happy running a tap and insert, I've heard conflicting opinions on if its a good idea.

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.

The other factor is the timesert kits are pretty similar price to the heads going on ebay. Maybe it makes sense to take the head to a shop who would have already invested in the tools and just pay for the insert.
____________________
1992 GPZ 500
 Back to top
View user's profile Send private message You must be logged in to rate posts

A100man
World Chat Champion



Joined: 19 Aug 2013
Karma :

PostPosted: 11:23 - 27 Jul 2021    Post subject: Reply with quote

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.


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
 Back to top
View user's profile Send private message You must be logged in to rate posts

JackDG
Renault 5 Driver



Joined: 23 Apr 2013
Karma :

PostPosted: 11:29 - 27 Jul 2021    Post subject: Reply with quote

Ok, I'm going to listen to the internet strangers and tap & insert if I can find it for a decent price.

Many thanks all!
____________________
1992 GPZ 500
 Back to top
View user's profile Send private message You must be logged in to rate posts

xX-Alex-Xx
World Chat Champion



Joined: 12 Sep 2019
Karma :

PostPosted: 11:51 - 27 Jul 2021    Post subject: Reply with quote

A100man wrote:
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.


Never heard that about helicoil- sounds like pub blather to me.


Helicoil is pretty much the standard in North America from what I've seen. It's always the first name to come up when this type of work needs doing.
____________________
DILLIGAF
 Back to top
View user's profile Send private message You must be logged in to rate posts

JackDG
Renault 5 Driver



Joined: 23 Apr 2013
Karma :

PostPosted: 22:45 - 27 Jul 2021    Post subject: Reply with quote

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
 Back to top
View user's profile Send private message You must be logged in to rate posts

jeffyjeff
World Chat Champion



Joined: 02 May 2020
Karma :

PostPosted: 22:51 - 27 Jul 2021    Post subject: Reply with quote

JackDG wrote:
Ok, I'm going to listen to the internet strangers and tap & insert if I can find it for a decent price.
Many thanks all!

We may be internet strangers, but we have good intentions and wish you the best as you work through your ordeal. Collectively, our knowledge and experience is significant, and probably more than those who offer "conflicting opinions". I, for one, have used helicoil inserts to repair spark plug threads on several occasions (2 and 4 stroke heads) without incident. If your engine were mine, thread inserts would be my first choice method of repair.
____________________
History shows again and again how nature points out the folly of men - BOC
 Back to top
View user's profile Send private message Send e-mail You must be logged in to rate posts

Easy-X
Super Spammer



Joined: 08 Mar 2019
Karma :

PostPosted: 11:16 - 28 Jul 2021    Post subject: Reply with quote

JackDG wrote:
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


I'd have a very close look at No.1 thread when you have it off the bike Thinking
____________________
Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter
 Back to top
View user's profile Send private message You must be logged in to rate posts

Robby
Dirty Old Man



Joined: 16 May 2002
Karma :

PostPosted: 15:05 - 28 Jul 2021    Post subject: Reply with quote

I'm wondering if no4 just wasn't tight enough and unscrewed itself halfway, then knackered the thread a bit popping out. Personally I would try running a tap down the plug hole first and seeing if I can then get a new plug tight enough.

Yes, you will get a small amount of aluminium shavings into the cylinder. Not enough for me to worry about, compared the likelihood of me cocking something up removing the head and drilling for a helicoil.
 Back to top
View user's profile Send private message You must be logged in to rate posts

A100man
World Chat Champion



Joined: 19 Aug 2013
Karma :

PostPosted: 16:19 - 28 Jul 2021    Post subject: Reply with quote

Robby wrote:
Personally I would try running a tap down the plug hole first and seeing if I can then get a new plug tight enough.


Bagsy not be the guy on the end of the spanner..

Thinking hmm..
I wonder if that's tight enough..
perhaps just a little more..
oh bugger!
Rolling Eyes
____________________
Now: A100, GT250A, XJ598, FZ750

Then: Fizz, RS200, KL250, XJ550, Laverda Alpina, XJ600, FZS600
 Back to top
View user's profile Send private message You must be logged in to rate posts

stinkwheel
Bovine Proctologist



Joined: 12 Jul 2004
Karma :

PostPosted: 17:17 - 28 Jul 2021    Post subject: Reply with quote

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.
 Back to top
View user's profile Send private message You must be logged in to rate posts

JackDG
Renault 5 Driver



Joined: 23 Apr 2013
Karma :

PostPosted: 18:31 - 28 Jul 2021    Post subject: Reply with quote

Used a torque wrench for the plugs last time - but even if I didn't tighten them up I don't want to be riding around or doing track days always wondering if the plug is gonna blow...


Heads coming off, gonna inspect the threads, likely will tap and insert all 4. I figure a 40,000 ally engine head it isn't an aweful idea!

Cheers all for the inputs, I'll continue to update/cry about buggering up the head!
____________________
1992 GPZ 500
 Back to top
View user's profile Send private message You must be logged in to rate posts

Islander
World Chat Champion



Joined: 05 Aug 2012
Karma :

PostPosted: 19:44 - 28 Jul 2021    Post subject: Reply with quote

JackDG wrote:
Used a torque wrench for the plugs last time - but even if I didn't tighten them up I don't want to be riding around or doing track days always wondering if the plug is gonna blow...


Heads coming off, gonna inspect the threads, likely will tap and insert all 4. I figure a 40,000 ally engine head it isn't an aweful idea!

Cheers all for the inputs, I'll continue to update/cry about buggering up the head!


Why would you drill tap and insert a perfectly good thread? It makes sense if the existing thread is badly damaged but makes no sense whatsoever if the thread is fine - in fact it's an unnecessary risk.

Also, no torque wrench is necessary. For a plug that's already been in service you go finger tight and then 1/8 turn extra. For a new plug, finger tight and then 1/4 turn.
 Back to top
View user's profile Send private message You must be logged in to rate posts

stinkwheel
Bovine Proctologist



Joined: 12 Jul 2004
Karma :

PostPosted: 20:08 - 28 Jul 2021    Post subject: Reply with quote

Islander wrote:

Also, no torque wrench is necessary. For a plug that's already been in service you go finger tight and then 1/8 turn extra. For a new plug, finger tight and then 1/4 turn.


Pretty sure it's actually 1/12 of a turn past finger-tight if the washer has already been crushed once.
____________________
“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.
 Back to top
View user's profile Send private message You must be logged in to rate posts

Islander
World Chat Champion



Joined: 05 Aug 2012
Karma :

PostPosted: 20:40 - 28 Jul 2021    Post subject: Reply with quote

stinkwheel wrote:
Islander wrote:

Also, no torque wrench is necessary. For a plug that's already been in service you go finger tight and then 1/8 turn extra. For a new plug, finger tight and then 1/4 turn.


Pretty sure it's actually 1/12 of a turn past finger-tight if the washer has already been crushed once.


I've always worked on 1/8th and 1/4 - it's what my dad taught me and one of the things that's always stuck with me Smile

I've never had one come loose or stripped a thread so aye. Reading this:

https://advrider.com/how-tight-should-your-spark-plugs-be/

It's pretty variable and brand dependent apart from plugs with a tapered seat rather than a washer - then it's pretty consistent at 1/16th. Laughing
 Back to top
View user's profile Send private message You must be logged in to rate posts

Pete.
Super Spammer



Joined: 22 Aug 2006
Karma :

PostPosted: 20:46 - 28 Jul 2021    Post subject: Reply with quote

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 Very Happy
 Back to top
View user's profile Send private message Visit poster's website You must be logged in to rate posts

Nobby the Bastard
Harley Gaydar



Joined: 16 Aug 2013
Karma :

PostPosted: 20:49 - 28 Jul 2021    Post subject: Reply with quote

Used a straw gaffataped to the e d of a vacuum cleaner when I wanted to swap the plugs on my fz and found I couldn't even get a socket onto the hex bit because of accumulated crap.
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050
 Back to top
View user's profile Send private message You must be logged in to rate posts

JackDG
Renault 5 Driver



Joined: 23 Apr 2013
Karma :

PostPosted: 16:15 - 15 Aug 2021    Post subject: Reply with quote

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
 Back to top
View user's profile Send private message You must be logged in to rate posts

photoman
Two Stroke Sniffer



Joined: 07 Aug 2021
Karma :

PostPosted: 07:20 - 16 Aug 2021    Post subject: Reply with quote

JackDG wrote:
Ok, I'm going to listen to the internet strangers and tap & insert if I can find it for a decent price.

Many thanks all!


A timesert or helicoil will cast you about £10-£15 so not a vast fortune
 Back to top
View user's profile Send private message Send e-mail You must be logged in to rate posts

JackDG
Renault 5 Driver



Joined: 23 Apr 2013
Karma :

PostPosted: 09:08 - 16 Aug 2021    Post subject: Reply with quote

photoman wrote:
JackDG wrote:
Ok, I'm going to listen to the internet strangers and tap & insert if I can find it for a decent price.

Many thanks all!


A timesert or helicoil will cast you about £10-£15 so not a vast fortune


Yeah, trouble is I can't find a kit with the tool for the insert for a cheap price. I can pick up a head for about 70quid so it's tempting. My current head also has a few inserts on the exhaust studs already I did borrowing the tool but can't borrow the correct size for the spark plugs
____________________
1992 GPZ 500
 Back to top
View user's profile Send private message You must be logged in to rate posts

doggone
World Chat Champion



Joined: 20 May 2004
Karma :

PostPosted: 09:17 - 16 Aug 2021    Post subject: Reply with quote

We all hoped you would weld it in.
 Back to top
View user's profile Send private message Visit poster's website You must be logged in to rate posts
Old Thread Alert!

The last post was made 2 years, 225 days ago. Instead of replying here, would creating a new thread be more useful?
  Display posts from previous:   
This page may contain affiliate links, which means we may earn a small commission if a visitor clicks through and makes a purchase. By clicking on an affiliate link, you accept that third-party cookies will be set.

Post new topic   Reply to topic    Bike Chat Forums Index -> The Workshop All times are GMT + 1 Hour
Goto page 1, 2  Next
Page 1 of 2

 
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You cannot download files in this forum

Read the Terms of Use! - Powered by phpBB © phpBB Group
 

Debug Mode: ON - Server: birks (www) - Page Generation Time: 0.09 Sec - Server Load: 0.4 - MySQL Queries: 17 - Page Size: 140.71 Kb