Maverick model engine starting problems

[thissentenceisfalse]

Hello all, I guess this is my first post, although I have been lurking for a while.

I know this is a long shot because of individual designs and machining, but I am hoping some good will come out of all the knowledgeable folks here.

Back in august, I started Phillip Duclos' model Maverick hit and miss engine with the ratchet mechanism for the exhaust valve. I have it 95% complete and am trying to start it. I have had no luck starting flipping it by hand, so I have been using a cordless drill to turn it over at around 3-400 rpm. I have what I think is a decent spark. It is somewhat white in color, the gap is about 30 thou. I am savvy with diesel engines, but I literally do not know much about gasoline engines, never owned one, rarely work on one. The spark will jump a little over 3/8 gap from the wire to ground, so its a strong spark from the coil.

As far as compression and valves go, I can cover the spark plug hole with my finger and it will pop it off slightly every time even if I push hard. While running with the drill, I slowly open my needle valve and it will randomly fire, eventually firing close to every revolution, but its touchy. Also, the firings seem very weak to me, and it will definitely not run under its own power.
The ignition timing is set to almost top dead center, slightly retarded. I have the exhaust valve set so that the valve is closed very close to the top of the stroke. I have messed around with both timings with little progress.


I shone a flashlight down my intake tube, where the venturi is and the fuel is kinda spraying out, but not misting at all. I wonder if this is my problem?

I would like to know how many others have completed this engine, and what your experiences are with getting them running.


Any input is appreciated!

Anthony

 

[Brian Rupnow]

I have found that these small hit and miss engines like a fair bit of advance on the spark timing. For first time starting, diconnect the "hit and miss" lever, as the engine should run okay without it and it can mess with your head. Don't make the mistake I did and have the gas tank higher than the carburetor. If there is any reduction of bore size in the center of the carburetor, that will create enough venturi effect to lift the fuel about an inch from a tank that sets slightly lower than the carb. Thats all the hit and miss magic I know.---Brian

 

[Mike N]

Is there any fuel coming out the back side of your piston? I have found that it is extremely easy to flood these little engines before the rings get seated. Take out the spark plug & squirt in a little 2 cycle engine oil. Once the engine runs for a few minutes the rings will seat & it run like a Swiss watch! This may take a few try's.

 

[Catminer]

Hi Anthony;
I think you should reexamine your ignition setup, spark should be bright blue. Yellow or dull spark indicates an ignition problem, also reduce your plug gap in half. Your description sounds like a compression problem also exists, should force your finger off the hole even when turning over slowly.

Peter

 

[thissentenceisfalse]

Alright, made some modifications.

Since I am such an amateur, I decided to use some viton Orings from work to use as piston rings. This engine does not have rings by design. I was confident that it had good compression, because it would in fact pop my finger even if you turned it slow. I wonder if it was leaking too much though. I adjusted the sparkplug to 15 thou and it is a really deep blue and looks nice. I took my .002 undersize piston I made and cut a nice oring groove in it and, just by trying it out tonight, it fires MUCH better, I did not attempt to get the fuel ratio right or get it to run because I am short on time tonight, and most every other night :. I will post my findings in the next week.

Thank you guys much!

Anthony

 

[thissentenceisfalse]

Success!

Thank you for your suggestions guys. I thought the compression was ok, but after the viton ring, it is 2x better. I am not ideally setup to machine the piston/cylinder to within .0002 of each other. I had tried getting it .001 within and polishing it, but it was not enough. I undersized my piston .002 and cut the oring groove for it. I am not sure how long the ring will last, but it takes literally 1 minute to get the piston out and change it, so I will live with it for now.

A little more about me...I am finishing vocational school and working at a caterpillar dealership as a heavy equipment tech. I just turned 20 and started this project last august. I have a late 50's bridgeport j head and a 60's 13" colchester student lathe.

Anyways..

I set the timing to almost TDC, maybe slightly retarded to help it start. I lowered the fuel tank to level with the carb needle and played with the fuel setting until it popped good. After some tweaking, I am able to start it by hand. It throttles up really good but i have to govern it myself since my fly weight is not attached yet. I just have to make one spring, and drill and tap one #2-56 hole and she is done!


Thanks again everyone

With much enthusiasm,

Anthony Basinger

 

[maverick]

Congratulations on a good runner. Please post some pics. It sounds like you have some good machine tools, more projects are sure
to follow.

Regards,
Maverick

 

[AussieJimG]

Video would be good Anthony

Jim

 

[popnrattle]

You did not say which fuel you were using(although I could have missed it. I have had better tuning luck with Coleman. Even tried non-ethanol(so-called) @ 3.65 per gal. Just as soon go ahead and pay the 10 buck per gal. and forget the headache and enjoy the consistency(Coleman is always been Coleman camp fuel and smells better too!) Kudos on the plug gap in a previous post. An old-timer enlightened me to the small gap adjustment(probably after watching me crank an old Briggs engine for 'bout a half-hour and getting a good chuckle, but was ok. I listen to old-timers!) I don't think you will be disappointed with an O-ring piston. Cfellows is the expert there.(thanks again).
Being a Hit-n-miss the intake probably needs to be weaker than you might think. uhhh...i fire @TDC 'cause I like to see how slow I can get 'em. uhh....I drilled my mixer for a 1/8-27 NPT... thats a 11/32 drill, only after a few choice words and a bit of reflection did I try making a "choke sleeve" to make the 11/32 hole on the bottom about a 1/4" inlet and then adjust the needle valve accordingly. Thats all I have at the moment and my fingers are getting tired. Hope this helps. Later, Rick.

 

[thissentenceisfalse]

http://www.homemodelenginemachinist.com/index.php?topic=17963.0


There you guys go! Video is at end of pictures, I hope you guys can get to them!

Anthony

 

[cfellows]

Congratulations on getting it running! That o-ring will last white a while. I use coleman fuel with a little wd40 mixed in for lubrication and I've never had to replace the o-ring.

Bet you're already thinking about your next project, huh?

 

[thissentenceisfalse]

Yes, Chuck....I fired my furnace for the first time yesterday, a couple of small pieces of refractory popped off but it is mostly in shape. I am venturing somewhat reluctantly, slowly and carefully, into metal casting.

I am aiming a a diesel this time. Not sure what, how, when, etc., but a true diesel has always been something I have wanted to try. A larger bore and stroke would be necessary, say 1.3125 by 1.5 or so? I had thoughts about using a commercial nozzle and use my Dumore toolpost grinder on the injection pump plungers. Your, and any other, input on this would be very much appreciated.



Thanks

Anthony