Paullaith Posted June 12, 2012 Share Posted June 12, 2012 Hi and thanks for looking at my topic, i was riding to work this morning and the bike was riding fine then after around 5 mile it lost most of its power. It was strugling to do 25 then when i got near work it cut out at the lights, when i tried to kick start it i got a pop from the exhaust and i think it seems down on compression. I rebuilt the top end 150 mile ago. All help will be greatly appreiciated. Link to comment Share on other sites More sharing options...
2 Wheels Posted June 12, 2012 Share Posted June 12, 2012 Did you re-torque the top end after the first 1 or 2 spins ? More info, could be out of fuel for all we know !! Link to comment Share on other sites More sharing options...
Paullaith Posted June 12, 2012 Author Share Posted June 12, 2012 Yes theres fuel going through it starts for a couple of seconds then dies and it dosnt sound right when its running. I dont have the tool to torqe the nuts up but a guy at work thinks it maybe the head nuts have come loose. They seem tight by hand but i will have to get the bike home to check it proppery. Link to comment Share on other sites More sharing options...
slice Posted June 12, 2012 Share Posted June 12, 2012 HI Paul, You can tighten the head down TEMPORARILY by hand just remember to do it in sequence, opposite and across and do each nut up just a little at a time, get it pinched enough to run you home and then do a proper job when your there, DON'T be a gorilla at it you just want to get home on it and just tight enough will work for a short journey, hope you make it ok! Link to comment Share on other sites More sharing options...
AndyDtr08 Posted June 12, 2012 Share Posted June 12, 2012 I would agree. Get home and check the compression. If you didnt re tighten the head nuts after you'd ridden it in a bit it could easily be a cylinder head gasket leak. I, personally, would have the head off and put a fresh gasket in and start again. 12-13 quid from yamaha for the peace of mind. Just remember to re tighten this time. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted June 12, 2012 Moderator Share Posted June 12, 2012 I found it nigh impossible to torque every nut on mine due to various gubbins in the way, so i torqued the ones i could and did the others by hand Link to comment Share on other sites More sharing options...
AndyDtr08 Posted June 12, 2012 Share Posted June 12, 2012 Yeah you can't get a torque on all of them. I've found that too. Have to just test the torque wrench on another on the bike and then try and match that feeling with a similar length spanner. Link to comment Share on other sites More sharing options...
Paullaith Posted June 13, 2012 Author Share Posted June 13, 2012 Ok lastnight i got the bike home as my boss lent me a wagon, all nuts/bolts were tight but when i took the exhaust of and operated the kick start and watched the piston it was hissing like air was passing the piston. Is this piston rings? Also it will start for a second then the exhaust pops and it cuts out. : ( Link to comment Share on other sites More sharing options...
Moderator Airhead Posted June 13, 2012 Moderator Share Posted June 13, 2012 hissing is normal paul, try another spark plug Link to comment Share on other sites More sharing options...
Paullaith Posted June 13, 2012 Author Share Posted June 13, 2012 Ok will do after work then il report back. Thanks. Link to comment Share on other sites More sharing options...
Paullaith Posted June 13, 2012 Author Share Posted June 13, 2012 Also is the back firing a sign of anything as it does it as soon as it tries to start and cuts out and it back fires when you try to start it if it dosnt start? Link to comment Share on other sites More sharing options...
Paullaith Posted June 13, 2012 Author Share Posted June 13, 2012 Put a new plug in and it wont even try to start, i took the new plug out after trying and it was soaking wet through and it smelt of petrol??? Link to comment Share on other sites More sharing options...
jimmy Posted June 13, 2012 Share Posted June 13, 2012 Are you getting a spark at the plug, cap, lead, coil Check all the way back and then go for the cdi unit. If any of your mates has a similar bike swap over the cdi and try that. Link to comment Share on other sites More sharing options...
Paullaith Posted June 13, 2012 Author Share Posted June 13, 2012 Yes theres a good blue spark there. Im starting to think head gasket? Link to comment Share on other sites More sharing options...
blackhat250 Posted June 15, 2012 Share Posted June 15, 2012 Yip sounds like lack of compression, how does the kickstart feel, ? is it easier than usual , if soft to kick over, strip top end, broken ring, is my guess, Link to comment Share on other sites More sharing options...
Paullaith Posted June 18, 2012 Author Share Posted June 18, 2012 Ok so ive had it all in bits, piston and ring looked fine so i put gasket seal on the head gasket and put it all back together then took carb off and give it a good clean. It felt better but still wouldnt start so i took the fly wheel cover off to find its the woodruff key : ( how do i get the nut off the crank when the fly wheel spins on the crank? Ps i know im an idiot lol. Link to comment Share on other sites More sharing options...
Moderator DirtyDT Posted June 18, 2012 Moderator Share Posted June 18, 2012 Bike switched off. Put the bike in gear and get someone to sit on the bike with the rear brake on. put a spanner on the nut and give the spanner a sharp crack rather than a push to start it off. You can get straps and other tools to hold the magneto. I have a pair of mole looking grips that have flat ends on one side - to hold the front sprocket - and studs on the other - to fit into holes in the magneto. Like this LINKY When the nut is undone you will still need to put the magnet/rotor off. There are specific tools but I prefer (and have) a puller set like this LINKY Link to comment Share on other sites More sharing options...
Paullaith Posted June 18, 2012 Author Share Posted June 18, 2012 Ok my mate is going to bring his impact gun home tomorrow s o will do it with that. Where can i get s woodruff key from? Thanks. Link to comment Share on other sites More sharing options...
Moderator DirtyDT Posted June 18, 2012 Moderator Share Posted June 18, 2012 The woodruff key is just a small piece of semi circular metal. I don't know why you want to change yours? It is on the shaft where the nut is you are trying to get off. It they break then the engine tends to run backwards. I would guess a new one is a main dealer purchase. Earlier you said that the plug was soaked in petrol. I would say that the bike was flooding and if you have a spark and are happy with the compression then I would check the float on the carb and if petrol was getting into the engine when the bike is stationary. I would dry and heat the plug up. with the fuel off, try and run the bike. Link to comment Share on other sites More sharing options...
Paullaith Posted June 18, 2012 Author Share Posted June 18, 2012 The woodruff key has broke the flywheel spins on the crankshaft. Link to comment Share on other sites More sharing options...
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