Hi guys, I’ve done a coolant change to my 2015 821 hypermotard. Felt i needed to do it as I have owned the bike since 2017 and not done one in my ownership. I did alot of reading up because i hear they can suffer with an air lock etc.. due to vertical cylinder and where the thermostat is Im finding the bike running hot. If im out on open road its around 79 °c but rises pretty fast up to 90°-100°c if cruising behind traffic etc.. Now before i did the change it was always running around 73-74°c and only rising to 79°c behind traffic. So im guessing i still have a little air lock in the system I’ve tried massaging the coolant pipes with the radiator cap off to get all the air bubbles out. Also tried running bike with cap off. I’ve drained the system and tried again with no real joy of sorting it. I’ve read up about vacuum bleeding the system, would this be my guarantee fix would anyone know ? Im very mechanically minded, as i do all my own work to my bikes but this has slightly stumped me at the moment. And help would be greatly appreciated Thanks lee
There should be a coolant bleed bolt at top of water pump housing... If you've done all the above run the bike with that point as high as you can get it by laying the bike almost over on its side and seeing if you can bleed any air out. You will probably need a spare pair of hands to tighten the bolt back up while you are holding the bike on its side.
yes fans kick in when they should at around 104°c. But i have never had the bike get that high before behind traffic
its not the fan thats im having issues with they are working as they should. Since i have changed my coolant as a routine maintenance i am finding the bike running alot hot than it used too as described in my first initial post. Im assuming there’s an air bubble/lock i can’t get rid of. will be having another go at sorting this next week. thanks lee
Try the bike on a headstock stand, then a rear paddock stand see if it helps the air move up to the rad. Failing that you could try one of those sports massager guns on the rubber coolant pipes
