The radiator cap on my '15 race R6 isnt stock. Stock is 1.1bar and silver. This one is 1.8bar and black. Does anyone know what the common replacement is for a stronger cap? Someone previously suggested this might be off a small dirt bike, but didn't give specifics. Also, is the stronger cap absolutely required for racing?
I found this on ebay. 2 bar from graves and seems like a decent price to me. 29.95 https://www.ebay.com/itm/Graves-Wor...m=232786365832&_trksid=p2047675.c100005.m1851
I can't speak to road racing, but in the woods a 1.6-1.8 bar cap is almost required. It still allows the system to vent before it gets critical, but at a higher pressure and temp than the measly 1.1 stock cap. There is a climb that I never made without boiling over on my GasGas 300 with the stock cap. I switched to the KTM 1.8 cap and never had an issue after that. I would only go to a higher bar cap if you have experienced pressure release conditions at a temperature less than 210*F. Otherwise, if the system is working you shouldn't need a higher bar cap.
If it's a black 1.8 bar cap it is most likely a KX 65 radiator cap. Those work really good. ( part # 49085-1077) 1.8 should be all you need for racing. I've used a 2.0 cap at Utah, but use the 1.8 everywhere else.
I have checked a lot of caps that are uprated to 1.8 and a few 2.0. (full disclosure, haven't checked ANY caps in at least a decade). Every one of them bypasses at 1.1 bar. Check to verify!
Thnx everyone The bike ran at good temps with the 1.1 cap this weekend at Buttonwillow. Mysterious, I did find ~4oz of cold water in my bellypan and an empty overflow about 10min after a race. I refilled the overflow, raced again, and found the overflow empty and belly pan dry. So I’m thinking I didn’t burp the system well enough. I’m gonna pick up a stronger cap too.
Check to make sure that the cap sealing area is clean and flat. I have experienced issues three separate times with either bad gaskets or the radiator neck having an uneven surface, causing the cap to leak. You can look at the rubber gasket on the cap and if it has uneven wear, or a gray area, it's bad.
small update. the motor was refreshed. the radiator (new OEM), cap (1.5), and hoses (Samco) were replaced. I got everything installed, filled up the radiator, ate dinner.... and came back to water on the floor the water pump seal was completely destroyed, likely accelerated by that white powered WaterWetter leaves in the system. I now suspect that the water I kept finding in my belly pan was due to this, not a poorly sealing cap. I replaced the water pump with a used unit with a pristine seal. I raced at Utah with MA. When more than a few racers were struggling with overheating, I was putting tape on the radiator to prevent the too low temps.
