AndyDtr08 Posted May 29, 2012 Posted May 29, 2012 What is this strange noise, never herd it before? Air escaping into or out of somewhere. Any ideas?
slice Posted May 29, 2012 Posted May 29, 2012 HI Andy, Ok listened to your noise, seems a bit odd but just a suggestion it is probably/possibly air being forced back past the rings on the compression stroke, if you look at your vid it only happens when the piston is rising towards TDC and drops off immediatly you pass the compression stroke. Course it might be nothing like that but it's a suggestion not a diagnosis. Do a compression test to see if its got the right pressure. Hope that helps a bit.
Moderator Airhead Posted May 29, 2012 Moderator Posted May 29, 2012 its the sound of air being forced back out of the inlet tract, normally there would be reeds in there and the motor would be turning much faster...so seating the reeds and no blowback
Moderator Cynic Posted May 29, 2012 Moderator Posted May 29, 2012 Perfectly normal, its air coming past the rings. Your lifting the piston at a speed so slow the rings don't really seal and the air comes past. When the piston is running at engine speed and covering the same distance maybe 4-5 thousand times faster than you are in the vid it will seal up ffine.
AndyDtr08 Posted May 29, 2012 Author Posted May 29, 2012 Ok guys thanks very much. A little more I should have added. I took the reeddblock etc out because I could hear it when kicked it over with it all together. Another point which might help diagnose is that the rubber inlet has had the sides cut away like mentioned as a de-restriction on the dtr.net site. Not by myself, I opened it up to find it like that. A reall bodge job of it too. I was told when I bought the bike that Stan Stephens did some work on it previously but no receipts to show that. The crank cases have definitely been split at somepoint and there is a black gasket gooey stuff with excess coming away. I've never heard a noise like it on any other DT's that I've had but maybe im just paranoid. Tomorrow Im going to have the exhaust off so i'll look up and see what the rings/ piston looks like. If i get any worries I'm gonna whip the engine out and take it apart for a better look. Another quick one. I'm no good with electrics. If the headlight is removed and the wiring from that just hanging down an not connected, will this create a break in the circuit and stop things working? I hooked up a battery and tried the new igniton barrel i fitted today and the servo didnt do anything and no electrics seemed to be there. Thanks for the help guys, much appreciated.
Moderator Airhead Posted May 29, 2012 Moderator Posted May 29, 2012 about the noise Andy...was the carb and exhaust on then? Cant say I was concerned about anything I heard in the video, engines make all sorts of noises when stuff is unbolted like that!
AndyDtr08 Posted May 29, 2012 Author Posted May 29, 2012 Yeah, exhaust is still on. DEP downpipe and standard silencer at the time. Carb, inlent manifold, reedbock, yeis bottle, carb to airbox hose, airbox. Snorkel missing. Sound was coming from the inlet area with all in place. I manouvered my dumbo ears around as i turned the kickstart to track down the noise before i started taking it apart.
Moderator Airhead Posted May 29, 2012 Moderator Posted May 29, 2012 Just listened again, ok i have another theory Because you are turning the engine very slowly, the compressed gas above the piston is leaking away as cynic said, you can hear that much but its the other noise you are concerned about isnt it? unlike when the engine is running and because the compressed gas leaked away...you are in fact causing a vacuum above the piston on the downstroke, when the piston uncovers the transfer ports air will rush in to this vacuum and at this point you will feel the kickstart lurch as it suddenly has an easy time, the noise is the air being sucked up the transfers
AndyDtr08 Posted May 30, 2012 Author Posted May 30, 2012 Well thats a relief. I don't know why I've never heard/ noticed it on any other DTR engines though. I'll probably have it apart today for peace of mind. It needs a clean up on the exterior anyway. When I bought the bike the seller said that he thought the reeds were blocked as when you put your finger over the plug hole, it sucked, rather than pushing your finger out. Surely it's going to do both depending on the direction the piston is travelling. He wasnt exactly mechanically minded so i dismissed it but just remember and thought it might be worth adding.
Moderator Airhead Posted May 30, 2012 Moderator Posted May 30, 2012 ...........as when you put your finger over the plug hole, it sucked, rather than pushing your finger out. Surely it's going to do both depending on the direction the piston is travelling. He wasnt exactly mechanically minded so i dismissed it but just remember and thought it might be worth adding. I just explained that Andy
AndyDtr08 Posted May 30, 2012 Author Posted May 30, 2012 Yeah I know, but what he was saying was that it was just sucking. Never blowing....ooh err...careful! Didn't get a chance to strip it down today as my Father was taken to hospital so has been sidelined.
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