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Engine basics => Engine set up tips => Topic started by: Tim Wescott on October 21, 2018, 10:28:07 PM

Title: Looking for crankcase leaks
Post by: Tim Wescott on October 21, 2018, 10:28:07 PM

How do the engine experts look for crankcase leaks?  I've got a pair of Fox 40 Schnuerle-porteds, one of which I'm thinking of putting into a scale plane.  The other one runs crappy and doesn't give a "puff" when the transfer port opens.  I'm pretty sure it's leaking out the front seal (it certainly barfs lots of raw fuel out the front when I try to run it!) but I'd like to make sure.

All I can think of is to find a position where the transfer is open and the intake closed, put a muffler on it, and blow into the exhaust while looking for leaks.  Is there a better way?

Thanks.

Title: Re: Looking for crankcase leaks
Post by: Dane Martin on October 21, 2018, 11:41:29 PM

Syringe instead of blowing, and in a pool of alcohol. Test a good one, that'll be your "allowable" amount of bubbles.

Title: Re: Looking for crankcase leaks
Post by: Tim Wescott on October 22, 2018, 09:03:07 AM

It's a bushed engine, although it's certainly big enough to have ball bearings.  I suspect it's in the same case as a 60! 

I think the other one is good -- I'm going to get it on the test stand and see if it'll work well enough for a scale plane.  If it does, then the leaky one is for spare parts only.

Title: Re: Looking for crankcase leaks
Post by: dennis lipsett on October 22, 2018, 11:13:29 AM

I have a NIB Fox 40 bushing motor. R/C but that isn't a problem with a carb switch. Just a heads up if you cant reconcile the problem.

Dennis

Title: Re: Looking for crankcase leaks
Post by: Tim Wescott on October 22, 2018, 11:36:27 AM

Quote from: dennis lipsett on October 22, 2018, 11:13:29 AM

I have a NIB Fox 40 bushing motor. R/C but that isn't a problem with a carb switch. Just a heads up if you cant reconcile the problem.

Dennis

Thanks Dennis.  It's for a scale plane, so the carb isn't even an issue!

My engine has the carb on a flange, though -- am I mistaken about it being a bushing engine?

Title: Re: Looking for crankcase leaks
Post by: dennis lipsett on October 22, 2018, 02:13:57 PM

Tim,

The flange mounted carb is from an earlier version. Did it have the over/under muffler or exhaust flange mount and was it a little larger or the same as the one I show. Parts are not to the best of my knowledge interchangeable in any way.

Dennis

Title: Re: Looking for crankcase leaks
Post by: Tim Wescott on October 22, 2018, 05:52:49 PM

Quote from: dennis lipsett on October 22, 2018, 02:13:57 PM

Tim,

The flange mounted carb is from an earlier version. Did it have the over/under muffler or exhaust flange mount and was it a little larger or the same as the one I show. Parts are not to the best of my knowledge interchangeable in any way.

Dennis

This engine (http://sceptreflight.net/Model%20Engine%20Tests/Fox%2040%20Schnuerle%20RC.html).