danidge Posted August 4, 2007 Posted August 4, 2007 right i have just rebuilt my tzr 125 1989 all of the engine parts are in extremely good condition, i have just done about 280 miles after the rebuild running it in gentally keeping it under 5000k and now its not starting atall. its not firing atall i dont know what the problem is because i have a reasonably good spark lots of compression carb seems to be working fine as you can smell the petrol when its kicked over without the plug in. the oil mix is set to standard from the haynes manual as is the fuel mixture. i really dont know why its not fireing, it should be as it has a spark :S if you have any ideas pleeeease help cause im stuck and i dont wana have to take it to the bike shop! thanks, dan xx
fosdyke Posted August 6, 2007 Posted August 6, 2007 Hi Check the ignition timing - if the bike has a flywheel magneto the woodruff key could have broken and put the timing out - it's happened to me a couple of times - and no matter how much you kick it - it just aint goin to go! On the bright side - if you can get the magneto off (you need a special puller) the keys are dirt cheap! (buy extras I did!)
danidge Posted August 6, 2007 Author Posted August 6, 2007 thanks dude il give that a look i took the head off today and looked into the barrel to see if i had broken rings but there didnt seem to be any damage to the berrel atall other than very fine up and down lines, i guess from running in as its only done 280 miles since the rebuild. one more thing the compression was only at 50 psi.. im not sure if it was the tester or i have a low compression problem but im not sure what the compression of the bike is supposed to be anyway. thanks for your help dan.
yoda Posted August 6, 2007 Posted August 6, 2007 Your compression pressure is low but ensure that you follow the manufactureers method of testing. It may be OK for low speed cranking.
fosdyke Posted August 7, 2007 Posted August 7, 2007 Hi 50psi seems really low 150 - 175 would be normal - as Yoda says check that you are using the compression tester correctly - and make sure you crank it several times with the throttle fully open. You are going to have problems starting it if the compression is under 100psi. Did you check the bore & rings for wear when you re-built the engine? And did you use new oil seals - could be an airleak on the PTO side. Don't take anything for granted - use a new plug, and fresh (that means straight out of the pump) petrol, with a thimble-full down the bore - see if you get a 'pop' - and check the timing - I cranked away for half an hour once before I realised the woodruff key had broken (common on a rebuild). Keep me posted
danidge Posted August 9, 2007 Author Posted August 9, 2007 Hi 50psi seems really low 150 - 175 would be normal - as Yoda says check that you are using the compression tester correctly - and make sure you crank it several times with the throttle fully open. You are going to have problems starting it if the compression is under 100psi. Did you check the bore & rings for wear when you re-built the engine? And did you use new oil seals - could be an airleak on the PTO side. Don't take anything for granted - use a new plug, and fresh (that means straight out of the pump) petrol, with a thimble-full down the bore - see if you get a 'pop' - and check the timing - I cranked away for half an hour once before I realised the woodruff key had broken (common on a rebuild). Keep me posted i did take off the head and check the barrel for signs of damage but there didt seem to be anything other than a couple of line that you can only just feel with your fingernail, it did have a new piston + rings and a rebore when it was rebuilt so that why i was a bit shocked about the compression problem. i did use new oil seals i also put in new big ends, little ends, conrod and main bearings. il investigate some more possably tomorrow, and again thanks for your help
danidge Posted August 13, 2007 Author Posted August 13, 2007 i did take off the head and check the barrel for signs of damage but there didt seem to be anything other than a couple of line that you can only just feel with your fingernail, it did have a new piston + rings and a rebore when it was rebuilt so that why i was a bit shocked about the compression problem. i did use new oil seals i also put in new big ends, little ends, conrod and main bearings. il investigate some more possably tomorrow, and again thanks for your help Right it was my rings which was a supprise cause they were new. my bottom ring as stattered and the top one was wedged in place because the piston at the front had some scoring on it that held the ring in place :S but the bore is still fine ? anyone have any ideas how this could have happened?
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