---------------------------------------------------------- Yak-List Digest Archive --- Total Messages Posted Wed 03/27/19: 6 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 04:04 AM - Re: Engine Vibration (Penco) 2. 06:06 AM - Re: Re: Engine Vibration (A. Dennis Savarese) 3. 06:22 AM - Re: Engine Vibration (Penco) 4. 06:27 AM - Re: Re: Engine Vibration (George Coy) 5. 06:45 AM - Re: Re: Engine Vibration (A. Dennis Savarese) 6. 09:41 PM - Brake Pressure (Jon Boede) ________________________________ Message 1 _____________________________________ Time: 04:04:39 AM PST US Subject: Yak-List: Re: Engine Vibration From: "Penco" Hello guys, I'm reviving this topic because I'm coming short of an explanantion. Bit of history : Bought the aircraft last year. It worked fine and then, some 5 month ago (didn't fly with it since) started to develop a strong vibration at higher RPM only. We had the prop balanced and even tried another one, we upgraded the spark plugs to the automotive kit. It made a definitive improvement to engine start, pickup time etc (gotta adjust the idle now). But that damn shaking is still there. The engine is basically smooth until 70-72% RPM and then vigourously starts to shake (I didn't really try above 90%). The weird part ? Sometimes, after I try lower power settings and the go back up in power, it doesn't. And then, picks it up again. I'm a little desperate for an explanation here. It's an old engine with low time remaining on it but still, I'd like an explanation, be it just for educational purposes. Many thanks, Penco Read this topic online here: http://forums.matronics.com/viewtopic.php?p=488284#488284 ________________________________ Message 2 _____________________________________ Time: 06:06:10 AM PST US From: "A. Dennis Savarese" Subject: Re: Yak-List: Re: Engine Vibration Does the vibration exist with and without the cowling installed?=C2- How old are the engine mount rubber shock mounts?=C2- Have you inspected all 8 of them on both sides very carefully along with the bolts and nuts?=C2 - Have you looked closely at the engine mount ring, tabs, bolts/nuts, arm s, attach points on the arms and the firewall?Dennis On Wednesday, March 27, 2019, 7:06:57 AM EDT, Penco wrote: Hello guys, I'm reviving this topic because I'm coming short of an explanan tion. Bit of history : Bought the aircraft last year. It worked fine and then, some 5 month ago (d idn't fly with it since) started to develop a strong vibration at higher RP M only. We had the prop balanced and even tried another one, we upgraded the spark plugs to the automotive kit. It made a definitive improvement to engine sta rt, pickup time etc (gotta adjust the idle now). But that damn shaking is s till there. The engine is basically smooth until 70-72% RPM and then vigourously starts to shake (I didn't really try above 90%). The weird part ? Sometimes, afte r I try lower power settings and the go back up in power, it doesn't. And t hen, picks it up again. I'm a little desperate for an explanation here. It's an old engine with low time remaining on it but still, I'd like an explanation, be it just for ed ucational purposes. Many thanks, Penco Read this topic online here: http://forums.matronics.com/viewtopic.php?p=488284#488284 S - WIKI - - =C2- =C2- =C2- =C2- =C2- -Matt Dralle, List Admin. ________________________________ Message 3 _____________________________________ Time: 06:22:36 AM PST US Subject: Yak-List: Re: Engine Vibration From: "Penco" Hello Dennis, The engine vibrates whether or not the cowlings are installed. I didn't check the rubber mounts, I figured if they would be damaged it would shake at all RPM... Any specific things I should look for when inspecting them ? Cheers, Penco Read this topic online here: http://forums.matronics.com/viewtopic.php?p=488286#488286 ________________________________ Message 4 _____________________________________ Time: 06:27:52 AM PST US From: "George Coy" Subject: RE: Yak-List: Re: Engine Vibration I presume you have done the usual compression checks. Have you removed the rocker covers and looked for broken valve springs? Have you checked the rocker clearances recently. As it happens around 70%, that is about where the manifold pressure goes from vacuum to pressure. Carefully check the intake manifold and various connections for leaks. Pay particular attention to where the intake pipes screw into the cylinders and the manifold. If you have one of the original Russian top dead center tools or can borrow one, put a 1/4 inch spacer on it and screw it in front plug hole on and cylinders 4,5 & 6 to check for possible hydrolock. George Coy -----Original Message----- From: owner-yak-list-server@matronics.com [mailto:owner-yak-list-server@matronics.com] On Behalf Of Penco Sent: Wednesday, March 27, 2019 7:04 AM Subject: Yak-List: Re: Engine Vibration Hello guys, I'm reviving this topic because I'm coming short of an explanantion. Bit of history : Bought the aircraft last year. It worked fine and then, some 5 month ago (didn't fly with it since) started to develop a strong vibration at higher RPM only. We had the prop balanced and even tried another one, we upgraded the spark plugs to the automotive kit. It made a definitive improvement to engine start, pickup time etc (gotta adjust the idle now). But that damn shaking is still there. The engine is basically smooth until 70-72% RPM and then vigourously starts to shake (I didn't really try above 90%). The weird part ? Sometimes, after I try lower power settings and the go back up in power, it doesn't. And then, picks it up again. I'm a little desperate for an explanation here. It's an old engine with low time remaining on it but still, I'd like an explanation, be it just for educational purposes. Many thanks, Penco Read this topic online here: http://forums.matronics.com/viewtopic.php?p=488284#488284 ________________________________ Message 5 _____________________________________ Time: 06:45:18 AM PST US From: "A. Dennis Savarese" Subject: Re: Yak-List: Re: Engine Vibration Yes, dry rot; cracking; protruding out beyond the end plates.=C2- Look f or sagging too.=C2- Look in your engine log book and see if you can figur e out how long ago they were changed. Don't forget to carefully inspect the engine mount and all attach points.Ch eck for loose accessories attached to the engine.=C2- ie: Generator? etc. Check the cooling louver ring, individual louvers and attach points of the adjustable arms for looseness.Dennis On Wednesday, March 27, 2019, 9:24:35 AM EDT, Penco wrote: Hello Dennis, The engine vibrates whether or not the cowlings are installed. I didn't check the rubber mounts, I figured if they would be damaged it wou ld shake at all RPM... Any specific things I should look for when inspecting them ? Cheers, Penco Read this topic online here: http://forums.matronics.com/viewtopic.php?p=488286#488286 S - WIKI - - =C2- =C2- =C2- =C2- =C2- -Matt Dralle, List Admin. ________________________________ Message 6 _____________________________________ Time: 09:41:55 PM PST US From: Jon Boede Subject: Yak-List: Brake Pressure Reading the maintenance manual, it seems like the QS-1 valve is supposed to go from 0 to 0.95Mpa (138psi) in 2.2 seconds or less... Is 138psi a good value for the maximum pressure for the brake at the wheel? Jon ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message yak-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Yak-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/yak-list Browse Digests http://www.matronics.com/digest/yak-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.