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ABC pinch on new motor

Crikey its tight

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Nigel R28/10/2018 12:30:03
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2439 forum posts
399 photos
I succumbed to temptation and picked up one of the irvine 39 motors that were recently turned out for the wot4 pro.

It's a beautiful bit of metal. Irvine production values really were right up there.

Anyway. That aside.

The engine is brand spanking new and had the most ABC pinch I have ever felt. I'm almost scared to turn it over - and so far i haven't.

I don't want to damage anything so what's the deal with the first start, should I try and warm it up somehow or just make sure there is plenty of lubrication and get it going as usual?
Ron Gray28/10/2018 13:57:07
1293 forum posts
341 photos

I had the same dilemma with a West 52, it needed ‘two hands’ to turn it over, it was so strange I contacted West who said not to worry about it, just run it. So for the first start I used an electric wrist but for all subsequent starts I backflip it. It got better after a few (20) flights but still is tight.

Steve Hargreaves - Moderator28/10/2018 14:13:58
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Warming it up won't hurt & may well help a bit.....use a hot air gun to get the cylinder nice & hot then start as usual. Short fast runs just slightly rich with a cooling off period in between are the best way. Don't run it rich & slow.....it needs to get up to temp as fast as possible....

Don Fry28/10/2018 14:15:56
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3244 forum posts
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Last November I bought an ASP 52. It was tight to stupidity. It was a Hobby King job, cheap as chips, so I just ran it. Pinch had tamed to tight good conpteesion after about 2 hours, and fully nice after the first 5 litres. Destroyed recently when the airframe disintegrated at 100 meters during frisky manoeuvres , and the engine hit the crushed/rolled stone patch we use as a runway.

I've just replaced it with a new secondhand ASP 60. Just the same. The similarity to its smaller cousin gets me thinking that how they do it now.

Edited By Don Fry on 28/10/2018 14:16:47

John Duncker28/10/2018 15:46:00
69 forum posts
7 photos

A hot air gun on the cylinder will make it easier to hand start.

As others have said it is really important to get them up to running temp ASAP. short bursts of full throttle and a few seconds of slow running. It is important to use a smaller than normal prop.

Don Fry28/10/2018 16:00:32
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3244 forum posts
39 photos

I just flew it.

Nigel R28/10/2018 17:33:12
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2439 forum posts
399 photos
Great stuff thank you chaps. I shall just get on with running it in the usual way. With some warming if I can arrange it.

I had a 36 many moons ago, I don't recall that having a pinch like this. Doesn't mean it wasn't. Memory being fallible and all that...
Tom Sharp 228/10/2018 17:53:13
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3311 forum posts
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As with many such situations, a good dab of Vaseline will work wonders. laugh

onetenor01/11/2018 22:53:48
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1884 forum posts

I've a used O,S. 40 with the same problem. Not too tight with the plug out.

Bruce Collinson02/11/2018 20:42:06
275 forum posts

One of my club mates turned up last Wednesday with a new OS AX, I think a 75, ostensibly to run and tune it in an airframe. It was just short of two hands to get over TDC. To cut a short story even shorter, it started with a reverse flick after about 6 odd tries, ran 2 tanks perfectly happily and flew a full tank an hour later.

I believe the protocol is to get them hot ASAP then run rich for a tank, gradually leaning out. Whatever, it was very tight and it runs very well. Hope this gives you some comfort. Is it about tapered cylinders in ABC engines?

BTC

Don Fry02/11/2018 21:22:31
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3244 forum posts
39 photos

I though the protocol is open it up, tune it to max, but if it starts to sag, cut and allow to cool off to cold, and start again. As soon as it hold power for 10 seconds, get it in the air, but don't let it sag, and don't do unlimited verticals, and keep moving the throttle.

Nigel R03/11/2018 08:59:45
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2439 forum posts
399 photos
My understanding also. Correct mix but short bursts of load. Getting longer over first hour of runtime. All on One prop size down from normal.

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