Piston Burn/Wash Pattern -- What does my weird pattern indicate?

DAMIEN1307

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That being said I'd rather fly the wright brother's original airplane than ever trust one of these china girls on an ultralight.
Just 5 years after the Wrights' first flight, Orville Wright was in the first fatal airplane crash, which left him severely injured and his passenger dead.
 

TheWizzerd

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Wasn't disputing the operating principles. Like I said the quality control and port timing etc is sloppy from engine to engine. You'll never get a perfect engine. There have been guys on here and youtube chasing it for years. If that's what you're trying to do good luck to you sir.

From what I've seen, most scooters / snowmobiles / RC engines are actually much better quality than these china girls.

There's a big difference. Take a look at the Phantom 85 thread ALONE to see the major differences from jug to jug. I have experience with sled motors and there is absolutely no comparison in quality.

With these , you get what you get. Try and make it as best you can. But at the end of the day it all depends on what the s**tty mold made and what the 13 yr old chinese kid decided to make.

I work in the automotive industry and the tolerances / QC on these engines are basically make it and forget it. But most of them work. That's why you get so many random people here complaining about their engines failing or doing whatever.
You get the same with engines sold/used as ultralight engines as there is no requirement for any form of control and literally anything can, and does get used. We are not talking about Cessna 182's here. Even the nicer purpose built UL engines have just as many issues as the china dolls. Ask me how I know..... an engine out, and a pull start failure mid air preventing restart on a PPG is not fun.

I agree about the china dolls, and yes, most of the sled engines are of better quality, but still doesnt bolster your argument of them being vastly different. Quality has little to do with what it is and how it operates. It may determine reliability/longevity, but doesnt change the fact they are still 2 strokes and function the same, and the concepts are the same and applicable to either.
 

TheWizzerd

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Just 5 years after the Wrights' first flight, Orville Wright was in the first fatal airplane crash, which left him severely injured and his passenger dead.
I fly once a week at Wilbur Wrights birthplace. There is a museum there with the only certified flying Wright Flyer left.
 

DAMIEN1307

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I fly once a week at Wilbur Wrights birthplace.
Back in the 80s, I was taught, and learned how to co-pilot and navigate with air charts on Cessna 150s, 152s, 172s as well as Piper Tomahawks.

I do not fly anymore in anything if I can help it, never did get over my fear of flying...lol...I'm even a "basket case" anytime I had to fly commercial passenger jets...lol.

I will get my speed thrills with two wheels on the ground, thank you very much...lol.
 

TheWizzerd

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Back in the 80s, I was taught, and learned how to co-pilot and navigate with air charts on Cessna 150s, 152s, 172s as well as Piper Tomahawks.

I do not fly anymore in anything if I can help it, never did get over my fear of flying...lol...I'm even a "basket case" anytime I had to fly commercial passenger jets...lol.

I will get my speed thrills with two wheels on the ground, thank you very much...lol.
The type of flying I do, PPG, or ultralight in general is definitely not a speed thrill. A bike with a china doll is generally capable of about twice what cruising speed on a PPG or ultralight is.

My average speed is about 23, topping off at about 42 in a nice down wind and trimmed out.

Maximum allowed speed for Part 103 is 63mph downwind. So definitely not a speed trip.

But, doing 30ish five feet off the ground on a PPG feels fast. You get to a few hundred feet or more and it feels SLOOOOOOW as molasses. You often just feel like you are stuck there hovering not gaining any ground.
 

TheWizzerd

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That being said I'd rather fly the wright brother's original airplane than ever trust one of these china girls on an ultralight.
All my china dolls have been surprisingly reliable. I hate to say it, but more reliable than some of the ultrlight engines I have had, and that many of my flying buddies fly on regularly.

One good example is the MZ34...which is considered to be a very reliable engine in the UL world, but as far as 2 strokes go, it certainly isnt, and has just about as bad QC as a china doll. Castings look every bit as bad. Craptastic exhaust that cracks every other flight due to the absolutely horrible crank balance. etc., etc.

But, for the same reason people buy china dolls for bikes is why people buy the MZ34's for UL's. They work, and are relatively affordable for the application, even if you have to fix a few things and tinker here and there.

Actually, you are lucky to get 20 hours on many UL engines without something hard breaking. Even on the higher end purpose built stuff. But after the fix you are usually good for 100 hours before a major overhaul is required. Not because you want it to stay airworthy... but because its wore the frig out and MUST be rebuilt.

The CD engines themselves are fairly reliable in my experience. Its the ancillary hardware getting it attached to the bike, and people tinkering with them trying to get another 1mph out of them that seems to cause most of the failures. There are some quite bad example out there for sure...but...
 

Chainlube

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No, not all the way at TDC in the pic. The piston is pretty much flush to the jug deck at TDC.

I understand the transfer wash is correct, and thats what you want.... toward the intake. What seems a bit odd is the streak straight from the intake to the exhaust with not much else in the way to the sides of that which I typically see. I understand there isnt a lot of time on it to let it really build up to tell also.

I am used to seeing a nice "mothman of point pleasant" pattern on the 2 stroke ultralight aircraft engines I am used to.

Was more curious if this is typical of the porting on these engines to create the "tongue" pattern, which I understand is not ideal.
Check the squish depth anyway, .7-.8mm. Once the engine is broken in, and you use less oil in your fuel the wash pattern will improve. Did you try wiping the oil off the piston, if it comes out clean with a quick wipe, then that's a fresh engine.
 

ImpulseRocket89

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Cool airplane talk aside I would hazard a guess that the roof angle on one of the transfers is slightly off, or there is just something goofy about the shape, so the charge is not coming in perpendicular to the bore axis and/or being interfered with via turbulence in the bore. This can definitely cause a mixing of the exhaust and intake charge and force some of it out. Knowing how these iron sleeve cylinder ports tend to be I wouldn't be too surprised.
 

TheWizzerd

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Check the squish depth anyway, .7-.8mm. Once the engine is broken in, and you use less oil in your fuel the wash pattern will improve. Did you try wiping the oil off the piston, if it comes out clean with a quick wipe, then that's a fresh engine.
It is at .8mm. Made sure to hit the .7-.8mm squish when I decked the jug and reworked the 47mm head squish to match the 49mm bore.

Yes, it is absolutely fresh. Its a brand new engine with only about 20 miles on it now. Put another 10 on it today after putting the pumper carb back on.
 
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