80LC Engine Strip

[miniman]

Well, the strip down of the 1982 80LC1 engine has begin.

As I've owned the bike since around 1990 (although shed stored 1994ish to 2015)  I have worked out that all of the seals are likely original, nothing has ever been replaced by me, same with the bearings. I only ever did a top end rebuild and rebuild the clutch back in the early 1990's.

All of the external seals are shot - oil comes out as fast as you pour it in, especially when it's warm so I though it's worth a total refresh.

Although I now have the engine out and some bits off i'll try to remember to take some photos from here onward and post for those interested to see.

I'll also be adding a few posts if and when I need some parts (already have all seals and bearings ready).

[miniman]

Head Off - seems undamaged

Barrel in pretty good condition considering it's age and the abuse it's had.

Exhaust side

Note the non standard porting.  I remember doing this around 1990 when I didn't know what I was really doing but it still managed good (125 beating) power at the time and reved off the counter, although power didn't really start to 8000

Thought id add a shot to show what happens if you don't use antifreeze.  Barrel spilt in 3 places and a friends dad welded it up for me  when it happened

Flywheel off, nice and clean stator etc.

however, I think the engine mount rubber is a little past it's use-by date!

so i've just ordered a pair, once I had located some, on their way from France as I type :-)

Tasks for today are to strip the rest of the casings and split them apart and see what the insides are like.

[miniman]

Just in from a couple of hours more work and thought I'd do this properly for anyone else to reference if need be.

Next step is to remove stator plate, trusty impact driver takes care of the screws. They will be replaced later anyway

Remove both screws followed by the wire going to the neural switch

I always put the screws back into the holes at this stage so I don't lose them, it may be a while before I reassemble.

Remove the wiring grommet from the casing and lift off the stator.

Store this away somewhere safe along with any other parts you take off.  I use a few plastic bowls when doing something like this.

Next, flip the engine over and loosen the screws holding on the clutch casing. In my case they were cap head so easy.

Yours may be crosshead and require the use of an impact driver again.  If they wont come out I don't suggest using a chisel on them as you risk cracking a casing.  Simply use a drill bigger than the shaft of the bolt (>6mm) and drill the head off. Easy to remove once things are fully apart later.  In my case all came undone. Lift off the side cover.  If it's stuck a *gentle* tab with a soft mallet may help, try to resist driving in a screwdriver in the joint you will only damage the alloy of the casings. This will reveal the clutch and kickstart shaft.

Next loosen the centre locknut and four screws holding the clutch springs against the clutch cover plate

I'll be changing the clutch springs but you can check them against the free length specs in the manual if you wish.

When you remove the cover plate you should find that the arrow on it lines up with the hole in the clutch basket, as below.  If it doesn't then someone has stripped it before and put it back together wrong

Next remove the cover plate.  Before removing the clutch plates note that there is (or should be) a rubber square section seal around the inside of the friction plate (pulled out of position in photo below).

Next you need to undo the central nut holding the clutch inner basket gear onto the gearbox mainshaft. There is a tool to hold the basket to make it easy, however I don't have one. 

I used an impact gun and a piece of rag to stop the basket moving.

Now, there are spacers and shims and washers on some of the parts you will remove, this being one of those situations.

I like to keep things in the right order for later cleaning and reassembly.  Cable ties do the job well for me, this is the whole clutch stack.

Next remove the large primary gear/basket outer

followed by the spacer and shim/washer

more to follow...

[miniman]

Remove gear change shaft by lifting upwards. Try not to disturb the return spring as it can be fiddly to get back in place, especially if you don't know how it fitted in the first place

Lift out the kickstart shaft and return spring

Next it's the turn of the small primary gear on the crank tail. This may have been easier with more of the engine assembled to add some rotational friction but an impact driver made short work of it with some rag around the gear.

Be aware that when you remove the gear there is a small key in the shaft and a shim/spacer. 

I held the key in place with some tissue and the assembly together with a tiewrap

Now to a bit of an oddity.  If you look to the right of the star plate below you will see a cylindrical object. 

This is the dowel that locates the clutch cover onto the crankcase. This hasn't just fallen off, it's been there the best part of 25 years and is still intact!

Here it is.

And it should be here..

Next remove the circlip from the idler gear

and the shim/spacer behind.  Again held together with a tiewrap for safe keeping.

Next remove the seal holder plate and splash guard. Also the selector star plate and detent arm/roller (not shown removed)

You are now in a position to split the crankcases

[miniman]

so, splitting the crankcases.

I used two pieces of scrap wood to support the case and keep it stable.

It also stops the crank getting damaged.

Remove the eight crosshead screws holding the crankcase halves together.  Again I used an impact driver.

Now the next part can be a real pig or very simple.  In my case it was easy.

You are trying to split the cases apart.  I used a lightweight rubber hammer and gently tapped one side of the engine casing and they split. 

do not hit the crank in any way unless you want to risk it being scrap. Apart from the ends being liable to damage you can put it out of alignment very easily (it's aligned to better than 0.03mm)

In my case the crank easily slid out of the clutch side bearing and the clutch side lifted clear exposing the gearbox and crank.

At this point you need to remember how the gearbox fits together, so several photos for later reference.

Remove all of the parts and store laid out to aid memory

So, now left with a crank in a crankcase half.

Rest the crankcase on wood, with outer face upwards.

Remove the crank oilseal (sorry, no photo) by drilling two access holes in it and prising it out

Now you have direct access to the crank bearing. Using a parallel punch, or similar, try a few exploratory taps on the bearing to see if it will move.

In this case it wouldn't even with moderate force.

You really don't want to distort or crack the crankcases so use a little physics to your advantage...

The aluminium of the crankcase will expand more than the steel of the bearings when heated.

I heated the case around the bearing so it was moderate hot - could still touch - using a blowtorch. You could use a hot air gun or a hairdryer.  Possibly even a kettle of hot water.

(be careful! oil is after all flammable!)

Now try tapping again, and the bearing easily moved. Tap alternating sides and working around the bearing

and there you go, crank out with no abuse.

All that's left to do is remove the bearing.

Lots of ways to do this, some  right, some wrong and some that will damage your crank.

I chose a bearing puller (because I recently bought one)

Congratulations, you now have several buckets/boxes/bowls of parts that was at one time a running engine.

Next part is to work out what's worn and reusable and what needs to be reworked.

[miniman]

A quick look at the crank for wear.

The main journals are in reasonable visible condition with minor rust staining from where it was stored for over 20 years untouched in a damp place. I'll need to make sure im happy with the diameters where the bearings sit but a first look with a micrometer suggests it's ok.

Next biggest worry is the condition of the big end.

Yamaha give a side clearance on the thrusts of 0.2 to 0.7mm so find a set of feeler gauges and select to find a tight sliding fit

then measure the feeler gauges (the sizes has worn off long ago...)

so that's 0.575mm which is within spec.

The dilemma is, do I replace the conrod and bearings/thrusts or not...

[wonkywheel]

Great photos,
Useful tool having an impact gun- saves time and knuckles.

Once i have cleaned the crankcase and components, I always do a dummy gearbox rebuilt (without the crank in) to make sure I have got the gearbox correct. It's a bit an*l, but better than having to rebuild and having to deal with crankcase sticky sealant.

If I was at your point I would seriously consider a new crank- with a new top-end and 30 year old mains- they might be a mis-match. Only you will know- and whether any spot rust has hit the mains.

I replaced the crank on my 125- I can now thrash will some peace of mind.

Enjoy the rebuild.

[miniman]

Jan 4, 2017 20:25:15 GMT 1 wonkywheel said:

Great photos,
Useful tool having an impact gun- saves time and knuckles.

Once i have cleaned the crankcase and components, I always do a dummy gearbox rebuilt (without the crank in) to make sure I have got the gearbox correct. It's a bit an*l, but better than having to rebuild and having to deal with crankcase sticky sealant.

If I was at your point I would seriously consider a new crank- with a new top-end and 30 year old mains- they might be a mis-match. Only you will know- and whether any spot rust has hit the mains.

I replaced the crank on my 125- I can now thrash will some peace of mind.

Enjoy the rebuild.

I thought I might as well document things - may be helpful for someone else in the future, I always take photos anyway for the rebuild stages.

Impact guns are a life saver :-)

The mains were shot and for the price id never re-use anyway even if they had only done 50 miles. The big end/rod I think i'll get replaced. I have the skills to check and realign to the right spec but not the press required for the crank pin so I'll probably get it done by others. If I had a spare I might have had a go sweating it in and out with a fly press I have access to but really need hydraulic press and some jig plates which I don't have.

I'll try to keep updating the post, although there will be a break while I clean lots of bits up.

I will be doing a dummy build as I have several new components to go in the gearbox that I have been collecting, not that the others are too bad, just because I can. I can then look at the correct shimming for everything. I have a factory manual so should be able to pickup all the nessesary info from that, if not i'll be asking questions on here.

[mattybeckett]

Great info and pics, keep up the good work

[miniman]

Well, managed to find another hour to do some more.

Next task is degreasing the crankcases and removing the remaining seals and bearings.

Lacking in photos im afraid as it a rather dirty job.

Coarse degreasing with soft brass brush, cut down paintbrush and some old petrol I drained out of something a while ago. This will get you clear of all of the lumps and for me almost 30 years of old oil, grease and road dirt.

Next step, hot water, washing up liquid and an old washing up sponge to agitate.

Then into the dishwasher for final degreasing on a hot wash.

Now, dishwasher tablets are rather aggressive and although they clean well they will leave the aluminium with a heavy oxide layer (but grease free)  This doesn't bother me as the bike isn't concourse or trying to be factory original, however I thought id have a go at removing some of it.  I have previously de rusted with Phosphoric acid (it does a fantastic job and you can but a lifetimes supply for the same price as a small pot of brush on rust remover) and noted that it did deoxidise aluminium as well, so thought id have a go on the engine cases. I know I could just get them blasted but I don't like spending money when I can get results i'm happy with myself with little effort.

Being cautious (this is 85% strength acid after all), and wearing gloves/overalls/goggles I brushed full strength acid all over the outer faces and agitated with a cut down paintbrush. Leave 1 min, use some red scotch brite to agitate, leave another couple of mins and wash off just to see the progress.  Well, see if you can spot which casing has been deoxidised?

Not too bad.  If id spent more than 10 mins total on the half a case I've don't then it would look a lot better again, or even soak in a weak solution of the acid for a while which is what I do with small steel parts before going through a pre plating and plating process.

Next job is to complete the other half and move onto the covers as well as measuring up a couple of the removed seals and ordering them up, also need a needle bearing which I need to measure, but that's easy.

In the mean time the new clutch basket has arrived along with new output shaft for the gearbox.  The clutch basket had significant rotational movement with respect to the primary gear and the sprocket had significant movement on the output shaft so both will be replaced and the old parts refurbished (one day!) for the spare parts box.

[miniman]

In addition the crank is now wrapped and boxed ready to send for a rebuild, when I can get to a post office.

[miniman]

I've realised I totally failed to update this on the reassembly. I'll try to see if I still have the photos..

[earthman]

Great thread, looking forward to seeing a complete bike, hope that you enjoy using it after all that effort.