After my last post here and following the advice i was given i finely got my MDS 40 PRO to throttle up smoothly on the ground but when i lift the plane up and hold it pointing skywards the engine splutters and dies .Can anyone tell me what the problem might be i have checked that the float in the fuel tank is not touching the bottom of the tank when the plane is pointing skywards If i can not get this engine to run reliable i am going to get an OS 40 LA is that a good idea?
Cheers
Ray [:@]

It may running to rich, lean it out a click or so.. I may have
that backwards in which case go out a click.. And test it again.
Is your tank height good where the outlet of the tank is fairly
close to the height of the engine needvalve?

It is too lean if it dies when held nose up -- or your clunk may be stuck at the nose-end of the tank, which ca happen if your plane got a bump on the nose, or is stored nose down. Either one will do it. If you engine is transitioning well, you are probably close to a good tune. Try richening it up a few clicks -- you may also have to slightly re-adjust the low speed mixture as well.

On the other hand, being an MDS, it may never run well -- sorry to be discouraging, but you would probably be better off selling it & buying something else -- almost anything else.

You didn't say if you reset the bearings. The engine is lean that's why it quit. If you have not reset the bearings I have no doubt that you have to run it that lean just to get it to run. If you launch that engine into the air it will quit and dead stick when it leans out even more as it runs. Don't forget that even after you reset the bearings the MDS engines require a lot of break-in.

Just don't fly vertical for a while!

These MDS motors take a loooooooooooooooooooong time to fully break-in.[:@] My finally ran right after about 30 flights, after initially running it on the ground. Sounds like it's also running too lean, check your clunk(again?) and all the fuel line for leaks. Do you have bubbles running up to the carb when you hold it up?

Also check for leaks at the carb base and the backplate. They can cause your problems. Black automotive silicone sealer after cleaning with brake parts cleaner can seal up most leaks. Also try an idle bar plug. I have read that these engines like idle bar plugs for some reason. Good luck with it.

Mark Shuman

I did 2 things to my MDS 40 that significanly improved the performance:

1. Installed a Fox glow plug with an idle bar

2. The engine started losing power and sometimes stalled for no apparent reason, acting a shtough it had an air leak somewhere, but nothing plainly visible. Richening the fuel mixture helped very little. What I did was pull the carburetor off, cleaned the o-rings, and applied 'Green slime' to the o-rings. Green Slime is a lubricant/sealant for o-rings and it's used primarily on RC glow-powered cars. This stuff was actually located in the cars section in the hobby shop. There's probably different names for this as well.

I'll tell you what, these two things really improved the performance of my MDS 40 - better transition from idle to high throttle and overall power and performance is improved. Hope this helps.

Thanks guys for all the helpful advice it,s giving me a lot of options to try this weekend even though it's forcast for snow here in the north east UK lets hope the forcasters get it wrong!!
Happy Flying everyone
Ray

There have been a few MDS engines show up at our club and they are usually very quickly replaced with either OS or Thunder Tiger engines. They also do not like much nitro content, either 0% or 5%. Higher than that and they don't like it. If holding the plane up makes the engine quit, it is too lean. Open the needle valve 2 clicks, restart and try it again. There should be no difference in speed when you lift the plane up. If you do decide to replace the engine and go with OS, do not get the LA series! They are a very weak engine. Look at the AX version instead. Also if you check the price differences between the 40 and 46 engines, get the 46. Its only a few bucks more and gives you much more usable power. [8D]

One thing you all forgot. I had a 40 LA (It was an RTR trainer) The air bleede right on the side of the Carb. That was the problem with mine.

MDS= Multiple Dead Stick!!! Hahahaaa ...

But serisouly ... I was informed that you need to run it in slowly and then flush the inside out, there will be bits of metal etc. After that it will be a good engine. Is that true?