Overheating 300 in climbing

[mariogt]

Hi to all,

i have a gas gas 300 2008, and i have a problem with overheating when the bike is climbing, the coolant is expelled from de radiator vent. I checked the the impeller (its like new), the radiator cap its OK, my carburation is:

180
40
needle in the middle position

Mix 50:1 with Motul full synthetic oil.

The working altitude is from 500 -- 1000 mts above the sea level.

This problem happens always when i was climbing, i dont know what is wrong with my bike, i have installed 2 radiator intercoolers but the overheating happends regularly.

My ridding skill its B rider (Expert class here in Chile), and i dont abuse too much of the clutch.

Bye and please help me

 

[sierrarider]

Your jetting sounds lean to me, although I'm no expert.

 

[mariogt]

if i go 40:1 this make my jetting richer ?

 

[FFRDave]

Carb Jetting, not fuel mixture.

Try a 185 main and a 42 pilot jet. This will be an increase from 180 main to 185, and from a 40 pilot to 42. It will put a little more FUEL into your air/FUEL mixture.

I run with this jet combo when I ride in cold weather, and it helps.

Too much oxygen (or inversely, too little fuel), makes for a real hot burn in the cylinder. I actualy melted my piston into my cylinder wall while riding in cold weather.

 

[sierrarider]

http://www.gasgasrider.org/forum/showthread.php?t=2162

I agree that you need a larger pilot jet based on others jetting at similar elevations. Adding more oil to your premix will lean your bike out more because it is getting less gas.

 

[mariogt]

Thanks for the tips, i will try 185/42 combo and see how the bike runs, but here in my city the temperature is very very high and very dry, 30 celcius (86F).

 

[Skidad]

Radiator cap could be bad. Slightly bend the tabs so it locks down really good and tight. You could try a higher pressure 1.4, 1.6, or 1.8 bar cap which will increase the boiling point more with each one. Also increases the pressure inside the cooling system though.

For your info many KTM 300's have boiling over issuse and allot of guys use the 1.8 radiator cap from the KTM 4 strokes with some success. The KTM caps fit the gassers fine. For some KTM's nothing works but adding a cooling fan or expensive wider radiators.

Change all your stock coolant to something like Engine Ice if you can get it. Do you have any sort of guards in front blocking air flow?

 

[mariogt]

Hi Skidad,

I dont have any radiator guard, only the stock plastics protectors, i will try a higher pressure cap but i think that my carburation is part of the problem because my spark shows a very very light brown color.

 

[jostby]

I agree with Skidad, check the radiator cap. If you are running too lean (lean = heat) you will also have detonation, or "pinging". I am at 300 lbs with gear and have never boiled my bike, even when I had it jetted lean and pinging. I still run the stock radiator cap also.

 

[iancp5]

Your jetting sounds lean to me, although I'm no expert.

I had an 03 300 and ran 38p, 178m and N1EF needle on 2 or 3. Also used 42p + CCK needle. It never overheated except when engine or rads were obstructed. I don't know if the 08's are very different though. I'd suspect something other than jetting you mentioned. Not to say it isn't running weak just 40p & 180m sounds ok. Do a plug chop on a climb. I'd be surprised if it's the pilot if this happens on climbs where I assume you're on the needle mostly.

Also putting more oil in will lean the mixture because there's then less gas but don't go the other way with less oil than 50:1

 

[mariogt]

thanks for your answers boys, i just get a ktm 1.4 radiator cap and in the afternoon i go to test my bike, i will inform any issue here

 

[mariogt]

Well, i just finished a 2 hours test with the new radiator cap (ktm 1.4) and finally no coolant lost , this confirms that the gas gas radiator cap was the problem. But the final test will be this saturday in the deep sands of "desierto de atacama" , into some zones of the Dakar 2009 route