quote:

ORIGINAL: OVER WORKED

Ok, I’ve been avoiding this thread but I think a couple of things should be set straight. So this is the one and only time I will reply to it. If you choose to believe me, that’s fine, if not that’s fine too... We sell over 150 engines a month, And I have been dong the tech support on them for 6 years. About 3% are returned with real problems, the rest of the customers just need a little help getting them dialed in.
1} Yes we have had a problem with sticking carbs, the clearance between the body and the barrel is too tight, and occasionally a deformation producing an edge at the venturi opening. The problem occurs in about 1 in every 75 motors. The new carb design is in testing now.
2} even though the engines are ringed we still run cylinder taper, so we need heat to expand the top for correct break-in. Four-stroking is bad in all our engines.
3} We did make the 75-90’s in both ring and ABC, the ABC has been discontinued, seems we cant get people out of the old habit of four stroking them during break-in and they were scoring the cylinder/piston and eating crank pins.
4} Artisian’s post#43 is wrong. Several things happen when the engine runs out of port timing that are sometimes difficult to understand. It’s not the same as closing the throttle and restricting the air. Some of the symptoms are fuel leakage from the back plate gasket or the front bearing, the engine will go lean, and you will see excessive cyl. head temp. The reason for this is the crankcase takes a full charge but it can’t get it up through the ports to the top end. As the piston comes down crankcase pressure becomes excessive and it has to go somewhere. On occasion you will notice fuel that actually spits out the carb, or some of the other symptoms of reversion.
5} our engine are ported for a max RPM between 11,000 and 12,500 depending on the displacement. Short port timing allows the engine to produce more torque, but restricts RPM. They like larger diameter props.
6} We use a very hard chrome on the liner that takes longer to break in than most other engines, most don’t develop full power for several gallons of fuel, again depending on the displacement and SPFC.
8} there have been enormous strides made in engine development and design in just the last couple years alone, partly do to metallurgy and a better understanding of flow dynamics. They are getting lighter, more powerful and more user friendly. What was standard just a few years ago no longer applies to some designs.
9} be careful what advice you take from the threads on the net, here or elsewhere. I can’t tell you how many times I have heard someone tell me “I’ve been doing it that way for 30 years, it’s always worked and I ‘m not about to stop now”. People with that attitude are idiots, avoid them. If it was true we would all be using AM transmitters and building our airplanes with Ambroid and carpenters glue.
10} Kangke has not changed owners, the man who started it still owens it, Peter Ma.
11} I was not trying to sell Artisian a Brison engine for his Cap 232-120, here is the exact wording of my e-mail to him, you decide for yourself.
“Ed,
I don't know too much about the Brillelli engines, I can tell you that a Brison 2.4 {40cc} is all the engine the airframe can handle.
Also the firewall was not designed to carry an engine weight greater that 3 lbs 5 oz.”

As I said I will not respond again to this post.

quote:

ORIGINAL: Artisan

quote:

ORIGINAL: mitchmcf

I too have a SK 90 and it runs so nice but did have one problem it would slowly lean out when in the air. No mater what we did it still would lean out and heat up but never dead-stick so I called the Tech. support and asked them and this is what they said. The first thing he asked was what prop I had on it and I told him it was a 14x8 mas and was told that it was to small to go to a 15x6 or 15x8 . what was happing was that in the air it would unload and get over 11000 rpm and it is not ported for RPM over 11500 so it would lean out once I put on the bigger prop no more lean condition and runs like a champ.

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What a crock!

Overloading an engine heats it up too much and advances the timing too far. The symptoms of having the timing advanced too far is an apparent leaning out of the engine and overheating. The correction to retard the timing can be accomplished in several ways. One can reduce the prop load, one can reduce the compression, one can drop to a cooler heat range glow plug, or one can reduce the nitro content in the fuel. All of this is prefaced upon the engine having adequate cooling air.

A 13x8 or a 14x6 is more appropriate for a .91 two-stroke. Also, being a ringed engine, it is going to need some break-in time running rich to seat the ring and to keep it cooled off during break-in.

If an engine runs past its porting/timing, nothing is harmed unless it is ridiculously high. Breaking-in ringed engines is done with a smaller prop than the normal flying prop, not a larger prop.

There have been no changes in technology that would warrant this advice. Someone doesn't know what they are talking about.

quote:

ORIGINAL: RC-Bearings

Mostly you who doesn't know what you are talking about When engines are run past their optimum port RPMS, they will lean out and get hotter. Extreme examples of this are trying to get the last bit of RPM from a hot engine when a tuned pipe is cut slightly too short. The symptoms will be blown and mangled glow plugs and a hot engine. Putting a slightly larger prop on that engine will keep it running, although not at its peak.

Larger engines are designed mainly for lower RPM ranges to take advantage of the efficiency gained by larger props. Another factor is noise. If you turn these larger props too fast, you gat a LOT of noise which is becoming frowned upon at many sites. A 15X6 is no where near too much prop for a .91 two stroke. Even .91 four strokes handle that size easily. The YS .91AC is famous for handling 14X10 and 15X8 props.

I would trust the manufacturer rep for an engine.

quote:

ORIGINAL: Artisan

quote:

ORIGINAL: mitchmcf

I too have a SK 90 and it runs so nice but did have one problem it would slowly lean out when in the air. No mater what we did it still would lean out and heat up but never dead-stick so I called the Tech. support and asked them and this is what they said. The first thing he asked was what prop I had on it and I told him it was a 14x8 mas and was told that it was to small to go to a 15x6 or 15x8 . what was happing was that in the air it would unload and get over 11000 rpm and it is not ported for RPM over 11500 so it would lean out once I put on the bigger prop no more lean condition and runs like a champ.

------------------


What a crock!

Overloading an engine heats it up too much and advances the timing too far. The symptoms of having the timing advanced too far is an apparent leaning out of the engine and overheating. The correction to retard the timing can be accomplished in several ways. One can reduce the prop load, one can reduce the compression, one can drop to a cooler heat range glow plug, or one can reduce the nitro content in the fuel. All of this is prefaced upon the engine having adequate cooling air.

A 13x8 or a 14x6 is more appropriate for a .91 two-stroke. Also, being a ringed engine, it is going to need some break-in time running rich to seat the ring and to keep it cooled off during break-in.

If an engine runs past its porting/timing, nothing is harmed unless it is ridiculously high. Breaking-in ringed engines is done with a smaller prop than the normal flying prop, not a larger prop.

There have been no changes in technology that would warrant this advice. Someone doesn't know what they are talking about.

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Nice to run into you again, Paul.

We're not talking about a piped engine. I am very familiar with the principle of which you are speaking. I probably ran piped engines while you were still in school. Even then, the engine doesn't blow backplate gaskets when ran higher than its timing. If it did, it could not pull fuel at all and it would just quit, not run lean. Ditto an unpiped .91.

Being a vendor (hobbyshop owner or engine reseller) does not automatically make one an expert, which means ones own pet theories (Kangke) will be taken to task upon occasion.

Ed Cregger




_____________________________

Artisan

"Flying models since the Fifties - I'll get the hang of this yet!!!"

(in reply to RC-Bearings)

quote:

ORIGINAL: XJet

I've noticed that quite a few of the new generation 90/91 and 50/52 engines have quite significant transfer-port restriction. This seems to be produced mainly because they're being made in 60 and 40-sized crankcases respectively.

As you make the bore wider, the ports have to become shallower -- there's only so much space between the liner and the outside of the engine after all.

I definitely noticed this with the TigerShark 56R engine that I bought a while back.

quote:

ORIGINAL: RC-Bearings

Glad to see you are still among the living! You an't THAT much older than me! BTW, I ran piped engines in the 6th grade!

quote:

ORIGINAL: RC-Bearings
One of the main limiting factors in 60-90 engines is that most engine designers use rear bearings only slightly larger in diameter than most 40 size engines. That is why the 40-50 size sport engines develop so much power while the 60-90 class seems anemic by comparison.