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here is the full story of it. parted out my first 2001 853 (2000 motor), kept the motor. had gotten a second 748 with a bad motor and lotsa lotsa performance parts for supreme deal. put the 2000 853 motor in my new 2001 748, ran great with no problems at all as did in my other 2001 i parted out. rebuilt the 2001 motor with an 853 kit, all parts were supplied by previous owner who decided not to go through with the project. brand new weisco pistons (853) and cylinders, was told it was a FBF kit, cylinders were professionally done as came in the original box. did the rebuild my self, done many on cars and jap bikes so i figured i could do this. got the rebuild done 2 moths ago, started up first try ran great. did several short ride around town taking it easy. by the way the first rid was down a deserted road where i would accelerate to 70mph and slow down quickly using the motor to slow me down, did that for 20 min to seat the rings. bike seemed to be fine on all the short trips. went on my first long ride a month ago with a group i ride with, about 200 miles. appeared to have no problems (wasnt checking either) speeds for me were reaching 110-120 mph 130 tops for short distances. finished the ride and ended up at a friends house, went for a short ride down another back road where we were really pushing it 110-130 mph for me for most of 20 miles. noticed my temp was rising above 180 (normal range for all my 853 bikes) to about 210. stopped at a gas staition and the radiator tank was empty, put a liter of water in it and drove home slower (about 80-90mph) without a problem, temps stayed around 180 except when stopped at a light near my house.

so heres what has been done. i took the coolant system apart change the thermostat with one from a motor i parted out and the cap as well. filled it took it for several 40 mile rides checking temps. seem ok tank stayed full for the most part, didnt go below the max line but a little bit, figure it was bleeding it self. did notice on the third ride that the over flow tank was filled all the way up. so i replaced the cap with a known good cap from my previous bike that had no problems. emptied the tank filled everything to exact specs and rode it several more times on the highway up to 90 mph always watching the temps and checking the tanks when i stopped. all seemed well. so i went on my next long ride yesterday. this time watching my speeds and temps along with it. started the ride on the same road as before, reaching speeds of 130mph sustained. temps went up to 190-195, figured this might be normal. stopped at the same gas station to check the tank, it was empty, put half a liter in the tank before it filled to the max line. continued with the ride, watching the temps and speeds. temp would stay at 180 if i rode at 90 or less, 100mph temps were at 190, would get up to 205 or so when at 120.

so i got home and took the panels off today, overflow tank was full agian with the radiator tank empty as before. took the whole coolant system apart to check it, everything looks good. radiator had almost no coolant in it, cylinders were full though. impeller looks new, no leaks found any where around the system. beginning to think i have a compression leak into the coolant system at high speeds. squish was set at just under 1mm, 0.96mm i think. didnt do anything to the heads except relieve the valves for better fuel flow (which would lower the compression a little), and lap the valves.

so before i pull the heads, what do you think, also had another problem which i kind of solved. this motor was making insanely high oil pressure. 40 psi when idleing at normal temps and off the gauge when above 1500 rpm. my 2000 motor didnt do this 16 psi at idle and 75 psi above 4k. put a gauge on both bikes, same gauge actually. changed the gauge same pressure. changed the oil pump with another 2001 oil pump, same thing. took the pressure relief apart on the pump, found out there are 2 sizes of plugs on the pump. a long and a short. shimmed up the plug for less pressure on the spring relief. this bought the pressure down to 80-85 psi above 4k, which was good. problem is i am finding lots of oil blow by in my airbox, changed both the valve that screws in and the plastic piece that go into the airbox. no change. could the high oil pressure be causing this.

that isnt my head as i didnt take pictures of it, these are pics i downloaded for the work i did to mine.


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