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After rebuilding my 1978 XS500 it refuses to start


AndyEllis55
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Hi all,

I have learnt a few things from stripping this bike down and rebuilding it. Do any of these points strike a cord?

1. try and get the bike started before stripping it down.

2. Do not order any replacement parts before stripping it down (not including any needed to get it running in the first place).

3. Clean and inspect every part before sending just the frame head stock and swing arm to be stripped (lots of other bits could use the same treatment).

4. Order as many replacement parts at the same time as possible, this cuts down on postage and waiting time.

5. If ordering parts from outside the EU check postage costs and import duty first (it gets expensive).

After saying all this I have enjoyed the experience and definitely want to do another one. Only snag now is that my rebuilt XS500 refuses to start!

I have stripped and cleaned the twin carbs, fuel is flowing into the float chambers, I have a good spark at the plugs, I have not messed with the timing so it should be OK, I have a new battery and a car battery to link to.

I did replace the old air box with K&N filters, but when I put the old box back on it still would not start. I am not sure if fuel is making it as far as the cylinders, but when I had the engine out I checked the valves and clearances.

When I take the air filters off the carbs are full of fuel and the suction from the cylinders seems OK.

Any ideas you can suggest to try would be greatly appreciated. Cheers Andy

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Try some quickstart fluid into intake or some fuel straight into spark plug hole. If spark is good and timing ok then you should get something, which would point to a fueling problem.

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As above, EASY START is your friend when it comes to a difficult engine, even really small sparks will make it fire. This stuff med_PDS04.jpg

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I disagree with using easy start. Yes it will start almost anything but that doesn't sort out the issue.

I would take the plugs out and leave out overnight. Pour a teaspoon of engine oil into each plug hole and rock the bike back and forth, in gear, to get the Pistons moving up and down to circulate the oil on the bores. I would recheck both inlet and exhaust valve gaps. Then a teaspoon of petrol into each bore, plugs back in and caps on and with choke on but no throttle try and start it.

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I agree with DT about using easy start as it is a dry fuel and not to be used except to give the engine a bit of help, I only suggested it as a way of showing that the engine runs then you can sort out why it won't run all the time. His idea is the proper way my way is a bit of a cheat really but gives you an immediate "will it run or won't it" so you at least know that your not wasting time trying to fix something that is just dead. If it won't start with easy start then your looking at an electrical fault cos if you spray ES direct into the carbs and it has spark then it WILL fire.

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