September 4th, 2007

Drove scooter to work in the morning. On the return trip, at about 50 more kilometers, the scooter started leaking coolant from the rear door that accesses the coolant overflow / reservoir tank. It would do this whenever it was under heavy load, i.e. going up a hill, starting out quickly from a complete stop, or throttling through turns.

Temperature gauge started showing needle JUST in the red zone, but not pegged or completely overheated. (Engine didn't smell hot, did not knock, ping, hesitate, blow smoke, or feel unusually hot compared to how it had been running.)

When I arrived home, I let the scooter cool down completely, and re-filled the reservoir tank to stock level. It was about an inch from the proper low level mark. Test drove the scooter. It still would blow coolant, and run in the same temperature condition as described above.

Refilled completely cooled scooter at the reservoir tank to proper level. Test drove scooter. Same problem(s) occurred.

Removed front shroud from scooter to gain access to the radiator. Once cool, the radiator had recovered only enough coolant to fill about 1/3 of the radiator capacity. Since the first day, the following symptoms continue to re-occur despite all other work, troubleshooting, experimentation in riding style. The only way the condition can be avoided is to never accelerate quickly, and never put it under load. This means that it would only ever perform at sea level, at best. The symptoms are as follows:

• Bike is cool to touch.
• Coolant is added to top of radiator by removing radiator cap. Cap replaced. Front shroud replaced.
• Coolant is added to top line of reservoir level, per scooter manual.
• Scooter is started, and allowed to warm up until engine speed levels out.
• If cap is removed from radiator, and throttle is quickly actuated to 1/2 to 3/4 of its travel, coolant blows from the radiator violently, and runs over the fill neck. If cap is left on and this same action is performed, coolant will continually leave the radiator until it overflows the reservoir tank, and spills from the lid.
• If the cap is removed from the radiator, and the throttle is SLOWLY actuated up to- and even past- the aforementioned point, it will NOT surge, but simply seem a bit more turbulent.
• When riding, if the scooter is under demand for quick acceleration, coolant is blown from reservoir tank lid.
• When riding, if the scooter is under demand going up hill, coolant is blown from reservoir tank.
• When riding and throttling through a turn or uphill, coolant is blown from reservoir tank.
• The scooter cannot be ridden in a normal state, certainly in a safe state when in traffic, without coolant being blown from reservoir lid.
• After this occurs a few times, the coolant level drops to 1/3 radiator capacity, and can be witnessed by either removing the radiator cap, or feeling the top and bottom of the radiator: where a substantial difference in temperature is notable. The coolant level also drops a minimum of 1/2" from the lower mark that represents a "good" coolant level, in the reservoir tank. The temperature runs in the mid white zone on the gauge UNTIL coolant is lost, at which point it generally stays about one needle-width into the red zone. It has never, to date, risen any higher than this, and has never reached the needle stop in the high red zone.