1989 3pg issues after top end rebuild

kingja68156 · 03-23-2016, 11:40 PM

I need some help....I have an 89 marathon 3pg. I just completed a top end rebuild on it. I took my time and was very meticulous when putting it back together.

After the rebuild it seems to be running really hot and begins to lose power untill it won't run anymore. Once it cools off it runs again. I'd say it runs good for about 5min. Engine temp was around 300 degrees.

I'm premixing fuel. This tank I'm at about 100:1 for break-in. What I believe to be the air screw on the carb was screwed all the way in....I backed it out two turns but didn't seem to make a difference. Engine temp was 276 degrees.

Compression before rebuild was 50psi....after rebuild it's only 60psi.

1. If I have a compression issue with the oil seals, why am I overheating?

2. Are both the piston rings identical?

3. Is this normal during the break-in period.....and for how long?

ez go go · 03-24-2016, 06:22 AM

I'm not much help on these two bangers but I will give it my best shot.. If your only pushing 60 psi after the rebuild you definitely still have a ring or seal issue.. What all did the rebuild include... Gimme a rundown of what was replaced..

cart around · 03-24-2016, 07:23 AM

Crankshaft seals have no affect on compression. They are below the rings.

Break in oil should be 40:1 for the first tank full.

Did you hone your cylinder so the rings would seat properly?

Rings go bevel side up. Did you check the end gap? If it is too tight, the rings expand at temperature, and seize the piston. I don't have a book to see what the proper end gap is.

If it isn't a ring problem, low compression could also be caused by the reed valves not closing all the way.

racin161 · 03-24-2016, 10:37 AM

40:1 on the fuel mix for the first tank. Ring end gap is .008-.016 shoot for .010-.012. As mentioned sounds like the ring end gap was to tight and is
seizing in the bore. Some rings may have a bevel and some may not. It sounds like you need to pull the jug again and I think your going to find your problem.

LOU

kingja68156 · 03-29-2016, 12:20 PM

The rings looked identical when putting them on the piston. I didn't check the end gap. I installed the piston and rings from the top of the jug and tapped it in with a rubber mallet.

I think I'm going to have to pull it back apart, take a look. I'm also going to increase the oil mixture.

Here is the Kit I purchased.
http://www.buggiesunlimited.com/golf...o-1989-93/4558

Thank for your help.

rmf350 · 06-25-2016, 06:52 AM

Did you ever find the problem. I have same issues

03-23-2016, 11:40 PM	#1
kingja68156 Not Yet Wild Join Date: Apr 2015 Posts: 11	1989 3pg issues after top end rebuild I need some help....I have an 89 marathon 3pg. I just completed a top end rebuild on it. I took my time and was very meticulous when putting it back together. After the rebuild it seems to be running really hot and begins to lose power untill it won't run anymore. Once it cools off it runs again. I'd say it runs good for about 5min. Engine temp was around 300 degrees. I'm premixing fuel. This tank I'm at about 100:1 for break-in. What I believe to be the air screw on the carb was screwed all the way in....I backed it out two turns but didn't seem to make a difference. Engine temp was 276 degrees. Compression before rebuild was 50psi....after rebuild it's only 60psi. 1. If I have a compression issue with the oil seals, why am I overheating? 2. Are both the piston rings identical? 3. Is this normal during the break-in period.....and for how long?
kingja68156 Not Yet Wild Join Date: Apr 2015 Posts: 11

03-24-2016, 06:22 AM	#2
ez go go Doin' the Wild Thang Join Date: Mar 2010 Location: Greenville, AL Posts: 1,063	Re: 1989 3pg issues after top end rebuild I'm not much help on these two bangers but I will give it my best shot.. If your only pushing 60 psi after the rebuild you definitely still have a ring or seal issue.. What all did the rebuild include... Gimme a rundown of what was replaced..

03-24-2016, 07:23 AM	#3
cart around Test before replacing Join Date: Aug 2013 Location: Ohio side of the Pennsylvania border. Posts: 3,495	Re: 1989 3pg issues after top end rebuild Crankshaft seals have no affect on compression. They are below the rings. Break in oil should be 40:1 for the first tank full. Did you hone your cylinder so the rings would seat properly? Rings go bevel side up. Did you check the end gap? If it is too tight, the rings expand at temperature, and seize the piston. I don't have a book to see what the proper end gap is. If it isn't a ring problem, low compression could also be caused by the reed valves not closing all the way.

03-24-2016, 10:37 AM	#4
racin161 Gone Wild Join Date: Feb 2011 Posts: 1,515	Re: 1989 3pg issues after top end rebuild 40:1 on the fuel mix for the first tank. Ring end gap is .008-.016 shoot for .010-.012. As mentioned sounds like the ring end gap was to tight and is seizing in the bore. Some rings may have a bevel and some may not. It sounds like you need to pull the jug again and I think your going to find your problem. LOU
racin161 Gone Wild Join Date: Feb 2011 Posts: 1,515

03-29-2016, 12:20 PM	#5
kingja68156 Not Yet Wild Join Date: Apr 2015 Posts: 11	Re: 1989 3pg issues after top end rebuild The rings looked identical when putting them on the piston. I didn't check the end gap. I installed the piston and rings from the top of the jug and tapped it in with a rubber mallet. I think I'm going to have to pull it back apart, take a look. I'm also going to increase the oil mixture. Here is the Kit I purchased. http://www.buggiesunlimited.com/golf...o-1989-93/4558 Thank for your help.
kingja68156 Not Yet Wild Join Date: Apr 2015 Posts: 11

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06-25-2016, 06:52 AM	#6
rmf350 Not Yet Wild Join Date: Feb 2016 Posts: 3	Re: 1989 3pg issues after top end rebuild Did you ever find the problem. I have same issues
rmf350 Not Yet Wild Join Date: Feb 2016 Posts: 3

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