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Chain break, now engine won't start


AndrewElvisFan
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New chain and sprockets on now. I was a bit surprise I had to adjust the rear wheel to the 5th marker to get the chain at the correct slack. Still wont start, but I think it is unrelated to the chain going. She was getting awkward to start anyway. I've checked all wires are in place, adjusted the timing chain, checked fuel is getting through etc. I do have spark at the plug, but appears quite weak and yellow. Mrs Elvis has had to go to work so I'll pick up another plug tomorrow. Fingers crossed that will sort things.

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Will do! The plug is about 6k miles and 12 months old. If I hadn't been ill over New Years none of this would have happened!

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Check the HT lead connections at the coil end and the cap end too and any coil earth. Pour a spoonful of fuel down the plug hole, replace the plug and see what happens.

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Didnt lock the back wheel up, by the time I had pulled over onto the hard shoulder I had already hit the engine stop so honestly don't know for sure.

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Most of the chain had rolled off but the last few inches were stuck behind the drive sprocket casing.

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Forgive my ignorance but is the flywheel behind this:

Posted Image

If this is it, do I need to remove the casing, or should I be able to see by removing fig 1 and 2?

My torch is beginning to fail now so I'm struggling to see anything!

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Yes Andrew but you need to take the whole case off, not just a cover. The flywheel should not spin independently of the crank (or piston). The flywheel needs to come off to change the woodruf key.

Great suggestion from Paul BTW.

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Page 4-44 in the manual is a good place to start and look at the diagram on 4-46. If it is the woodruf key it should be able to be fixed with the engine still in the frame and no changes to the timing.

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Cheers for that. I can get a finger in and I cannot turn the flywheel so I'm hoping that means the woodruff key is good. I'll get the casing off tomorrow and check properly.

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Remove the casing, use a puller and the woodruff key will be sitting in a slot on the crank (if its still there). I asked if the burst chain had stalled the engine, which if it was wrapped round the engine sprocket, it would have done then there may be some damage to the valves of may have knocked the ignition timing out.

If as you say it was becoming a crap starter with a poor spark could indicate an ignition cdi fault. They usually just fail, but my sons old sr125 went through 3 cdis during his ownership (problem being buying from a breakers meant replacing a 20yr old part with another 20yr old part)and one of those displayed a weak yellow spark. Unfortunately the only testing method is by replacement

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