tzr123 Posted June 19, 2009 Share Posted June 19, 2009 Hey erm yeah i got conned on my bike :angry: :angry: , It ran for 2 weeks then found out the 3rd sparkplug was stuck and wasnt working, i got it sent off to get fixed and after a month or 2 found out it had no compression in 3 of the pistons and something like 45 in 1. Whats this all about? Can any one help? Also this is going to sound retarded but is it the top end of bottom end that needs to be changed, cause i found a complete top end for sale but wasnt sure if it would sort the compression out? Cheers Danny Link to comment Share on other sites More sharing options...
junker Posted June 19, 2009 Share Posted June 19, 2009 the top end would be responsible for no compression, but buying a complete new head may be a bit overkill! and plus if you are buying a used one, hich you probably are, you are getting into a whole nother can of whoop-ass on your wallet! who says that the "new"one is perfect? it likely has the same problem yours has Bad compression means: A) that your piston rings in your cylinder head is not sealing correctly to the cylinder walls a valve is whacky and staying open or something... or is broken off (but it wouldn't run) C)you have a gigantic leak in your head gasket and/or heads (which you would see) I listed them in order of probability btw The 90% chance cause of the problem is A! And good news: a hone and new ringset is way cheaper than your "new" top-end! Obviously getting to the root of the problem and narrowing it down to a specific issue is the first order of action... so did the mechanic who told you it is broken tell you if he saw anything that made it break??? info: The seal is to prevent the air/fuel mix (pre or post-igniton) from spraying down into your crankcase, right past your pistons (blow-by). When a ring slides up and down, it is snug against your cylinder wall, and scrapes it, your oil is splashed up by your crankshaft onto the piston to further help lubricate this scraping (for less wear) and further SEAL the rings. Now over time this scraping eventually wears the rings down, by nature. If your motor has not undergone a restoration since the day it was built, then your rings are probably thin strands of steel and are not sealing. Also, Yamaha likes to make the heads and cases out of aluminum, which is awesome for lightweight but when it gets too hot, it tends to actually warp and distort its shape (it is a soft metal, screwdrivers will gouge it). FZR's were raced, alot! especially 400's Racing means cornering with low gears and high rev's, therefore high temperatures, therefore probable warping. Thin Rings + Out Of shape Cylinder Bores = no compression Solution= hone cylinders bores and replace rings. It is a fairly do-able task if you have time and a place to rent tools from, or just go and get a price from a shop. Or maybe make a deal where if you disassemble the motor and just bring him the head and piston crowns (cuts a bunch off of labor costs) one thing that has me confused is the extreme amount of compression in that 4th cylinder. It almost seems like all the other three decided to take a load off and dump into that cylinder... but that's almost impossible Link to comment Share on other sites More sharing options...
tzr123 Posted June 19, 2009 Author Share Posted June 19, 2009 Okay wicked cheers for the help Yeah the 3rd spark plug was stuck so we got the mechanic to heli-coil that hole(this is the one with around 45psi in it). Nah the mechanic didnt really tell me much which i was bit concerned cause i recon he may have cause the problem worse, But the garage i took it to before made it ten times worst it sounded like it had a sore throat after it came out of there, but the stupid retards told me it was "sweet as a nut" Ill carry on stripping the bike down prehaps later on today, or tomorrow Ill keep you posted if its one of those problems, its probably all Cheers Danny Link to comment Share on other sites More sharing options...
junker Posted June 26, 2009 Share Posted June 26, 2009 here is a link to an older topic that may be of some use to you! http://www.yamahaclub.com/forums/index.php?showtopic=13063 Link to comment Share on other sites More sharing options...
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