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HomeAircraftHelicopterEngines Plugs Mufflers Fuel › MP2 Cracking
09-01-2003 09:55 AM  14 years agoPost 1
Flight Engineer


Gisborne, New Zealand

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Looking for help and ideas on the following problem.

I am running a Raptor90/webra91/MP2 combo and have just replaced my MP2 due to cracking around the pipe to header flange (pipe side). However after fitting a new pipe and doing 5 flights yesterday I find a slight crack starting to appear on the edge of the top bolt hole.
Obviously some sort of resonant vibration is creating a problem here. There is no significant out of balance problem with the heli, and one suggestion made has been that I may be running the motor too rich which is setting up this destructive vibration with the "4 stroking" of the engine. This sounds feasible and next flight I intend to do some leaning out, but any other ideas or experience with similar problems would be much appreciated as I can't really afford 1 MP2 per weekend flying.


09-01-2003 10:03 AM  14 years agoPost 2
Tom Carne


Western Australia

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Not saying your choice is wrong but having just read Model Heli World's review of the Webra 90 they suggested the best muffler/pie option was the Hatori 700 and 470 tuned length. I had the MP2 on my YS bot noted I always had fuel running back into my engine after leaving it idle for a while causing fuel lockup.

No rain on flying days:)

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09-01-2003 12:43 PM  14 years agoPost 3
Al Magaloff


12,199 Posts- Enough Time Wasted. See Ya!

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The MP2 header has been changed, to prevent the oil running back. Lean out that motor . Touch the back plate, I'll bet it's cold now. Lean it out until the back is warm to touch, not hot. Also, e-mail Curtis for his take on it. Who really knows more about MPs?

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09-17-2003 09:58 PM  14 years agoPost 4



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MP2 "Weld it UP!!"
Have you tried welding the pipe to the header?

I have and it works great. If a bolt comes loose the muffler's not going anywhere!!!

All you need is a 120v wire feed welder, aluminum wire and Argon gas!!!

Let me know if you need some help!

I've welded two and have a few of my club members ready to do theirs.


09-17-2003 10:08 PM  14 years agoPost 5
Secret Squirrel

rrKey Veteran

New Zealander living in Melbourne, Australia

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I think the issue here is in the way in which the motor is running in this heli, not the MPII. Two have cracked in short succession of each other.

The engine itself doesn't sound that great and as Dean mentioned, it four cycle's pretty regularly.

Dean, next time we're at the field (though with this weather it's looking like a fair while away!), we'll go through that engine tuning a bit more eh, cause I'm sure that if you don't do something about that engine, it's going to crack that HT700 I sold you in short time as well!


Simon Lockington

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