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Author Topic: Launch RPM for a K&B GH .35?  (Read 1190 times)

Offline Paul Taylor

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Launch RPM for a K&B GH .35?
« on: April 26, 2006, 06:39:04 PM »
I need help.
I am not very good at all setting needles. I rely a lot on my tach when I fly with Ryan.

If you had to take a S.W.A.G. at what the launch rpm should be for a K&B GreenHead .35.
No muffler, 10x5 APC on a ARF Streak running 5/29 Louis Home brew.

Thanks!
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Offline Steve Helmick

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Re: Launch RPM for a K&B GH .35?
« Reply #1 on: April 26, 2006, 07:47:58 PM »
Never had a Green Head...asked Santa for a .35GH one year.... got a McCoy .19RH POS.

General rule of thumb (since these are said not to be 4-2-4 engines) would be to get a tach reading at peak and back it down 1.5k, for a place to start.

I have heard that Greenhead .29, .35 and .45 were serious vibrators, so expect some tank problems. Stiffen the nose if possible.   ^-^ Steve
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Offline Randy Powell

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Re: Launch RPM for a K&B GH .35?
« Reply #2 on: April 27, 2006, 02:59:12 PM »
I flew a GH .35 when I was a teenager. It ran a 4-2-4 (according to my fuzzy memory). But I don't have a clue on ground RPM. I'd guess around 9,000 somewhere.
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Offline Paul Taylor

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Re: Launch RPM for a K&B GH .35?
« Reply #3 on: April 28, 2006, 08:48:30 AM »
Thanks. Now I have a jumping off point. j1

I just do not want to fry the engine.

\pt\
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Offline Bill Little

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Re: Launch RPM for a K&B GH .35?
« Reply #4 on: April 29, 2006, 10:48:05 PM »
Quote from: RootBeard on April 28, 2006, 08:48:30 AM
Thanks. Now I have a jumping off point. j1

I just do not want to fry the engine.

\pt\

This is another of the "old" engines that needs a LOT of castor in the fuel.  I wouldn't go less than 25%.  Fox Superfuel would be good if you can get it.
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Offline Paul Taylor

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Re: Launch RPM for a K&B GH .35?
« Reply #5 on: April 30, 2006, 07:13:34 AM »
Thanks Bill for all your help.

I will run the same home brew that I run in the foxes. :D

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Offline Bill Little

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Re: Launch RPM for a K&B GH .35?
« Reply #6 on: April 30, 2006, 07:25:58 AM »
Hi Paul,

I couldn't remember if we ever said anything about fuel. (??)  You'll like the K&B I think.  They were good engines in their day!  (and not so bad now)  ;D
I really enjoyed the phone call!
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Offline Tom Perry

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Re: Launch RPM for a K&B GH .35?
« Reply #7 on: April 30, 2006, 10:32:24 AM »
Paul,

I would try pointing the plane straight up and adjust the needle for a steady wet two cycle.  When you put it back down it should go back to a four cycle.  At this point check what the RPM is then go ahead and launch.  The engine should  unload after launch and RPM will increase.  See how you like it.  If too lean turn the needle out and eigth of a turn check the RPM and launch again.  If too rich do the oppisite.  When you find a setting that works record the RPM and weather conditions.

There are too many variables to recommend anything but a ballpark setting RPM wise.  Different props, fuels, degree of engine wear, glowplug, ambient conditions etc.

If you havn't run the engine in a while you will also have to warm it up and or flush the fuel system to get rid of any build up from sitting around.

It wouldn't hurt to keep a small log of your results. 
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Offline EddyR

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Re: Launch RPM for a K&B GH .35?
« Reply #8 on: May 03, 2006, 05:48:04 PM »
I still use them quite a bit in sport planes and I run them just at the point where they are  going into a 2 cycle. In a Streak it is going to be fast,maybe 85 mph.They work well with small props 9/6,9/7.Like Randy I would guess 9000 rpm.I have used them in old time stunt with a Tatone peace pipe muffler and using muffler peasure with a 10/5 and it would do a Fox type run. A K&B Green Head in a AAsr is a very friendly but quick combination. When I was a kid that was the set up every one wanted at the local field.
Ed
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Offline Tom Perry

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Re: Launch RPM for a K&B GH .35?
« Reply #9 on: May 05, 2006, 03:28:46 PM »
Paul,

Have you had a chance to sort out this engine yet?

 :)
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Tom Perry
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