KR-1S.co.uk Forum

Hi, i have managed to get my hands on a fairly good rgv 250 rad and want to fit it to my 1S.

However, the rgv rad only has a fill hole bolt where as tha kr1s rad has a cap and expansion tank pipe

Anyone done the conversion and got any tips??

do i need the expansion tank with this rad???

Cheers, Kris

I think you will need some sort of expansion tank for sure, a plastic bottle does fine for racing.

you need to get the rgv cap as well, and get all the coolant pipes, thermostat housing and T section (should be a few breakers have them).. or similar stuff. I did the same thing and asked here as well.

viewtopic.php?t=409&highlight=rgv+rad

I then did it another way just to have the filler more accesable and save space under the tank for air feed.

yep you also need the RGV thermostate housing, which includes the filler cap. When I had one fitted I blocked off one of the inlet pipes on the RGV housing using Aldrite. If you want one I'm sure I have one sat in my garage somewhere.

i did it a far easier way although it requires faffing about come rad refill time. ill post in a min, just off for a smoke/brew in the shed.

right, all i did was fit as you would normally with a std one, using the inlet/outlet(need to join 2 bits of hose as a. the rgv has a bigger bore inlet/outlet pipe and b. the position of the lower pipe on the rgv rad/clutch casing side is a bit awkward and benefits by been joined with an appropiate bit of tubing or better still some hose the correct shape and flexible enough to fit the bigger rad pipe but still seal the smaller kr1/1s pipe of the water pump housing. some people put a bigger hose (the same size as rgv) over a std kr size hose on the water pump housing to make up for the diffrent size which imo is the best option as it looks neater and works effectively. all i did for the filler is drill the plastic bolt on the rgv rad all way through, bond a peice of tubing into the hole so it protrudes enough to fit a length of pipe same bore as fuel pipe (about 10') join the pipe using 3-5' of bigger pipe(slips over smaller pipe) and run to a water tank or as i do a 250ml catch bottle. the air in the rad goes to the bottle as does a bit of water, when the bike cools the vaccum effecet ensures the water goes back into the system. bond using araldite or similar. the only snag is you need a small funnel when filling the rad as its a small hole to fill. also takes longer than a proper filler, obviously. it does work though and the rgv rad is a treasonable size for a race bike, the std kr rad is pathetic. not even suitable for a w/cooled moped!

Thanks for the replies chaps, im working through my kr winter/spring refit and find all your advice makes interesting reading. I've found the rad will fit but the plumbing has puzzled me a tad.

If i go ahead and decide to use the RGV filler/stat housing which thermostat do i use and which do i remove - the RGV or KR one???

Thanks again, Kris.

Which every is the easist to remove which in most cases is the RGV one.

whichever works best as Elf said.

I replaced the temp sensor/gauge for calibrated one - fitted in the head as standard. Also I dont use either thermostat anyway (restricts coolant flow slightly).