Power – GT125
- This topic has 9 replies, 3 voices, and was last updated 4 years ago by .
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Let us know the results of the compression test results (after the engine is hot, and crank bike full throttle with both plugs out) but tell the mechanic also cause sometimes they leave one plug inside causing bike to fire, the spark plugs must be physically out of the engine not just disconnected from the HT casps.
Just adding to what Tom said above ^ , go with what he says , even clearances pay dividents (valves too loose or too tight gets worse when bike is hot) thus , alas , the speed woes happen as valve head isn’t being 100% efficient.
If we can deal with the engine from top to bottom , before we can focus on any parts outside of the engine (whatever is under the frame responsible for keeping the bike going)
Clutch may be next , have macro meters and vernier calipers ready to measure the clutch , HP losses can happen on heat fatigued old springs and worn glazed up clutch plates , hence Korea says in their service books clutch should either be “looked at” or “changed” around every 4/5k due nature of the heavy bike with 2 hungry pistons , it can tax the clutch a bit.
keep us posted!
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According to the service manual the compression service limit is 8kg (113psi), it should sit around 10-12kg (140-170psi). So you are at the service limit and it would indicate that things are a miss somewhere. Probably just valve clearance, if a valve stays open or does not open properly the compression is adversely affected and you get a rapid drop off in HP. Combine low compression with a slippy clutch, carb issues or exhaust leaking near the head then bike will be greatly under powered.
How old is the bike?
What mileage has it done?
Do you know its service history?
Service history is important because a bike set up properly with the correct oil etc will last and perform beautifully. If a bike has been run with low oil, wrong oil or even too much oil it can quickly damage the rings causing compression loss. Running a lean (hot) bike can also damage the piston and rings, I have seen pistons burned through from running lean. A discoloured exhaust is often a visual sign of a bike running too lean and hot.
If an owner just ignores dropping speeds and power loss it will mess things up badly, unfortunately the poorly cared for bike is often passed on to a new owner who has no idea a numpty did not care for it.
The first step I would take before assuming terrible things (you have not mentioned excessive exhaust smoke which would indicate rings) would be check the valve clearance. These are really tough little engines, but they need to be cared for.
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Bloomin hell, what a journey you are having.
Is it carb or EFi? Are you sure it was fuel not water that was the excess liquid?
For those reading this;
Hydro locking is where you have to much liquid in the cylinder. When the stroke of the piston goes to compress the fuel air mix the excess of liquid cannot be compressed by the piston. This means that something has to give. The result is usually a bent piston rod but it can shatter the cylinder walls/piston etc. This results is a seized engine due to the damaged internals.
The usual cause of hyro locking is water getting in the the cylinder chamber but can be caused by excess fuel etc.
If an engine is hydro locked, say from flooding, then removal of the spark plugs allows the excess liquid to flow out without damaging the engine internals.
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