wayne509 Report post Posted January 18, 2014 (edited) Just sold a bike (Scorpa SR 125 with the sherco 125 2T motor and radiator etc) and unfortunately the head gasket has apparently blown on the fellas first time out on it. Surely the pressure relief valve should have let water/pressure out first shouldn't it? It blew a water pipe off then after putting it back on and filling with water it started chucking steam from the exhaust. I want to help with the bits to fix the bike and wondered if there is an easy way to test the pressure valve before I shell out for another? Edited January 18, 2014 by wayne509 Quote Share this post Link to post Share on other sites
cabby Report post Posted January 18, 2014 Did he put oil in his fuel ? Quote Share this post Link to post Share on other sites
wayne509 Report post Posted January 18, 2014 Did he put oil in his fuel ? I would think the bike was still on the same tank of fuel as when I sold him it. I filled the tank from the same mix of fuel my other lads 125 is running. If anything it would have been running a touch rich. Definitely not the cause. The bike does have a S3 high compression head on it though .... probably the culprit but would think the pressure relief valve would have shown symptoms before it failed totally Quote Share this post Link to post Share on other sites
thats_a_five Report post Posted January 18, 2014 By the pressure relief valve, are you referring to the radiator cap? If so, most radiator shops can test it. Quote Share this post Link to post Share on other sites
wayne509 Report post Posted January 18, 2014 (edited) By the pressure relief valve, are you referring to the radiator cap? If so, most radiator shops can test it. No not the radiator cap. To fill the radiator there is a cap but it is basically just a bolt. There is a separate pressure relief valve just next to it. You can see the part here ... part 8 Edited January 18, 2014 by wayne509 Quote Share this post Link to post Share on other sites
steve_earle Report post Posted January 18, 2014 If it has built up enough pressure to pop a hose off and the relief valve didn't relese then I would certainly change the valve to be on the safe side. Presuming the hoses were secure in the 1st place. The problem you may have is the the new owner doesn't know too much about bikes and the original cause needs to be determined 1st. You need to know if the fan was working and the waterpump is operating properly. Another cause of head gasket failure especially with a high comp head is reving the nuts out of it can pop the inner o ring but I doubt it will be admitted if that was the cause, If so a cheap fix just half an hour and 2 o rings. I would reccomend the bike is looked at by someone who knows exactly what they are doing otherwise you will end up keep giving them parts untill they accidently fix it. Good Luck. Quote Share this post Link to post Share on other sites
wayne509 Report post Posted January 18, 2014 (edited) Hi Steve I believe the new owner is returning to trials after many years and does have experience in fettling bikes. As far as whats wrong with it .... We know the fan is operating properly as we ran it up to temp when he was viewing it. My lad has been riding it twice a week for 6 months with no issues so I am putting it down to co incidence and sod's law. I have advised him to check the waterpump but pretty confident all is ok there as a complete kit was fitted about a month ago. He is going to take the waterpump cover off turn the motor over by hand and check the impeller is turning as it should and there is no damage to it. I am going to get him new water pump seals for the sake of a couple of quid and yes you are right .... never mind checking the old valve I will just get him a new one and obviously new head o rings. I gave him the standard head too so think he is going to go with fitting that as everyone I have talked to say those high comp heads are more trouble than they are worth. Hopefully this will sort everything out Edited January 18, 2014 by wayne509 Quote Share this post Link to post Share on other sites
copemech Report post Posted January 19, 2014 Hi Steve I believe the new owner is returning to trials after many years and does have experience in fettling bikes. As far as whats wrong with it .... We know the fan is operating properly as we ran it up to temp when he was viewing it. My lad has been riding it twice a week for 6 months with no issues so I am putting it down to co incidence and sod's law. I have advised him to check the waterpump but pretty confident all is ok there as a complete kit was fitted about a month ago. He is going to take the waterpump cover off turn the motor over by hand and check the impeller is turning as it should and there is no damage to it. I am going to get him new water pump seals for the sake of a couple of quid and yes you are right .... never mind checking the old valve I will just get him a new one and obviously new head o rings. I gave him the standard head too so think he is going to go with fitting that as everyone I have talked to say those high comp heads are more trouble than they are worth. Hopefully this will sort everything out I was going to comment, yet your last sentence may sum it up. I do not know of a pressure test set for this, although one may me devised with adaptation. One thought would be removing the old one for inspection, as it is likely a simple spring loaded ball, and insuring it is not seized. No further info and I am not in the mood to break mine to find out! Ha! Cheers, Quote Share this post Link to post Share on other sites
steve_earle Report post Posted January 19, 2014 They do run hot with a high comp head, I'm going to have to fit the uprated water pump to mine when the weather heats up. Quote Share this post Link to post Share on other sites
Ft76 Report post Posted January 3 Hi there , I’m having trouble with my sons sherco 125 2003. it was popping the thermostat out put a new one in and now coolant coming out not from the thermostat but from the radiator somewhere . how do I check the blow off valve as I suspect the problem lies there any help or tips very much appreciated as this bike is slowly draining the life and wallet out of me 🤔🤔 Quote Share this post Link to post Share on other sites
