2017 300rr over heating

[Goatse]

I'd start with swapping the rad cap. Even if it's borrowing one from a buddy to see. A leaking rad cap will lower the boiling point of the coolant and allow it to boil over. Check all the hose clamps and make sure they're tight as well.

If not that, I'd then look at the waterpump impeller.

[Johnno]

Actually that's ^ an easy first elimination. At least look at the cap, maybe bleed the system. There's no coolant where it shouldn't be?

I've ridden my 300 in technical terrain, struggling, in 40C heat more than a few times and it never over heated.

[hawaiidirtrider]

Is there an issue with the thermostat it's self?

He said he took it out.

[hawaiidirtrider]

I'd start with swapping the rad cap. Even if it's borrowing one from a buddy to see. A leaking rad cap will lower the boiling point of the coolant and allow it to boil over. Check all the hose clamps and make sure they're tight as well.

If not that, I'd then look at the waterpump impeller.

That sounds good. Cheap too. Id just put a higher pres rad cap just to do anyway right away. It’s so cheap. Overflow tank as well.. so cheap and easy. The fan costs the most but it’s a guarantee best bang for your buck. My friend says he can tell his 250rr runs noticeably cooler with the upgrade impellar. Every bike here riding gnarly slippery mud can boil and willboil so cooling mods are common. I hate boiling so I investigate all cooling mods and will systematically add on any cooling mods as time goes on. My bikes are ok as far as cooling now but I like overkill. So eventually I will put on big radiators that I already have on the side and I’ll put on the better impellar hiflo. The only other cooling mod beyond that is a cool head with larger volume coolant capacity. So thatcan be s4 or vhm or RK head.

Here’s the other thing. Riding style or gearing? Is that changed. Sometimes I can boil and my friends Beta wont.. or I won’t boil and my friends beta will boil? Is that a possible factor? A slippery section with a little extra clutch work can overheat a bike easier. It’s how the bike is ridden as well. I don’t know if that’s considered a legit factor in your case but Id adjust my gearing to lessen overheating too. Im just throwing other possible issues. What info youve posted so far doesn’t have any obvious possibilities.

[nigelbates]

Nothing changed on the bike before / after the issue. I put KTM o rings in the head. I will strip the bike again this week check everything inc air leaks, new exhaust o rings, put new rad cap on, check water pump impeller, everything I can think of. I know my way around a bike, have been working them myself for decades.

[bikesparky]

Nothing changed on the bike before / after the issue. I put KTM o rings in the head. I will strip the bike again this week check everything inc air leaks, new exhaust o rings, put new rad cap on, check water pump impeller, everything I can think of. I know my way around a bike, have been working them myself for decades.

I have a '16 300 Racing and after the initial crap O-rings I replaced them with KTM ones. Since it's always 30C plus here I removed the thermostat and run a cheap silicone hose kit. A fan is a must in this climate if doing slow stuff so I fitted one from new. I never have any problems, the fan only comes on if I really mess around in deep gullies with no wind or air movement. The 300s don't run that hot so you shouldn't have any issues neither if all is good. And I don't run rich jetting neither BTW.

[nigelbates]

I agree, bike get used the same all year, same terrain same rider same everything apart from the weather which is currently the coldest it gets here and now its started over heating.

[hawaiidirtrider]

I agree, bike get used the same all year, same terrain same rider same everything apart from the weather which is currently the coldest it gets here and now its started over heating.

Well I look forward to seeing what the issue turns out to be. I hopeyou figure it out quick. I hate boiling bikes.

[nigelbates]

I have had the bike stripped right down and couldn't see any problems, everything suggested has been check along with all the usual stuff I would do after an event. Will have to ride the bike on some tough terrain and see what happens.

[hawaiidirtrider]

I have had the bike stripped right down and couldn't see any problems, everything suggested has been check along with all the usual stuff I would do after an event. Will have to ride the bike on some tough terrain and see what happens.

So no mods added?.. no higher pressure cap or overflow tank or fan etc??