help required regadring FZR250

hi !! well i have a coolant overflow prb from the water reservoir with my 1992 FZR250, but it only happens on high rpm, on low rpm everything is fi9, there are certain checks which i`ve already made like, opened the radiator cap and started the engine and rev up but no air bubbles were seen from the radiator, when i increased the rpm ( with the radiator cap open ) the water level in the radiator went a bit down and when the rpm were normal then a slight overflow was noticed( guess this is due to the expansion of water due to heat and the mass flow on high revs ), i also checked the water reservoir hole for the pressure release, but it is clear too, but still having the overflow prb, radiator cap seems quite fine ( the seating area ), bike is a bit heating up, fan is gud too and radiator has been serviced too, the only thing that is bothering me is this that y this is happening on only high rpm ?? i mean wither u run the bike 50 km on low rpm this prb won`t happen but if u run it for 5 km on high rpm then there u go with the overflow from water reservoir ?? i removed the cap of water reservoir and put a plastic arround the mouth still did`nt solve the prb ?? so is there anyone who can help ??

 

thx @dave and @koma
the water level in the reservoir goes below the FULL MARK, it`s almost empty after the overflow. as it continues overflowing, one think that came in my mind that as the radiator cap is a non-return v/v with some spring tension holding it on to the seating area, so is`nt there any chance that it is malfunctioning ?? and one more thing i dun have to add water in the radiator even after the spill, lets say only 10-15 ml is to b added when there is overflowing from the reservoir, but the expansion bottle is fully emptied. well one more thing is`nt there any head pressure invloves in the water reservoir ?? i m sure during the design that point must have been considered, so either my bike is creating some xtra pressure in the water body or is there something wrong with the head pressure in the reservoir ?? but again this only happens on high revs <!-- s --><img src="{SMILIES_PATH}/icon_sad.gif" alt="" title="Sad" /><!-- s --> plz suggest some solution for this prb ?? i m looking forward for ur help. thx.

 

one more prb !! when bike is cold started then it take a very very long self :s

 

thx @dave well one more question regarding overflow !! is that necessary that the mouth of the water reservoir should b air tight ??? not talking abt the hole for the pressure relief !!! the hole is well cleared, but i have wrapped a plastic arround the opening of the reservoir, so is that suppose to b air tight ? if is it so then i guess i have had solved the prb with the overfloww.

 

ya the same item # 25, i was using a plastic piece arround the mouth, now have fitted back a rubber cork( taking care not to block the hole ) now i`ll go for a ride tommarow then will tell u guys that wat happened. Dave i took the bike to max. revs in the 1st and 2nd gear with the radiator cap open and water level a bit lower from the cap but can b seen from the top but still could`nt notice a single overflow from the radiator, so i think its not the gasket or the head ceack i should b worry abt, the prb lies somewhere in the thermostat or something else, by the way Dave can u post a link of pdf format for thermostat, i do have that japnese version but its not so much gud to understand from there !! so can u plz post a link ?? thx.

 

@dave
thx man !! well dave it seems like i have got the prb it was the cap of that bottle, the rubber cork is working fi9, well now i have one more question, Dave where i live in ( Pakistan ) the ambient temperature during this seasons does`nt go below 30-32 at night, so i was thinking wat if i remove the thermostat and blank the pass line and make it direct ?? though thats gonna effect the performance for a little while unless the engine got a bit heat up, but it`ll take care of the temp for sure !! any suggestions ??

 

hmmm.. well frictional resistance could cause a major prb while the engine running cold, so i guess i have to drop the idea of removing the thermostat, well here is another question, this time its the temperature gauge, well at the time when i turned the igntion on then it moves a bitt up lets say 3-4 mm and while riding the bike, the needle moves only 2-3 mm more, but touching the radiator cap clearly indicates that the water temp is approx. 80+ so the needle must have to b somewhere in the mod section of the gauge, i checked for the ground connection on the thermostat body and while i touched it to the engine body the needle moves to the top, so this means nothing wrong with the gauge or the earthing connection, so any suggestions ? and Dave plz can u explain DIY in a little easy way, and if can b explain through a pic then it`ll b quite helpful. thx.

 

H:\DCIM\100MSDCF\DSC00052.JPG
how to upload the pic ?? well i have taken a few shots of the thermostat unit, if u can explain something from the pic ?? wat should i check ??

 

@dave can i have ur email add, i want to send u some pics and offcoz a bunch of questions that i have to ask regarding the pics. thx

 

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@dave i have put a red circle arround in pic 50 and 52 !! can u tell me wat are those things for ? and where is the ground connection for the temp gauge u were talking abt ?

 

hmm thx anyway, i`ll try to open that out, lets c.