Post by lackthereof on Jul 10, 2014 15:53:10 GMT -5
Background:
So last August my 49cc Lifan commuter scooter vanished from the parking lot overnight. I was pissed. It was running perfect, only had about 3000km on the odo. It was pure stock other than 5g weights for hill climbing.
This Tuesday, 11 months after it disappeared, I got a call from the sheriff asking me to come down to the impound yard and identify something that might be my scooter. It was mine (at least, I think it is) - it has the same reoriented kick starter, and the same marks on the carb from where I took it apart to fix a stuck slide. No way to verify, as both the VIN and engine serial number were filed off. It was in pieces.
.
It had been spray painted, and most of the body panels were broken or missing, but I did manage to haul it home and reassemble the body out of the handful of unbroken parts.
The odometer picked up about 1000km while it was missing.
So once I got it more or less street-legal again, I set about test firing it. Looking over the engine, the battery was very dead, and the wiring harness a complete tangled disaster, looks like someone who didn't know anything about anything was trying to diagnose some elusive electrical gremlin. The bottom cooling shroud was missing, the factory air box had been removed and replaced with what looks like a K&N-style automotive crankcase breather, and the muffler had been gutted. The throttle cable was way too tight and holding it far off of idle, which made it not want to fire and then idle at a cruising RPM.
It took like 20-30 kicks and lots of fiddling with the throttle to get it to start and stay running, but once I got it to idle properly it seemed to run fine. Stalled very easily when cold. I didn't want to run it very long with the missing lower cooling shroud, so once it was stable I did a single 0-35 mph test pull and then parked it. Once moving it accelerated without much difficulty (although from the sluggish way it "shifts" I think the variator guides are trashed).
The problem:
Hard starting when cold. Before the scooter's unscheduled vacation, when cold it would start on ONE kick, rain or shine, winter or summer. If you didn't hop on and give it some throttle within 5-10 seconds, it would chug and stall, but there was never a problem with initial starting. After my test ride and letting it sit & cool overnight it seems to be even worse. It's got hardly any compression - I don't have a compression gauge but it kicks over way too easily. I pulled the spark plug to check its condition and gap - found that someone replaced the factory no-name plug with a cross-threaded NGK in otherwise good condition. While the plug was out I did the "thumb test" for compression - it wasn't able to blow my thumb off.
So it seems natural to me that the low compression is likely to be my entire problem. I pulled the valve cover and did a quick check of the lash. I didn't break out the feeler gauges but merely made sure everything was moving freely and wiggled the rockers at TDC - nothing's binding, and the valves aren't being held open.
So what am I likely looking at here? I assume it's been severely overheated from running without the cooling shroud. Is it likely to need a new head & valves, a piston & jug, or both? What kind of damage should I expect to find in a situation like this if/when I open it up?
I don't plan on keeping it - I've already replaced it, I just want to get it repaired to the point that a layperson can start it easily so I can sell it.
So last August my 49cc Lifan commuter scooter vanished from the parking lot overnight. I was pissed. It was running perfect, only had about 3000km on the odo. It was pure stock other than 5g weights for hill climbing.
This Tuesday, 11 months after it disappeared, I got a call from the sheriff asking me to come down to the impound yard and identify something that might be my scooter. It was mine (at least, I think it is) - it has the same reoriented kick starter, and the same marks on the carb from where I took it apart to fix a stuck slide. No way to verify, as both the VIN and engine serial number were filed off. It was in pieces.
.It had been spray painted, and most of the body panels were broken or missing, but I did manage to haul it home and reassemble the body out of the handful of unbroken parts.
The odometer picked up about 1000km while it was missing.
So once I got it more or less street-legal again, I set about test firing it. Looking over the engine, the battery was very dead, and the wiring harness a complete tangled disaster, looks like someone who didn't know anything about anything was trying to diagnose some elusive electrical gremlin. The bottom cooling shroud was missing, the factory air box had been removed and replaced with what looks like a K&N-style automotive crankcase breather, and the muffler had been gutted. The throttle cable was way too tight and holding it far off of idle, which made it not want to fire and then idle at a cruising RPM.
It took like 20-30 kicks and lots of fiddling with the throttle to get it to start and stay running, but once I got it to idle properly it seemed to run fine. Stalled very easily when cold. I didn't want to run it very long with the missing lower cooling shroud, so once it was stable I did a single 0-35 mph test pull and then parked it. Once moving it accelerated without much difficulty (although from the sluggish way it "shifts" I think the variator guides are trashed).
The problem:
Hard starting when cold. Before the scooter's unscheduled vacation, when cold it would start on ONE kick, rain or shine, winter or summer. If you didn't hop on and give it some throttle within 5-10 seconds, it would chug and stall, but there was never a problem with initial starting. After my test ride and letting it sit & cool overnight it seems to be even worse. It's got hardly any compression - I don't have a compression gauge but it kicks over way too easily. I pulled the spark plug to check its condition and gap - found that someone replaced the factory no-name plug with a cross-threaded NGK in otherwise good condition. While the plug was out I did the "thumb test" for compression - it wasn't able to blow my thumb off.
So it seems natural to me that the low compression is likely to be my entire problem. I pulled the valve cover and did a quick check of the lash. I didn't break out the feeler gauges but merely made sure everything was moving freely and wiggled the rockers at TDC - nothing's binding, and the valves aren't being held open.
So what am I likely looking at here? I assume it's been severely overheated from running without the cooling shroud. Is it likely to need a new head & valves, a piston & jug, or both? What kind of damage should I expect to find in a situation like this if/when I open it up?
I don't plan on keeping it - I've already replaced it, I just want to get it repaired to the point that a layperson can start it easily so I can sell it.
