87 Marathon with new motor down on power

NetMXer · 11-14-2007, 09:02 AM

I've just rebuilt my 87 Marathon with a complete new engine kit (crank, piston, rings, cylinder, bearings, seals) and it really seems to be down on power. This cart had been sitting for two years prior to the rebuild but before that, the power was also pretty weak which I attributed to the poor condition of the engine. Now that I can pretty much exclude the engine as being the cause of the power problem, I'm starting to look for other possible causes. I'm going to swap out the muffler with one from another cart to see if that may be restricted. I've also read on here that problems with the drive and/or driven clutch could reduce power output. Is there any way to diagnose if those are the cause of the problem?

Dero · 11-14-2007, 01:53 PM

Just take off the muffler. if it runs better without, thats a problem.

mb523 · 11-14-2007, 04:35 PM

When you put the piston in, did you make sure the F was facing the flywheel. In other words, can you see a port in the piston from the exhaust port on the cylinder?

NetMXer · 11-14-2007, 05:31 PM

I put it in correctly but at the time, I didn't know what the "F" on the piston stood for. Since I replaced the piston, crank and rod, I just looked at how the piston was mounted on the old rod and mounted the new piston in the same direction. Most of the motorcycles I've worked on usually have an "I" for intake side or "E" for exhaust. I was wondering what the "F" meant and never even thought about the flywheel.

BTW: I think I got the problem solved. I just had the governor set too slow. Once I adjusted that, it's got pretty good power now. I still think I need to replace that old muffler though. After going for a 10 minute ride, smoke comes out of the tailpipe for the next 1/2 hour. It's probably got 20 years of oil and carbon built up in there.

mb523 · 11-14-2007, 05:38 PM

I bet... mine was the same way. Also... the rings need time to break in... in time it will increase!

caddymankc · 11-14-2007, 06:26 PM

Quote:

Originally Posted by Dero

Just take off the muffler. if it runs better without, thats a problem.

Dont you need some backpressure cause its a 2 stroke?

mb523 · 11-14-2007, 10:37 PM

Quote:

Originally Posted by caddymankc

Dont you need some backpressure cause its a 2 stroke?

They do... too much backpressure causes poor performance (blockage from excess carbon). It is just a test.

11-14-2007, 09:02 AM	#1
NetMXer Gone Wild Join Date: Oct 2007 Location: Virginia Posts: 210	87 Marathon with new motor down on power I've just rebuilt my 87 Marathon with a complete new engine kit (crank, piston, rings, cylinder, bearings, seals) and it really seems to be down on power. This cart had been sitting for two years prior to the rebuild but before that, the power was also pretty weak which I attributed to the poor condition of the engine. Now that I can pretty much exclude the engine as being the cause of the power problem, I'm starting to look for other possible causes. I'm going to swap out the muffler with one from another cart to see if that may be restricted. I've also read on here that problems with the drive and/or driven clutch could reduce power output. Is there any way to diagnose if those are the cause of the problem?

11-14-2007, 01:53 PM	#2
Dero Gone Wild Join Date: Jan 2007 Posts: 731	Re: 87 Marathon with new motor down on power Just take off the muffler. if it runs better without, thats a problem.
Dero Gone Wild Join Date: Jan 2007 Posts: 731

11-14-2007, 04:35 PM	#3
mb523 Peanut Join Date: Feb 2007 Location: Western Massachusetts Posts: 656	Re: 87 Marathon with new motor down on power When you put the piston in, did you make sure the F was facing the flywheel. In other words, can you see a port in the piston from the exhaust port on the cylinder?

11-14-2007, 05:31 PM	#4
NetMXer Gone Wild Join Date: Oct 2007 Location: Virginia Posts: 210	Re: 87 Marathon with new motor down on power I put it in correctly but at the time, I didn't know what the "F" on the piston stood for. Since I replaced the piston, crank and rod, I just looked at how the piston was mounted on the old rod and mounted the new piston in the same direction. Most of the motorcycles I've worked on usually have an "I" for intake side or "E" for exhaust. I was wondering what the "F" meant and never even thought about the flywheel. BTW: I think I got the problem solved. I just had the governor set too slow. Once I adjusted that, it's got pretty good power now. I still think I need to replace that old muffler though. After going for a 10 minute ride, smoke comes out of the tailpipe for the next 1/2 hour. It's probably got 20 years of oil and carbon built up in there.

11-14-2007, 05:38 PM	#5
mb523 Peanut Join Date: Feb 2007 Location: Western Massachusetts Posts: 656	Re: 87 Marathon with new motor down on power I bet... mine was the same way. Also... the rings need time to break in... in time it will increase!

Today
BGW	Sponsored Links __________________ This advertising will not be shown in this way to registered members. Register your free account today and become a member on Buggies Gone Wild Golf Cart Forum

Similar Threads
Thread	Forum
My 80 EZ-GO Marathon	Gas EZGO
Any motor mod recomendations for an 87 Marathon?	Gas EZGO
My 86 Marathon	Gas EZGO
how to take off the body of marathon	Gas EZGO
Marathon Chassis	Golf Carts and Parts