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OS Irvine 46 query

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RC Plane Flyer22/05/2019 11:31:48
624 forum posts
22 photos

I have one of the above 2strokes that has given impeccable service from new and replaced the bearings once. It is now developing a minor problem in that after a long flight time over 6 mins or so when I get it back down it looks like it's spitting fuel out of the carb all over the head and plug . Any

suggestions please

Nigel R22/05/2019 12:00:01
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2968 forum posts
471 photos

Is it running as well as it always did?

If you bring it down after your 6 minute flight, can you see the fuel being spat out and whether it is coming from carb or front bearing?

Jon - Laser Engines22/05/2019 12:50:23
4765 forum posts
179 photos

If its spitting out of the carb it sounds like its running backwards :\

RC Plane Flyer22/05/2019 13:08:13
624 forum posts
22 photos

Can confirm it's not the front bearing area and running right way. I have in my mind the piston liner worn and getting too much back pressure in chamber ?? Cause spitting out of carb

Braddock, VC22/05/2019 13:18:58
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1626 forum posts
76 photos

Two things spring to mind, firstly the liner is shedding its chrome plating, can be checked by looking through the exhaust port though the delamination normally starts on the exhaust side in which case remove the cylinder head and scrutinise the bore, if it's ok the other thing that I've had with irvines is the gudgeon or wrist pin failing completely and breaking in two at the end of one of the relief bores in the pin, generally can only be found by dismantling the engine and, tbh, if it's that spares will be a problem.

Beneath is a picture of one of the two failures that I experienced, no spares so used the shank of a suitably sized hss twist drill dremelled off and trimmed to suit; circlips to retain the pin are hard to come by, remove with a magnetised scalpel blade for retention.

img_0159.jpg

Engine Doctor22/05/2019 13:34:03
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2267 forum posts
25 photos

Re " not coming from front bearing " Often these engines wear around the crankshaft allowing crank case pressure , not to be confused with Blow by to push fuel mix out of the front bearing . This can be cured by fitting a sealed bearing instead of the shielded bearing fitted as standard .. Its usual to remove the inner seal although they can both be left in . In extreme cases you cam also fit a sealed bearing to the rear of the crankshaft but remove the outer seal ( facing the Crank pin. A leaking font bearing often throws the fuel clear and appears to be coming from the carb. I have repaired a few of these Irvine engines over the years and they seam to be prone to spitting fuel , far more than other makes Blow by wont cause the problem as any gases blowing into the Crankcase will only cancel out the vacuum causing poor running . If Compression is good then it wont be blow by.

Going by your description I would double check that its not the front bearing leaking I sure try replacing the rear bearing with a sealed type with the rear seal removed . All bearings are available from Simply Bearing ..

Jon - Laser Engines22/05/2019 13:37:43
4765 forum posts
179 photos

If the problem is easy to replicate take a little video

RC Plane Flyer22/05/2019 13:53:44
624 forum posts
22 photos

What a great forum this is with help,advise and been there . Just taken the head off and found the culprit delamination of chrome near exhaust port. Well that's a right off now quick Google for new piston liner comes in at 75 pounds if available will have to do some more searching unless like OS will an ASP set up match ??

Braddock, VC22/05/2019 14:46:56
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1626 forum posts
76 photos

Ripmax.com, mkiv irvine 46 listed at £26.99. Get part number from website, also part no of retaining circlips and order via sussex model centre, delivery within the week.

Braddock, VC22/05/2019 14:54:20
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1626 forum posts
76 photos

PS I'd get the gudgeon pin as well it's peanuts. Delamination usually starts at exhaust side following insertion of something hard enough to crack the plating through the exhaust port whilst jacking out the liner eg when replacing bearings wink.

Use only wood or plastic.

RC Plane Flyer22/05/2019 15:25:58
624 forum posts
22 photos

Thanks for that awaiting reply via contact page

Percy Verance22/05/2019 16:03:00
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8109 forum posts
155 photos

RC Plane Flyer

Just Engines do a recon set of parts specifically for the OS chrome peeing fault. Quite a bit cheaper than OS bits.....

E mail them to get the low down.

RC Plane Flyer22/05/2019 16:18:45
624 forum posts
22 photos

Hi Percy. It's the OS version Irvine but will give the a call anyway.

It's awhile since stripping an engine and I am at the stage trying to get the conrod of the crank pin ( the liner is out ) where the best place for the crank pin to get the rod off top,bottom middle ????

Braddock, VC22/05/2019 18:18:01
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1626 forum posts
76 photos

Bottom

Braddock, VC22/05/2019 18:21:11
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1626 forum posts
76 photos
Posted by RC Plane Flyer on 22/05/2019 15:25:58:

Thanks for that awaiting reply via contact page

Wouldn't bother contacting ripmax, sussex model centre will do all that and charge you ripmax prices.

Just engines don't do an aftermarket liner for irvines I think it's safe to say, they used to do one for the OS Fx series but I think they don't do one for the Ax series now, maybe wrong though.

RC Plane Flyer22/05/2019 19:07:28
624 forum posts
22 photos

Hi Braddock had E Mail from Sussex models around 1630 to say all parts are made to order ?? had a second e mail at 1723 advising price and part numbers and 2/3 days delivery ??? . Will make a phone call tomorrow to see which is correct. Really struggling with this con rod at any position

conrad taggart22/05/2019 23:07:24
78 forum posts
4 photos
Posted by RC Plane Flyer on 22/05/2019 16:18:45:

Hi Percy. It's the OS version Irvine but will give the a call anyway.

It's awhile since stripping an engine and I am at the stage trying to get the conrod of the crank pin ( the liner is out ) where the best place for the crank pin to get the rod off top,bottom middle ????

You might find this video useful - shows a complete strip down to allow the bearings to be replaced

**LINK**

Braddock, VC22/05/2019 23:55:30
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1626 forum posts
76 photos
Posted by RC Plane Flyer on 22/05/2019 19:07:28:

Hi Braddock had E Mail from Sussex models around 1630 to say all parts are made to order ?? had a second e mail at 1723 advising price and part numbers and 2/3 days delivery ??? . Will make a phone call tomorrow to see which is correct. Really struggling with this con rod at any position

I generally phone. If it's in Ripmax catalogue online generally it's available so you should be ok. Irvine parts are what's left after they ceased manufacture. You may be ok with the OS made engines as they tend to produce parts for some time.

Removing the Conrod can be difficult, quite important to get the top end of the rod toward the rear of the gudgeon pin then and grasp the rod with an L shaped tool near the big end, it should come off. Remember to mark the rod so it goes back the same way it came off. Some Irvine's have an oil hole drilled into the bronze bearing and this face of the rod should face toward the crank web.

If all else fails grip it with a pliers and pull, it HAS to come out. Any damage caused by the pliers can be dressed with some form of abrasive, as long as it's smooth it should be ok.

Please remember it's your engine and my advice assumes competence, if you damage it in any way it's your responsibility not mine, I'm just telling you how I do it.

Remember anything you read on the web is 99.9999% bull I just may be the odd 0.0001% or I may not 😉

Edited By Braddock, VC on 22/05/2019 23:56:29

RC Plane Flyer23/05/2019 09:17:24
624 forum posts
22 photos

Thanks to all for the tips for removal of stubborn rod but pleased to say it's out. It turns out a little caster on the gudgeon pin stopped it sliding across easily, so phone call and card to hand next step

Braddock, VC23/05/2019 10:36:14
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1626 forum posts
76 photos

Well done, it reminds me I didn't offer up the one tip that may have helped with that, aerosol carb cleaner, the kind used to clean carbs, this will shift most crud and, if necessary, you can use it to clean the Mass air flowmeter on your petrol car where the results may surprise you.

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