Engine Compression test data-base for Kymco Scooters ?

[scooterfan]

An easy way to determine engine condition on any given engine is to do a simple compression test on an engine. Knowing what engine compression on any giving engine (in good condition) is suppose to be, always have several benefits.  For example - a potential buyer of any given scooter can easily avoid buying a lot of problems - just by doing a simple engine compression test in advance. At a later stage of ownership a simple engine compression test can also be very helpful - helping an owner to make informative decisions.

In short - I think it could be very helpful if we could have some sort of "data base" - regarding engine compression results on different engines on our scooters.

The first "problem" though - the spark plug on my scooter (Agility 125) has a small diameter and I can not use my compression tester to test the scooter's engine compression. Does anyone know whether suitable adapters are available to do a proper compression test on a scooter with such a small spark plug hole ?

The diameter on my scooter's spark plug is about 0,388 inch /  9.88mm.   (See pictures below)

[eamartin]

I wanted to test the compression on my Agility 50 4T and had the same problem.  I found an adaptor (10mm) made by Lisle, part # 20530.  It worked perfectly.  I believe it was 14mm on the female end.

[scooterfan]

I wanted to test the compression on my Agility 50 4T and had the same problem.  I found an adaptor (10mm) made by Lisle, part # 20530.  It worked perfectly.  I believe it was 14mm on the female end.

Thanks for the info.
As a matter of interest - can you remember the mileage on the scooter, as well as the compression test readings at the time of the compression test ?

[eamartin]

This scooter was not running when I dragged it home and had virtually no compression (thumb test).  Upon removal of the head, I layed it upside down on my workbench and poured kerosene onto the valves, watching it all drain immediately.  I installed piston rings, valve seals and lapped the valves.  Compression reading was then 127psi (cold engine).  Odometer reads about 7700.  Is that kilometers or miles on these USA machines? 

[stuo]

Multiply 14.7 (atmospheric pressure) times the rated compression ratio: If the engine is rated 10 to 1 the compression should be 147 pounds.

[scooterfan]

 Compression reading was then 127psi (cold engine).  Odometer reads about 7700.  Is that kilometers or miles on these USA machines?

That compression reading sounds perfect for your engine.
I see other owners in your country refer to "miles" on their scooters. I guess the indication on your odometer will be miles.
In our country the indication on all vehicles are kilometers. The distance reading  on my Agility 125's odometer is kilometers, and the speed indicator is km / hour as well as miles per hour.

[scooterfan]

Multiply 14.7 (atmospheric pressure) times the rated compression ratio: If the engine is rated 10 to 1 the compression should be 147 pounds.

Thanks, but unfortunately Kymco did not reveal all pressure ratios on all different models - only about 50% of ratios on scooters listed at this forum seem to be available.

Some compression specs about scooters listed at this forum:

Xiting 700i:
Compression ratio not available.

Xitting 500:
10.5 :1  =   147 pounds / 1062 Kpa.

Downtown 300:
10.8 : 1 =   159 pounds / 1096 Kpa.

People GT 300i:
Compression ratio not available.

Xiting 250:
10.6 : 1 =   156 pounds / 1076 Kpa.

Grandvista 250:
Compression ratio not available.

People 250:
Compression ratio not available.

Bel & Win 250:
Compression ratio not available.

Like 200i:
9.5 : 1  =   140 pounds / 965 Kpa.

People S200:
Compression ratio not available.

Yager GT 200i:
Compression ratio not available.

People 150:
9.2 : 1 =    135 pounds / 931 Kpa.

People S 150:
Compression ratio not available.

Super 8 150:
Compression ratio not available.

Bet & Win 150:
10.6 : 1 =   156 pounds / 1076 Kpa.

Agility 125:
9.6 : 1 (one source) =   141 pounds = 972 Kpa.
11.1 : 1 (another source)  =   163 pounds / 163 Kpa.

Movie 150:
Compression ratio not available.

Super 9 50:
Compression ratio not available.

Super 8 50:
7.2 : 1 =   106 pounds / 731 Kpa.

Vitility 50 (2T and 4T):
7.2 : 1 =   106 pounds / 731 Kpa.

People 50:
7.2 : 1 =   106 pounds / 731 Kpa

Agility 50:
11 : 1 =   163 pounds / 1124 Kpa

Zx 50:
7.2 : 1 =   106 pounds / 731 Kpa.

Like 50 2T:
7.2 : 1 =   106 pounds / 731 Kpa.

Compagno 50 i and 110 i:
Compression ratios not available.

[stuo]

14.7 pounds is at sea level. Higher altitudes, lower air pressure. Multiply by compression ratio and allow a loss of about 10% for valve and ring leakage to give a real world reading.