Kansas Corey
Member
Sorry guys, I have searched and read countless threads with the hopes of understanding the health of my engine, but still need some help. Here are the basics: 1979 Honda CT70 with 2,035 miles and unknown ownership prior to my purchase several months ago.
When I bought it, it seemed to idle okay but bogged down terribly at anything more than 1/2 throttle. I pulled the carb, cleaned it, and readjusted after install. Now it starts typically 1st or 2nd kick, but doesn't seem to like idling very well after approx. 1 hour of easy trail riding. In fact, it kept dying at one point.
Fast forward a little bit, my spark plug has black soot on it, my exhaust always seems to smell heavy (rich fuel - not oil I believe), and if at any point I open the choke, it dies instantly regardless of cold or hot. My thought was too rich at this point. Additionally, at idle, unless I adjust the idle speed screw to a fast idle, there is clicking noise (sorry - don't know how else to describe it) which I though was the valves. They have since been adjusted but were very close to specs and the noise remains. I've tried to play with the pilot (air mixture) screw but anything besides the starting point of approx. 1.5 turns out seems to cause the idle to fall even lower and the engine typically dies. Currently needle is in the furthest down (richest) position possible.
So... Having said that, I thought I would test the compression. Engine was warm, choke open, and full throttle for the test. Call it 127 PSI after about 7 kicks and then, with about 1 tsp of oil added through spark plug hole, measured 140 PSI after the same 7 kicks. Compression tester is a loaner from Auto Zone but looked to be solid and in good shape without much use.
What am I missing at this point? It seems to run well enough to ride causally and it'll never be a daily commuter, but something just doesn't set right with me. I feel like I honestly don't know the subject matter well enough to effectively diagnose what, if anything, is going on. Any thoughts or suggestions would be greatly appreciated.
I should mention that I live in the San Francisco bay area and only in the last 2 days got this beast street legal. As such, I have not had a chance to test top speed, but my guess is roughly 30 mph. Don't let this be the killer thought though, it has a 4-speed transmission from a 1983 Honda ATC, but previous owner didn't change the front & rear sprocket so I'm currently rockin' 15T and 35T which I assume need to be updated (best starting guess is 14T and 45T but that's another conversation).
Sorry for the long post!
1983 Honda ATC transmission (listing for my future reference):
1st = 11/36 = 3.27
2nd = 16/31 = 1.93
3rd = 20/27 = 1.35
4th = 23/24 =1.04
When I bought it, it seemed to idle okay but bogged down terribly at anything more than 1/2 throttle. I pulled the carb, cleaned it, and readjusted after install. Now it starts typically 1st or 2nd kick, but doesn't seem to like idling very well after approx. 1 hour of easy trail riding. In fact, it kept dying at one point.
Fast forward a little bit, my spark plug has black soot on it, my exhaust always seems to smell heavy (rich fuel - not oil I believe), and if at any point I open the choke, it dies instantly regardless of cold or hot. My thought was too rich at this point. Additionally, at idle, unless I adjust the idle speed screw to a fast idle, there is clicking noise (sorry - don't know how else to describe it) which I though was the valves. They have since been adjusted but were very close to specs and the noise remains. I've tried to play with the pilot (air mixture) screw but anything besides the starting point of approx. 1.5 turns out seems to cause the idle to fall even lower and the engine typically dies. Currently needle is in the furthest down (richest) position possible.
So... Having said that, I thought I would test the compression. Engine was warm, choke open, and full throttle for the test. Call it 127 PSI after about 7 kicks and then, with about 1 tsp of oil added through spark plug hole, measured 140 PSI after the same 7 kicks. Compression tester is a loaner from Auto Zone but looked to be solid and in good shape without much use.
What am I missing at this point? It seems to run well enough to ride causally and it'll never be a daily commuter, but something just doesn't set right with me. I feel like I honestly don't know the subject matter well enough to effectively diagnose what, if anything, is going on. Any thoughts or suggestions would be greatly appreciated.
I should mention that I live in the San Francisco bay area and only in the last 2 days got this beast street legal. As such, I have not had a chance to test top speed, but my guess is roughly 30 mph. Don't let this be the killer thought though, it has a 4-speed transmission from a 1983 Honda ATC, but previous owner didn't change the front & rear sprocket so I'm currently rockin' 15T and 35T which I assume need to be updated (best starting guess is 14T and 45T but that's another conversation).
Sorry for the long post!
1983 Honda ATC transmission (listing for my future reference):
1st = 11/36 = 3.27
2nd = 16/31 = 1.93
3rd = 20/27 = 1.35
4th = 23/24 =1.04