84 Marathon no power

Rcarlson · 05-05-2019, 03:13 PM

I have an 84 Marathon with 2PG 2stroke engine. I rebuilt the engine a few years ago and it ran great until recently. I've had all kinds of troubles getting it to go. It runs great on jackstands but can't pull it's own weight up a hill. It just barely moves. Compression is 120 with a trusted tester. I've been through several carbs, new fuel pump, just did HEI ignition conversion. I've removed the exhaust, no difference. I run premix, 128:1. I changed out all the old fuel. I've read several similar posts on here but the OP never came back and said what the fix was. I have sprayed starting fluid around the crank seals and don't notice any difference.

cart around · 05-05-2019, 03:32 PM

Does the engine sound like it's running strong?

How wide is your drive belt? 1 3/16" is new less than an inch is junk.

Remove your drive belt, and squeeze the plates of the driven clutch together with your hand. If the plates lean towards each other, the clutch is worn. That will cause a huge power loss.

Rcarlson · 05-05-2019, 05:53 PM

Ok i will check on that. I had the rear end jacked up earlier and I don't have a brake dragging. After barely making it up the hill into my shop, when I went to park it, it wanted to keep running. It was dieseling and backfiring. Could I have a timing issue?

cart around · 05-05-2019, 07:12 PM

Have you tried switching the red and blue wires from the pulsar after performing the hei mod?

Rcarlson · 05-05-2019, 08:54 PM

Yes, I did just try switching the pulsar wires and it ran worse. Engine seems to run good on jackstands. I don't see anything wrong with the clutch and my belt is well within spec. I'm thinking of pulling the fly wheel and checking the alignment of the pulsar. Any tips for pulling the fly wheel?

Rcarlson · 05-06-2019, 08:42 PM

Pulsar looks good. Crank seal is a little oily but not much. I might replace it while I can access it. I retraced all of the HEI conversion wires and see nothing wrong. One question...does it matter which coil I am using? I have a 12V coil out of a 68 Ford truck in it right now.

cart around · 05-06-2019, 09:24 PM

I used a cheap round $15 coil with no problem.

05-05-2019, 03:13 PM	#1
Rcarlson Not Yet Wild Join Date: Apr 2019 Posts: 8	84 Marathon no power I have an 84 Marathon with 2PG 2stroke engine. I rebuilt the engine a few years ago and it ran great until recently. I've had all kinds of troubles getting it to go. It runs great on jackstands but can't pull it's own weight up a hill. It just barely moves. Compression is 120 with a trusted tester. I've been through several carbs, new fuel pump, just did HEI ignition conversion. I've removed the exhaust, no difference. I run premix, 128:1. I changed out all the old fuel. I've read several similar posts on here but the OP never came back and said what the fix was. I have sprayed starting fluid around the crank seals and don't notice any difference.
Rcarlson Not Yet Wild Join Date: Apr 2019 Posts: 8

05-05-2019, 03:32 PM	#2
cart around Test before replacing Join Date: Aug 2013 Location: Ohio side of the Pennsylvania border. Posts: 3,496	Re: 84 Marathon no power Does the engine sound like it's running strong? How wide is your drive belt? 1 3/16" is new less than an inch is junk. Remove your drive belt, and squeeze the plates of the driven clutch together with your hand. If the plates lean towards each other, the clutch is worn. That will cause a huge power loss.

05-05-2019, 05:53 PM	#3
Rcarlson Not Yet Wild Join Date: Apr 2019 Posts: 8	Re: 84 Marathon no power Ok i will check on that. I had the rear end jacked up earlier and I don't have a brake dragging. After barely making it up the hill into my shop, when I went to park it, it wanted to keep running. It was dieseling and backfiring. Could I have a timing issue?
Rcarlson Not Yet Wild Join Date: Apr 2019 Posts: 8

05-05-2019, 07:12 PM	#4
cart around Test before replacing Join Date: Aug 2013 Location: Ohio side of the Pennsylvania border. Posts: 3,496	Re: 84 Marathon no power Have you tried switching the red and blue wires from the pulsar after performing the hei mod?

05-05-2019, 08:54 PM	#5
Rcarlson Not Yet Wild Join Date: Apr 2019 Posts: 8	Re: 84 Marathon no power Yes, I did just try switching the pulsar wires and it ran worse. Engine seems to run good on jackstands. I don't see anything wrong with the clutch and my belt is well within spec. I'm thinking of pulling the fly wheel and checking the alignment of the pulsar. Any tips for pulling the fly wheel?
Rcarlson Not Yet Wild Join Date: Apr 2019 Posts: 8

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05-06-2019, 08:42 PM	#6
Rcarlson Not Yet Wild Join Date: Apr 2019 Posts: 8	Re: 84 Marathon no power Pulsar looks good. Crank seal is a little oily but not much. I might replace it while I can access it. I retraced all of the HEI conversion wires and see nothing wrong. One question...does it matter which coil I am using? I have a 12V coil out of a 68 Ford truck in it right now.
Rcarlson Not Yet Wild Join Date: Apr 2019 Posts: 8

05-06-2019, 09:24 PM	#7
cart around Test before replacing Join Date: Aug 2013 Location: Ohio side of the Pennsylvania border. Posts: 3,496	Re: 84 Marathon no power I used a cheap round $15 coil with no problem.

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