07' 300 overheating...I think(4 stroking, and coolant on engine)?

[CDBiker220]

Hi, just bought an gasgas 300. And after riding hard for about 15 min. it started to 4 stroke when coming back from idle (jumpy idle but higher than usual) also i noticed a few specks of coolant over the left side of the motor, and think it came from the coolant overflow hose. I checked the waterpump impeller and it looked fine to me(plastic one). And then checked the sparkplug and it was a nice light brown color. So any ideas were to go from here. I know nothing about the jetting but it seams to run great. I thought i heard it detonate though a few times when on WOT but could have just been chain slapping or something.

 

[noobi]

Radiator cap may have worn out, or been damaged. Replace it with a KTM rad cap, its a higher pressure rating, and see if its makes a difference.

 

[GMP]

If its surging with a hanging idle your lean for some reason. Plug color is unreliable to diagnose a 2stroke across all the ranges. Look at your jettting and rule out any air leaks. Agree on the cap though, go with a 1.8 bar, and ditch the expansion tank just run a crossover hose. These bikes do not run hot, even in extreme conditions like slow steep climbs and tight sand woods they rarely burp the cap when setup right.

 

[CDBiker220]

How should I go about checking to see if jetting is correct or too lean? I thought the plug would be white if the jetting was off. I will check everything over tonight after work to confirm no air leaks or anything. My buddies dad had similiar behavior on a 07 KTM, ended up being bad crank seal. Hoping thats not the case.

 

[GMP]

You don't jet a 2stroke by plug color unless you really control the conditions and isolate the throttle positions. Even so there are too many variables in fuel, oil. You can be too lean in some areas and too rich in others and have a plug with color. For example my bike is jetted close to perfect IMO and produces a dark brown plug overall after an average ride, perhaps a bit lighter after a high speed ride, still what you would consider rich by textbook or 4stroke standards.

Pull the carb and record your jetting, then report back and consult the jetting database to see if your at reasonable settings. Check the rubber coupler between the manifold and the carb for cracks and distortion from overtightening. I bond mine to the manifold with grip glue and dont go crazy tight with the clamp. These are cheap and a good idea to change when you do reeds or top end work. You can do a quick and dirty air leak test before any disassembly by carefully spraying starting fluid near the manifold and crank seal, revs will increase if drawn in. If it is a crank seal (not likely) its simple on this bike, done from the outside in minutes.

 

[CDBiker220]

Jetting specs

Main - 178
Pilot - 42
Needle - N1EF 2nd clip down


Im at 1200 ft. and it has been about 45F out while testing. Looks like reasonable jetting to me. Could those settings still be lean causing it to run hot and 4 stroke? Also thought i heard some detonation at WOT. has a gnarly pipe if that makes any difference, also overflow tank is gone and just has a tube coming out where i believe coolant was leaking from, picking up 1.4 bar KTM cap today(didnt have 1.8 in stock, just giving me one off a new bike). Ive heard of a chop test to see WOT mixture, just kill the engine and pull in clutch at WOT and then check plug?

 

[stainlesscycle]

Ive heard of a chop test to see WOT mixture, just kill the engine and pull in clutch at WOT and then check plug?

yes, but: you need to be at wot and under load... i ride a big long uphill, at wot, then kill engine/pull clutch. read plug right there...

to me, your jetting does not look lean at all.

 

[lankydoug]

Check for an air leak, if it doesn't have one give it what it want's an go rich a step on the main. Too rich wont kill your engine like to lean will and you will have feedback to compare to.

 

[CDBiker220]

Put in 180 main and rode in yard some pretty hard, no 4 stroking but still ended up with coolant splattered on engine, Didnt come from overflow tube as I put a paper towel on it while riding to see if anything came out and it didnt. Need to find the source of the coolant..maybe a loose hose connection. Ran the bike in neutral sitting still till pretty hot and found no leaking anywhere but after hard riding you can smell coolant and see dropplets all over the motor. Not sure if i trust the clip type hose clamps. may try normal hose clamps.

 

[kendunn]

Put in 180 main and rode in yard some pretty hard, no 4 stroking but still ended up with coolant splattered on engine, Didnt come from overflow tube as I put a paper towel on it while riding to see if anything came out and it didnt. Need to find the source of the coolant..maybe a loose hose connection. Ran the bike in neutral sitting still till pretty hot and found no leaking anywhere but after hard riding you can smell coolant and see dropplets all over the motor. Not sure if i trust the clip type hose clamps. may try normal hose clamps.

I had this happen and it was indeed one of those clip on clamps when the motor got a bit hot. Lose them, especially the lower right one on the water pump, it is easy to get knocked around down there and leak.

 

[CDBiker220]

Ok. Got the coolant leak fixed, was just a hose clamp. Went for first real hard ride today. Bike is still running hot, was 4 stroking with high idle after nasty hills, also was detonating when at WOT for more then a sec or 2. I need to go back to the 178 main jet, with the 180 it would start to load up a lil after long slow sections. So i dont think I can jet it any richer. Any ideas where to go from here.

 

[GMP]

If your spending a lot of time on the needle the main change won't matter. Try going richer on the needle just to see if things improve.

Now your down to a possible air leak, or timing thats too far advanced. Which ignition do you have? 2K-3 should have a locating key in one of the slots to fix the timing. 2K-2 stator does not and must be positioned correctly. Post a pic of your ignition.

Look for an air leak as discussed before.

You said the bike has a good alloy impeller. Does it rotate with the crank? With the rad cap off can you see coolant flow? Sounds like a dumb question but gears have failed and being this is a used bike anything is possible.

 

[CDBiker220]

I believe it has 2k-3 ignition(wires exit at 2 oclock) but will take off the cover to check. I will try a clip richer on needle with original 178 main. Also it has plastic impeller but looked like good shape. Will check for air leak today after I get some starting fluid.

Also this weekend while riding an event i ran into the previous owner(got the bike from a shop so never met the owner) he recognized the bike and his name is still on the suspension specs on the forks. He said he never had problems, and had the jetting perfect after being too lean when he got it. However he ran 50/50 race gas mix. He said only because of habit not because he thought it was neccessary. I dont want to always have to buy race gas, but im wondering if that helped cover up a problem. This bike should be fine on 93 octane correct?

Also thank you for the help so far, i love how this bike runs and handles and I'm determined to get it perfect.

 

[GMP]

The bike should run fine on 93. I used to run 50/50 for consistancy but it got too expensive and 93 pump is fine if the mix is fresh with good jetting. Startron treatment seems to work very well also.

If your wires are at 2 o'clock you have a 2K-3 which should have an insert in the top slot to fix the timing. You should be able to see it. If its not there then of course the timing could be off.

When you do your leak test also check the crank drain bolt for a good seal on the cases. Loctite and a new washer is good insurance. You might consider a leak down test to check for a leak as well.

If all looks good, some bikes just like richer jetting, for various reasons, mechanical tolerances being one. I had a 250 like that, wanted a lot of fuel. You could always rejet from scratch starting rich, using the database for a guideline. Go through the carb and check your float height first.

First things first though, troubleshoot as suggested.

 

[CDBiker220]

Well i think i solved it. Decided to really clean the carb, turns out the float height was off alittle, also the pilot jet had something in it. seamed to clear out when spraying carb cleaner in it. Now the bike seams to be running good. I did some big long hills yesterday with no four stroking or detonation. Wasnt as nasty as the muddy hills i was doing last week but still a good test.