O.S. 70 surpass looses rpms at full throttle.
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O.S. 70 surpass looses rpms at full throttle.
Hi all.
I have a O.S. 70 surpass 4 stroke that I bought on ebay (probably not the best place to buy a reliable engine).
The engine seems to run and idle well. However, the engine rpm will peek at about 90% throttle.
When I push the throttle the extra 10% to full throttle, the engine rpms are reduced by 300 to 400 rpm.
I am using a new glow plug, and have adjusted the valves twice. i have also tuned the low and high speed settings as best as I can.
Can any one help me understand why I am loosing rpms at full throttle?
Thanks
#2
RE: O.S. 70 surpass looses rpms at full throttle.
G'day Mate,
It's probably lean, richen 1/4 turn, if it's on a plane, lift the nose vertically, & make sure the RPM's don't drop.
Then fly it, if it looses RPM in the air, throttle back & land & richen some more, until it runs without loosing RPM's.
Cheers
It's probably lean, richen 1/4 turn, if it's on a plane, lift the nose vertically, & make sure the RPM's don't drop.
Then fly it, if it looses RPM in the air, throttle back & land & richen some more, until it runs without loosing RPM's.
Cheers
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RE: O.S. 70 surpass looses rpms at full throttle.
alan0899
thanks for the tip. I have tried to richen and lean the fuel mixture. the engine acts the same regardless if it is running lean or rich.
thanks for the tip. I have tried to richen and lean the fuel mixture. the engine acts the same regardless if it is running lean or rich.
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RE: O.S. 70 surpass looses rpms at full throttle.
IMO:
To make 'like new' one OS 4 stroke is quite easy.
-Buy the 2 main bal bearing and replace them .
-Buy one piston ring and replace it .
-clean all the engine before remount it, and not lose to clean the valve conduct and valve polishing .
You'll find again all the lose power .
To make 'like new' one OS 4 stroke is quite easy.
-Buy the 2 main bal bearing and replace them .
-Buy one piston ring and replace it .
-clean all the engine before remount it, and not lose to clean the valve conduct and valve polishing .
You'll find again all the lose power .
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RE: O.S. 70 surpass looses rpms at full throttle.
My guess is that the LowSpeed needle is too lean, that renders the HighSpeed needle ineffective above a certain point. Richen the LS needle about one half turn then try to peak the HS needle.
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RE: O.S. 70 surpass looses rpms at full throttle.
Thanks for the tip rosnik,
I am not sure what you mean by this statement, can you clarify?
"-clean all the engine before remount it, and not lose to clean the valve conduct and valve polishing ."
thanks
I am not sure what you mean by this statement, can you clarify?
"-clean all the engine before remount it, and not lose to clean the valve conduct and valve polishing ."
thanks
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RE: O.S. 70 surpass looses rpms at full throttle.
Thanks for the tip Hobbsy,
I did adjust the low speed idle for the best idle speed, but I will try to richen the idle screw and see if that helps.
I did adjust the low speed idle for the best idle speed, but I will try to richen the idle screw and see if that helps.
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RE: O.S. 70 surpass looses rpms at full throttle.
The low speed needle is for engine running like the high speed needle. The low speed is more important to engine performance than the high speed needle, imo. Too rich causes problems all over the place, and too lean causes backfires. Tune where you get the best transition *just* rich enough where it doesn't wheeze or backfire as you advance the throttle.
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RE: O.S. 70 surpass looses rpms at full throttle.
Hobbsy
Ibow to your supreme knowledge.
Idid exactly as you said and the engine ran great. No rpm drop off at full throttle.
Iam starting to figure out that for each low speed setting, there is high speed setting that works the best for the low speed setting.
If your low speed setting is not correct, you can still adjust the high speed setting to get a seemingly optimum setting evan if the low speed setting is off.
You have to go back and forth to get the right combination.
Thank you again for the info. I hope to be knowlegable enough to help people on these forums.
Thanks again.
Ibow to your supreme knowledge.
Idid exactly as you said and the engine ran great. No rpm drop off at full throttle.
Iam starting to figure out that for each low speed setting, there is high speed setting that works the best for the low speed setting.
If your low speed setting is not correct, you can still adjust the high speed setting to get a seemingly optimum setting evan if the low speed setting is off.
You have to go back and forth to get the right combination.
Thank you again for the info. I hope to be knowlegable enough to help people on these forums.
Thanks again.
#14
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RE: O.S. 70 surpass looses rpms at full throttle.
An incorrect low speed will screw up attempts to set the high speed. Hobbsy always advises to peak the high speed, leave it there, and set the low speed correctly. Go back and set the high speed a few hundred rich. This really is the best method to tune a 4 stroke,
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RE: O.S. 70 surpass looses rpms at full throttle.
ORIGINAL: blw
An incorrect low speed will screw up attempts to set the high speed. Hobbsy always advises to peak the high speed, leave it there, and set the low speed correctly. Go back and set the high speed a few hundred rich. This really is the best method to tune a 4 stroke,
An incorrect low speed will screw up attempts to set the high speed. Hobbsy always advises to peak the high speed, leave it there, and set the low speed correctly. Go back and set the high speed a few hundred rich. This really is the best method to tune a 4 stroke,
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RE: O.S. 70 surpass looses rpms at full throttle.
1Q, my very first RC engine was an Enya .46 MKII which I still have. I know that many on here advise to not get a fourstroke first. The only mistake I made, (according to some), was using Fox fuel with 20% castor for its first two seasons. This did not have the devastating effect that some think. It only got a brown muffler. I used the same fuel in a Saito .80 and 1.50, no ill came to them either.
#18
RE: O.S. 70 surpass looses rpms at full throttle.
ORIGINAL: Hobbsy
1Q, my very first RC engine was an Enya .46 MKII which I still have. I know that many on here advise to not get a fourstroke first. The only mistake I made, (according to some), was using Fox fuel with 20% castor for its first two seasons. This did not have the devastating effect that some think. It only got a brown muffler. I used the same fuel in a Saito .80 and 1.50, no ill came to them either.
1Q, my very first RC engine was an Enya .46 MKII which I still have. I know that many on here advise to not get a fourstroke first. The only mistake I made, (according to some), was using Fox fuel with 20% castor for its first two seasons. This did not have the devastating effect that some think. It only got a brown muffler. I used the same fuel in a Saito .80 and 1.50, no ill came to them either.
With my Enya 60-4C, I find if I start rich and lean it until it runs smooth, it's still 1000rpm rich of peak. By smooth I mean clean four stroke, no missing or popping. The 600-700rpm I gain using the tach doesn't sound much different to me. Again, this is my first season with a 4-cycle, and being an old Enya, it's got it's own learning curve. I still find it comical seeing castor "goo" spraying from the exhaust at fast rpm. I don't know why.