No power in top gear - 35 MPH top speed vs 55 MPH - K-pipe 125cc

[makeway]

My Kymco Kpipe has lost a lot of its power. It maxes out around 35 mph instead of the 50-55 it used to get. It actually maxes out in 3rd gear for the most part, and when I change to 4th gear don't get much more speed at all.

I've cleaned /rebuilt the carbs, and cleaned the air filter.

Any suggestions as to what to check next?

It starts right up, and I have it idling around 1.5k

[Stig / Major Tom]

Doesn't sound like the valves need adjusting - since it starts right up.
But what are your miles - and when was the last time they were checked?

Stig

[makeway]

It only has around 800 miles. I'm not sure if the previous owner ever checked them or not.

I can add that to my to do list.

I'm going to check it's compression tonight too, does anyone know what the compression should be?

[randyo]

how quickly did the power loss happen ?

mine had power loss just within a few miles,  I learned after my motor wouldn't even start, that air cooling isn't enough, you should really add an oil cooler,  these things overheat and eat oil.

[makeway]

It pretty much never has the power. Yes it does seem a little weaker after a 20 minute ride. But even when I first start it up it tops out around 35 MPH

[Stig / Major Tom]

Sounds like you might describing a soft seize,?
After it cools, does it run better?
I'm not thinking any new air-cooled vehicle should require an oil cooler?
Stig

[randyo]

Sounds like you might describing a soft seize,?
After it cools, does it run better?
I'm not thinking any new air-cooled vehicle should require an oil cooler?
Stig

nothing new about the k-pipe motor, its 70 year old technology, when you buy an aftermarket replacement motor, it comes with an oil cooler

[makeway]

Sounds like you might describing a soft seize,?
After it cools, does it run better?
I'm not thinking any new air-cooled vehicle should require an oil cooler?
Stig

After it cools it tops out at maybe 37 mph instead of the 35 mph.

[randyo]

when I bought mine used with barely 3000 miles, I was told it had already had the top end done. I put another 800 on it before it was unbuttered toast (where did the oil go?) That is when I decided to replace the whole motor, I was looking for a 140cc, cause it would be an easy swap, I ended up with a 190cc 5 spd. still an easy swap, but required a custom exhaust, now I'm just shifting from 4th to 5th at 55,  I still ride at the same speeds 40-50 on the roads I travel, just shift a lot less

[wymple]

Take it to a dealer. A bike struggling that bad has a serious issue with timing or fuel & something is not right.

[leomagnus]

This might sound like a strange idea, but in italy when you by scooters/bikes, they put a washer like flange on the exhuast pipe going to muffler, which reduces the outflow, thus reducing the speed. Normally when you buy a new one, the dealer would remove the flange/washer from the exhaust connection. Did you check if you have any blockages in the exhaust piping? Its just a though to make sure that everything is flowing freely

Dean

[Viper254]

I think it's possible we're discounting valve clearances too readily. They're quite often set too tight from factory, and this behaviour sounds about right for valves too tight - it's almost free or actually free to check them anyway