This and cleaning the oil strainer, are pretty much all there is to an engine service on the Benley series engines, apart from checking or changing the spark plugs, and possibly adjusting the carburettor. This Handy How to, created for you by Donna, following the instructions in the Haynes Manual.
Haynes Manual, under 'Routine Maintenance', Page 28: "Four Monthly or 2,500 miles" (just for reference) Tef says that's every other oil change, that should be done at about 1,250 miles. But Tef reckons should be done every 1000, to be on the safe side, and worth doing Tappets & Cam-Chain tensioner, with each oil change, at least for the first few thousand miles of owning the bike, to tell how much adjustment they need. We've also had a couple that have 'wound off'; so worth keeping an eye on. So, what the book says:-
Simple enough; seat up, petrol 'off'; disconnect petrol hose at tap; pop the side panels; undo tank bolt, carefully lift the tank off, lift the plug caps off the spark-plugs and tuck the leads up out of harms way.
THIS is the fiddly bit!
Two chrome bolts on top of the rocker cover are easy enough (10mm AF Spanner. A cranked one helps; or a socket, but a 6 sided one is reccomended. A 12-point socket can 'slip' as the chrome nuts are a bit rounded on the corners, being 'cosmetic)
There isn't much room around the top of the engine to get the rocker cover out, and with the rockers inside, it can be rather annoying, and the ignition coils and brackets all get in the way! TRICK: is to 'roll' the cover forwards over the rockers, so that the curvie bit in the front of the cover goes around the frame tube...
THEN, you can rotate the cover out of the gap, sort of pivoting around the frame tube. EASY! (when you know how!)
Oh! Already taken the leads off! Meanwhile, removing the spark plugs is the topic of another How2: Remove & Refit Spark Plugs!
And out they come. Remember to do both sides, and worth checking them against the book, while they are out. (Page 115!)
And giving them a quick clean, & checking the gap.
OK, A deep socket then! & A torch to see all these 'ere marks theyz babbling about.....
Marks?! TL, TF, TR, TLDR!?!?!?!? WHAT! "TEF! Wazaal this mean?"
Teflon-Mike: You need to rotate the engine round its cycle so that the valves are closed, and the cam has taken all pressure off the valve before you check the tappet clearance; what's called 'on the rock' where the rocker can actually be wiggled a bit..... So, you rotate the crankshaft, until the T1 or TL marks can be seen in the little window at the top; That means that the piston is at top dead centre, only it can be at top dead centre between the compression & power strokes, or top dead centre between the exhaust & induction strokes, so you also have to watch the timing marks on the cam shaft to tell which one it is. You want it to be between the compression & power strokes, because that's when the valves are both closed, and the tappets 'on the rock' the gaps at their widest point, where you can measure them. THEN you wind the motor on 180 degrees of the crank, or 90 degrees on the cam, which puts the right hand cylinder at top dead centre between the compression & power strokes, so you can check that cylinder's clearances.
Yeah! "TEF! Wazaal THAT mean?"
Teflon-Mike: Look at the slot in the end of the cam-shaft. When its pointing towards the back of the bike, like THIS
Teflon-Mike: Check the tappets on the Left Hand Cylinder. When it is pointing straight up, like THIS
Teflon-Mike: Check the tappets on the Right Hand Cylinder.
Oh, RIGHT! Why didn't you just say that to start with! Jeez!
Err... what about the CD & CM's though, they the same?
Teflon-Mike: Book gets to that in a minute. Doesn't say anything about the cam-slot again; just says on the CB rotate the crank half a turn, on the CD & CM a full turn.. so that would have the cam-slot pointing forwards on them, I think.
OK... I can do this bit, now. THANK-YOU! Bugger off back to your camera and take photo's!
OK, so got the cam shaft slot pointing the right way; give the rocker a little 'wiggle', check that it's 'on the rock'. If it's tight, then either the tappet clearance has closed up, which isn't good, or you haven't got the timing marks set straight! So wind the crank round again and try again, wiggling the rocker until it does go loose, or you are sure you are at the right 'timing'.
Sliding the blade between the tappet & valve, it's sort of a 'feel' thing, you cant explain. Blade ought to be kind of 'stiff' to tug through the gap. If you aren't sure; pick the feeler gauge blades a size up and a size down from the one you need, and the smaller one should slide really easily, larger one not go in at all.
On this occassion it wasn't; so I adjusted some tappets on an engine we had 'lying around' that wasn't in a frame!
I did this with the feeler gauge under the adjuster. Make sure that the rocker is all the way up, then screw the adjuster down. & you will feel when it grips the gauge.
When its 'set' wind the lock nut back down with your finger, then slide the feeler gauge in and out to make sure it is properly set.
WARNING: the adjuster has a VERY fine pitch thread and it is VERY easy to over tighten it and strip the threads. It is also very easy to not tighten the lock nut enough and for them to work loose.... Tef says; its easier to fix a loose nut, than a stripped one! After adjusting the tappets, go back round them all and do a final check-tighten. Then after a hundred miles or so, it IS worth lifting the rocker cover again, and again, just checking non have wound off.
So, inlet, on the Left Hand Side checked; can check the exhaust on the LH-cylinder.
Then, rotating crankshaft to the timing mark for the other cylinder; inlet on the Right Hand Side:
Right! Yeah! What did Tef say? slot in cam pointing straight up on my CB125, forwards on a CD or CM.....
Then the Right Hand Cylinder's exhaust.
And THAT is the tappets checked!
OK.... Tef says DONT do this! Do the cam-chain tensioner first! You'll see why!
Yeah, err... OK! THIS is what I did!
THIS is the bolt at the top, between the carbs that Haynes says "don't touch"! So I touched it! It holds the Cam-Chain Tensioner in place inside the engine, BUT, Tef says that the bit that needs to move to let the tensioner take up slack, MAY be pinched in place by this bolt... so to LOOSEN it SLIGHTLY... like as in maybe 1-Turn MAX.
This is the Cam-Chain Tensioner stud & lock-nut they are talking about, between and beneath the carburettors.
Loosen the lock-nut, not the stud. In THEORY, the spring in the tensioner mechanism, should pull the tensioner blade down and take up the slack in the chain, as soon as the stud is unlocked, and you may 'feel' it 'tug' as you undo the nut. BUT!
Known 'niggle' on these engines, and THIS was why we undid the bolt they say 'do not touch'; the tensioner mechanism 'sticks'! So we slacken off that 'Do-not-touch' bolt, then give the top of the tensioner blade a 'little wiggle' to make sure it is 'free'.
THEN with a spanner on the square of the tensioner stud, to hold it still, the lock nut can be retightened, and THEN, don't forget to nip up the 'do-not-touch-bolt'!
Tef Says: If the cam-chain is noisy after repeated attempts to adjust it; its probably Donald-ducked. Tasking the head off and fiddling with it wont tell you much, and you'll have to split the crank-cases to loop a new (endless) Cam-Chain over the crank! DON'T think "Oh! Well, I'll put up with the rattle!" It can be rather nasty when they SNAP!
NOW: we can put the cover back on like Mr Haynes said to after doing the tappets!
Check the condition of the Rocker-Cover seal. These do NOT have to be replaced every time the cover is removed, but they do go hard with age, and the rubber seals on the retaining bolts are often forgotten.
Re-Assembly is the reverse of removal! FAFFING FIDDLY! As removal align the curvie bit of the cover around the front down tube of the frame,
Then sort of twist the cover over the top of the engine. Tef says don't worry too much about the seal falling out of place, just yet, but don't let it snag or yank it, try and get it over the rockers with the cover.
Then it can be tilted back over the rockers, careful to get the rubber seal between the case and the cylinder head.
It will almost certainly be a swine, and fall out, but just be gentle.... and tickle it back into the rebate in the casing as you lower it into place
paying attention around that curvie bit, where it likes to pop out when you're not looking!
Then the cover bolts can be jiggled into place, screwed in, and then tightened down. The cover may need a little re-alignment to get the screws in straight. Don't force them.
And then do the cover up evenly tightening down a little on each side in turn, so it goes down straight.
Tef tells me THIS is what WD40 is REALLY for! (Not lubing chains, or loosening rusty bolts, but) Spraying onto the electrics inside the magneto cover, before we put the cover caps back on, to keep the damp out.
Inspection caps back in. And refer to How2: Remove & Refit Spark Plugs!, if needed...
To replace the spark plugs! HT leads can then be put back on the plugs, and the tank and side panels re-fitted, and the engine 'run up' to check for nasty noises or leaking oil. and JOB DONE.
See, even a GIRL can do this!