mont man Posted January 23, 2018 Report Share Posted January 23, 2018 Hi, My 2008 Future 4rt 300 (Wiggys old bike) once warmed up starts to release an uninterrupted (even with revs) & continuous jet of steam from the top valve cover breather hose (a drip of water forms approx every 10 seconds from the condensate forming in the hose). First thought it was head gasket so replaced this, no luck, so I then swapped a complete top end from a standard 250 working bike (apart from leaving on the aftermarket S3 barrel & piston which all looked fine) & ran it twice for about 25 minutes (not ridden just on tick-over with a few revs of the throttle) & both times it boiled up within 3 minutes, fan kicks in as normal, engine sounds normal, no steam from bottom crankcase breather or radiator, no white smoke from exhaust, water pump impeller fine & both engine & transmission oils still perfect with no sign of water & oil emulsifying. With the standard 250 valve head now fitted the only difference with this Future bike to a standard one is a small brass decompression valve (reducers engine brake) fitted to crankcase just below barrel (probably similar to what Honda fitted as standard from 2014 onward). A long-shot but has anyone had a similar issue or may know the cause? Thanks in advance. Quote Link to comment Share on other sites More sharing options...
huski Posted January 23, 2018 Report Share Posted January 23, 2018 Does the water level in the rad drop? Quote Link to comment Share on other sites More sharing options...
mont man Posted January 23, 2018 Author Report Share Posted January 23, 2018 27 minutes ago, huski said: Does the water level in the rad drop? I haven't checked but most likely minimal as I don't want to risk damaging the replaced top end - which is on loan! Surely it could only be coolant due to the constant uninterrupted flow of steam? before the top end replacement was put on it had been ridden for a 3-4 hours with the same problem & the coolant loss was about 30ml. Quote Link to comment Share on other sites More sharing options...
mont man Posted January 23, 2018 Author Report Share Posted January 23, 2018 42 minutes ago, oni nou said: I thought the crankcases were machined larger to accept the 300 aeffe cylinder on a Future 4rt .. I never noticed but most likely crankcases have been machined for the 300 big bore kit. The S3 barrel & piston were probably added by one of the previous owners as Wiggy's bike would have had Future parts, the rest of the top end I removed is Aeffe. Quote Link to comment Share on other sites More sharing options...
mrturtle Posted January 23, 2018 Report Share Posted January 23, 2018 (edited) pressure test the cooling system and cap? ignore that sorry just re read your post Edited January 23, 2018 by mrturtle numpty Quote Link to comment Share on other sites More sharing options...
boringac Posted January 23, 2018 Report Share Posted January 23, 2018 Have you checked your water pump is working? Quote Link to comment Share on other sites More sharing options...
mont man Posted January 23, 2018 Author Report Share Posted January 23, 2018 4 minutes ago, boringac said: Have you checked your water pump is working? I checked it before I had the top end replaced & it all seemed good. Quote Link to comment Share on other sites More sharing options...
robido Posted January 23, 2018 Report Share Posted January 23, 2018 Sounds like a blockage and not circulating Quote Link to comment Share on other sites More sharing options...
scifi Posted January 23, 2018 Report Share Posted January 23, 2018 (edited) When Petrol burns it creates water... Hydro-carbon... HCO + O2 = H2O + CO2. So maybe some Combustion gasses are getting into the valve chest, either through the valve guides or past the piston rings. The crankcase should be connected to the valve chest via the oil drainage hole. Does the exhaust also emit steam.. Can you block all the breathers, to see if the crankcase is building up pressure? Best of luck.. Edited January 23, 2018 by scifi Quote Link to comment Share on other sites More sharing options...
nigel dabster Posted January 24, 2018 Report Share Posted January 24, 2018 9 hours ago, mont man said: I never noticed but most likely crankcases have been machined for the 300 big bore kit. The S3 barrel & piston were probably added by one of the previous owners as Wiggy's bike would have had Future parts, the rest of the top end I removed is Aeffe. wiggys bike was never 300 just 270 i think. I hope its not the bike that future put a "road map" on for scotland and melted a termignoni within a very short time....... Quote Link to comment Share on other sites More sharing options...
nigel dabster Posted January 24, 2018 Report Share Posted January 24, 2018 10 hours ago, oni nou said: I thought the crankcases were machined larger to accept the 300 aeffe cylinder on a Future 4rt .. not 300, if it was wiggys. Quote Link to comment Share on other sites More sharing options...
mont man Posted January 24, 2018 Author Report Share Posted January 24, 2018 8 hours ago, scifi said: When Petrol burns it creates water... Hydro-carbon... HCO + O2 = H2O + CO2. So maybe some Combustion gasses are getting into the valve chest, either through the valve guides or past the piston rings. The crankcase should be connected to the valve chest via the oil drainage hole. Does the exhaust also emit steam.. Can you block all the breathers, to see if the crankcase is building up pressure? Best of luck.. No steam from exhaust, I'll have a go blocking the breathers on the weekend. Thanks Quote Link to comment Share on other sites More sharing options...
mont man Posted January 24, 2018 Author Report Share Posted January 24, 2018 9 hours ago, oni nou said: if water/coolant is being emmited as steam from the valve cover breather then you must have water/coolant migrating fom the head gasket somewhere..... is the barrel/cylinder damaged[as it is the only original top end part that is common to the problem on both occasions] on the mating surface or not flat somewhere along its face that mates against the head. The barrel all looked good before assembly, with no sign of damage to the previous head gasket. Probably have to try another barrel next. Quote Link to comment Share on other sites More sharing options...
scifi Posted January 24, 2018 Report Share Posted January 24, 2018 The more I read your first post... ' Jet of steam coming from the valve breather'... The more convinced I am that the crankcase is building up pressure. We had a 40k miles VW that had a blocked crankcase breather filter, if we removed the oil filler cap after a minute of engine running, lots of gas would explode from the filler opening. We cleaned the crankcase breather filter in petrol and that cured it. The VW sends all the crankcase gasses into the inlet manifold, so that the engine burns them. . Quote Link to comment Share on other sites More sharing options...
mont man Posted January 24, 2018 Author Report Share Posted January 24, 2018 52 minutes ago, scifi said: The more I read your first post... ' Jet of steam coming from the valve breather'... The more convinced I am that the crankcase is building up pressure. We had a 40k miles VW that had a blocked crankcase breather filter, if we removed the oil filler cap after a minute of engine running, lots of gas would explode from the filler opening. We cleaned the crankcase breather filter in petrol and that cured it. The VW sends all the crankcase gasses into the inlet manifold, so that the engine burns them. . When I ran it last time I unscrewed the engine oil dipstick slowly until off, no pressure felt against the cap & no steam just oil getting chucked out from the turning gears. I'll block the breathers like you mentioned earlier the next time I try running it. Quote Link to comment Share on other sites More sharing options...
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