Katflap,
I now have a water pump housing to play with. The plan is to figure out how to create a bypass circuit. After a few visits to the normal outlets (Home Depot, a hydraulic repair place, AutoZone, a fastener supply house) it seems that I'm stuck with using NTP fittings. For those of us who are not machinists, NTP = National Pipe Thread. These are tapered threads and they have the advantage of sealing as you screw in the fitting. On the other hand, with our thin wall thickness there is the danger of fracturing the casting as you screw in the fitting. Oh, and you need a NTP tap to cut the threads. I have the tap on order.
Cruising Alibaba I saw that someone lists a water pump housing that has two inlets! I guess this is for some other application, maybe a 4 wheeler. At any rate, this would seem to be the answer to our prayers...except it lists for $160 and both outlets look to be 3/4".

are they cast aluminum? i would be tempted to tig on a nipple instead.

My experience, limited as it is, is that cast aluminum is a real bitch to weld to. There is something about the molecular structure of cast metal that just does not lend itself to welding. Smarter guys than me have warned me about this. I can do TIG, MIG, and stick but I'm not warm and fuzzy when it comes to cast aluminum. I have considered brazing to the aluminum just to build up more metal for the tapping process. If you figure out a way to TIG a nipple you will be my hero, please post your results here.

I agree peter, you do need a good bit of "meat" on the water pump housing to withstand screwing in an NPT fitting.

I wonder if it is possible to find a replacement bottom hose that already has a branch piece of the right size for the by-pass moulded into it.

When I was a kid, me and some mates would head down to the local car scrap yard and rummage around to find bits like this to get things to work.
Those days are gone, everything over the counter now.
:ohno:

:lmao:

some are better than others, I've had a lot of success will repairing aluminum transmission housings (welding to build up material where a mount was ripped off, etc) and I've tig welded cast intercooler ends to the core structure.

but yes just using filler rod to build up a thick boss on the housing to drill and tap would be a good idea and easier than tigging a nipple.

if you feel froggy, give it a try.
http://www.ebay.com/itm/3-8-HOSE-BAR...dVTj6T&vxp=mtr


http://www.ebay.com/itm/4pcs-3-8-BAR...tW52lD&vxp=mtr

re: coolant temps of 55c-60c whilst riding.

I have now tested my thermostat and its fine. I also checked my spare and that's good too.

I'm at a bit of a loss to explain it. Could this be just natural air cooling combined with a bit of coolant flow through the thermostat by-pass hole :hmm:,
I guess I could try and fabricate a "jiggle pin" but I'm put off by the thermostat being horizontal.

I will still be going ahead with fitting the by-pass but I am now not expecting a lot of difference. After I've done the by-pass maybe I might try making an engine shield of some sort.

OK, if I understand this correctly...you have a 180F thermostat (82C) but the engine is only getting up to 160F (60C). I'm wondering if the thermostat is opening, sending 180F coolant to the two radiators where it is cooled so effectively that it returns to the engine below 160F and thus brings the thermostat to close until ....no that does not make sense unless you are seeing big swings in the temp. OK, brain trust, let's figure this out.

I have a spare water pump housing now. Measuring the wall thickness it looks like about 3mm, not nearly enough to get a good seal with tapered threads.

My thermostat is a stock 70c rating, whilst riding the coolant temp rarely goes above 60c unless in very slow traffic.
Even if I stop and let the temperature rise until the fans kick in (aprox 80c), once I start riding again, the temperature decreases back down to between 55c-60c.
With the thermostat completely closed at these temperatures and though it seems unlikely, I was thinking that perhaps it was air flow on the engine that was bringing it down so far.:hmm:

I wonder
If you were able to get a straight threaded barb connector, maybe it might be possible to tap and screw it through the water pump casing and then secure it with a thin nut on the inside. :shrug:

Pretty much ready to fit now, I just require a length of 8mm ID hose and some spare time :)

Both sensor fittings in my thermostat housing are 1/8 NPT, so I am using a 1/8 NPT 90 deg. barb.

The bottom hose seems to be aprox 22mm (water pump end) reducing to 18mm ( radiator end).

The self sealing barb didn't distort the hose as much as I originally thought. Just got to hope it doesn't leak !

Attachment 6299

Attachment 6300

The ID of that housing is probably only about 1" and thus a tight radius. A nut inside the housing would only grab on the edges unless I was able to use a thicker nut and grind a radius onto the nut. At that point I wonder if the coolant flow would be restricted too much.

Just a thought, the Thermobob was designed for a 650cc engine and thus had to cope with three times more heat being generated. A 3/8" bypass might be more than we need for our 250cc lump, particularly if the existing air flow cools the block so much.

Heat generated is more proportional to HP created than displacement. It takes about 8 HP to push a KLR at 60 mph, and maybe 7 for your 250s so the heat generated is less, but not 1/3.

Besides, the 3/8 statement I made a few posts back WAS on testing a 250... a Kawasaki KLX250.

Kat, those stats barely have to open to flow enough in cool weather... you just need a hotter stat!

OK, making some progress now. I built up the aluminum on the water pump housing, milled a flat, and drilled/tapped for 1/4" NPT. Paint now drying to hide all my faults!
https://photos.smugmug.com/Motorcycl...IMG_1633-M.jpg

I will most probably be ordering a Hotter stat at some point soon and give it a go :tup:

Nice work Peter :tup:,
are you going to do the same for the thermostat housing for the top connector or re use a sensor hole

My by-pass is now done :yay:

My initial impressions are good but the results are a little limited.

My by-pass internal diameter of 5mm (3/16") is nearly half the size of watt-mans recommended 3/8" and also I'm still using the original stat of 70c.

Out riding - before = 55c - 60c

Out riding - now = 63c - 67c

On the whole the temp remains a lot more stable with less fluctuation settling for the most part at about 65c.

Warm up was perhaps a little slower.

The ability to cool down when the fans kicked in (80c) seemed to be as good as before.

What I think I've gain so far -

No more thermo shock, the engine now warms uniformly :tup:

Nearly 10c hotter running temp. This I think is good for the engine in general and good for helping get rid of the contaminants in the oil. :tup:


With the by-pass is fitted I'm happy now to fit a higher temp rated thermostat in the future

Attachment 6317

Attachment 6318