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Old 12-17-2004, 11:21 PM   #21
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I tried some stuff on a thunder tiger a few years ago that was shared by a racer..(this is one-way stuff with a dremel...)

Connecting rods are almost always square..grind off the corners to make it more aerodynamic and reduce the drag in the crank case...if the engine is doing 20K, then the connecting rod is going back and forth 40,000 times a minute..This also reduces the rotating mass..

widen the exhaust port as much as possible...

lapped both the piston and liner with 2000 grit emery paper and oil...

did some stuff with the top of the transfer ports, but I can't remember exactly what...

As I recall it added about 2000 RPM....

The sooner you fall behind, the more time you will have to catch up.
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Old 12-19-2004, 07:47 PM   #22
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I think I have done most of everything I could to an engine for more speed and have had some good results but the longevity of the engine is seriously shortened. There has to be a compromize somewhere on this and just 1 good run for me is not it. Maybe for Paul when he is competing and only needs that good one.
If you are still playing with the KB40 for speed I could give you a couple of ST's or VR's to also play with. For everybody, Paul has been probably the only guy to get as much top end out of an old KB type that I know of. He also has some real fancy .049's that Andrew would drool over. The type made in a land that was previously unfriendly and they only have one blade on them.
Paul if you want a couple let me know your snail mail address.
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Keep the shiny side up and the wheels down
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Old 12-19-2004, 09:31 PM   #23
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would that be the OS .21 DF engine.? Rear tuned pipe with Perry carb. I have one on an old Hustler Delta. Runs best on 25% nitro.
Tried for my kamikazi pilots licence. Flunked the test.
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Old 12-19-2004, 11:18 PM   #24
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John..I Wasn't really happy with the is far easier to add cubic inches if I need more power. Frankly I was surprised it still ran after the radical surgery, but it did run, fly, and make some serious RPM's....

The sooner you fall behind, the more time you will have to catch up.
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Old 01-05-2005, 05:57 AM   #25
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Another option to boost power is to bore out the throttle barrel. More air in, more fuel in equals more power, to a point. You CAN go too far and suffer fuel draw problems making good muffler pressure to the tank important. Boring out the muffler nipple, as suggested, as well as larger diameter tubing here can help.

I routinely do this with the Norvels and get a good boost.

Also consider experimenting with differing prop brands. MA and wood props are a no no. IMO
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Old 01-05-2005, 09:35 AM   #26
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Hello John and THANKS for the kind words.

YES, I have been racing with model engines for over 30 yrs & flying pure speed models at the international F.A.I. level for over 20. I have seen much advancement & also made quite a few mistakes myself on the road to more power. All of them SEEMED to be a good idea at the time.

YOU have hit the nail right on the head with your statement:
"more power = seriously shortened engine life" HOW TRUE!!

Although I continue to learn & gather knowlege about these fascinating little motors I would tend to shy away from some of the advice I see given here.
i.e. Filing on a con-rod is only a good idea ONLY IF you can shot peen it afterwards, to restore the fatique strength. After a few catastrophic
rod failures, I no longer consider this an option.
Filing on an exh port is ONLY to be done if one is familiar with good
de-burring techniques, otherwise a LOT of damage can be done.
Lapping is also a procedure that if improperly done can decrease power & starting ability. In light of the variables, i.e. I don't know the condition/fit of the bearings, condition of the piston/sleeve, fit of the head & head (deck) clearance, ability of the modeller, just to name a's really a shot in the dark to give out solid info on-line. Sorta like a doctor trying to diagnose you over the phone without being able to see you or administer basic checks.

That being said, I have found quite a resonable performance increase when using certain APC brand PROPS! Sometimes one has to try out several to zero in on the best PROP FOR THE APPLICATION, but once found it really is "bolt-on horsepower". Since I learned a long time ago:
" IT'S ALL IN THE PROP & HALF IN THE ENGINE" I've paid as much attention to props as I have to motors. Food for thought.............

And YES, I may perhaps be the last person to still actively compete
in speed with a K & B 40, but mostly for research/economy reasons.
Although the performance spread is getting bigger all the time, I find it amusing to see certain Nelson users being beat by an "antique" on occassion (like this years US Nats). Thanks for the engine offer but sadly, due to family life, I no longer have much free time to dabble in this kind of thing as I once did...sure can be fun though!!

I am slowly proceding with the "McSchiribo" barstock .049 engine though.
(30,000+ r's on 10% fuel is music!!)

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Old 01-07-2005, 10:12 PM   #27
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Originally Posted by Flypaper
would that be the OS .21 DF engine.? Rear tuned pipe with Perry carb. I have one on an old Hustler Delta. Runs best on 25% nitro.
Mine is the 25VF with OS carb. Still haven't ran it although it is installed on my shrike. I've had the shrike done for about a year not but haven't installed any radio gear. I found a super good deal on a cermark F-20 so i've been flying that whenever i get the urge to fly a fast plane. I expect the wings to fold after about 4 or 5 high speed passes.
MAAC #50437
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Old 01-08-2005, 08:02 AM   #28
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It might just hapen to U 2
it did on 2 of them shrikes here with GMS 28 `s
some fast very groovy easy flying machines
seal the gaps and reinforce the back and spars if possibl;e
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Old 01-09-2005, 07:39 AM   #29
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clarence lee books

Where can I buy the full set of clarence lee books to get some valuble info working with engines. I looked in the rcm book and found that I could only order volume IV reprint from 1981-1985. Is the another book out there or anyone selling the past volumes of The r/c engine by clarence lee.

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Old 01-09-2005, 08:47 AM   #30
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There are three RCM/Clarence Lee books on general R/C engine topics and one book published in 1985 devoted to four stroke engines. The books are mainly edited reprints of the questions and answers published in the RCM magazine. I found it a bit of a chore when trying to find an answer to a specific problem.

Although it deals with only 2-stroke engines there is, in my opinion, a much better book available. The title is "2-Stroke Glow Engines for R/C aircraft" the author is David Gierke. The book is published by Model Airplane News.

Ed S
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