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Mack .28 Problems

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Joined: 14 Jun 2010
Posts: 1
Location: Tallil, Iraq

PostPosted: Mon Jun 14, 2010 5:10 pm    Post subject: Mack .28 Problems Reply with quote

I just purchased the Hyper 7 with a Mack .28 Engine. I broke it in just as the directions say. I am having a problem getting the engine to idel at a good lower rpm. It seems to always want to idel to high then when i get it too idel lower it dies. The idel seems to jump high to medium back and forth, not just one good constant ideal. When I pick the buggy up and open the throttle to rev it up and then let go of the throttle it doesnt want to idle back down right away, I have to hit the brakes before it will. I am running O'Donnell 30% fuel being I am in Iraq and the temps are higher here with a hot plug (it came with the engine). The needle valve seems kinda hard to turn along with the throttle stop screw. They seem a little harder than they should be, is this normal? I have not touched the mid range. And I can't keep the heat down. Broke it in at 170-190 but it runs at 275-300 no matter what I do. I can tune an O.S. 40 for an aiplane all day but can't get this RC nitro down!! (this my first nitro rc)
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Joined: 23 Aug 2009
Posts: 383
Location: Western, PA

PostPosted: Fri Jul 16, 2010 10:54 pm    Post subject: Reply with quote

Lets set the idle first. Take the filter out and set the opening at @ .5 to 1.0 mm when fulli close. Once you have that done no need to touch the idle screw for nothing. Lets doble check the midrange, take the HSN housing (there is a niple where the fuel get in the carb) and take it off, look at the needle should have a little hole, that hole it should be align or let put it this way, that little hole should be looking at you. Put the housing back in to the carb and you done no need to touch it again for nothing. LSN and HSN make sure they are flush with their housings. Check the fuel and pression hose are in good shape and secure. Now we can start the engine, once the engine is running let it get in temp and also let the chassis get warm , once they are warm or hot, listen to the idle you will look for a steady idle no matter if you have to lean or rich the LSN look for a steady idle. Once we have the idle set run the car for a few minuts and look how performs and always keep a blue stream of smoke( no need temp gun). if you need to adjust the HSN do it 1hr at a time and every time you make a change run the car and bring it home to see how is doing. If you lean the HSN make sure you rich the LSN if need accordingly same thing if you rich the HSN make sure you lean the LSN if need it, always looking for the steady idle. Because the high temperature of your location you should use a medium plug, beside you will save a little gas also.

The problem that you are having is a lean tune, once the engine stop take a few seconds to fill it up with fuel then comes down the idle. High idle = lean tune low idle = rich tune or right on the money (This is with the idle opening set like a said before @ .5 to 1.00 mm)
Set the idle opening in this engines are very important. Hope this help. Good Luck and burn nitro .

Sorry I have to put it in the end, This is a link that will help you or you can see with the ilustration what I mean with align the hole. http://ofna.com/forum/viewtopic.php?t=4339
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