Friends, I am going to cross post this in the other forum for maximum advice input, so if you saw it there and already chimed in, thank you. I have a recently acquired 1996 Sprint 900 that I gave the full CRK treatment to over last winter. This summer has been spent tuning and tweaking. not more than 500 miles in total I'm sure. Baseline: Bike had 36k kilometers so what...20k miles and had spent 2007-2018 in a garage with no movement. Full teardown, engine out of the frame. Valves within spec, carbs gone through and waterpump/clutch/motor checked for abby normal stuff. Built up with Motad Venom 3 into 1 exhaust, CRK "Ram Air" foam air cleaner and final carb settings as follows: 44 Idle circuit jet Dyno jet needles in the 3rd position 137.5 mail jets A/F screw 2 turns out...pops a little in decelerations, will back out another 1/2 turn. Stick coils from 600TT Flushed radiator and cooling system several times. CRK kit does away with temp gauge and uses a warning light. My Issue is it may or may not be running hot. left to idle on the table, the motor heats up, the temp warning light comes on and after quite a while the fan cycles on. I replaced the 23 year old temp sensor and tried again...same scenario. New Hoses, new thermostat, filled with waterless coolant. Better but the light still comes on and then goes off after a little while, but comes on again shortly. I suspect the new sensor is lower than stock. IR Thermometer shows 180 F at the sensor in the head, 190-210F at the top of radiator at hose outlet. 140F at bottom of radiator. Head temp stays around 200 and exhaust dont seem too high. I flushed system one last time and put 100 miles on her, I could smell that coolant sweet smell a little when I stopped but think that is all the coolant I spilled on the motor in numerous changes and flushes. Also when very hot the idle is a little uneven and lumpy. I have seen no spots of coolant on the engine, or under the bike, also the exhaust feels dry and no condensation that I can see. I have double checked and tightened all clamps. So...all that's left is the 23 year old radiator cap and the OE water pump. What is the consensus and personal experiences of the forum members as well as best guesses? I am very happy with the bike but I live in fear of blowing a head gasket when it could be avoided.
Vecchio Lupo. Is it that hot. May just need settling and remember they did run quite hot anyway. Check the coolant after a run to see if it needs topping up or air in the system and cap sealing tight. Regards Joe.
210°F is = to 98°C , if I recall correctly the thermo fans didn't switch on until 106/107°C , so sounds like your bike is running OK , maybe you need to Richen the fuel mixture slightly !!
Final verdict: I replaced the 24 year old radiator cap , to go along with the new hoses, temp sensor, fan sensor, fluid flush and refill with waterless coolant (thank you Edd Chyna fir the recommendation). I then ran a heat cycle and bled/refilled the system. and according to my infra red thermometer the fan cycled on at 102 celsius. My CRK kit idiot light was shining bright from way before the fan kicked on. I wired up my OEM temperature gauge and made a mount using a new exhaust stud and a electrical ring fitting sourced at the DIY store. Capped the instrument with a red top to a chain lube can, and...great looking temp gauge. From cold; it took 15 minutes for the bike to get hot enough to cycle the fan. The temp gauge never went into the danger although it was close up there. It dropped when the fan cycled and it appeared to be operating within specs. I no longer fear the blowing of said head gaskets and I feel much better watching a gauge rise rather than waiting for the panic of a warning light.
