---------------------------------------------------------- RotaxEngines-List Digest Archive --- Total Messages Posted Wed 08/26/15: 3 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:44 AM - Re: 912 80hp violent vibration on cold start (AmphibFlyer) 2. 10:38 AM - Re: Re: 912 80hp violent vibration on cold start (bjones) 3. 11:34 AM - Re: Re: 912 80hp violent vibration on cold start (FLYaDIVE) ________________________________ Message 1 _____________________________________ Time: 05:44:32 AM PST US Subject: RotaxEngines-List: Re: 912 80hp violent vibration on cold start From: "AmphibFlyer" froghair wrote: > Wondered if anyone has experienced this: > > On cold start, anytime OAT is below ~60F, with full choke (enricher), engine will start but shake violently as though not running on all cylinders. I have to coax it to take any throttle increase for up to ~30 seconds. As soon as it will take throttle, it breaks out of this 'harmonic' and runs normally and will do so until allowed to cool back down to ambient temperature. Mick, another possibility is that the gearbox needs shimming. There's a mandatory 600 hour inspection of the gearbox, but it can need this work even at 300 hours if the engine has often been allowed to idle below about 1800 rpm, especially with a heavy prop. The gearbox contains a dog clutch that's supposed to accommodate the strong pulsing when a cylinder fires at low rpm, but what wears first is the Belleville washers (which are springs that look like washers). When they get loose, or when the prop shaft gets excessively worn, the cylinders will fire, but the rpm won't increase to the point where the spark timing can advance from the retarded start timing to the advanced run timing. (I forget the specific degrees.) When this happens the engine is likely to rock violently. If it does start, it will then run smoothly and will restart when still warm. For a while, until the wear gets worse; then it won't start, period. One sign of this condition is that the engine might make a chicka-chicka-chicka sound when it's trying to start. The remedy is to remove the gearbox and add shims until the Belleville washers are tight enough. Gearbox removal is easy, but you'll need a good Rotax shop to do the shimming. A somewhat similar condition is when the sprag clutch (the starter drive) gets worn. When that happens the engine will fire once and the starter will disengage immediately--too soon to keep the crankshaft turning until the next cylinder can fire. That's quite violent on the 100 hp 912S, but I've not seen it on the 80 hp 912 or the 914. (The gearbox repair is much easier to do, by the way.) Read this topic online here: http://forums.matronics.com/viewtopic.php?p=446442#446442 ________________________________ Message 2 _____________________________________ Time: 10:38:39 AM PST US Subject: RE: RotaxEngines-List: Re: 912 80hp violent vibration on cold start From: bjones CiAgICAKSSByZWNlbnRseSBoYWQgY2FyYnMgZ29uZSB0aHJ1IGJ5IGFhIGV4cGVyaWVuY2VkIFJv dGF4IHNob3AuwqBGbG9hdCBib3dsIGdhc2tldCBkaWQgbm90IEZVTExZIHNlYXQsIGFsbG93aW5n IGZ1ZWwgZGFtcG5lc3MgdW5kZXIgYm93bC7CoDkxMiA4MCBocCBFbmdpbmUgcmFuIHZlcnkgcm91 Z2ggdXAgdG8gbWF5YmUgMjUwMCBycG0sIHByb2JhYmx5IHN1Y2tsaW5nIGFpciBhbmQgcnVubmlu ZyBsZWFuIHdpdGggcG9wcGluZy9iYWNrZmlyZS4gQSBUYXAgd2l0aCBzbWFsbCBiYWxsIHBhbiBo YW1tZXIgdXB3YXJkIHVuZGVyIGZsb2F0IGJvd2wgc29sdmVkICJsZWFrIiBBTkQgcm91Z2ggbG93 IHJwbSBydW5uaW5nLlllcywgSSBrbm93IGEgcGFydGljbGUgY291bGQgaGF2ZSBiZWVuIGRpc2xv ZGdlZCBvciBmbG9hdCBtYXkgaGF2ZSBiZWVuIGJ1bXBlZCBmcmVlIEJVVCBsZWFrIHN0b3BwZWQg YW5kIGxlYW4gcnVubmluZyBiYWNrIGZpcmUgZGlzc2FwcGVhcmVkIHRvZ2V0aGVyIHNvIEkgYmV0 IHRoZSB0d28gd2VyZSBjYXVzZWQgYnkgZmxvYXQgYm93bCBub3QgYmVpbmcgc2VhdGVkIGFsbG93 aW5nIGZ1ZWwgb3V0IGFuZCBhaXIgaW4uQkogS2l0Zm94IElWIDkxMiBXYXJwIERyaXZlLgoKU2Vu dCBmcm9tIG15IFZlcml6b24gV2lyZWxlc3MgNEcgTFRFIHNtYXJ0cGhvbmUKCi0tLS0tLS0tIE9y aWdpbmFsIG1lc3NhZ2UgLS0tLS0tLS0KRnJvbTogUm9nZXIgTGVlIDxzc2FkaXZlcjFAeWFob28u Y29tPiAKRGF0ZTogMDgvMjUvMjAxNSAgMjA6NDYgIChHTVQtMDU6MDApIApUbzogcm90YXhlbmdp bmVzLWxpc3RAbWF0cm9uaWNzLmNvbSAKU3ViamVjdDogUm90YXhFbmdpbmVzLUxpc3Q6IFJlOiA5 MTIgODBocCB2aW9sZW50IHZpYnJhdGlvbiBvbiBjb2xkIHN0YXJ0IAoKLS0+IFJvdGF4RW5naW5l cy1MaXN0IG1lc3NhZ2UgcG9zdGVkIGJ5OiAiUm9nZXIgTGVlIiA8c3NhZGl2ZXIxQHlhaG9vLmNv bT4KCk1vc3Qgb2YgdGhlIHRpbWUgdGhlc2Ugc3RhcnRpbmcgaXNzdWVzIGNvbWUgZnJvbSBvbmx5 IGEgY291cGxlIG9mIHRoaW5ncy4gCgpXZWFrIGJhdHRlcnkgYW5kIG9yIHRvbyBzbWFsbCBhIHNp emUgd2lyZSBmb3IgdGhlIHN0YXJ0aW5nIHN5c3RlbSBhbmQgb3IgYmF0dGVyeS4KCkNhcmJzIG5v dCBzeW5jZWQsCgpJZGxlIHJwbSB0b28gbG93IG9yIHRvbyBoaWdoLAoKT2xkIGJsYWNrIGNvbG9y ZWQgc3RhcnRlci4gVGhlIG5ld2VyIGdvbGQgY29sb3JlZCBoaWdoIHRvcnF1ZSBzdGFydGVyIGlz IGJldHRlci4gSXQgZG9lc24ndCB0dXJuIGZhc3RlciBqdXN0IGhhcmRlci4KClVzaW5nIGEgcHJp bWVyIHN5c3RlbcKgIGluc3RlYWQgb2YgdGhlIHJlZ3VsYXIgY2hva2Ugc2V0dXAuIChUaGlzIGlz IGEgYmlnIG9uZS4pCgotLS0tLS0tLQpSb2dlciBMZWUKVHVjc29uLCBBei4KUm90YXggSW5zdHJ1 Y3RvciAmYW1wOyBSb3RheCBJUkMKTGlnaHQgU3BvcnQgUmVwYWlybWFuIApIb21lIDUyMC01NzQt MTA4MMKgIFRSWSBIT01FIEZJUlNUCkNlbGwgNTIwLTM0OS03MDU2CgoKCgpSZWFkIHRoaXMgdG9w aWMgb25saW5lIGhlcmU6CgpodHRwOi8vZm9ydW1zLm1hdHJvbmljcy5jb20vdmlld3RvcGljLnBo cD9wPTQ0NjQxOCM0NDY0MTgKCgoKCgoKCl8tPT09PT09PT09PT09PT09PT09PT09PT09PT09PT09 PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09Cl8tPcKgwqDCoMKgwqDCoMKgwqDCoCAtIFRo ZSBSb3RheEVuZ2luZXMtTGlzdCBFbWFpbCBGb3J1bSAtCl8tPSBVc2UgdGhlIE1hdHJvbmljcyBM aXN0IEZlYXR1cmVzIE5hdmlnYXRvciB0byBicm93c2UKXy09IHRoZSBtYW55IExpc3QgdXRpbGl0 aWVzIHN1Y2ggYXMgTGlzdCBVbi9TdWJzY3JpcHRpb24sCl8tPSBBcmNoaXZlIFNlYXJjaCAmIERv d25sb2FkLCA3LURheSBCcm93c2UsIENoYXQsIEZBUSwKXy09IFBob3Rvc2hhcmUsIGFuZCBtdWNo IG11Y2ggbW9yZToKXy09Cl8tPcKgwqAgLS0+IGh0dHA6Ly93d3cubWF0cm9uaWNzLmNvbS9OYXZp Z2F0b3I/Um90YXhFbmdpbmVzLUxpc3QKXy09Cl8tPT09PT09PT09PT09PT09PT09PT09PT09PT09 PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09Cl8tPcKgwqDCoMKgwqDCoMKgwqDCoMKg wqDCoMKgwqAgLSBNQVRST05JQ1MgV0VCIEZPUlVNUyAtCl8tPSBTYW1lIGdyZWF0IGNvbnRlbnQg YWxzbyBhdmFpbGFibGUgdmlhIHRoZSBXZWIgRm9ydW1zIQpfLT0KXy09wqDCoCAtLT4gaHR0cDov L2ZvcnVtcy5tYXRyb25pY3MuY29tCl8tPQpfLT09PT09PT09PT09PT09PT09PT09PT09PT09PT09 PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PQpfLT3CoMKgwqDCoMKgwqDCoMKgwqDCoMKg wqAgLSBMaXN0IENvbnRyaWJ1dGlvbiBXZWIgU2l0ZSAtCl8tPcKgIFRoYW5rIHlvdSBmb3IgeW91 ciBnZW5lcm91cyBzdXBwb3J0IQpfLT3CoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKg wqDCoMKgwqDCoMKgwqDCoMKgwqDCoMKgIC1NYXR0IERyYWxsZSwgTGlzdCBBZG1pbi4KXy09wqDC oCAtLT4gaHR0cDovL3d3dy5tYXRyb25pY3MuY29tL2NvbnRyaWJ1dGlvbgpfLT09PT09PT09PT09 PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PQoKCgo ________________________________ Message 3 _____________________________________ Time: 11:34:53 AM PST US Subject: Re: RotaxEngines-List: Re: 912 80hp violent vibration on cold start From: FLYaDIVE What do you expect! On Tuesday, August 25, 2015, michaelrosenberg wrote: > mickyrosenberg@icloud.com > > > I have tried many different options for starting from a lot of different > advice. All options end with the same issue which is perfectly describe > from Froghair on the initial post of this thread. > > Basically, cold weather starry is: > > Fuel pump on (5secs or leave on) > Enriched on > Throttle closed > Start > > Engine cranks over well and immediately fires and starts, resonance or > shacking happens for 10-30 seconds. Slowely removing enriched or adding > throttle has no effect. I can pith the throttle to the firewall and has > zero response. Engine probably resonated at around 1000RPM(ish)...... No > throttle response means I can not effect this. > > Once everything smoothed out I warm it up at approx 2000RPM and it will > idle around 16-1800RPM. > > Once it moved out of this resonant time, it purrs. > > I can only put it down to a fuel delivery or enriched issue. Once I get > the engine running smooth at idle, I added some enriched to see what would > happen and exactly the same symptoms occurred. Engine wound back to low RPM > and resonated again. I kind of expected it to happen in this scenario, how > ever the starting issue I have no control over. > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=446424#446424 > > -- Sent from Gmail Mobile ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message rotaxengines-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/RotaxEngines-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/rotaxengines-list Browse Digests http://www.matronics.com/digest/rotaxengines-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.