tltel Posted December 5, 2012 Report Share Posted December 5, 2012 Sting32. Not a bad answer,to my question, Thanks! But I was thinking that surely the rad cap is designed to release pressure, before the seals let go, otherwise any time the engine got too hot you would end up with water in your gearbox. But I suppose if the seals were worn anyway, it could finish them off! Shercoben Have you got it sorted yet? You said in another post that you have been working on a 98 gasser, water pump seals should be easy enough for you to do. You can get the kit which includes the shaft from gas gas uk next day delivery. Its a good way to learn mechanics, there are loads of help videos on youtube. It seems you and your mates have quite a few bikes between you, it helps to know how they work. Good luck TLTEL Quote Link to comment Share on other sites More sharing options...
jse Posted December 6, 2012 Report Share Posted December 6, 2012 But I was thinking that surely the rad cap is designed to release pressure, before the seals let go, otherwise any time the engine got too hot you would end up with water in your gearbox. But I suppose if the seals were worn anyway, it could finish them off! The cap is designed to release pressure at a certain point but it releases it through the vent hose that, if closed off, overides the set point. Jon Quote Link to comment Share on other sites More sharing options...
sting32 Posted December 6, 2012 Report Share Posted December 6, 2012 Sting32. Not a bad answer,to my question, Thanks! But I was thinking that surely the rad cap is designed to release pressure, before the seals let go, otherwise any time the engine got too hot you would end up with water in your gearbox. But I suppose if the seals were worn anyway, it could finish them off! Shercoben Have you got it sorted yet? You said in another post that you have been working on a 98 gasser, water pump seals should be easy enough for you to do. You can get the kit which includes the shaft from gas gas uk next day delivery. Its a good way to learn mechanics, there are loads of help videos on youtube. It seems you and your mates have quite a few bikes between you, it helps to know how they work. Good luck TLTEL Just like any other equation, It is NOT just straight line... The set point for max pressure the cap can hold is (I dont know, but lets guess that it is like 10psi) Compression would be I guess, up to a hundred PSI, and pretty good volume. I think that most think of radiator as a solid, but it's pressure would escape out the cap, but you need to realize and visualize it EXACTLY like a balloon loses air out the blow hole (not a pin prick, as you know a pin prick creates a hole as big as the balooon itself. So, there would be more than 10psi in the radiator UNTIL all of the pressure was "equalized" or let out. But only until the next compression! So for the few MANY milliseconds it might have up to 100psi to shove water into the oil, for say, a many milliseconds, while it bleeds off pressure through that tiny hole in the radiator cap. but then gets another "pulse" from the compression... Which happens how many times a second? without a hole the size of the piston/cylinder to let pressure out, you COULD not see it let off fast enough to leave a helluva lot more than 10 psi in the water jacket. Water heating up causes expansion, but it is so much less volume or rate of expansion, so cap can let it out quick enough. Least that is how I think it is. Quote Link to comment Share on other sites More sharing options...
thats_a_five Posted December 6, 2012 Report Share Posted December 6, 2012 Sting you are right in desribing the high pressure pulsing that comes with each compression stroke. It is waaayyyyy more pressure than you will get from heat expansion. I do not know the exact numbers for a trials engine but consider these general numbers. Radiator cap release pressure 11-13 pounds per square inch (PSI) Compression for worn engine 110 to 115 PSI High compression engine 155 to 165 PSI. Not many rubber seals can handle 150 PSI. If they could, reeds and valves woud more likely be rubber than metal. Quote Link to comment Share on other sites More sharing options...
tltel Posted December 6, 2012 Report Share Posted December 6, 2012 Sting32 and JSE I was'nt disputing your senario's, you would have to be pretty unlucky to have head O ring failure and a crimped over flow hose,but it could happen if the bike was put back together in a rush or by someone not used to working on these bikes. Unfortunately it does look like the head needs to come off to check the seals. TLTEL Quote Link to comment Share on other sites More sharing options...
shercoben12 Posted December 6, 2012 Author Report Share Posted December 6, 2012 hi I've got the parts -water pump kit- so i will take it apart this weekend thanks for all the help ben Quote Link to comment Share on other sites More sharing options...
sting32 Posted December 7, 2012 Report Share Posted December 7, 2012 Make DANG sure you put seal in the right way, take pictures if you have to, and Youtube has a video (from the DVD owners manuals that Importer created for the USA customers.) If that helps, http://www.youtube.com/feed/UCuuOSB4N2iUkW8dbbH7HJpw (looking for user named gasgasinfo) They updated youtube, so I cant find anything, and I dont have time to re-hunt. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.