fbpx

 

  • Re: Lost 700 rpm somewhere

    by » 9 years ago


    Right...there is 100 difference betwwen both tacho's...meaning the origonal shows 6000 max when the new shows 5900.

  • Re: Lost 700 rpm somewhere

    by » 9 years ago


    Bill, thanks.... both egts are the same. What I did notice though if it helps diagnose the problem, is the last inch of throttle does not increase the rpm at all. In other words..whether I push the trottle 80% in or firewall it...makes no difference...still only get 6000 max.

    I was hoping to get a Rotax mechanic to service it...but he had a short stay in hospital which has slowed things down a bit as work has backed up for him. He is not even answering emails at present. So, even though O have never messed with these engines befpre, I may give it a try and check the needle as Ian suggested, and a compression check as Bill said. By the way, what is the best way to compression test? I heard online soomewhere you cant use the normal tester for these rotax 2 stroke engines.... is that right?

    Mike

  • Re: Lost 700 rpm somewhere

    by » 9 years ago


    Mike,

    You can use a regular automotive type compression tester. I prefer the ones you screw in rather than the ones you hold in place. A lot easier to use if you are working alone. Leave the mags off, take one plug out of each cylinder and screw the tester into one cylinder. open the throttle so there is no manifold vacuum and crank the engine a few seconds. Normal compression should be somewhere between 110 and 140 psi. on each cylinder.

    The throttle problem could be several things. If there is too much pitch in the prop, you will not reach 6500RPM no matter what you do. Once the throttle is wide open, prop pitch is what limits the RPMs.

    You could have a throttle cable that has somehow gotten out of adjustment. Pull the air filter off and open the throttle all the way. As you look into the carb, the throttle slide should be completely up in both carbs. If they are not fully up, pull the throttle all the way to idle and gently lift the cable housing where it goes into the cable adjuster on top of the carb. It should have one or two MM of loose play before slide begins to lift. No more. Could also be a loose cable clamp in the throttle quadrant. Both slides should be the same height at idle and both should begin to rise at the same time as the throttle is opened.

    These are easy things to check before tearing into the engine and most of the time it turns out to be something simple.

    Bill.

  • Re: Lost 700 rpm somewhere

    by » 8 years ago


    Hi Mike

    I see this post was about 9 months ago..

    Did you ever resolve your "lost rpm" problem ?

    I have acquired the same problem a while back after I had a big non-engine "service" done to my trike over a period of 3 months - replacing lots of rusted parts (coastal plane) where the trike was stripped (except engine) and all rusted parts replaced. This of course involved a lot of dismantling and re-assembly.

    Pre this I used to get +- 6500 max RPM on my Rotax 582 blue head (new shortblock done about a year ago, 100 hrs since)
    Now it wont rev higher than 5800 - also the last 20/25% of throttle opening makes no diff. Prop was not touched

    We have tried many things but currently are stumped

    Thanks
    Peter

    Thank you said by: Michael Regan

  • Re: Lost 700 rpm somewhere

    by » 8 years ago


    Can you tell be ear if its not making the same kind of RPM as it used to,

    an independent tach is useful to check these things out just in case the a/c tach is giving you a false reading,

    I bought one of thos cheap tiny tach look a likes of ebay just for test purposes...been very useful.

    Nick.

    Thank you said by: Michael Regan

You do not have permissions to reply to this topic.