Adventure Bike Rider Forum

Ok then boys I'm being a bit dense here, I'm cracking on with my Tuareg project and I've now got to the point of filling the rad/rads.

Like a few other dirt bikes I've seen its got twin rads but no reservoir bottle, the only liquid cooled bikes I've had have had a single rad and reservoir bottle, so basically I'm stumped on how to go about filling these up.

There's two connected rads, one on either side of the frame, one with a cap and one without but both piped to each other and in part to the engine, 2 stroke 125 rotax lump for reference.

I know about obviously bleeding the air from the system and working the pipes to get the air out but what's got me stumped is if I need to fill both these rads or is one an expansion tank or some such?

Like I said being dense :laugh:

In years gone by we didn't have expansion tanks as separate items, just the tank at the top of the radiator, and I imagine that's what's happening on your bike. The two rads should fill together as they're connected. As long as you work any air out I can't see there being a problem.
(My guess is that, for an off-road bike, the manufacturer wants as few vulnerable pipes dangling around as possible, so no extra expansion bottle)

As per some cars, if the rad itself doesn't have a cap then the only way to fill it is via the expansion bottle but if there isn't one of those then it must be connected to another inlet somewhere which I reckon in this case is via the other radiator. Maybe view it as one radiator, but in two halves?

Hvae you checked for a bleed vent screw somewhere near the top of the rad without the cap?

Andi_Archer wrote:Hvae you checked for a bleed vent screw somewhere near the top of the rad without the cap?

I agree, if I remember correctly, the DRZ has got similar.

Fill em up and there may be a bleed on the engine, top of the sealed rad or water pump or actually no bleed at all. The ktm 2/ we just fill, run then check/top up.

Most KTM MX and enduros are like that--fill up with decent modern coolant to just above the fins and run with the cap off to let it vent/circulate. Let it cool and fill again to just above the fins (leaving expansion room)--run it for a while and check again just in case some trapped air has been released--you need to get it hot enough to open the thermostat. On 2 smokes there is usually a bleed screw on top of the head to make sure that this space is completely full--just needed when you first fill it up.

Cheers for the help guys, I'll have another look at it in a minute and see if I can track down a bleed screw (thumbs)

Sorry if I didnt catch it bit what make and model of bike is it?
The DRZ air bleed is here on top of the left section:

Fill it and lean it over with the open radiator at the top. Cap on and run, let it cool down and top up. Use any bleed screws present as filling.
I always fill them to the top and let expansion get rid of what's not needed, better than not enough.