Ricky Posted February 17, 2014 Share Posted February 17, 2014 Hey guys, some of you may know my YZF is f**ked I'm going to be doing a compression test on it tomorrow and need some questions answered What would the ideal compression be on my Yamaha YZF 125? It's a single cylinder (obviously)I may have drained the battery a bit trying to start it (my bad) is that a problem? It still turns over but slower How do I know when to stop turning the bike over?Sorry I'm a massive noob, I just want to do it right Quote Link to comment Share on other sites More sharing options...
Tango Posted February 18, 2014 Share Posted February 18, 2014 Pull the spark plug out and put your finger in the plug hole and spin the starter....there should be enough compression to blow your finger off the hole....a quick and dirty check.....but it'll tell you if there's compression there or not. Then ideally you should have a fully charged battery when trying to start it.Did the bike just stop....or did it cough and splutter a bit first? Quote Link to comment Share on other sites More sharing options...
Guest Posted February 18, 2014 Share Posted February 18, 2014 On average.. Of what ive seen.140 - 160 psi mark, = spot on compression (generally from a brand new engine or so)120 - 130 psi mark, = good compression, wouldnt concider it needing rebuilding just yet..110 psi or below, = id concider it to be on the weak side, and needs work..With my engine rebuild (All top end rebuilt), i was getting 134 psi.. and thats brand new everything, piston, rings, barrel, head, gaskets, valves etc..id give the battery a full charge before testing, so that the starter motor has enough umph to get that piston to the top and give an accurate compression reading.. Quote Link to comment Share on other sites More sharing options...
Ricky Posted February 18, 2014 Author Share Posted February 18, 2014 Thanks you guys Hey tango the bike was coming down hill and I heard a horrible clicking noise so I slowed down and then kaplunk the engine stopped and won't start When I first tried starting it the bike was making a horrible noise like clickity noise but now when I start it doesn't have that noise it just sounds like it won't fire Thanks petrolhead I'll use this today Oh and yes guys I did have oil in it Quote Link to comment Share on other sites More sharing options...
Grumpy Old Git Posted February 18, 2014 Share Posted February 18, 2014 Looking into my crystal ball I predict that you will not be able to feel any compression with the 'finger test'.I further predict that you have either snapped the crank or the piston rod.A'new' engine (you may get a cheap one from a breakers) or, many hours of strip down, identify parts, order parts and rebuild.There again, I could be wrong but from your description of the sounds heard and the symptoms, I think you have got a serious problem.If you are extremely lucky, it may be a cheap fix.Good luck. Quote Link to comment Share on other sites More sharing options...
Joeman Posted February 18, 2014 Share Posted February 18, 2014 Hey tango the bike was coming down hill and I heard a horrible clicking noise so I slowed down and then kaplunk the engine stopped and won't start Thats the noise my Mirc made when its cam chain pully snaped and the timing chains came off. like the noise of someone dropinng a heavy chain on the floor.If thats the case with you, your engine is dead - RIP. Quote Link to comment Share on other sites More sharing options...
Mr Fro Posted February 18, 2014 Share Posted February 18, 2014 I further predict that you have either snapped the crank or the piston rod.As I gaze in to the ether I see a bent valve... Quote Link to comment Share on other sites More sharing options...
eastanglianbiker Posted February 18, 2014 Share Posted February 18, 2014 I further predict that you have either snapped the crank or the piston rod.As I gaze in to the ether I see a bent valve...or broken and dropped valve into crown of piston smashing it Quote Link to comment Share on other sites More sharing options...
Stu Posted February 18, 2014 Share Posted February 18, 2014 I think your wasting your time doing a compression test personally I would just dive in and start pulling it apart Quote Link to comment Share on other sites More sharing options...
Ricky Posted February 18, 2014 Author Share Posted February 18, 2014 I tried doing a compression test but I didn't have te correct attachment for it, I tried doing the finger test and yeah, very little air was being pushed out...FUCKS sake!I'll dive in to the engine tomorrow, been sorting a friends Chinese moped Quote Link to comment Share on other sites More sharing options...
Stu Posted February 18, 2014 Share Posted February 18, 2014 f**k the YZ and get the TZ on the road Quote Link to comment Share on other sites More sharing options...
Ricky Posted February 18, 2014 Author Share Posted February 18, 2014 f**k the YZ and get the TZ on the road I'll have some new pictures soon on the TZR soon got some tires on order, and a few other bits and pieces that will be on shortly I'm just being a lazy f**ker and need to get my arse into gear and the money isn't exactly rolling in The YZF is my main form of transport so that will need sorting first though I'm afraid Quote Link to comment Share on other sites More sharing options...
Stu Posted February 18, 2014 Share Posted February 18, 2014 so whats your plan? rebuild or just stick another engine in? obviously you will need to know what has actually gone on it although I suspect a dropped valve Quote Link to comment Share on other sites More sharing options...
Joeman Posted February 18, 2014 Share Posted February 18, 2014 so whats your plan? rebuild or just stick another engine in? obviously you will need to know what has actually gone on it although I suspect a dropped valve Dont we know someone who's dad can fix dropped vales in 10mins?? ;)Whip the head off, see the damage, buy a new engine. Quote Link to comment Share on other sites More sharing options...
Stu Posted February 18, 2014 Share Posted February 18, 2014 yeah i was thinking the same joe Quote Link to comment Share on other sites More sharing options...
Ricky Posted February 18, 2014 Author Share Posted February 18, 2014 Can you forward me there number please joeman Well, I'm going to take the head off tomorrow, and take some pictures and then post them on here so you can all tell me it's f**ked and I'll probably try a rebuild, I cant afford a new engine, the last mechanic charged me around 800 quid to find me one and fit it for me! Quote Link to comment Share on other sites More sharing options...
Stu Posted February 18, 2014 Share Posted February 18, 2014 http://www.ebay.co.uk/itm/Yamaha-Yzf-R1 ... 27deebce47 Quote Link to comment Share on other sites More sharing options...
Ricky Posted February 18, 2014 Author Share Posted February 18, 2014 Hmmmmm, that looks more than perfect! If all the evidence works out i'd be happy to spend that It's only got an hour left on it so I can't get that one, have to wait till I get money Quote Link to comment Share on other sites More sharing options...
Joeman Posted February 18, 2014 Share Posted February 18, 2014 The forum should start doing "payday loans" for when cool stuff comes up on ebay and members needs to borrow some cash Quote Link to comment Share on other sites More sharing options...
Stu Posted February 18, 2014 Share Posted February 18, 2014 The forum should start doing "payday loans" for when cool stuff comes up on ebay and members needs to borrow some cash you must have read my mind although it would never happen due to the risk of people doing one hmmm wonder what interest rate I could charge Quote Link to comment Share on other sites More sharing options...
Joeman Posted February 18, 2014 Share Posted February 18, 2014 The forum should start doing "payday loans" for when cool stuff comes up on ebay and members needs to borrow some cash you must have read my mind although it would never happen due to the risk of people doing one hmmm wonder what interest rate I could charge We're going totally off topic, but the engine's knackered anyway, so i'll carry on...you can mitigate the risk of someone running off by spreading the loan across a number of members.So lets say someone needs £300 to buy a new motor. 30 people lend £10 each, the loan is settled on the agreed date, and each get back £11. the borrower has paid £30 in interest, and nobody has risked more than £10."Peer-to-peer lending" at its finest Quote Link to comment Share on other sites More sharing options...
Stu Posted February 18, 2014 Share Posted February 18, 2014 you have far too much time on your hands joeman although that sounds like a cracking idea and yeah off topic but as you say f**ked engine who cares now Quote Link to comment Share on other sites More sharing options...
Ricky Posted February 18, 2014 Author Share Posted February 18, 2014 Hahahahahahahahahaha I would never borrow money of the lovely members of this forum I can imagine what the rally would be like if I hadn't paid you all back Yeah, anyway I'm still going to take the cylinder head off because I have nothing better to do tomorrow, and maybe by some stroke of luck, it's only the piston rings Quote Link to comment Share on other sites More sharing options...
Adam Posted February 18, 2014 Share Posted February 18, 2014 Don't forget the YZF shares the same engine as the WR so have a look at them as well might be a cheaper one. Quote Link to comment Share on other sites More sharing options...
Ricky Posted February 19, 2014 Author Share Posted February 19, 2014 Don't forget the YZF shares the same engine as the WR so have a look at them as well might be a cheaper one. Ooooh, I didn't know that Thanks for the info, that'll broaden my search a little more Quote Link to comment Share on other sites More sharing options...
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