After my bike warms up good it gets real sluggish. It takes about 15 minutes for this to occur. When it happens I have to rev the bike real high or it will die out like its not getting or getting to much fuel. I've cleaned the carb, new plugs and wires.

You need an auto electrician with a pro grade scan tool computer to record what happens after 15 minutes to make this happen. The $5k machines can do that.

Sounds like your transmission has failed.

Maybe this will help. This is a common problem that I have had with my GV250. Almost the same bike mechanically by Hyosung.

If the battery is low on charge and you are lucky enough for the bike to start. As per normal when first started it revs higher because the bike is cold, this turns the alternator fast to give you the electricity you need to keep the bikes computer working properly. Bike will warm up and revs drop down, alternater not turning as fast, not as much electricity being made. Bike will either stall or rev up and down irradically to try to produce its own electricity. This will occur when the battery charge is low and bike is at low revs, for example when you slow down for traffic or you stop.

If this is your problem. To resolve it when you are out on the road, keep the revs up, twisting your throttle gently when you are going slow or stopped. Give the bike a good long run on the open road to give the battery some charge from the alternator.

Make sure your battery is maintained. If you dont use your bike for a while it will lose charge just sitting there doing nothing. Give the battery a good deep cycle charge or take the bike for a good long open road ride.

Being springtime, I'm thinking you may have had your saw sitting all winter with last years gas in it. If so, you'll need to clean the carburator and spark plug real good, then put fresh gas in it. Always remember to run your saw out of gas before putting it away. Gas only stays fresh for a few weeks and will foul up your sparkplug as well as plug up the inside of your carb when it gets stale.

hello lloyd...... definitely pull the carbs and rebuild them. Since you did everything else right, this alone should fix the problem. Joe
Thanks for choosing Fixya!

Hi,
this could be something in the fuel pump. As the cold motor draws more fuel, it may just be just ok for the engine, but after it is warm, it draws less and may "suffocate" it that way. Same goes for air filter, take a peek if it is not ready for replacement. Has this happened suddenly, or has it occurrend during a long perion of time?

This is a fairly common problem with performance bikes. The problem comes from your thermostat. The thermostat is designed to open and close at a certain temp. What I suspect is happening is that your thermostat is opening too early for the bike to get to operating temp, hence the long time to warm up. Once you open up the bike warms up and the oil viscosity thins to operating temp and the engine revs more freely. Now your idle screws are set for a "cold" bike and revs high.

The other side is that the oil you are using may not be designed for your bike. Often people put performance synthetic oils in their bikes to perform better, but the production bikes are designed for thicker oils. Oils like 5w40 will be very thin allowing your bike to rev faster due to thinner oil, but you are causing extra wear on the parts due to less oil barrier.

First I suggest make sure you have the correct spec oil for you bike, then check that you have the correct thermostat in your cooling system. A performance bikes usual operating temp is between 95-105 deg C. This means your thermostat should only open at about 88deg C to start the regulation process.

Yrs, carb needs cleaning

mileage? last transmission service? replace fluids and filter... internal pressure in trans is low and a good service will likely remedy this

Had the same problem. I had to remove battery, take apart the battery terminals, sand them a little, then put it all back together. Make sure the screw on the front of the terminal holding the inner bar in place if very tight. Have had no problem ever sense. Good luck.