Hey folks! Great to be here. I like being hands-on with motorcycles but I'm breaking new ground with respect to working on an engine and carbs. Please excuse my lack of knowledge; I'm learning as I go along.
When my 1979 1000SP arrived from across the country, she was in non-running condition. I charged the battery, put in some gas, and tried starting her. She sputtered to life on the choke and I considered it a win. The previous owner had mentioned issues with plugs getting fouled, especially on the right cylinder. I quickly realized that the choke (enricher?) on the right carb was sticking on the throttle cable and by itself. I lubed it and cleared it of the throttle cable. I replaced the fouled spark plugs (NGK BPR6ES) with new non-resistor plugs (NGK BP6ES) and also replaced the caps with new non-resistor caps (NGK 8381 LZFH) after I found one broken. The bike would run but it was as if it was running on 50% power (which was actually what was happening), with surges of power at times. I checked the air filter and carbs. All good, but what a pain that air filter was to get into! I should have checked the coils first. One of them was leaky, so I replaced it with an identical Bobina. Finally, she ran. I fixed the speedo to figure out how fast I was going by eliminating the broken L joint at the end. Touched an indicated 100mph but was still experiencing misfires.
I pulled the plugs and here's what they looked like:
Left cylinder plug:
There is sooty residue on the thread but the electrodes look slightly scorched. I want to try enrichening the mixture, but I'd rather focus on getting the right cylinder happy first.
Here's the right cylinder plug:
It shows a soot mark on the electrode and the top is oily as well, indicating that some oil is getting past the rings. Based on the color of the electrodes it seems like the cylinder is getting a lean mixture, but that's less of a concern compared to the oily deposits.
I used a boroscope to peer into the cylinders. The left cylinder had been clean before (when I got the bike). Now I see oil seeping onto the top from the edges. I don't know if the color of the piston at the edges is unusual.
The right cylinder was coated with carbon the first time I saw it, likely due to the double whammy of a stuck choke and a bad coil. After going through a can of Seafoam I can see the top of the piston. I'm going through another can of it right now; let's see if it removes more carbon. There's a mark on the top of the piston that makes me wonder if it is hitting the spark plug. I don't hear any weird sounds when riding, however. Any ideas?
The OTC compression tester arrived today and I just ran a compression test on both cylinders. The left one reads 170 psi while the right one's at 125 psi. This was done when the engine was almost cold, so I'll rerun the test tomorrow after warming up the engine. I also got an OTC leak-down tester but I don't have an air compressor to use it with yet; I plan to acquire one. Based on this quick test it does seem like there's an issue with the piston rings / valves on the right cylinder. The leak-down test should help disambiguate this further.
There's also a peculiar idling issue I'm experiencing. When I'm stopped, the revs start climbing gradually until it's running at around 2.5K RPM. I've adjusted the idle screws to get it down but then at times the engine just wants to stall and needs to be revved. So basically the engine's not able to idle at a steady RPM.
I'll continue figuring things out using whatever resources I am able to find, but it would be great to get inputs from folks that have seen these issues and know what's happening. Thanks in advance!
When my 1979 1000SP arrived from across the country, she was in non-running condition. I charged the battery, put in some gas, and tried starting her. She sputtered to life on the choke and I considered it a win. The previous owner had mentioned issues with plugs getting fouled, especially on the right cylinder. I quickly realized that the choke (enricher?) on the right carb was sticking on the throttle cable and by itself. I lubed it and cleared it of the throttle cable. I replaced the fouled spark plugs (NGK BPR6ES) with new non-resistor plugs (NGK BP6ES) and also replaced the caps with new non-resistor caps (NGK 8381 LZFH) after I found one broken. The bike would run but it was as if it was running on 50% power (which was actually what was happening), with surges of power at times. I checked the air filter and carbs. All good, but what a pain that air filter was to get into! I should have checked the coils first. One of them was leaky, so I replaced it with an identical Bobina. Finally, she ran. I fixed the speedo to figure out how fast I was going by eliminating the broken L joint at the end. Touched an indicated 100mph but was still experiencing misfires.
I pulled the plugs and here's what they looked like:
Left cylinder plug:
There is sooty residue on the thread but the electrodes look slightly scorched. I want to try enrichening the mixture, but I'd rather focus on getting the right cylinder happy first.
Here's the right cylinder plug:
It shows a soot mark on the electrode and the top is oily as well, indicating that some oil is getting past the rings. Based on the color of the electrodes it seems like the cylinder is getting a lean mixture, but that's less of a concern compared to the oily deposits.
I used a boroscope to peer into the cylinders. The left cylinder had been clean before (when I got the bike). Now I see oil seeping onto the top from the edges. I don't know if the color of the piston at the edges is unusual.
The right cylinder was coated with carbon the first time I saw it, likely due to the double whammy of a stuck choke and a bad coil. After going through a can of Seafoam I can see the top of the piston. I'm going through another can of it right now; let's see if it removes more carbon. There's a mark on the top of the piston that makes me wonder if it is hitting the spark plug. I don't hear any weird sounds when riding, however. Any ideas?
The OTC compression tester arrived today and I just ran a compression test on both cylinders. The left one reads 170 psi while the right one's at 125 psi. This was done when the engine was almost cold, so I'll rerun the test tomorrow after warming up the engine. I also got an OTC leak-down tester but I don't have an air compressor to use it with yet; I plan to acquire one. Based on this quick test it does seem like there's an issue with the piston rings / valves on the right cylinder. The leak-down test should help disambiguate this further.
There's also a peculiar idling issue I'm experiencing. When I'm stopped, the revs start climbing gradually until it's running at around 2.5K RPM. I've adjusted the idle screws to get it down but then at times the engine just wants to stall and needs to be revved. So basically the engine's not able to idle at a steady RPM.
I'll continue figuring things out using whatever resources I am able to find, but it would be great to get inputs from folks that have seen these issues and know what's happening. Thanks in advance!
