The outside of a motorbike engine seen up close near the exhaust

Home Repair And Restoration

Somewhere Between Honda And I...

Blog Date 01 Jan 2023

By Ren Withnell

... there's an idiot.

CBF125 Tappets. Remove the nearside fairing panel (easy, most of the tabs and fittings are now broken). Remove rocker cover. In 5th gear use rear wheel to nudge the engine over as it's easier than removing the big allen access cover on the engine. Set tappets with screw n locknut adjusters. Replace rocker cover. Zip tie the fairing panel back in place. Half an hour.

CB500X Tappets. Start by psyching yourself up 3 months before the task. Ensure you have at least 3 weeks where you won't actually need the bike. Ensure you have a good supply of plasters, bandages and Valium. Finally before opening the toolboxes ensure you have come to terms with your own mortality and that of your motorcycle. Proceed.

You can now follow my instructions - CB500X Tappet Adjustment. Or... can you? There's always something.

On the right side engine case there's an access thingy to allow you to turn the crank. 

The cover is a round disc with a 17mm hex nut in the middle
The Cover
The cover being undone on the right side of the engine cases
Removing the cover

That there is a 17mm hex on a disc of what at least looks and feels like the same material that the crankcases are made out of. Behind that outside face is a 45mm thread and a big rubbery o-ring. 

The inside of the cover shows a large thread and the o-ring
The o-ring and thread (note the size of the thread).

This is not rocket science - undo this cover with a 17mm socket and beneath this use a 14mm socket to turn the crank. I have removed this cover at least 7 times, twice on this bike and the rest on my other bike and PocketPete's CB500X. 

Today is different. With fingers still bleeding and sore after doing serious battle underneath the tank and electronics tray and pipework and evap can and EGR and Uncle Tob Cobley and All, I grab the ratchet and 17mm socket. NNNNNnnnggH! Huuurgh!! Eeeeuuuurgh! Cor blimey that's tight. NnnnNNNnNNNGH! Oh crap, I'm at risk of rounding off the soft alloy 17mm nut.

I know, bit of shock treatment will sort that. I extract the UgaDugaDuga gun (plug in impact gun). This thing will remove the tightest of nuts with ease by jolting the nut. The jolts actually reduce the stress on the nut by using short sharp taps rather than long winded painful heaves from 80kg gorillas that think they're smart. 

What looks like an electric drill but has a 1/2 inch drive, it's an impact wrench
UgaDugaDuga. POWER!

UgaDugaDugaDugaDugaDugaDugaDugaDuga brrzzzt! Easy. Ah. No. Wait. The cover is still in place save for the nut. Poop, and other words to that effect. It takes another 10 minutes with a centre punch and hammer to remove the cover. Poop. Perhaps my shock theory is "open to critique". 400 foot pounds of torque might have been just a tad too much.

We see the engine cover with the nut ripped right off

Fortunately Fowlers will send me a replacement through the post for just over £25. Just search for "11332-MGZ-J00"

The cover is in place with a rough bolt fixed through the hole
There - fixed it.

No, no no no, not even I would do that. This is SIMPLY so I can replace the cover and seal the engine, keep the dirt and bugs out, while I'm awaiting my delivery. Mind you, in a pinch this would work "out in the field".

Did I overtighten it when I put it on? No, no I don't think so, I certainly wouldn't have been heaving on it. So what's the problem? 

First off we have a 45mm diameter thread, that's a BIG thread. The thread is around 7mm deep - so let me think... 45mm times pi gives us a 141.4mm circumference. Times this by 7 gives a 989.6 square millimetres of thread surface area. That's roughly 10 square cm. That's a LOT of thread. A LOT of thread gives us a LOT of friction.

Materials. This is some kind of alloy against a similar if not the same alloy - I'm figuring mostly aluminium. Being a rather soft material aluminium galls. Throw in some oxidisation and you have a recipe for things getting very stuck indeed, and over a large surface area.

Finally add an alloy nut with which to try and turn all this stuck together surface area. 

The solution? Errrrr. I think a simple cover held on with 2 or 3 regular M6 bolts? Extra machining, extra costs. A big steel cover? Possibly, that's what most other Hondas have. Maybe, when the new cover is fitted I never remove it again and just nudge the engine over with gearbox in 6th and the rear wheel. Like I do on the 125. Doh.


The part has arrived in good time and good order. Haynes recommends lubricating the threads with grease and smearing the o-ring with oil. This I have done. The next time I do this task I shall try to remove the cover - but if it fights me I shall leave it in place and use the rear wheel technique. I have put most of the bike back together and I am now bathing my poor hands in soothing balm.

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Reader's Comments

Ian Soady¹ said :-
My XBR has a similar cap over the crank nut but it has a screwdriver slot which - as usual in the case of these things - has been butchered in the past. But it came off quite easily using a bit of 2mm thick flat steel - using a scredriver is what damages them. The cap over the timing marks is smaller and a screwdriver is fine. Except.... when I removed that the disc with the slot parted company with the thread. Fortunately that wound out quite easily and a replacement from David Silver was cheap enough.

That setup you have looks daft Ren - that hexagon is bound to be a weak spot and of course given a big hexagon everyone thinks you need a big socket and a long breaker bar.....

What I do find infuriating is trying to see the timing marks through that tiny hole, which with the bike on the centre stand is too low for my ageing muscles to crouch down for and too high to lie on the deck. To make life easier next time I do the valve clearances I've put a dab of red paint on both the 17mm flywheel centre bolt and the flywheel rim to make finding TDC easier. Not precise but near enough that I can nudge it either way easily enough.

It would have been far better to put a window at the end of the camshaft which would (a) be at a better height (b) make sure I was on the right TDC. You may laugh but a bloke on the FB XBR group actually set his tappets on the wrong TDC and wondered why it was so rattly. Oddly enough it did start!

I always find nudging it with the back wheel is a bit hit and miss as there's so much slop in the drive train. Plus you need arms like a gorilla to do that at the same time as looking through that silly little hole.
09/01/2023 16:09:05 UTC
Upt'North ¹ said :-
Crap on a crap stick.
But did the tappets need adjusting?
09/01/2023 17:16:12 UTC
Bogger said :-
Lads you are complicating the issue.

In reality it's a very simple job.

Fist pick up the phone to the dealer. Book the bike in for said work. Deliver the bike to them on the correct day at the allotted time. When the work is done, collect your bike and pay the bill.

See how simple was that.

09/01/2023 19:53:35 UTC
nab301 said :-
That can't be your bike Ren , it's far too clean.... would a hot air gun on the main engine casing have helped while somehow cooling the damaged part?
09/01/2023 20:34:27 UTC
Ren - The Ed¹ said :-
Ian Soady - the tappets (shims) on the CB500X require the removal of the rocker cover to check and adjust - as such I can see the cams just fine. But yes if you have the style of the XBR with adjustment "caps" then a small window at the top would be fantastic rather than guessing TDC.

Upt' North - would you Adam and Eve it!
Inlet 0.16mm - all 4 were around 0.15mm
Exhaust 0.27mm - 0.30, 0.29, 0.30, 0.26.
No they did not need adjusting. SWINES!!

Bogger - You've gotten too much money. Anyhow I know you're prone to a bit of tinkering yourself so shurrup.

nab301 - Didn't fink of dat. In the heat (ha!) of the moment I was in gorilla mode. I have an old hair dryer in my toolkit that would warm the case up lovely then perhaps cool the cap/cover thing with a wet rag? Might have helped but we'll never know now because I'm a nidiot.
10/01/2023 08:53:49 UTC
Upt'North ¹ said :-
Yes I would Ed, I think they may refer to it as sods law.

10/01/2023 11:32:51 UTC
ROD¹ said :-
Is it my age? Or are bikes getting to complicated and annoying to work on.
I remember well the older generation saying that my gt380 was complicated, with need of dial gushes to set the three sets of contact breakers, and having to set up the two stroke oil pump ect, so it probably is my age.
I find my old BMW very easy to work on and service.
I had planned to sell the bike October time last year and buy something newer this spring, but my problem is that I can not find a newer bike that really does what I want.
A newer BMW RT would be my first choice at the moment, but why pay a load of money for the electronic stuff that I do not really need, and the more complicated and time consuming service procedure.
10/01/2023 14:53:36 UTC
Ren - The Ed¹ said :-
ROD - yes they are more complex and indeed annoying to work on. It is the way of all things it seems. I recall when computers were simple enough to build your own, now you need to be a super nerd to know what's what and what's not. I recall when speed limits were simple - street lights 30, no street lights 60. Now at every junction there's a 20 then 30 then 20 then 40 then 50 then 20... I recall when a TV had 3 channels and I could tune each one. Now there's loads and I can't suss whether it's online, satellite, terrestrial or carrier pigeon. Hell I'm still coming to terms with SCART.

It's called getting old. My first inkling was having to ask Sharon's daughter how to turn on that there "Netflix" thingy. I am still pretty much on top of it all but I am acutely aware I'm slipping back, slowly, but definitely surely. There will come a time when I'm like my own Grandad was, having to write notes on how to use this new fangled phone, notes on how to pay my gas bill online and notes on how to operate the keyless car. Then one day the procedure won't follow my notes and that's it, game over, no hope and all is lost.

I can hear Silicon Pines calling already - and I'm a programmer by trade.

Silicon Pines is a satirical place for the technologically challenged. It seems the images have been lost but you can still get the gist.
10/01/2023 16:11:14 UTC
Ian Soady¹ said :-
Never come across that Ren (obviously I'm even more out of date than you). Amusing stuff.

I often tell people about the days when a 5MB disc drive was the size (and approximate weight) of a car spare wheel. And when the manufacturers tried to squeeze 10 MB onto them they repeateddly crashed. Now we have 128 GB and more on something the size of my little fingernail.

One thing I can't understand is that the self-same copper telephone wires that struggled to transmit 9600 baud reliably now carry 15Mb/s (ie more than 1000 times as much) with few problems. Scotty would think the laws of physics had been broken.
11/01/2023 11:07:55 UTC
ROD¹ said :-
I am even more out of date. The world of computing is amazing.
My son works on performance cars, and designs and builds performance exhaust systems. He thinks nothing of plugging the cars into his laptop and reconfiguring the engine management system to work with the new exhaust system.
Does the copper telephone wire cope with the extra data because it is now digital as opposed to analogue?
As I say, I am totally out of date, so probably wrong as usual.
11/01/2023 15:15:49 UTC
Ren - The Ed¹ said :-
The copper wire can reliably cope with 50Mb/s subject to distance from the box on the street corner - and quality of connections between. Nowadays it's heading towards most folks having fibre-optic to the actual house!

Ian - I believe a good chunk in the data speed improvements came from the concept of multiple "channels". With the old dialup (where you could not use the phone and modem at the same time) the data was passed quite literally as beeps and boops. Once you remove the traditional "voice" system designed to transmit sound and insert ADSL - the ends are connected not to more wires but computers. You send high speed "on"s and "off"s at high frequency and keep a low frequency channel for voice - this means you can make a phone call at the same time as send data.

Then FTTC - Fibre to the Cabinet. This means the cabinet at the end of the street has a high speed fibre optic connection and a shorter copper wire to your house. This means the offs and ons can be sent faster without getting muddled up.

FTTP - Fibre to the Property. This means you have fibre optic cables to your house. These can carry INORDINATE amounts of data. The 0s and 1s are sent as light AND many channels of light. Some 0s and 1s are sent as red light, some as blue light, some can be sent in UV and IR too. So now you have many channels on a speed of light connection.

So yes ROD, them wires were once analogue, they are now digital :).
11/01/2023 16:08:18 UTC
Ian Soady¹ said :-
Thanks for that very clear explanation Ren. I've not bothered going for fibre as we get a reliable 15+ Mb/s through our copper wires here - easily enough for zoom, iplayer etc although it does occasionally drop out briefly. I have no idea whether we have FTC although coincidentally there is a big openreach building just round the corner. I think it used to be a telephone exchange.

Plus I'm not even sure how the copper wires get into the house - there's no overhead wire. However, when Redditch New Town was built they didn't want ugly TV aerials on the houses to they were all wired for cable - in the 1970s! I guess that the phone line comes in through that connection which is a mysterious pipe coming out of the ground into a square box on the outside of the house. There's aways some mystery to solve.
11/01/2023 16:31:18 UTC
Upt'North ¹ said :-
Ren, you're so clever!
12/01/2023 10:11:08 UTC
Ren - The Ed¹ said :-
Not clever, I can read stuff.
12/01/2023 18:15:34 UTC
Upt'North ¹ said :-
You can read?!?
I sed u was cleva.
12/01/2023 23:04:21 UTC
Ren - The Ed¹ said :-
Ay Kan reed gud. Ay Kan spell reet gud an awl.
14/01/2023 07:41:44 UTC
Crofty said :-
Ren my NC700X was just the same, the cover on the NC didn't have a hex nut it had a hex socket which eventually rounded off. I don't think i over tightened it but it still ended up seizing. If memory serves the NC I had needed the tappets set/checked every 8k, I later increased it to 16k but since I did over 70k on that bike it was off regularly and at about 50k I had to chisel it off and replace it
15/01/2023 17:10:48 UTC
Upt'North ¹ said :-
Just had a thought on this Ed, yes I do know I shouldn't.
Do Honda specify 'o' ring change on the inspection cover?
If so, have you?
If not, has this allowed metal to metal contact and subsequent seizure?
I'll go back to sleep now.
15/01/2023 23:29:48 UTC
Ren - The Ed¹ said :-
Upt' - I don't know what Honda themselves advise but my Haynes says "inspect and replace if necessary". Obviously for a tight fisted Scrooge such as I that means "unless it's in several pieces and can't be glued back together".

Crofty - so it's not just me then! Woohoo! This is one of those things that will be very unlikely to surface during the warranty period and even if it does it's easy to argue "you broke it you mechanical assassin". I'm wondering if something like this would be more, errr... reliable?

I know it's an oil filter cover but 3 little bolts rather than one big nut (that'll be me).
Posted Image
17/01/2023 08:18:57 UTC
Rob Wilson said :-
I have just had the same experience on my V-Strom 250. Doing the 6000 mile service (and being a good boy checking the valve clearances) tred to remove the cover, which has a 10mm hex sunken hole in the middle...... fit snug 10mm hex key....try to move. Nothing. Get breaker bar moves! Except it doesn't... just rounds the hex hole nicely.
Remove with centre punch and hammer after much cursing. Cover is trashed.
It's annoying as I had this off at the 3000 mile service without any problem.
The bit of OK news is that a new one is about £9 + postage. Still annoying though.
And the valve clearances were still fine :)
Great site by the way!
17/02/2023 23:17:51 UTC

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