OK - important - very bloody important. Dirt bikes get dirty. Dirt bike chains get very dirty. The oil sticks the dirt to the chain & it wears the chain & sprockets out like you have lubricated them with lapping paste. Be warned - do not neglect the chain & sprockets.
Here's a thought for you. A typical chain runs around a 42 tooth rear sprocket, and 17 tooth front sprocket. Chain is typically about 120-150 links long. Each link has one 2mm pin, with a roller bearing on it, with two side plates, bearing on two more side plates.
That is three bearing surfaces and five moving parts, per link. Therefore, you have something like 600 or moving parts and 360 bearing surfaces in your final drive chain. That is probably more moving parts, and more bearing surfaces than in all of the other systems of the motorcycle put together.
Next, the highest loading is when the entire drive force is being transferred through the faces of just five teeth on the drive sprocket. That is, five 2mm pins taking all of the force generated by the engine, that itself is usually supported on a couple of two inch bearings!
Think about it - you don't neglect the lubrication of your engine, because you know that it wont like it - but the number of moving parts in your chain, and the loadings on them are far greater - so why don't you give it more than a passing thought?
The Montesa's have a semi enclosed chain. Sort of. If you look at the pictures, there's a black plastic channel that covers both chain runs top & bottom, leaving just the run around the sprockets exposed. It was de-rigeur in the late '70's and early '80's.
It actually does have some advantages too. The first is that because the chain actually runs through the guard, if the chain comes off, snaps or 'whips', it can do a very good job of stopping it doing any harm to the rider. Secondly, its supposed to act as a bit of a lubrication 'reservoir', and thirdly, clean the chain of any major muck as it goes round. Draw back is that it adds a lot of drag to the drive train, and it can clog up with grass, mud and damp.
If you notice, mine has had the bottom run removed to make life a bit easier, because it does add drag, and the bottom run is prone to 'snagging' with the slack.
Now, the reason I stress the importance of chain maintenance, is that I learned the hard way. Chain tension is important, too tight, or too slack and it wont run smooth. If you leave it, just a couple of days, with crud on it, it will rust, and it will tighten up, and it wont run smooth. If it doesn't run smooth, it will slop or snag.
Here's my horror story. I rode the Montesa on the weekend, and put her away on the Sunday night. I'd cleaned her, but not oiled and tensioned the chain. The tensioner block was a bit worn, and the spring a bit weak - but it didn't seem to matter much, the sprockets were in reasonable shape, the chain wasn't red rusty, and there wasn't too much play in it.
I pulled her out for a quick pootle, the following Thursday evening, as I had about half an hour to spare. I fired her up, and trundled her up to my practice area. I wasn't going quick, I was in third gear, at about third throttle, I suppose doing about ten or fifteen miles an hour.
BUT, a couple of the chain's links were a bit stiff with muck and rust, and it snagged - two links bunched going onto the rear wheel sprocket, lifting the chain off the run, and de-railing it off the cog.
The now loose chain whipped and bunched so that a mass of links got drawn in by the front sprocket and smashed into the mag cover, knocking a hole in it, and taking the lugs for the front sprocket cover off the chain guide. The tail of the chain wrapped itself around the rear sprocket bolts, and locked the rear wheel.
The engine stalled and I fish-tailed.
Now, circumstances being what they were, I didn't just fishtail to a nice steady halt in a straight line, I low sided her, and she slid away from me - normally not a big problem. Maybe a bruise and a bit of injured pride, except - I was wearing work overalls, and the leg had ridden up out of my boot. It caught on the footpeg, and as the bike twisted away from me, it took my leg with it, wrenching the tendons in my knee.
It was the first of a string of injuries that have seen both my knees permanently damaged.
I know I am probably over dramatising, and that it wasn't just trials riding that's to blame - badminton, skiing and general physical abuse plays a big part too, but still, it serves to illustrate just how easy it is for one 'silly' incident to have a much larger, longer lasting effect.
DONT neglect your final drive. DONT think 'I'm only...'. DONT think, 'Its OK'
Now, chain tension. Between 3/4 and one inch (20-25mm ish) play up and down. That's the usual recommendation, but the Cota has a slip block tensioned, so.
Lift the bike up and support it with the bash plate on something solid, so that the rear wheel is just off the ground with the suspension full extended. A couple of old wheels, tyres or a milk crate is normal for the job, if you haven't got a proper stand.
Now, the tension gets tighter as you use up suspension travel. So with the suspension fully extended, you want to tension the chain so that the slip block is JUST putting tension onto it.
Now, turn the rear wheel to pull the chain through and make sure you have the sprockets aligned, and there are no tight spots.
Then, and its easier if you slip the shocks of thier top mounts here, fully compress the suspension and make sure that the chain doesn't go tight, and the tensioner doesn't run out of travel. Again turn the wheel, to make sure there are no tight spots.
When you are happy, nip up the rear wheel axle, having made sure that the snail adjusters are holding the axle in the right possition.
Now lube the chain, by dribbling or spraying oil onto it as you turn the wheel to feed it past where you are applying it.
A tip here - apply the oil to the TOP of the chain, between the side plates of the links, so that the oil gets under the rollers and between the plates. I have seen only too often people wasting oil spraying a nice thick film of the stuff over the outside of the links, and only on the one side too! The oil is needed INSIDE the chain, and it wont get there through the side plates and rivets - so add the oil from the top or bottom & coat the rollers that actually bear on the sprocket - OK?
Then get into the habit of doing this as a ritual, preferably before every time you ride.
And, while you there, keep a close eye on the state of the sproket teeth - remove them and turn them back to front periodically to even out the wear pattern, and change them as soon as they start to look thin - DONT wait for them to get pointed, or worse, hooked!
As for the chain, keep an eye on how much you have had to adjust it - when you have had to draw the chain back as far as the swing arm slots will allow, its a good guess that its time for a new chain - DONT think you can get a just few more miles out of it by removing a link or two!
If the chan has stretched, then the effective 'pitch' has increased, and there's more room between the pins than intended. Run a stretched chain, and it wont drop on the sprokets accurately, and will be far more inclined to 'catch' or derail. For the extra use you might get out of it; its REALLY not worth it.
And lastly - dont be afraid to take the chain off from time to time and clean it and lube it thoroughly. IF you are really conscientious, you could even 'pickle' it. This is another good practice.
After an ride, clean the bike up, and remove the chain. Run it under a tap to get the worst of the mud and crud off it, and use a nylon brush, a nail brush is about right, with a bit of detergent to make sure its thoroughly clean.
Then, you 'pickle it' by dropping it into a jar of oil, with a good lid, that you keep for the purpose - an old wire coat hanger, cut into an 'S' hook, is a good way to allow you to put the chain into and out of the oil, without getting too messy.
What oil you choose is up to you, but EP90 gear oil's a favourite.
When you come to remove it, hang the chain over the jar for a few minutes to let the excess oil drip off, then squeegee the last off with an old rag, before re-figment.
This has two or three advantages;
Firstly, it keeps the chain from rusting from un-removed muck, crud and moisture.
Secondly, it keeps the chain well lubricated for each ride
Lastly, if some-one tries to steal your bike, it makes it a bit more difficult for them to try and ride away!
Picture scene of thief hot wiring ignition, starting engine, revving furiously, and stabbing frantically at the gear lever, but going no-where! Not a 'hard' security measure, but for an opportunist who sees it in the garage after the kids have left the door open...
A variation of pickling, is 'Hot Dip' librication.
I'll outline the principle; Oil is a fluid, if it can flow into the bearing surfaces in a chain, it can flow out again.
Grease on the other hand, wont flow into the bearing surfaces, but if you can get it in there, there's more chance of it staying put and doing some good.
So, rather than oiling the chain, if you were to heat some grease, so that it goes fluid, then soak the chain in it, it would get to where it is wanted. Let the chain cool down, and the grease should go solid again, and stay put.
An old saucepan, an old camping stove, and a pound of grease is about ideal, though you can substitute a blow lamp for the stove, or even use your kitchen hob, provided your wife/mother/significant other gives permission or is out.
Don't try and use her favourite casserole pot though, or you will be for the high jump.
Place chain in pan. Empty pot of grease on top. Heat on stove. Simmer gently for about fifteen minutes, until a light golden colour, with a pleasant aromatic aroma!
Remove heat, and allow the chain to cool, in the grease. When the grease has solidified again, you may remove the chain, and squeegee off the excess grease, for use next time. Careful though, it may still be hot!
Allow the chain to fully cool, and either pickle for fitment at a later date, or re-fit to machine.
Hot dipping is a good way to lube the chain; when you put it in the heat, the old oil should 'boil' out of the links, expelling with it a lot of the crud that might have got in there. It will contaminate the new grease, but not significantly.
Some 'old hands', and this is an antique technique, though still very useful, prefer to 'double dip' boilng the chain in parafin (sounds SCARILY dangerouse!), old engine oil, or even household vegetable oil, to clean it first, then doing a hot dip in grease to lubricate it.
Hot dipping is not something you necesserily want to do each time you ride the bike; as plain pickling; though I used to hot dip as part of my pre-trial prep, so perhaps one time in three; just as a 'good practice'.
One advantage of hot dip, especially if you pre-boil it to expell crud; it can reclaim a chain that's been allowed to 'nip up' from not being cleaned and which has gone rusty and tight.
But as a guideline; if you are laying the bike up; pickle the chain while stored, then hot dip before giving recommissioning it.
So lastly, similar to sprockets; you can fit the chain in any one of four orientations; if you mark an arrow pointing along the face of one link, you can fit the chain so that the arrow is;
1/ on the inside of the sprocket moving forwards
2/ on the inside of the sprocket moving backwards
3/ on the outside of the sprocket moving forwards
4/ on the outside of the sprocket moving backwards
As with the sprockets, its a good practice to periodically change the orientation of the chain to even the wear.
Each link doesn't go through a full turn under load, it only goes through a few degrees, leading to uneven wear on one side of the pin
flipping the chain over or turning it backwards moves where on the pin the loading wear occurs - it can extend your chain life a bit, but mainly it stops the pin developing wear ridges which can make it more inclined to snag.