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The problem with the original Paso cooling system design is that the polyethylene tank is under pressure and in time splits at the seam from thermal cycling. There is also an availability problem with the tank itself, as well as the unique Y radiator hose that it connects to. Most bikes incorporate a radiator cap either on the radiator on in the upper radiator hose. The coolant tanks in these designs merely serve to keep air out of the system while allowing the coolant a place to expand. Their overflow is vented to the air and they hold no pressure. The Paso can be modified to work in this fashion with a few changes. First, locate a radiator filler neck from a 95-98 Honda CBR 600F3 or CBR 600SE. You can also use the radiator cap and short radiator hose that attaches to the bottom of this filler. Second, cut the Paso upper radiator hose just before the vertical bend and Y going to the coolant tank (see figure). Third mount the new filler neck just above the radiator with a short piece of radiator hose. The cut radiator hose will now attach to the 90 degree portion of the filler. Route a 3/16” overflow tube from the filler neck to the bottom of the coolant recovery tank. The larger opening in the coolant recovery tank can either be adapted using hose and fittings or the inside can be tapped for a ¼” NPT thread if in good shape. Put a hose clamp on the outside of the exit pipe to keep the plastic from splitting, file it to 7/16”, then carefully thread it internally. A ¼” NPT to 3/16” barbed fitting can be installed with automotive Goop and the 3/16” hose attached to it. Now remove the rubber gasket from the coolant tank cap and cut a slit that allows it to vent thru the center valve in the cap. Add antifreeze thru the filler neck, install the radiator cap, fill the coolant tank, and you’re done! Because your coolant tank no longer needs to hold pressure, it can be repaired with Goop if it as leaking prior to this modification. Since my upper radiator hose was in good shape where trimmed, I did not search for a pre-formed alternate source for it. Straight 1” heater hose may work or the hoses from the Honda filler neck, please pass along suggestions!
http://mysite.verizon.net/anigro754/id1.html

Thx f sharing!

Shellboss,

CAn you send the info on this direct to me so that we can archive it??

You pictures too??

Hi Jon, I sent you a PM requesting an e-mail address to send to, thanks
Art

Art, just send to slocumjon AT gmail .com

An alternative to automotive Goop is Hot Melt glue.
If you picked up the Honda radiator cap with your filler neck, it is rated at 1.1 Bars (approximately 16 psi). To run at the lower pressure that the Paso was designed for, pick up a Stant #11227 radiator cap or equivalent at the local auto parts store.

It would be nice also, if those old inch measurements will changed to normal metric sizes, as metric sizes are more used in whole world and its just going to metric sizes! (Also in usa and U.K. little by little...) Ducati uses only metric units sizes in threads...

It's not so easy.
I'm still not accostumed to think in Kw rather than in HP....
Ciao

I worked for a US company that converted to metric back in the 70's. Unfortunately, the US component suppliers never switched, so everything became a mixed bag. Even Ducati uses British Standard Pipe for their newer exhaust pipe plugs, go figure!

Shelboss wrote:I worked for a US company that converted to metric back in the 70's. Unfortunately, the US component suppliers never switched, so everything became a mixed bag. Even Ducati uses British Standard Pipe for their newer exhaust pipe plugs, go figure!

Also for oil pressure switches, and some brake/clutch lines.

BSP is the EU standard for most hydraulic and pneumatic connections. I agree it's weird, but I guess it was originally selected for three reasons - the availability of a tapered standard, to differentiate energy carrying threaded holes from normal holes, and to appease the British, who were reluctant to join ISO.

I just did this mod after a long run of 90+ degree days here in Seattle (WoooHoo!)

Anyway I thought I'd share my experience:

I found that I could invert the original Y-hose (top hose) and it fitted the Honda filler neck nicely.

Upside to this is that I put a bung in the original narrow neck that went to the reservoir and that sits down by the frame in a vertical position and gives me a nice point to drain coolant from the upper part of the system. It also means I can revert to standard config should I ever need to, since I didn't have to damage the stock (and hard to find) Y-hose.

Now to fix the coolant reservoir cracks with something and I'm done!

Cheers
Andrew

guys check this out. looks like the tank can be plastic welded. Here is a video showing how. https://www.youtube.com/watch?v=k_Fkhz2G9Is

Yup, that should work. Also can use just an old soldering iron. Just need some filler rod that is the same resin. Most likely Polyethylene, but might be polypropylene.