2025 YZ 85 overheating issue

chump6784
Posts
1776
Joined
5/9/2011
Location
AU

Hey guys. My son has a 2025 yz 85. On the weekend it started spitting steam out of the overflow pipe and I could smell coolant. It ran fine at the races on Saturday. Sunday he did practice and 1st moto with no issues but for the 2nd and 3rd moto it was running hot. There are no visible issues with the bike, no dirt in the radiator etc.

I have a new top end ready to go in it but just wondering what would cause that and if there is something I should be looking for when I pull it apart

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Factor E
Posts
982
Joined
9/22/2011
Location
So Cal, CA, USA
7/29/2026 11:45pm

Rad cap, impelller

FGR01
Posts
6144
Joined
10/1/2006
Location
USA
Fantasy
7/30/2026 5:42am

Might have developed an air leak and is running lean.  Might be burning through the head o-ring and pushing pressure into the colling system.

ikeG
Posts
130
Joined
6/15/2023
Location
Home, PA, USA
7/30/2026 2:52pm

Our last new yz65 blew a head o ring immediately and the head bolts were only finger tight when I took it apart.  

8/1/2026 6:04am

Check if the clutch plates are smoked too. 

The Shop

btroxler
Posts
172
Joined
5/22/2017
Location
Saltillo, MS, USA
8/6/2026 11:23am

1st Change Radiator Cap

2nd Pull head and see if you are getting coolant by the O-Rings

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