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help with surpass 70

Old 08-27-2003, 01:19 AM
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Default help with surpass 70

I just purchased a surpass 70. I broke the engine in according to manufacturers recommendations on a stand. I then installed the engine sidways in my VQ models P51 mustang.

On my first attempt, it seemed to fly OK up until 1/2 throttle or so. ANything above 1/2 throttle would not result in any increased speed. It didn't bog down or quit, it simply kept at the same RPM as if it was still at 1/2 throttle.

I brought the plane in. I discovered my problem was likely that I had not cut enough of an air inlet in the cowl. I removed the cowl, cut a bunch of it out so improve airflow, and tried again

My second attempt was this evening. THe engine runs perfect at low speed. It idles like a charm. It runs up to full throttle on the ground without any problems. I have it backed out about 2 full turns. WHen I took off, it seemed to fly allright initially, but then would bog down. In particular, as soon as I do any loops, rolls, inverted, and quick changes in throttle it will bog down or stop alltogether. This resulted in about 6 deadstick landings this evening.

I brought the plane down several more times and fooled around with the high speed mix. On the ground, It still seems to want to run at 2 full turns out, but keeps stalling and dying in the air. Incidently, there seemed to be alot of oil along the side of the fuselage after my brief runs and white smoke was coming from muffler on the ground. This implies that it is too lean, but whenever I tried leaning it out further on the ground, it would die.

I know what you are going to say, that this sounds like a fuel problem. Well, I already replaced the cheap VQ models tank and put in a nice dubro tank. It is airtight. THe fuel clunk rests on the bottom of the tank near the back. THe tank is well insulated with foam. THere are no kinks in the fuel line. I even disconnected my remote fueler, bypassing it, and it still does the same thing.

ANy thoughts?? Thanks.
Old 08-29-2003, 04:48 PM
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Default help with surpass 70

I have an almost identical problem with an identical engine. Mine is mounted on a GP Big Stik 40. I get to about 70% throttle and anything over that, even though the barrel moves, adds no additional RPM. In my case it is not a problem, as I have power out the giggy, but it is curious. This is my first 4-stroke, and it could well be common.

If you're getting a lot of white smoke it is too rich, not lean. I fuddled with mine, and other 'experts' fuddled with mine, and ended up screwing up the idle. An experienced 4-stroke pilot worked with me and he set everything back to the factory pre-sets (close throttle, screw in mixture control all the way tight, then back it out three turns, close needle valve fully then open it 3 turns, start engine, run up to full throttle, turn needle valve clockwise until maximum RPM is heard). Once there, drop to idle for 5 seconds and then feed in full throttle quickly. If it falters, hesitates or stalls you're to lean. If it is sluggish you're too rich.

Good luck.

Oh, forgot to ask. What prop are you swinging on the nose? I have a 13 X 8 and it may be enough to halt the high-end a bit. Are you overtaxing the little tyke with something larger?
Old 04-26-2004, 11:24 AM
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Default RE: help with surpass 70

im no expert but i have one and they run about 2-2-1/2 turns out i have noticed they need lots of break in at first you should run the first 7 or 8 flights rich after break in they will except a more lean mixture but for first flights should be slobering rich hope this helps.
Old 04-26-2004, 01:38 PM
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Default RE: help with surpass 70

First off, your idle mixture may be 'way too lean. Richen it a lot, start the engine at part throttle and get the high-speed needle leaned to peak RPM. Now retard the throttle and work on the low-end.

You may be trying to idle the engine too low. Anything below 2200-2500 is good.

The centerline of the fuel tank must be level with the center of the carb, or no more than 3/8-inch lower.

Smoke from the muffler is good. The more the merrier...that means that you're on the rich side.

Cooling an a cowled mode may be a problem. You have to make sure that air entering the cowl actually goes through the fins on the cylinder. Many times the air goes into the cowl, bypasses the engine, and exits. Result is no actual cooling. Some models may not cool well even if the engine's fully-exposed. The large flat plate of the firewall disturbs the air enough that the engine doesn't cool properly, but this is quite rare.

On the test stand, we normally turn an APC 12 x 8 prop between 10K and 11K RPM. Anything that allows the engine to turn in the high 9's or better and fly your model the way you like is a good prop.
Old 04-30-2004, 06:32 PM
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Default RE: help with surpass 70

[]also just purchased a surpass 70 II, cannot get it to run well. finally found the valves were set with no clearance, adjusted them and things got better but, still a poor transition from idle to full throttle. had to use an idle bar glow plug to keep it running. after 3 tanks of fuel (15% nitro) finally can keep it running, but on a 13X7 get only 9600 rpm. at half throttle and a steady needle setting, the engine cycles slowly from light steady smoke (a little rich) to no smoke to puffs of heavy smoke. about out of ideas..all lines have been checked for leaks and the tank seems to be ok. IDEAS??? altitude, 3200 ft. attitude, sinking!

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