RD350 LC engine stripped

1980 Yamaha RD350 LC 4L0 Restoration – Part 4 (Stripping The Engine)

Project Elsie Episode 4 – Stripping the engine.

Ok I know I started the engine strip in the last exciting episode but this episode will be even more exciting and the strip will be completed – how much more excitement do you want?

So with the flywheel from hell finally removed the next job was to take the other engine side panel off and have a look to see what everything in there looked like. Rather good was the answer. As is normal one bolt was a swine to get out but fortunately I could get the mole grips on it and persuade it to give up it’s futile quest to remain in place. The clutch looks brand spanking new and all the gears look pristine – there is nothing in there to suggest 40 odd thousand miles of use so I am happy it’s all reusable. The oil pump looks good, there was oil in the exit pipes so it looks like it was doing it’s job when the bike was last run. I don’t trust these things, I have seen a lot of engines destroyed from problems with autolube pumps, particularly on outboards, they just make me nervous. The first half a tank of fuel after the rebuild will be premixed at about  to 25 to 1 so that I have a chance to see the pump working and bleed any air out of the system without the risk of damage. Once I have seen 2 stroke being pumped out of the two pipes I will reconnect them and then run the autolube system as Yamaha intended.

If you look carefully there are traces of red silicon sealant everywhere including several places you don’t want it.. There is a quite a bit in the crankcase, in the water ways and pretty much everywhere else, making sure I clean out every last bit is going to be time consuming but totally necessary.

RD350 LC engine internalsAll of the other bits came off without too much drama, the clutch, starter assembly etc all complied with my requests and almost disassembled themselves – the only exception being one small screw that hold on the input shaft bearing retainer behind the clutch. It is held on with 2 screws, one came out the other simply wouldn’t budge – no biggie though as you can separate the two halves of the crank case by just taking one or other of the two screws out.

Yamaha did a nice thing by stamping numbers next to all the bolts to show you what order they need to be removed and replaced in – don’t think I have ever seen that on a bike engine before. There are a total of 16 nuts and bolts in either 10mm or 12mm that need to be removed before the halves can be split.

Everything looked pretty good, the clutch plates and springs appear to be virtually new, a couple of plates were stuck together which would have made finding neutral an awkward and possibly futile exercise.

RD350 LC clutch plateIncidentally, I have never had a clutch apart on one of these before and a couple of things surprised me. The first was that the metal plates are not entirely round – each one has a part taken off one side. Apparently Yamaha did that to ensure that to unbalance the plates slightly in such a way that centrifugal force helps prevent clutch noise. I am guessing that as I have never seen it on another bike the idea wasn’t as good as it seemed. When reinstalling the cut off bits have to be spaced equally at 60 degrees to the previous disc so that the assembly is balanced when it is all together. They were not right on this bike, that will be corrected when it all goes back together.

A word of warning here – the primary gear and pump drive pinion go on the end of the crankshaft and have a washer followed by the retaining nut. This washer is a thing called a Belvillle washer – it is important to keep hold of this and not swap it for any other kind of washer. It is actually a conical spring. They have several other names but must not be confused with a standard washer – I just thought you should know. I’m good like that.

With the engine now fully open I could see the gearbox for the first time and also check each main bearing individually and fully. Not good. Two of the mains feel slightly less than perfect, as we have to have the crank apart anyway replacing them seems like the only option really.

RD350 LC gearboxThe gearbox has been seriously mangled with 6th gear being the particular victim. I haven’t seen such a mangled mess of mutilated metal in a very long time – I have no idea what happened other than of course a major seize up of the engine at high speed. Whatever it was both pinions need to be replaced, so that’s another couple of bits to be sourced.

 I can’t go any further on the engine now until the parts are in hand so the next exciting episode will focus on the exciting task of sorting the brakes out – please try not to wet yourselves. If the weather improves a bit I will get the frame outside and de grease it, there are a couple of areas of rust that need dealing with and a wee bit of painting to be done. There is also some electrickery jiggery pokery to jiggery poke including fixing the badly bodged fuse box.

So that’s it for now, please join us next time for more fun and frivolity.

Article sponsored by Wemoto.

Article provided by David Powell of Boston Bike Bits.

Boston Bike Bits