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Paul Breisch Lil Brother


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  #1  
Old 01-22-2014, 06:03:32 PM
Larryt043 Larryt043 is offline
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Default Paul Breisch Lil Brother

Recently I purchased a 1/4 scale Lil Brother engine. It has been sitting on a shelf for quite some time so I cleaned it and re lubricated everything. The previous owner had it running some time ago, so it does apparently run. I mounted it on a base with the fuel tank and after straightening the crankshaft which had been bent a bit during shipping it's time to try it out. So, I hooked up the fuel tank and the coil assy that came with it (motorcycle) fueled it up with some coleman fuel, hooked it to a battery and nothing. I had no spark whatsoever. I tried a few different things and still nothing. So, I had a model t buzz coil sitting around and after cleaning up the contact points and a few adjustments got a nice buzz and spark. So, I wired it all up and get a very nice spark at the plug. Seems to time out correctly but still will not fire up. I tried priming the cylinder and get a little kickback when turning it, but it still will not take off. I even cleaned everything out and decided to try gas, thinking it just couldn't fire the coleman fuel. Acts the same with gas. Compression seems Ok, not a ton but there is a noticeable resistance. Took off the head and found it to be fairly carbon d up so I cleaned everything and reinstalled. Still nothing. So, I have fuel, spark, timing and compression seem ok and not happening. Any thoughts on this one? I appreciate any suggestions. I am at a loss with it right now. Thank you.
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Old 01-22-2014, 07:09:06 PM
Manorfarmdenton Manorfarmdenton is offline
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Default Re: Paul Breisch Lil Brother

Have you tried spinning it with an electric drill? Neither of my Red Wings would start by hand when first built, but did oblige when spun with a cordless drill. After running in they now always start by hand, first pull over compression.
I wonder from your description whether the compression is down? 'noticeable resistance' doesn't sound like very much to me? John.
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Old 01-22-2014, 08:09:38 PM
littlelocos littlelocos is offline
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Default Re: Paul Breisch Lil Brother

Hello,
Given the time on the shelf, I'd recommend checking to make sure the valves both work smoothly and that the seats are clean. These can get gummed up. Are you getting any hissing at the valves indicating leaking?

It would also be an easy check to back the piston out to make sure the rings aren't stuck as well. Are you getting any blow-by or bubbles around the piston when you rotate it over slowly?

Compression should be pretty bouncy if all is well.

Let us know how you make out.
Todd.
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Old 01-22-2014, 08:33:42 PM
Heller D. Davis Heller D. Davis is offline
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Default Re: Paul Breisch Lil Brother

Did you check and clean the fuel check valve? This has to work properly for it to run.
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Old 01-23-2014, 07:41:28 AM
Larryt043 Larryt043 is offline
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Photo Re: Paul Breisch Lil Brother

Yes, I tried the drill idea hoping it would do the trick. It seemed as it was spinning to try to fire, but as soon as I would let off it would stop. I am going to pull the piston again and take another look at the rings. I have read where many have used O-rings and there are actually two there which appear to be nylon. The piston is aluminum. On the check ball I am not sure. The mixer is not as I have seen used on these, and I am not sure it has a check ball. I have added a pic (I think) to show what it looks like.
Thank you for the replies!
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Old 01-23-2014, 08:55:14 AM
Larryt043 Larryt043 is offline
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Default Re: Paul Breisch Lil Brother

This morning I worked the motor over very slowly. I did notice a hissing at the cylinder skirt, and believe it is losing compression there. I will pull the piston again and see what I can come up with. Are o-rings a good idea? Not sure if I can re-vitalize the rings in there, they really don't take much effort to reinstall the piston back into the bore. Actually I don't think they were an issue at all, like they were possibly shrunken into the ring grooves. Idk.
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Old 01-23-2014, 10:55:13 AM
gbritnell gbritnell is offline
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Default Re: Paul Breisch Lil Brother

Hi Larry,
Pull the head off. Remove the intake/carb assembly. Remove the exhaust pipe. Now at this point you can either make an adapter to fit into both the intake and exhaust ports or just put it up to you lips and suck. You shouldn't be able to pull any air through the ports. If you do then the valves aren't sealing and need to be looked at. They could just be carboned up a little or are in need of a light lapping.
While the head is off rotate the crank to BDC. Now put the heel of your hand over the cylinder and flip the crank. The crank should bump back against the compression.
When I originally built my Little Brother engine the drawings didn't call for any type of piston sealing, rings or O rings so I built it that way. The engine would run but it was hard to start. I eventually made 2 iron rings for it and it runs great now.
Ignition timing should be about 5-10 degrees BTDC. With the use of points they would be timed to spark when opening but with using a buzz coil the spark would be when they close so the timing would be different. I don't even know if you could get the timing where it should be by using a buzz coil as the cam is machined for the exhaust valve opening and ignition timing all in one.
As far as small bubbles coming out of the back of the piston when rotating against compression my engines will do that too if they are flooded. Gas is very thin and it doesn't take much compression leakage to bubble the gas past the piston.
gbritnell
http://youtu.be/U56CU_o5LyQ
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Old 01-23-2014, 12:22:33 PM
Larryt043 Larryt043 is offline
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Default Re: Paul Breisch Lil Brother

Well, I added a couple of o-rings and brought the compression up. (Before I saw your post) I tried the drill again, and it began to pop. Eventually I got it to actually start, but ran for only about 2 or 3 revolutions. It seems to be flooding at one point, then starving the next. Yesterday actually I did have the head off and had to clean up the underside of the head and the valves. Lots of carbon build up in there and I suspected a valve not closing properly. Lol, yes I ended up using my mouth to verify that there didn't seem to be any leakage. As far as the buzz coil, would you suggest I try the motorcycle coil again? I found from the previous owner that I was using the wrong voltage, and should have been using 12 volts ( I was using 6) Is there a an ignition that works well with this size engine? I havent found one as of yet, but would like to. Thank you!
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Old 01-23-2014, 12:44:15 PM
gbritnell gbritnell is offline
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Default Re: Paul Breisch Lil Brother

Hi Larry,
For the sake of size a lot of people use the ignition systems from S&S machine. Apart from that you can use a traditional point coil setup. The Little Brother was my first I.C. engine and at the time there were no other ignitions available so I made a box and inside I put a 12 volt automotive coil and a ballast resistor. I had 5 terminals on the box, one for engine ground, one for the points, one for the HT lead to the plug and the other 2 were for the 12 volt hookup. The ballast resistor is just to drop the voltage on the coil so it doesn't overheat but I suspect with a slow running hit and miss engine you could probably get away without it.
As far as you motorcycle coil it all depends on what it is and where it came from. It could be 12 volts or if it's old it could be 6 volts.
gbritnell
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Old 01-23-2014, 04:23:10 PM
Larryt043 Larryt043 is offline
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Default Re: Paul Breisch Lil Brother

Your engine runs and looks great! I took a break from messing with the engine. Came back to it and the compression is down. I don't know if the o rings shrunk or what, but huge difference. There is also noticeable wear to them, so I guess they weren't the best fix. So now I am on the search for some rings for it. The bore is .750 so I believe I would need .753 rings. I think cast rings since the nylon ones didn't appear to hold up real well either. Is there a place that sells only rings? I am beyond any doubt incapable of making piston rings. I am still learning machining and wouldn't do well at all making them. I have found a few places with rings, but not in the size I need. Thank you!
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