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  • Re: Loss of power with air filter installed

    by » 8 years ago


    Ben did you check the needle position as in my earlier post.

    Thank you said by: Ben Monzingo

  • Re: Loss of power with air filter installed

    by » 8 years ago


    Yes sir, sure did. Actually replaced all brass in carbs, cleaned carbs. Also pulled the muffler to see if muffler restriction. I was able to get a little more RPMS with muffler off but still not full rpm. It's not prop pitch...checked that. The only thing I haven't checked really is rotary valve timing, exhaust port side piston condition (left the y pipe on), fuel lines before fuel pump.

    I didn't really think it would be fuel lines as they are fairly new polyurethane blue but worth a shot.

    I run the dual mikuni pump in series with a facet pump.

    I've changed everything electrical so I don't think it's electrical.

    I don't think it would be timing the rotary valve....those things wouldn't just jump time all of a sudden would they?

  • Re: Loss of power with air filter installed

    by » 8 years ago


    You state that you gained some rpm with muffler off. The engine will not produce full power with the exhaust removed. It is dependent upon the expansion chamber to aid scavenging. If everything else is correct and removing the exhaust increases output then you need to correct the fault with the exhaust.
    Dennis

    Thank you said by: Ben Monzingo

  • Re: Loss of power with air filter installed

    by » 8 years ago


    Thanks all. I pulled the exhaust, checked out cylinders and there was some very slight scoring on cylinder skirts. Does this look normal?

    I blew air through the muffler and there does not seem to be any blockage.

    I checked needles and they are good.

    I went ahead and took out 3.5 degrees from the prop pitch (this is a new setup with less than 10 hrs so I have not dialed in prop pitch anyhow). I was able to get to 6800 rpms now. The pitch seems too fine. However, it only sometimes would get up to 6800 rpms, other times it would load up right around 4000 again. I would back off the throttle and slowly accelerate to full throttle.

    It seems to me I have a compression issue or maybe a stuck ring?

    I also was getting extremely high water temps....200 degrees....which that hasn't happened before. I only ran it for about 10 minutes after warming up. Then again it is 100 degrees and humid down here in Texas and I really don't think I have the most efficient cooling setup.


    Is it possible to show good compression at starting rpms but still have a compression/blow by issue?

    I will say that this engine has always ran rich.....it likes to foul plugs...and really no matter what you do with the carbs, needle, main jet.

    Thanks for the help.

    Ben

  • Re: Loss of power with air filter installed

    by » 8 years ago


    3.5 degs is a massive amount to need to take off the prop...have you a std book pitch for your a/c and fitted with the 503.

    I do wonder that you are masking your prob in making the prop pitch so fine...letting the motor almost run with a very light load.

    It does sound like your motor is running rich.

    I know I asked before but I'm not sure you understood me...but it is so easy to incorrectly fit the jet needle on the wrong side of the plastic cup...it leads to a very rich mix...are you 100% sure your needle is where it should be...as I say it can go in 2 ways only one is correct.

    Nick.

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