4L1 Crankcases queries

[rolie]

I've finally had my 4L1 crankcases vapour blasted and I'm happy enough with the outcome.





I've a couple of minor queries that I'd like your advice on:

1. I assume the mould used for the bottom case was nearing the end of its life. The photo shows the finish.



It's purely cosmetic but do I just leave it like this or should I get my file out?

2. Both cases are engraved 1A 208 but the bottom case has another number scored out.



I assume this means they were originally not a pair and the lower case has been replaced at some stage. Am I right or could there be a more innocent explanation?

Thanks

Rolie

[bare]

Cases are oem line bored. Matching each other case Numbers is 'Important' :-)

[4l04ever]

As well as the line boring, the faces on each side are machined as a pair.

One of the checks your can do to verify if they are matching is by checking the clutch gasket face and see if there is a step between the top and bottom sections.

rdlccrazy.proboards.com/thread/50406/matching-top-bottom-engine-casings

[midlifecrisisrd]

Couldn't that just be a hung over Monday morning thing

I've never seen any numbers corrected especially on mismatched cases

The fact the non matching number has been engraved, scored out, the same wrong number engraved again, scored out again then the matching number engraved sounds like the kind of thing I'd do when my heads up my 4rse

Steve

[rolie]

I paired the cases together to have a look at how well things lined up.





















They seem good to me, though I'd welcome comments.

Hopefully it points to Steve's theory of a tired engraver with his head up his '4rse'

Rolie

[yamman1066]

i think you need a matching set to be 100%

[muttsnuts]

some one has engraved that number on the bottom case who wasn't the same person who engraved the top case, the writing is completely different, just look at the "A" the "2" and the "8", they are very different, all of the cases I have seen (which is a lot), the top and bottom engraving is identical e.g. done by the same person

also a few of those journals look to have small steps in them between the 2 halves, might be just the way the photo is, but if there are any steps between the journal faces in each case when bolted together that is another tell tale that they aren't the matched pair, the point here being the bearings that sit in those journals aren't going to budge much, which means something else has to give to clamp around the bearings equally and be aligned

[JonW]

Im with Dave on this, they dont look like a matched pair to me.

How much this will matter depends on how 'out' they are. If it was running ok when you got it and stripped it (or it had worn out cyls/pistons etc even of if you never saw it run) then id say its possibly ok to use as some one else has proved it for you, but its not a perfectly engineered set obviously.

The lower case finish is pretty normal, they were sand cast (i guess?) and yam were making money on our bikes so they were built to a price and not that well finished; just look at the frame welding lol

I agree also that no factory worker in Japan would engrave the wrong number of scrub it out and change it like that. I imagine the process was to put two raw cast cases together, engrave a number and then perform the line boring and squaring up of the faces etc. they are usually oriented the same like someone did one after the other at the same time, not one now and one later... id not expect a worker to forget what number they were engraving in the one directly under and only an inch or two apart from the one they just did.

And... to forget in such a way they story went: Guy at the workstation is not feeling it today, Engraves IA208 and then has a brain fart for the 2nd engraving "IA... er... 196...? damn, no! ok, I meant 198...?!" The supervisor comes along and shouts 'No! youre an idiot Engraver-san...! The number is 208!" and engraves it on for them... hmm... haha...

Of course, it could happen and Yam wouldnt have thrown stuff away if it worked of course... and it is weird that these numbers are so close etc... but it feels 'unlikely'.

[steve63]

I bead blasted a set of cases last summer and the finish on them was a bit ropey to say the least. I don't remember other cases being that rough but I've not looked at any cases this closely for years.
I wouldn't touch them. Anything you do will only make them worse. You're only going to scratch them with a file and wish you'd left well alone.
Picture of the engraving for comparison.

[rolie]

Thanks for your comments.

I must admit the implications of the engraved crankcase numbers have taken a bit of a shine off the restoration project. Maybe I should have left ii in the boxes I put it in in 1994 and bought a Fireblade! It would certainly have been cheaper but I’d have probably gone mad during the covid lockdowns. It’s been fun so far. 🙂

Jon, irrespective of what happened with the engraving, you’re comment on the impact of unpaired cases is apposite. I bought the bike in 1991 and used it for 3 years, although to be honest it didn’t do that many miles. It was never on a Dyno but was running well for those years. The pistons are std and I’ve just replaced the rings with std rings as there’s no significant wear. The barrels are good and when I split the cases a few months ago there were no nasty surprises. Hopefully this indicates the two halfs are not a bad whole.

I must admit I still have questions about the engraving. 198 written and scored out twice and replaced by 208 still seems very strange to me. The numbers are only 10 apart and must date from the same time in the factory. I’ve looked closely at the engraving, and while the A1 198s look like a different hand, unlike Dave I think the 208s are actually by the same hand. The engraved dots, strokes and shapes look the same to me except for the collapsed bottom loop of the 8. It’s all academic I know but it does seem odd. Also, would someone replacing the bottom case in the 1980s even bother with engraving? The bikes weren’t a ‘classic’ back then. Why would they?

Like Hercule Poirot I feel my ‘little grey cell’ itch!

Rolie

[steve63]

There were plenty of bikes with miss-matches cases knocking around back in the day for various reasons. Personally speaking neither me nor any of my mates actually knew what these numbers were and what they were for. The innocence of youth eh? 🥴
I really wouldn't stress about it.

[4l04ever]

They look close enough to build. Build it then check everything turns okay and then leak down test them to make sure they are sealed good.

[rolie]

Thanks Steve. Life’s too short to stress about things like this 🙂.

The engine rebuild is underway! All good so far and if it starts at the end I’ll be happy. Having low expectations can sometimes be an advantage! I can only be delighted.

Rolie

[headcoats]

If you were 18, you would just have bolted it back together and got on with it :-)

[tony2stroke]

Mar 11, 2022 20:47:15 GMT 1 headcoats said:

If you were 18, you would just have bolted it back together and got on with it :-)

The cases wouldn't have been vapour blasted either 

Lets face it in the old days you got another engine from the local bike breakers, matching numbers, who cares. I need it for work tomorrow.

Most likely a 350 engine while you were at it 

[steve h]

You can always get a jewelers loupe and have a close look at the mating points of the 2 case halves and see if any small marks give a clue as to being a pair.
If the cases are cleaned up at those points after casting, it might tell you either they are or are not a pair.

[dusty350]

The fact this has been a running engine, with no obvious issues, would encourage me to crack on and rebuild it. The alternative is another set of cases - circa 200 quid and more nowadays, then add your vapour blasting and it's nearer £250+. You have nothing to lose by rebuilding what you've got. Use a good 3bond sealant and be really anal about how you rebuild everything. I would use genuine gaskets, and leave nothing to chance, but then that's the same for any engine really. I use sealant on genuine inlet gaskets too as that's a prime place for a leak. Get it all built up and then do a leak down test. If it holds pressure then bolt it in the frame and go and enjoy the Spring/Summer.
I bet there are plenty of bikes flying around with mis matched cases. Some will know about them, others wont, especially if the generator has never been off. Of course it's not ideal, and some engines will be a bad mismatch, but you have already proved yours ran fine "as is", so a careful rebuild will hopefully see you back on the road

Dusty

[muttsnuts]

the main thig here is if using them to double check that all bearings/shafts etc rotate freely, but also and this is important, the bearings/shafts have no movement either up and down or sideways, so long as you are good on those fronts then the cases should be ok, but you need to check those things as part of the build process, I do this even on matched cases, but then I do build alot of engines

[dusty350]

+1 on that. I bolt mine up dry, with no sealant, and double check everything for movement/tightness etc. Then unbolt and add the sealant, triple check everything and then bolt back up. Time consuming but worth the extra effort

Dusty

[headcoats]

Do a dry build first with gearbox and crank in and torque it up to spec then carefully rotate the parts to feel for any resistance

Dusty beat me while I was typing LOL

[rolie]

As ever, thanks for the advice guys. I will of course act on it.

I’ll do a dry build and keep my Threebond 1215 in its tube for now. Hopefully I’ll be able judge if everything is moving as smoothly as it should be and any play is acceptable (hopefully there’s none) before moving on. I’ll get someone more experienced to cast their eye over it.

The leak down test looks straightforward enough if you have the necessary kit. Being a complete novice at this I don’t, and I hopefully won’t be doing this more than once. It would be great if some kind soul would sell me or preferably rent me a kit for a few days if that was possible. Failing that I could at least 3-D print the exhaust and carb bungs if anyone has a 3D CAD file or an STL file they would share. Unless there’s an easy alternative like taping half a potato to the openings 🙂 it would be really appreciated as it would save me the effort of producing my own as a one off exercise.

Rolie

[avb]

Mar 8, 2022 18:09:17 GMT 1 steve63 said:

I bead blasted a set of cases last summer and the finish on them was a bit ropey to say the least. I don't remember other cases being that rough but I've not looked at any cases this closely for years.
I wouldn't touch them. Anything you do will only make them worse. You're only going to scratch them with a file and wish you'd left well alone.
Picture of the engraving for comparison.

ive blated loads of LC crankcases and these pics are quite common .castings getting older.imperfections in the moulds causes the spikey bits.not much you can do about it.the very early cases look like mirror finish after blasting.same applies to valve caings

regards

amdy

[oldbritguy]

I have a set of banshee cases which have loads of little casting spikes.
I will look at a few options of smoothing them as it will make them less likely to hold onto oily grime and much easier to clean too
John

[dusty350]

I guess varying grades of wet and dry will reduce the rough surface and not scratch the end product. Do that before vapour blasting would be preferable I think.

Dusty

[steve63]

Mar 13, 2022 13:41:22 GMT 1 avb said:

Mar 8, 2022 18:09:17 GMT 1 steve63 said:

I bead blasted a set of cases last summer and the finish on them was a bit ropey to say the least. I don't remember other cases being that rough but I've not looked at any cases this closely for years.
I wouldn't touch them. Anything you do will only make them worse. You're only going to scratch them with a file and wish you'd left well alone.
Picture of the engraving for comparison.

ive blated loads of LC crankcases and these pics are quite common .castings getting older.imperfections in the moulds causes the spikey bits.not much you can do about it.the very early cases look like mirror finish after blasting.same applies to valve caings

regards

amdy

These are quite late cases. I have some non tie bar cases. When I do them I'll see if there is any noticeable difference.