My ossa runs fine on trial and enduro sections but overheats on any short road sections ? Fan seems to be working and head seems ok ? 

Any ideas ? 

Fuel mixture too lean?  Pull the spark plug after it acts up and see what it looks like.  It's called a 'plug chop'

Do you have the dual map capability?  There were specific richer maps for road use.

Pure water has the best heat transfer properties.  The more antifreeze in the cooling water, the worse the heat transfer becomes.  Of course, no antifreeze means you lose boil-over and corrosion protection.

I have used a product called MoCool by Motul in roadracers where antifreeze is prohibited: https://www.motul.com/lv/en/products/mocool

 

Thanks it is dual mapped wild and mild , does that mean remapping the ECU ? 

had summer coolant in it , but that boiled and now replaced for water . 
 
just odd that you can throttle it to bits in 3rd and 4th all day on trials but boils over after 10 mins in 5th and 6th on road 

Mixture is 100/1 as birketts recommend 

The radiator is in an atypical place on the OSSA. I suspect the fan can't push as much air through it as if it were hanging out in the breeze like a conventional trials bike.

I'd be curious what 2 maps are in your bike.  As far as I know there never was a hard/soft map combination.  Here is a list of the final .KDA maps produced: https://www.ossa-efi.com/home/pc-software/map-loading-software

K-Scan will tell you what map is in the ECU, but won't change it. 

Thanks that’s really interesting I’m on the factory engine with the termi exhaust so will try the road sections in Map 2 setting and see how it goes , and heat protect the seat as burnt my ass 😀 as termis aren’t designed for the explorer seat conversion . 

Also, using K-Scan you can globally enrich the mixture (up to 15%).  The will help cooling, but also will tend to soften the performance (which might be a good thing for a Factory being ridden as an Explorer).

Globally enriching the mixture will also decrease range by a corresponding percentage.

Heard something interesting on the weekend, how much oil do you run in the transmission?  Apparently OSSA need more oil than called for to avoid transmission friction problems associated with sustained engine speeds.  Something in the realm of 100cc extra.

Things I’m looking at that I may have overfilled  the rad … removed 5% to allow expansion .

as the bike is a factory version with dual mapping trying the higher speed  in map 2 setting or maybe having it remapped 

I never had any overheating issues in my Explorer, I’ve tried several different maps. (But mine was not wired for two maps). 

A bit richer could help - also it is not very hot where I live. I installed an electric water pump on my old one when the original failed and could not source. It is still working very well for new owner. I did have to fabricate a mount and guard. 

For gearbox oil level. What I was told, originally bikes had 350cc. Many were having 6th gear issues- but nobody in Italy was. The importers there were putting in 450cc instead and that solved it. Later bikes had the breather relocated- but I still have to extend the hose. The importers here would run it up over the frame, then down to over the chain. So if any excess came out it would lube chain rather then just make a mess. 

 

That is what I was told