251LC

I guess no one thought much of the F2 frame repair lol

Ok, back to this build....

And then onto cyls.... Like a good Airfix kit or Mecano set, it’s all about collections of parts to assemble and doing it in stages:

Stage 1: PVs



Yep, that’s a lot of bits... and it’s missing the screws for the PV caps in the pic lol Oh... and the exhaust studs which I must have robbed for something else so i had to locate 2 rezinc’d ones from spares. It does include NOS PV bushes (already out of their Yam packets by this time) which are silly rare now even in Aus which was a big market for 250s back in the day due to registration rules.

I cleaned up the cylinders with a blade. re cut all the threads and then used a stone over the reed cage area as I often find that people do these up so tight they pull up the threads. This time i was lucky and they were ok.

As the PVs got the 3 new bushes it meant that the NK plates didn’t fit as they’re designed for the baggy old wizards sleeves of a slot to fit in, so I had to slim ‘em down a smidgen. With the new parts fitted it’s all very tight and new feeling in there now.

Stage one done:








Stage 2: building up the intakes... New Yamaha rubbers, old OEM 250 reeds (ready for clean up with the brush and blade) and thick gaskets I think from an AC set I got years back, it was the only LC/250YPVS sized set I had available and of course rezinc'd bolts.



You can see them done in the next stage along with some natty stickers i bought from Norbo years ago for the PV end caps.


Stage 3: fitting the cylinders to the bottom end.






Pistons onto the bottom end



Then cylinders and lastly it’s time for the head. This was fitted with and OEM gasket along with some copper gasket spray (which i have never used before, but after the issues with my LC head gasket Ive decided to use it from now on) and rezinc'd nuts which really lift the look of any engine rebuild. Im using a new 50DegC Yamaha snowmobile thermostat on this build, but am waiting for the rubber from Norbo until I can fit it, which is why its not got the housing fitted in the later photos. The beauty of that unit is that it doesn't need a step un spacer to work and only costs US$30.



And we’re done! Its all very pretty and new looking considering what I started with. in the pic you can also see im using Samco hoses with stainless steel copies of the OEM wire hose clamps.

All set up here for the pressure test using Dan's kit with my solid alloy exhaust plates and new spark plugs:







In all this build up the only issues I had were with the TKRJ piston clips which were just horrible to fit and also a strange one with the PV joiner. It looks new and yet it didn't fit tight. Checking it with some other units i could see it was slightly larger in all dimensions (and was touching the PV seals) than the others and yet the flat land was also slightly smaller and as such didn't fit the PVs. weird. I've never seen an aftermarket version of this part that wasn't CNC so I find it hard to believe someone would copy this nasty cast item and get it wrong enough for it to be larger and so wrong... so it must be OEM, maybe for another bike? hmm... I swapped to another clean and very much like new unit and it slipped on perfectly.

Thanks for the kind words Alex! Im wondering if you ever sleep

I do agree its a thing of beauty and for once Ive gone a bit bling with this one by polishing the YPVS head and fitting the natty stickers as I think they go well with the clutch window and polished stainless motif on there. Usually I shy away from bling but I do like a change

Excellent job on the frame repair. I wish i had your skill to do that. The Valve engine does look a beautiful thing when its built up.

Fabulous work Sir.

So.... I expect you’re wondering what happened with the pressure test?

Well... It lost pressure, not fast but steadily. I was a bit gutted but the YPVS do tend to leak a bit on these engines, so I grabbed the window cleaner (works really well for this and dries ‘streak free’ of course) and...

The YPVS was fine. No leaks at all. Hmmm... I carry on doing my rounds... To find the usual failure on the intakes. Not awful and very very slow for once, but there all the same.



But that wouldn’t account for the loss I was seeing.... So, in case the schrader valves on the test kit were passing I blasted some window cleaner on them and this fast leak was very annoying to find:



Seems the leak was through the actual plastic of the pressure test kit. WTF?!

To be honest I’ve been wondering about the longevity of 3D printed parts for a while and it seems that there is little of that feature built in with most 3D printing, it’s more about the here and now and not about the future. I’m not 100% sure but I’ve not seen anyone else have an issue with this kit so can only assume that it must be because we get warmer temps here in Aus than the UK.... but if the extra 15-20 degree garage temps are killing plastic parts while they sit in my toolbox, then I worry for even for the colder climes as 15deg is hardly any heat differential at all. Just imagine how hot any part that sits in the sun or anywhere near a running engine would get.

I know there are different plastic wire options and maybe this kit uses the wrong type, but I think the biggest problem is that most parts are not made ‘solid’. To save on material they are made with a honeycomb center which means they are inherently weak for any pressure use. They are also made of melted dots or runs of liquid plastic ‘wire’ and as such were never a single formed item, so when gently heated (or aged?) they return to their dot form. This means that the beautifully made and contoured parts can become porous.

Had they been solid the air could not escape so easily, but all it has to do in this design is slip past the outer layer and then pass across the inner honeycomb and through the outer layer again. The outer layers are only as thick as card, say 1mm max, so any cracking or breaching of those thin areas means the part is ‘done’.

I should add that my pressure kit is not a well used set of parts, these bungs have been used only once before as this is my 2nd kit and before that I used my own kit from plumbing and pool shop parts. Anyway, I don’t blame Dan for the failure as such, I think its a wider problem of the plastics and techniques used in 3D print manufacturing that’s the issue really. But, you should be aware if you have such a kit that this could happen to you.

FWIW I had already had issues with the exhaust parts of this kit which had been left under pressure (locked up on the exhaust nuts) for almost 2 months when I became ill and not only warped but actually cracked. Today I snapped this one open like a dry twig to show the inner structure used in the manufacture of these parts. I’d already replaced these with some 10mm thick alloy plate (you can see it in the engine photos).



I guess I’ll end up finding something else in plastic or making up alloy parts for the intakes now I guess. Sigh. These engines need to be pressure tested, I just never thought it’d be such a slog to make up a kit to do that.


Anyway, to end on a better note, I sealed the intakes with a gentle smear of 1211. Should be fine now, they were barely leaking but better to have them right.

I'll have to make up something to fit in the inlets. That means taking on inlet to our equiv of B&Q (Bunnings) and looking at the plumbing pipe and end caps. I used end caps that were a perfect fit on my 421 with 34s, but these manifolds are smaller of course. Once Ive found something I'll have to put in the shraders and seal them in etc. At least plumbing plastic is made solid and designed to hold pressure so will work now and in the future.

Its not the valve Toby, its the plastic housing.

Yes I guess that would work as it would form a barrier for the air. I think at this point it would be simpler to find a more solid solution as one of my others cracked and snapped off where you pull these out from the manifold. Tehy have a nice place for your finger and thumb, but if you squeeze when they are brittle they just break off.

I agree is not ideal. I really only put it up here to illustrate what i believe is a 3D printing issue. We may well see more of this kind of problem over time as quite a few guys have been offering 3D printed parts for restos etc

Thanks mate, I also thought that about once every 30 seconds while I was doing the repair. I just cant see how you could damage that bit enough and not ruin the engine cases (which were fine) so I think it was done 'post mortem', ie when the bike was off the road and at the end of its life. Weird tho.

Thanks Steve.

What's weird is that it was cut out of the roller. The swinger, forks etc were firmly bolted on and hadnt been off in years, so it was kicked on its side and hacked with a grinder. bizarre.

Hi jon

Looks real good, a work of art on that frame ( i did notice )

Not sure if you noticed but the inner side closest to the joint castle seal on the LH barrel ( the right one in your pic) does seem to be fully set home

Love that engine,hope mine looks the same too

Time to put the engine in the frame.... A mate (thanks LB!) came round and within 5 minutes the engine was off the stand and in the frame. I could have done this on my own or with help from the Mrs, but he and I have done this as a team before and as he has done his own engines in these bikes plenty of times he knows exactly what to do and its a simple job when done together and we don’t scratch or damage any of the paint or powder. Thanks mate!

Engine was bolted in with green zinc’d engine plates and more of the rezin’d bolts and next up the rad went on (with it’s flashy new fah-ler stainless cap that I found in my spares as Id bought it years back) and the hoses put into place with more stainless wire clamps. I was a bit disappointed that I had to trim the expensive Samco hoses to fit, but its a YPVS kit on an LC so I guess that was always a possibility.

I also bolted on the converted kickstarter that was made by my mate Mark in Texas. YZ alloy kicker with modified YPVS knuckle. I actually pulled this apart, tidied and glass blasted the alloy part and rezinc’d all the knuckle parts and it looks like new now.



This long shot I really like. The garage art looks like its about to eat the mirrors and clocks off the bike haha.



Ok, enough frivolity... time to get cabling... NOS 360 code tacho, New OEM 4L0 throttle, new 29L PV cables and new 51L clutch. I hate to think what this lot cost, but hey nice new cables mean a much better experience of using the bike so all good. I left the PV cables disconnected from the servo until Ive cycled it, Ive no idea at this point if the thing might want to move through 180Degrees when its powered by the controller which would destroy the cables, so for now they remain loose.





A bit later on and we are getting there... Sadly its covering up what was a nice clean looking engine lol I also fitted a new oil supply line (90445-09021-00) which fitted really well considering its not a formed pipe, only straight. It is grey though which is a shame.



With that side mostly done, I need to start on the other side, which is looking a bit bare.



More when I’ve summoned up the mental strength to remove the plug and replace the stator grommet, never any fun!

Thanks Howard, There is still a way to go yet, plus ive got a few parts to come from the UK as well which wont be here for a few weeks, that'll slow me down... and then there is the paint, hmm...

Actually the garage is a problem. I have to put one of the cars in when it hails (and drive like hell to a covered car park nearby in the other) and that means shoving everything to the side at 100mph as the warnings are short. Im also running more and more out of space as I build boxes into bikes. My old garage setup was great for storage or parts and sub assys, but as Im building up Ive got bikes in front of tools, benches and boxes and its not at all ideal. The VFR in the pics finally picked up by its new owner (haha hes on here and will read this lol) this week so that's helped but once I start on the LC2 this 51LC will be in the VFRs place and im back to not having enough room again. grrr... time for a big garage reshuffle I think.

Haha, yeah thats about right! It needs a regig and more of the stuff from the rafters used on bikes. All the pipes are ready for projects etc.

Kicker info:

Hi Phil, no electrics sorted yet so its not run, but as I mentioned earlier someone suggested it will spin pink. We'll see if theyre right when its running