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Jan 17, 2012, 05:24 PM
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Question

MDS .40 carburator problems


Hello! I have an old MDS .40 glow engine, and, the reliability of the carburator is very poor. It is impossible to make a smooth transition between idle and high speed. Somebody know the solution? The best way is to change the carburator? Is a replacement of this carburator available? Is it possible to fit some OS carburator to the engine? Any help is appreciated! Thanks!
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Jan 17, 2012, 09:38 PM
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earlwb's Avatar
You might peruse this thread here, that I have linked to, to see if what I did on some Russian engines is the problem you are having or not. I needed to make a new low speed needle to fix a over rich low speed condition that affected the mid range too.
http://www.rcuniverse.com/forum/m_10139055/tm.htm
Farther down into the thread I go into more detail about my solution to the problem.
Jan 17, 2012, 10:47 PM
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Carb fix


Make sure the O rings are in place. You must relocate the muffler pressure tap to the center of the D on MDS on muffler flange. Remove the main needle assembly and with a spotting drill chamfer the seat the needle screws into. This will fix your problems.
Jan 20, 2012, 04:33 PM
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Thread OP
Thanks a lot for your help! anybody knows where I can buy a new C2 carburetor for this MDS engine if I make something wrong with the repair of the problem?
Jan 20, 2012, 09:50 PM
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earlwb's Avatar
Usually everyone goes for a Perry Carb instead. They work really well.
http://www.perrypumps.com/prod01.htm
Just choose a carb with the outer housing size to match the hole in the crankcase intake and also pick a inside bore size to match as needed.
Now if you have a lot of engines, you could use a carb you saved after wiping out a engine or wearing it out.
You could try the MDS engines company in Russia, they might have some parts. At this time I am not sure they are really around anymore, but maybe they are.
http://mds-engines.ru/eng/cat_air.shtml
Jan 20, 2012, 11:20 PM
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I TOBOR's Avatar
The probablem is not that the carb is unreliable, the short taper on the LS needle means that it has a very narrow sweet spot. The Perrys also have very narrow midrange sweet spot.


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