al860, I'm pleading with you. Please give up on this one and go get an engine that runs. Removing the plug to prime an engine isn't the way to do it and your doing so indicates you need more experience before tackling this engine. I have been doing engines since the mid 50's and it took me most of the last season to get mine to run. You will only frustrate yourself by continuing.

That said, You can disregard all posts by persons that do not have an MDS 40. They are well meaning but just don't understand the gravity of the problem. You can disregard all posts recommending changes to nitro. When the engine is fixed it will run on any nitro level as proven by empirical results. You can go to Dub Jett's web site and use the procedure he has for setting the carb. It will work on the MDS. Because you have not yet reset the bearings on the crank you can only get these engines to run in a very narrow range of settings and the low setting is exceedingly important. These engines go from not running lean to not running rich in a quarter turn or less so the low end has to be smack on. My experience was that after the bearings are reset it behaves just like all other engines and is easy to set up.

Please, go buy an OS or Thunder Tiger your nerves will thank you.