72 GT550 Compression Question
Posted: Fri Apr 03, 2020 10:39 am
Hello everyone, this is my first post. I got a GT550 a few months back and have had more spare time recently to dig into it.
A little backstory, it sat in my grandparents barn in Iowa since 1985 with oil in the tank and gearbox and no gas. It’s not pretty at the moment thanks to humidity and pests, but everything seems to be workable - most importantly the motor kicks over. I’ve got a couple of 70s Hondas, but this is my first two stroke.
I’m in the process of sorting out the carbs, airbox, spark, and compression to see what I’m getting myself into. The first problem I’ve run into is compression.
The bike doesn’t currently run so the best I can do is a cold compression test with the kickstart. I had the carbs and headers off while running the compression test on each cylinder since those needed to come off for cleaning. I figured a good reading for this bike would be 150-160 psi. After 10 kicks on each cylinder I got: Left: 200 psi, Middle 125 psi, Right: 200 psi. After the tests, I noticed the L&R exhaust ports leaking oil, but the middle was almost bone dry. I don’t think any oil was left in the top of the cylinders when the bike was put up. I think it was just oil pulled in from the pump. Like I said, I’m new to 2 strokes and am not sure what’s normal here. I understand the oil helped create a better seal for L&R - giving a higher compression reading, but I don’t get why the middle is different. Maybe a blocked line? See photos in link. https://imgur.com/a/wB9E0Jc
This is my first noob issue of many, but I’m looking forward to sorting it out. I’m not planning to keep the wind screen on when all is said and done, but keeping it on the bike for now is my best option for storage. I’m not sure if there’s a market for those, but let me know if you’re interested.
A little backstory, it sat in my grandparents barn in Iowa since 1985 with oil in the tank and gearbox and no gas. It’s not pretty at the moment thanks to humidity and pests, but everything seems to be workable - most importantly the motor kicks over. I’ve got a couple of 70s Hondas, but this is my first two stroke.
I’m in the process of sorting out the carbs, airbox, spark, and compression to see what I’m getting myself into. The first problem I’ve run into is compression.
The bike doesn’t currently run so the best I can do is a cold compression test with the kickstart. I had the carbs and headers off while running the compression test on each cylinder since those needed to come off for cleaning. I figured a good reading for this bike would be 150-160 psi. After 10 kicks on each cylinder I got: Left: 200 psi, Middle 125 psi, Right: 200 psi. After the tests, I noticed the L&R exhaust ports leaking oil, but the middle was almost bone dry. I don’t think any oil was left in the top of the cylinders when the bike was put up. I think it was just oil pulled in from the pump. Like I said, I’m new to 2 strokes and am not sure what’s normal here. I understand the oil helped create a better seal for L&R - giving a higher compression reading, but I don’t get why the middle is different. Maybe a blocked line? See photos in link. https://imgur.com/a/wB9E0Jc
This is my first noob issue of many, but I’m looking forward to sorting it out. I’m not planning to keep the wind screen on when all is said and done, but keeping it on the bike for now is my best option for storage. I’m not sure if there’s a market for those, but let me know if you’re interested.