Marathon Engine Issues

[2strokesandsplat]

Hello all! I am new to this forum but have browsed for a few weeks getting info for my build. I have just acquired a early 90s Marathon EZGO. I was told when I bought it that it ran and was parked and never touched for years. This is hardly ever true which seems to be the case as I go through the motor. He also said he got it to fire off with some starting fluid. I have first tested spark which is doing great. So, starting off with good news. Next is fuel. After blowing out the fuel lines and cleaning the filter, the fuel pump is receiving gas but not pumping. I took it apart and everything looks clean and clear. I cleaned it anyway and put it back together. Tried it again and still no luck. So I thought, let's just try some starting fluid and see if it will try to run. So, I grab the can and spray a bit while pressing the pedal. Engine is turning and seems like everything is moving well but just won't even try to start. Now I am stuck. It has spark, fuel, and air...what am missing here?

[racin161]

Have you checked compression? are we talking 2 cycle ? kind of need more info there are a lot of people that can help with the proper information. Welcome to BGW

[2strokesandsplat]

I am renting the compression tester today. I will post the results when I get them. I just figured with gas and spark it would at least try to run even if it does have low compression. I am super new to carts so any help is MUCH appreciated!

[Dave Box]

There is one thing missing in your equation. You need spark, fuel, compression AND crankcase pressure to make a 2 stroke work.
However, did you prime the pump? If not you need to disconnect the line to the carburetor, wrap a shop rag around the fuel tank filler to make a seal and now blow hard until you see fuel from the pipe. Now reconnect the line and crank the engine. Please stop using aerosol spray to start the engine. Your engine needs oil in the fuel and you will damage the bearings. Mix some 2 stroke oil with gas at the ratio of 128:1 and put some in a squeezy bottle. Now if your engine will still not fire you can remove the rubber hose to the carburetor and squirt some directly into the air intake.
Now if you do that and the engine does not even try to fire (and you are 100% sure you have a spark) then the crankcase is not developing the pressure to suck the fuel into the cylinder and that, sadly, means that you have some fun times ahead.

Dave

[2strokesandsplat]

I primed the pump and removed the line from the pump to the carb. I blew until fuel came out. Then I cranked it and no fuel was coming out of the other side of the pump. That's when I abandoned the fuel system for a second to see if it would even try to run. I am not a fan of using starting fluid either but I tried the spray bottle method with no luck. I also figure the oil injection would inject oil as it's cranking...true? (I usually take those off on 2 strokes so I don't really know how those work). Anyway I have pulled the spark plug and tested for spark and it's firing good. Sprayed gas in the carb with no luck, and tried starting fluid as a last ditch effort with no luck. I'm guessing the compression is going to be non-existent. Hooray rebuild time! :(

[Dave Box]

If your compression is below 100 psi then it is time to consider a rebuild. Before you do it will be worth while to grab the drive clutch and try to lift the engine. If you see any movement of the crankshaft in relation to the engine block then you have issues with the bottom end as well. You can find the top end kit for around $200 and the complete engine kit for <$400. If you elect to just do the top end it is essential that you also buy and fit two new crankshaft seals as well (these are included in the complete kit). If there is any movement at all on the crankshaft and you fit new seals, they will be ripped to shreds in a few engine hours and you engine will stop running.
It is a good idea to remove the oil pump but we can discuss that sometime in the future. But first the compression ..........

Dave

[2strokesandsplat]

Well bad news. I tested the compression and it tested at 90psi. Not good. So, a friend of mine came over and we pulled the exhaust off and this is what we see when looking into the motor. Looks like a top end rebuild is in my future. I did the crank test and tried lifting up on it and it was solid so i think the bottom end is o.k. I will order the kit (unless there are any objections or other things to try) and I will keep everyone posted with progress. Thank you all very much for the replies and I cant wait to dig in!

[Dave Box]

Just a few more tips then,

When you remove the cables from the starter label them. Also use a thin wrench under the cable to stop the stud spinning, If the stud does spin the wires on the inside will rip off

Make a note of the pattern of the head bolts some are different as they hold the cooling shroud on

Ensure that you put the new piston in the right way. The port faces the inlet side. Get it round the wrong way and by a cruel trick of engineering the engine will run but just barely.

Don't forget to change these crankshaft seals, they are the reason that your engine does not start.

Good luck
Dave

[CClark56]

Interesting thread, kinda in the same boat, at least half way... starter turning, got spark, carb is good and all that. So just waiting to hopefully borrow a compression tester and find out if we're actually both in the same boat lol.

[2strokesandsplat]

One quick thing to do is pull of the exhaust and look up into the motor. If your piston looks like mine, you may as well forget the compression test and order your rebuild kit! Lol