Engine breather causing issues HMMM

[Mike_DooM]

Hey All,

My good old nc23 Honda cbr400rr was rebuilt last month and putting out a good amount of psi on all cylinders!. However recently I had sudden loss of power on the motorway. Then after pulling over and leaving it for a while the power came back. I found this very strange. Then I discovered down the track when I unplugged the engine breather tube the problem would fix itself. But its not like I want to leave it this way indefinately. Any ideas what could be wrong? The tube is not blocked (duh) But perhaps engine pressure is building up in the crankcase and it cannot be released? I just hope it hasn't caused any damage to my rebuild crankcase/cylinder block. This has been a project bike, so I'm only a noob here. Any clues/hints would be most appreciated.

Over to you petrol heads...


MD

[Motu]

It doesn't sound too good - you may have seized it,that was the sudden loss of power.....and the excess pressure from the breather means a lot of blowby,from damaged rings.

[Mike_DooM]

Hmmm that doesn't sound too good aye. Thing is.. it definately didn't sound like it was siezed... I will run another compression test and maybe a leak down test to see how those cylinders are. But something isn't right with the breather unless it was blocked or something. At the moment I have the breather hanging out the side and it runs fine lol! I had a mate who races, told me alot of dudes take off the breather tube to the air box....

It shouldn't be damaged rings considering they were all new about 1000kms ago.. And I don't have any smoke or nasty noise... And the last compression test after 300km or so showed all of the cylinders were way above normal.

Cheers for the feedback.. I'll run another test...

MD