Propworn

My Feedback: (3)

If you use an electric start you may rub against the back plate if you leave the gasket out. If you decide to go the silicone route put the back plate on dry and spin the engine over with the electric starter and remove the back plate and look for any signs of rubbing.

Dennis

Bax

My Feedback: (11)

Actually, with almost all two-stroke glow engines, you'll see swirl marks on the rear cover even when a proper gasket is installed. That's because the connecting rod floats on the crankpin. It will always tend to rub slightly, but the rear cover's not eroded much because of the oil film that's there. One reason why our fuel needs so high an oil content. You don't want to see strong cut marks from the rod rubbing the rear cover.

N1EDM

My Feedback: (2)

Thanks for that, Bax...

Bob

Propworn

My Feedback: (3)

Yes and if there is light swirl marks with the gasket in place there may be even deeper marks in that cover without the gasket. The heavier oil content is for the lubrication of the large and small end of the rod because there is no bearings.and to help with cooling. Engines with bearings throughout require much less oil as low as 100 to 1. Remember the crankcase volume on a two stroke is critical for best performance that is why the backplate and the crank pin and connecting rod operate in such close proximity to reduce the crankcase volume. Saying that this rubbing is why we need higher oil content just doesn't make any sense as there are quite a few gas motors with the same configuration running as much as 100 to 1 oil content without any problems.

Dennis

1QwkSport2.5r

The thickness of the paper gasket is so negligible, I doubt there would be any problems if one didn't use one. Typical model engine gasket paper is roughly .010" and the amount of fore/aft crankshaft movement can exceed that figure by double. Using a thicker thrust washer can take up some of that slack if it's alarming. The crankshaft will only be able to move fore/aft when starting and low throttle settings. Once at rpm, the thrust of the prop pulls the crank forward away from the backplate. I think this is not as big a deal as some make it out to be.

And the high oil content is really intended for controlling ignition timing, lubing the rod bushings, and lubing the crankshaft. I've found using 25% castor in bushing crankshaft engines to be cleaner and better running than 20% castor, or even the synth/castor mixes that are common in commercially made fuels.

Propworn

My Feedback: (3)

if you chose not to use the gasket it is prudent to check how much its rubbing. Too much and the aluminium shavings can make short work of the bearings. On an old Brat .28 with the gasket removed the motor would not even turn over. Put one back in and it ran fine. Like Sport said once its running everything gets pulled forward if you hand start your engines its less of a worry but if your using an electric starter and forcing back on the crank the rubbing may be excessive.


Dennis

1QwkSport2.5r

Agreed on checking it beforehand for excess rubbing/friction. I think there's a little common sense required and I think for those involved with this thread, that it would make sense to check the engine before trying to run it for any issues.

Propworn

My Feedback: (3)

You would assume as much but sometimes when someone says something like the thickness of a .010 gasket would not make any difference some of the less experienced may just leave the gasket out and assume because one of the experienced guys said not to worry about it might not bother to check. I work in a world where we try to make everything monkey proof and just when we think we have it they come up with a better monkey.

Dennis

1QwkSport2.5r

Yeah, well like I said... Part of this hobby requires a little common sense. Not everyone is as capable. If you're less experienced, maybe you should be using OEM parts of finding someone more capable to work on the engine. If you work on your engine and don't know what you're doing and wreck it, that's on you. Again, common sense and using your head.

Propworn

My Feedback: (3)

But we all started some place and if it wasn't for those few that took the extra time to go into a bit more detail the learning curve would have been much longer. I don't know about you but If I can speak up and maybe save someone just starting out a few mistakes why not. I like to interact with all levels of expertise from the raw beginner to those who can teach me a thing or two. I don't have a minimum level in the pecking order that I feel I'm wasting my time working with them. No one has to have a minimum level of experience to approach me. I love the hobby and enjoy sharing it all with whom ever is interested regardless of experience. In fact I'm taking out a raw beginner to introduce him to the club tomorrow at 9 am and at the same time meeting a student whom I've never flown with simply because he sent an email out asking if an instructor was going to be out at the field tomorrow. I love this stuff I get to make two new friends.

Dennis

Hab

Lot of great suggestions on making gaskets. Would anyone know of a place where small gasket punches can be found?
I tried using a small piece of brass tubing of the right dia. hole needed slightly tapered as a punch .. but I know there has to be
someone some where producing small gasket punches for this purpose. Any recommendations ?

Thanx - Ken

blw

My Feedback: (3)

Hi Tim, thanks. I'm usually lurking and letting you guys do the work.

I was just wondering about RTV. I hate the vinegar smell.

1QwkSport2.5r

I don't like the vinegar smell either.


Propworn: All I'm saying is if someone thinks what works on one engine works on them all may be wrong and they should do their due diligence to ensure what they're doing is correct or will work. One cannot teach someone everything. People have to learn some things on their own too. If someone is avid enough to make their own gaskets, I'd bet they know what they're doing. Raw assumption? Sure is.

In this hobby, there's about a hundred ways to skin a cat. I certainly would not tell someone to do something a certain way if I knew for fact it was wrong or wouldn't work.


Anyway, I can agree with some and disagree with others... We can all still be friends though, right?

Propworn

My Feedback: (3)

Try Harbour Freight

Propworn

My Feedback: (3)

And it doesn't mater how much you try and save someone grief some will insist on doing everything wrong. All you can do is try.

Dennis

1QwkSport2.5r

Very much in agreement there. Cheers!

rgburrill

I've used the high temperature RTV for muffler gaskets. Works great.

Hab

Thanks prop... but I already looked in Harbor. Looking for a set that will
do like 4-40, 6-32, 8-32, 10-32 etc. Only punches available in Harbor are for
making auto gaskets... too big. They start off at 1/4" go up to like 5/8" Have a set
of those out in the box. Looking for a small set. Only other place I can think of would be
Napa. - Blue Point tools. But I don't see anything that small.

1QwkSport2.5r

I know the office supply chain stores carry different size hole punches - or at least they used to. Small tiny circle punches, star, square, etc... Might be worth a look.

Propworn

My Feedback: (3)

Leather tooling maybe I think thats what they were called when I bought mine at Princess Auto.

http://www.princessauto.com/en/detai...et/A-p8548059e

Amazon has all kinds look under hollow punch set.

http://www.amazon.com/Co-link-10pcs-...llow+punch+set

MrMotor

What I have used for years is a paper punch from an office supply store in a 1/8 inch size. You can find all kinds of 1/4 inch ones and when you are lucky, you will also find the smaller ones that work for 4-40 bolts and a tight fit on 6-32 bolts and of course similar metric sizes also.

fiery

My Feedback: (2)

Sets of hollow point punch tools are available from most tool suppliers. They are not expensive. Propworn has a good link above. Well worth it if you work on model engines as part of your hobby.

blw

My Feedback: (3)

I would sand brass tubing so it cuts. I've a few sizes on hand but not enough. You always need them for balsa anyway is the way I look at it.

Mr Cox

There are plenty of tools available for making the holes, I use this type;

kenh3497

I use a drill bit..... Cut the hole to fit over the back plate and set the gasket over the back plate with the back plate on the bench, gasket up.. Use an appropriate sized bit and push it (the part that goes in the drill chuck) through the bolt hole. I usually grind the the end of the drill flat so the edges are nice and sharp. DO NOT use the fluted end of the drill bit. That technique fails miserably. Don't ask how I know Doing it this way the back plate becomes the "die" and the drill bit is the "punch". Now bolt up the back plate and gasket to the engine. Use an Exacto to trim off the excess gasket material.

Ken