1980 Yamaha RD350 LC 4L0 Restoration – Part 9 – Now We Are Motoring

RD350LC Barrels, crank and pistons - ready to fit!Project Elsie Part 9 – Now we are motoring.

So with all the lovely parts back first thing to do was check everything was present and correct. It all appears to have been done to a very high standard, the digital vernier combined with the bore gauges confirmed everything was spot on. We have all new rods, little ends, crank pins, bearings, seals, gaskets, pistons, rings etc. No skimping on this – it’s all good stuff.

Before any of this nice shiney stuff goes anywhere near the engine casings everything is getting a damn good scrub. I am not interested in making the engine look pretty, I am interested in making damn sure no bits of detritus can get in there and cause havoc later. The cases got washed, dried, inspected, washed again, blown out with compressed air and checked again. I am now happy with them, if I was going to polish them up now would be the time to do it. The oily rag principle however will be adhered to without reliability being compromised.

Before I started putting it all together paranoia crept in and I thought I better check the new bearing retainer that I had made for fit. It fitted fine so I hardened it and then checked it again as quite often steel does funny things when being heat treated. I have replaced the gnarled old JIS headed screws for some Allen headed ones so if anybody has to do the job again it will be a lot easier for them. A wee dab of threadlock will be applied on final assembly.

RD350 LC engine bottom endSo now it’s out with some of Grenville’s finest RTV sealant as per Yamaha’s instructions and the two halves will be brought together. Best remember to fit the crankshaft first I suppose, fitting it after would be a lot more difficult 🙂 The new crank seals will go in at the same time – bit of an anomaly to watch out for here. In the old Haynes manual it talks about fitting the right hand crank seal with the castelations to the inside but one of the photos shows the castelations clearly on the outside. If you look further where other bits are being added the castelations are definitely on the inside and abut the main bearing. Both seals get a smother of grease between the lip seals before being put in place.

It’s all quite simple from here, as stated in all the best manuals replacement is a reverse of removal. Once the two halves are together I like to leave them for a bit just to let the goo go of, it’s a bloody good excuse for coffee and biscuits.

The bearing retainer I made earlier is the first bit to go on as you can’t get at it once the clutch basket is installed. Next comes the two gears that drive the oil and water pumps, followed by the Belville spring washer and the nut. The washer is the locking device for the nut – the outer gear is not keyed so the nut needs a reasonable amount of torque on it to make sure it can’t come undone.

RD350 LC kickstart shaftNext in is the kickstart assembly, it’s important to make sure the tang of the spring is located correctly before hooking the other end of the spring over it’s retaining peg. On some bikes it’s a real pain, on this one it was so easy I was sure it was wrong. Quick check of the manual and I was happy again. It’s always worth double checking when working this deep in an engine – putting it back together and realising something deep inside is wrong is not funny. Unless you are an onlooker in which case it’s hilarious.

All seals and o rings were replaced as I went including the one on the water tube, the main bearing seals, the gearbox output shaft seal, the clutch pushrod seal and the gear change seal. All of these came with the seal set, a couple were duplicated in the gasket set. When installing them be really careful to make sure they are the right way round otherwise they won’t do their job. Don’t be afraid to use plenty of oil when reassembling either, the lips are easily damaged .

RD350 LC clutch installedThe clutch goes in next making sure the spacers and washers are all in the right order. The metal plates went in as per the instructions with the ground off side being 60 degrees round from the last plate – I described this way back in part 2 or 3 or something. Be careful when putting the large o-r ings in not to get them twisted – I used one of the metal plates to push each one back which seemed to work rather well.

I plopped the two cylinder base gaskets in place and called it a day – tomorrow I will install the pistons, barrels and head. Depending on what else is going on I may even get the engine finished and ready to go back in the frame.

As another day of isolation dawns the workshop beckoned and work continued. First job was to clean up the head, remove the old gasket and make sure it was flat. All pretty straightforward stuff if you have the right kit. I used my engineer’s plate to make sure it was flat – it was. I then put a sheet of brand new wet and dry on it and worked the head over it just to make sure it was absolutely clean. I couldn’t get a 1 thou feeler gauge in anywhere, it’s the flattest head I have ever seen.

RD350 LC piston and ringsNext job was to install the pistons and rings – the ring kit had 3 rings per piston, the fattest ring goes in the bottom groove, the spring washer type ring also lives in that groove and has to be inserted first. The rings must be installed so that when closed up in the bore they form a seal around the locating pins, thus:

It’s vital to make sure the pistons are installed in the correct orientation ie with the arrows pointing forwards towards the exhaust ports.

The bit I hate is next – where you have to squeeze the rings closed and push the barrels down in to position. I always think I am going to break a ring or something. I needn’t have worried, they slid in to place perfectly with just the right amount of resistance you would expect from a brand new engine. My best tip at this point is whatever you do make sure the openings to the crank case are sealed with cloth. The chances of not getting the circlips for the gudgeon pins in first time are quite high, if you drop one in the case you might have to undo it all again, which would be a mare having just applied silicon RTV.

RD350 LC cylinder headWith the barrels in place it’s time to bolt the head down remembering to put the gasket in first – writing side up. I spent quite some time trying to remember where I had left the head bolts before I had a eureka moment and remembered I had put them in safe keeping in my other workshop. I have no idea why I did that and even less idea why I have just admitted to it. Oh well.

RD350 LC engine and barrelsEverything got a good coating of quality two stroke oil to help the fitting and bedding in process, it’s surprising how as you add each oil seal the engine becomes a bit harder to turn. It is a lot tighter now than a used engine but it will soon loosen up, in fact just turning it over by hand a few dozen times has already helped a wee bit. Next bits to go on were the rubber inlets and the reed valve blocks, new gaskets were fitted, of course – every single seal and gasket will be new. I have not done the head bolts up fully at this stage as it’s much easier to do them with the engine in the frame. Talking of which I think it’s high time that’s exactly where it should go.

I wish all engines were this light and easy to fit, it went straight in with hardly any effort, a crow bar between it and the frame allowed me to line it up without assistance and pop the two fixing bolts in place. They were torqued up and the job’s a good un.

I had already oiled up my rag and rubbed it around the places that would be hard to get to with the engine in place.

RD350 LC complete engine ready for installThe bike is now the most complete it has been for a good few years. Tomorrow I will strip and clean the carbs and put them back on the bike, I shall fit a new air filter while I am at it – I need to repair or replace the top that somebody had drilled a load of holes in, not sure which way to go with that yet.

It’s looking good though.

As I was on my own I tied the cables up out of the way while I man handled the engine in to place. This one is much easier than the big fours that I usually work on but even so small things like that can make the job so muck easier and therefore safer. I don’t think the owners would be too chuffed if I damaged the bits it’s just taken them six weeks to find and no small amount of money to buy.

I will fit the engine panels tomorrow, the left hand one will have to come back off when the chain and sprockets arrive but it will help keep everything clean until then.

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Article provided by David Powell of Boston Bike Bits.

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