350 LC restoration

1980 Yamaha RD350 LC 4L0 Restoration – Part 11 – The Homeward Straight

bleeding the RD350LC oil tankSo I did a few other jobs since the last update, just minor stuff but still quite important. The gearbox was filled with oil – the specified amount of 1500ml went in there. No signs of any leakage so that’s a bonus. The two stroke oil tank also needed filling and the system needed bleeding. To do that all you have to do is make sure there is a fair bit of oil in the tank and then open the bleed screw on the pump body. It took a while before oil started to come through, I knew the pipe was clear as I had flushed the tank to get out any debris before I started. Eventually it come through though, there were some air bubbles in it so I left it for a while and all I get now is oil.

In doing this I found another problem that needs addressing – the oil light isn’t going out. I have put about 1.5 litres of oil in there now but it’s still not going out. It goes out if I disconnect the sender so it looks like a new sender may be needed. I’ll deal with that later.

There should certainly be enough oil in there for the light to go off. I put another litre in after this and the light still stays on so I’m sure the sender has gone bad.

I fitted a decent second hand battery that I had on the shelf – these bikes take very little current as there is no electric start so it’s only powering the CDI and the neutral light.

RD350LC 2-stroke oil tankUpdate on the oil light – I didn’t realise there is a check circuit through the neutral switch. The idea is that if the bike is in neutral the oil light comes on to show that the bulb and wiring is working ok. If you come out of neutral and you have oil the oil light goes out, if the oil is low it stays on. I verified all was well by putting it in first and the oil light went out so that’s panic over.

I now have to chase down all the other electrical faults. I have rewired the back light where I had identified an intermittent short so that’s all good now. The rear brake light switch is very sticky but the wiring is ok and the brake light will work – the front brake light switch is well and truly buggered and will need replacing – one is on order. The headlight low and high works fine, the side light circuit doesn’t – there is an intermittent that I think is on the 12 v feed to the handlebar switch, I ran out of day to verify that but tomorrow is another day I’ll have a look then. The horn doesn’t work – the button is missing. Fortunately a spare switch pack came with the bike so I am hoping I can make one out off the two and get that working. The two lights for the instrument illumination are not working – think it’s bulbs. The indicators all come on but only the left ones flash – that’s weird not sure what that will be. It’s enough to keep me busy though, that’s for sure and all of it’s needed if we are to get an MoT on this thing, which was one of the “must have” criteria. 

RD350LC fusebox Electrical gremlins aside all I need now is the exhaust gaskets and the idle screws and some coolant and I can see if it runs. It has plenty of compression, the carbs are clean and I have spark on both pots so it should go. The spark thing was a bit of a surprise really, I hadn’t tested the CDI previously nor had I tested the charge or trigger coils, the ignition coils or any of the associated wiring. All I did was connect everything up, bung a jump pack on it and kick it over – that’s Japanese reliability for you right there. It’s a damn good thick blue spark too so that’s very encouraging. Oh, I will replace the throttle cable first too, the last thing I want is for the brand new engine to rev it’s nuts off.

I have some decent Motul coolant that gets diluted 50/50 that will do nicely on the coolant front. Yamaha suggest a 1.8 litre capacity, the Motul stuff comes in 1 litre containers so that will work out nicely with slightly better performance to keep it cool in summer and unfrozen in winter.

I slept on the electrical issues and came to the conclusion I was looking at two separate intermittent problems – the main one being a dodgy connection behind the headlamp – the 8 way multi connector that provides the live feed to the switch pack. All sorted now so that’s another one off the list.

The indicator problem was the relay, I had another one, different type but it does the trick

While I was at it with the electrics I remembered from way back that the fuse box had a broken fuse holder and the previous owner had bypassed the fuse to make it work at the risk of melting his wiring. I had recently broken an old XJ900 which used a similar fuse box so I was able to steal one of the fuse holder terminals from it and graft it in to the LC’s fuse box. So that’s another minor but important thing off the list.

Just discovered that the horn fitted to the bike and the one that came loose in the box of bits are both buggered. One is open circuit the other has continuity but doesn’t oscillate. The 350 was different to the 250 in that it came with a pair of horns – a hi note one and a lo note one. I think it would be cool to put a pair of genuine ones on if we can source them.

First I have to fix the broken horn switch though.

The one on the bike is missing it’s button but it looks like the previous owner intended to address this issue as the bike came with a spare lower half of the left hand switch pack, which contains the horn button.

The horn switch is a pain to get to as the indicator switch sits above it and it’s all very fiddly but has to be spot on or things stick or don’t work – all things that make the MoT man get emotional and reach for the special red pen used to highlight defects. I had to unsolder the old one, remove the replacement from the spare unit and then solder it in place in the original switch pack. It all worked splendidly and the button now works reliably. All contacts were cleaned while I was in there.

It’s just really minor stuff now while I wait for the few remaining engine parts, tyres etc. I put the rear fairing back on, the chrome grab rail, the handle to help putting it on the center stand that no longerRD350LC switchgear

exists and the two side panels. The seat was given a damn good clean, the latches were lubricated and the seat plonked in position – it is now taking on a very RD like appearance.

A few bits of paint have gone on hear and there where you don’t want rust getting a hold but most of the black bits have been left with the age in them, as per instructions. The panels have been given a wipe over so they look presentable.

That’s it for now, I have to wait a few days for some more bits to arrive so it seems like an ideal time to break. I was hoping to start it by now but without the needle jets it’s not going to happen, I don’t have anything in stock I can borrow them out of either. I tried to get the rear tyre off – no chance, couldn’t get anywhere near it so when the tyres arrive it’s a trip to the tyre shop – the bloke there only charges me a tenner a wheel so it’s not going to break the bank. So seeya next time, Dave.

Article sponsored by Wemoto.

Article provided by David Powell of Boston Bike Bits.

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