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Okay...here's what has happened so far w/ my daughter's bike (which she still doesn't know about 'cause her birthday isn't until Wednesday)
First, a brief recap...
Picked up a 1987 Rebel 450 that ran a bit rough. PO said that he suspected that it might need a carb sync/cleaning. Discovered that right cylinder wasn't firing and I didn't feel a good vacuum through the right carb, which suggested a compression problem (this is when the freak-out started). Ran about half a can of Seafoam directly through the fuel line to try and blow out any crud I could, then dumped the rest in the tank.
Here's what has happened since then. Thankfully, one of the guys I work with is another motorcyclist who was willing to give me a hand with some troubleshooting. Tried to do a compression test, but my gauge doesn't have the proper size adapter to fit the spark plug hole, so we went a different route.
First: Pulled the cam cover and made sure that the valves were adjusted correctly. Checked for broken springs, or anything else that might indicate a reason for a valve to be hanging up. Clearances were good, and everything else looked okay.
Second: Pulled exhaust and noticed that right side pipe did NOT have any oily residue inside, which would indicate a ring problem that would allow oil blow-by as well as loss of compression. So far, so good.
Third: Pulled carbs/manifolds where they connect to the engine. Discovered that PO had previously painted engine, as evidenced by the "X" outline left behind when the tape that he used to mask the intake ports was removed. Removed the rest of the paint from the mating surfaces for the manifolds to ensure a proper seal when manifolds were bolted back on.
Fourth: Set engine to TDC on the compression stroke for the right side and squirted MMO into both intake and exhaust ports...3 days later, same amount of oil was still covering both intake valves and the exhaust valve as well (big sigh of relief!)
Soooo...not a compression problem? Onward w/ the troubleshooting. I have also been in contact w/ a guy in Florida who has a lot of experience with these bikes. He was leaning towards an electrical/ignition problem, and sent me out a "test kit" consisting of a known good CDI and coil along with a new set of spark plug wires w/caps that I needed anyway. I also noticed while the carbs were off that the idle mixture screw(?) for the right carb was completely seated, whereas the left carb was out one full turn...so I turned the right side out one full turn to match.
Fifth: While carbs were unbolted, pulled the bowls and noticed a fair amount of sediment in the bottoms, so I pulled the mains (right main pretty clogged), the slow jets, etc. and went through a couple cans of cleaner trying to open up passages. Went through accelerator pump, both slides (diaphragms look good), pulled the petcock and cleaned it as well.
Put everything back together (new o-rings for manifolds, new spark plugs and wires, new exhaust stud to replace the one that had the nut -no kidding- JB welded to it and had vibrated off when the engine had been previously running, new vacuum lines, new fuel line and added an inline filter) and cranked it over. After sputtering and coughing pretty hard, it runs...but still kind of rough. It is firing on both cylinders now, which is great. When I try to open the throttle, it will bog down a bit, but will eventually rev hard. If I try to ride it, as soon as I put it in gear and try to launch, it will bog down unless I give it a lot of choke. This is where I'm looking for advice. I'm sure the carb sync needs to be done...but what else? It still backfires through both carbs a bit at idle. I'm quickly running out of time to get this done before her birthday, which is what I'm really hoping to do. Any help is greatly appreciated...and thanks for enduring this long post.
First, a brief recap...
Picked up a 1987 Rebel 450 that ran a bit rough. PO said that he suspected that it might need a carb sync/cleaning. Discovered that right cylinder wasn't firing and I didn't feel a good vacuum through the right carb, which suggested a compression problem (this is when the freak-out started). Ran about half a can of Seafoam directly through the fuel line to try and blow out any crud I could, then dumped the rest in the tank.
Here's what has happened since then. Thankfully, one of the guys I work with is another motorcyclist who was willing to give me a hand with some troubleshooting. Tried to do a compression test, but my gauge doesn't have the proper size adapter to fit the spark plug hole, so we went a different route.
First: Pulled the cam cover and made sure that the valves were adjusted correctly. Checked for broken springs, or anything else that might indicate a reason for a valve to be hanging up. Clearances were good, and everything else looked okay.
Second: Pulled exhaust and noticed that right side pipe did NOT have any oily residue inside, which would indicate a ring problem that would allow oil blow-by as well as loss of compression. So far, so good.
Third: Pulled carbs/manifolds where they connect to the engine. Discovered that PO had previously painted engine, as evidenced by the "X" outline left behind when the tape that he used to mask the intake ports was removed. Removed the rest of the paint from the mating surfaces for the manifolds to ensure a proper seal when manifolds were bolted back on.
Fourth: Set engine to TDC on the compression stroke for the right side and squirted MMO into both intake and exhaust ports...3 days later, same amount of oil was still covering both intake valves and the exhaust valve as well (big sigh of relief!)
Soooo...not a compression problem? Onward w/ the troubleshooting. I have also been in contact w/ a guy in Florida who has a lot of experience with these bikes. He was leaning towards an electrical/ignition problem, and sent me out a "test kit" consisting of a known good CDI and coil along with a new set of spark plug wires w/caps that I needed anyway. I also noticed while the carbs were off that the idle mixture screw(?) for the right carb was completely seated, whereas the left carb was out one full turn...so I turned the right side out one full turn to match.
Fifth: While carbs were unbolted, pulled the bowls and noticed a fair amount of sediment in the bottoms, so I pulled the mains (right main pretty clogged), the slow jets, etc. and went through a couple cans of cleaner trying to open up passages. Went through accelerator pump, both slides (diaphragms look good), pulled the petcock and cleaned it as well.
Put everything back together (new o-rings for manifolds, new spark plugs and wires, new exhaust stud to replace the one that had the nut -no kidding- JB welded to it and had vibrated off when the engine had been previously running, new vacuum lines, new fuel line and added an inline filter) and cranked it over. After sputtering and coughing pretty hard, it runs...but still kind of rough. It is firing on both cylinders now, which is great. When I try to open the throttle, it will bog down a bit, but will eventually rev hard. If I try to ride it, as soon as I put it in gear and try to launch, it will bog down unless I give it a lot of choke. This is where I'm looking for advice. I'm sure the carb sync needs to be done...but what else? It still backfires through both carbs a bit at idle. I'm quickly running out of time to get this done before her birthday, which is what I'm really hoping to do. Any help is greatly appreciated...and thanks for enduring this long post.
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