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HomeAircraftHelicopterMain Discussion › os50, hatori 540, uniflow system problem
09-01-2003 07:43 AM  14 years agoPost 1
brian chan


Hong Kong

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Hi, Can any friends here give me some advices or tips.
My helicopter is Raptor 50 v1 with
os50 engine, gear ratio 9.56
hatoril 540 pipe, + 541 header.
The gaps between the pipe and header is about 4mm.
fitted with 550 cc fuel tank

Recently, I fitted a big fuel tank and at the same time introduced uniflow fuel system to Raptor. I am using two small aluminium tubes obtained from small size fuel tank for airplane for the uniflow. The internal diameter of the tubes is a bit smaller than the diameter of the original plastic black tube. Will it affect the matter ?

I found that the "idling" throttle has to be set higher than usual. Add a little bit higher idling throttle will result higher idling speed which engages the clutch. Lowing the idling throttle a bit will stop the engine. Very difficult to find the "middle" point. The "idling" seting rang is narrower.

Giving full throttle to fly and then landing the heli will stop the engine. I noted that turning the "low speed needle" of the engine to "anti-clockwise" direction from the "center" can lower the idling speed but the engine can stop suddenly. Turning the "low speed needle" clockwise from the centre can increase the idling speed and torque causing the clutch engaged. Why ? For OS50, I though that turning to anti-clockwise will get leaner and leaner, the idling speed should be up but not down.

Ending up, I fully turn the low speed needle clockwise. Now it is 90 degree clockwise from the centre. The high speed needle is one turn now. The engine is very hot but with many smoke without any unburn fuel emitted from the pipe. When I open up the high speed needle from 1 turn to 1 1/4 turn open, the engine will lack of power to climb. The engine and the pipe is with the kind of "smell" of overheating but the glow plug OS8 Plug is good without any sign of overheating. It is still very shinning. Why ?

I hope friend can give me tips in respect of their present setting of os50 needles.
If it is the hatori causing the problem, please advise what is the best alternative muffler for os50.

My Raptor 50 is about 8.5 pounds (without fuel). With fuel is 9.5 pounds. Is it too heavy for a 50 helicopter ?

Thank you in advance for your kind attention and tips.

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09-01-2003 02:35 PM  14 years agoPost 2

rrElite Veteran


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For all needles, clockwise = leaner counterclockwise=richer. So probably you tuned something wrong.

Could also be you're off the pipe

9.6 gear ratio, isn't that the ratio for the OS32?? Your engine RPM will be very high with that. Another reason to run hot?

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