colingw

All,

I just opened up one of my old reed valve Cox .049s, to find a small amount of what I believe to be rust inside. Well, I think it is rust. It is a deep maroon colour, almost black.

It is mainly on the inside of the piston, with a little bit on the big end of the con rod.

Everything still moves smoothly, it wasn't gummed up. Compression is fine.

Is my engine doomed?

If not- can someone suggest a course of remedial action to save it.

Thankfully it seems to restricted to just the one engine, and even if it is crocked I have a TD .051 piston & liner I could substitute, thereby creating a reed valve .051.

cheers,
Colin

Mr67Stang

First of all I am no pro here. I have however been able to take seized engines and make them run again. you said it turns freely and has good compresion. I would soke it in castor oil and rotate the crank by hand working the castor in as much as possible, then drain it completely. I would then be ready for a test run. Ensure your glow element is not flooded with oil first. It would be a shame to burn out the element.

colingw

Someone suggested to me that it may not be rust at all, and that the dark red colour is consistent with oxidised castor oil residue.

I have checked and there is shiny metal underneath, and the dark red stuff is oily in texture.

Maybe not rust at all?

I'm going to give it a thorough clean & oiling tonight.

cheers,
Colin

Mr67Stang

Based on what you just said... no, it's not rust. Clean it. Lube it. Fly it.

lukesp

Metho and pipe cleaners and away you go!


Luke.

colingw

Shaggy toothbrush and a good oiling solved the problem. I'm fairly sure it wasn't actually rust, just oxidised oil.

Next problem - a "new in box" Cox .049s I bought recently is tight just like a new Norvel. I know this is normal for Norvels, but a Cox black widow????? Should I just do the 'oil it and turn over 100 times' thing like for a new Norvel, or do I have a problem here?

--Col

lukesp

Sounds like exhaust port damage. Is it tight all the way or only past the exhaust ports ?

Luke

colingw

Only toward the bottom of the stroke, so yes.

No obvious burring of the exhaust ports, but I guess even a microscopic burr would cause this.

lukesp

Yep. I won't say it's easily fixed but it can be. A sharp exacto No11 can be scraped around the port edges to remove any wire edge that happens to be there. I have done this with great success, but other times, particularly when the damage is from the Cox spanner, it can be difficult to clean up. It's still quite fixable though, just can take time.

Luke.

colingw

Luke,

Thanks. I'll try the #11 blade and see if it does any good.

Any other tips if that doesn't help?

--Col

combatpigg

My Feedback: (3)

I wonder what percent of all COX engines ever made have been ruined with the spanner wrench in the exhaust ports? I'll bet at least 1 in 10. remember that 99% of these engines got sold to the general public, not to the geniuses we have here .

lukesp

I have had several very tight Cox engines in the past, but it's usually abuse related and you stated that your's was new. The strangest one was a distorted piston, most of them are from spanner (wrench) slip, and man, that can really do some damage. I also suspect one of them had a distorted cylinder. Nothing would fix it.

However, if your's is new then it's probably a wire edge in the exhaust port somewhere, or someone slipped the wrench in and turned the edge a little.

You could always lap the piston to the liner with Autosol or the likes, but I'm always wary of that. Things can get somewhat pear shaped and then you have a mess to clean as well. Once again, I've done it but I wonder if it's wise to do. Is this an open exhaust cylinder or a slit exhaust ?

colingw

Further to this:

It must be a very small burr or distortion, because there is no obvious marking or damage to the piston.

I am hopeful this engine can be rectified and broken in without having to replace the piston & cylinder.

colingw

Open exhaust.

Nothing obvious when I examine it - sides of piston don't show any damage that I can see.

lukesp

Ha! Well, this genius here has caused wrench damage three times until the message finally got through. Don't use the wrench on the exhaust ports! I found myself reaching for it again just the other day, it's too easy to use rather than cut flats.

Luke.

lukesp

Give it a scraping, lightly of course, test fit, scrape again. The cylinder's are softer than an exacto blade and it can be surprising how quickly you can redeem a "bad" cylinder. If the damage is bad then it's usually obvious, burring around the exhaust openings etc.

Luke

colingw

Aha! While there is no obvious damage to the side of the piston, or to the exhaust ports, there is a slight coppery coloured scratch on the top of the piston. Forensic evidence points to a wrench accident.

Speaking of geniuses, when I was 14 I wrecked a Babe Bee .049 with the Cox wrench. The replacement piston & cylinder I bought at the local hobby store was of the slitted exhaust type - no way to stuff that up.

I don't even have a Cox wrench suitable for a reed valve .049. I do have a TD one in my TD .049 box, which I only ever intend to use for taking glow heads off.

lukesp

All the flea market/garage sale Cox engines I buy have gone down the wrench path. Most are redeemable, some are not. The worst aspect of wrench damage is the fact that its usually on the vertical sides of the port, not the easily cleaned horizontal edges, damn those children and their fathers and their Cox wrenches!

lukesp

Now Colin, I know you are not a fool, I know that. However, I feel I must warn you, never never ever be tempted to use the dremel to free up the port. Someone I know, it could have even been me, succumbed to the frustration and reached for the Dremel. Do not do this , I know.

colingw

That was me when I was starting out ...

I am suspicious that you are right about vertical edge damage too.

As the piston comes up, the tightness begins at the point where the exhaust ports are about half covered.

I will report back on the success or otherwise of the #11 blade in rectifying it. If all else fails, you're on the other side of town and experienced with fixing these suckers ...

I also have a TD .051 piston & cylinder which I could drop in as a replacement.

colingw

Oh dear! I bet that didn't end well.

combatpigg

My Feedback: (3)

I know that I have done the spanner wrench trick while trying to get a frozen glow head loose from the cylinder. Now, all I use is a pair of pliers on the finned part of the case, I don't even bother with the flats, unless I'm building an engine. You could repair slight wrench damage with a pointed grinding stone.

lukesp

Yep, don't throw it away if you can't clear it. I make house calls.
Actually, don't ever throw any of the single port No2 pistons away either, they can really get you out of trouble when you have a loose fitting SureStart.

I have always regarded it is a strange thing that Cox persisted with the port wrench for so many years, I mean after all, their target market was children and young teens if the advertising art was anything to go by. I was a ham fisted kid, and I'm pretty sure all my friends of the same age were no different.

lukesp

That is always the case with me. When they're frozen it requires the torch and some thought if there are no flats present, and I suddenly think the exhaust port wrench is a GOOD idea, less effort etc. Nope. Too high a failure rate.

And those wrenches!! They bend with the least effort!![:@]

lukesp

Agreed, but I'm a clumsy man, CP.