Radiator over heating

[Colin Gunn]

Hi can anyone help I’m having issues with the radiator over heating when I’m sitting in traffic or give the bike some beans????

Thanks

 

[PhilCrowder]

Sounds like it wants flushing. There are several products available for car radiators such as Holts. I had a BSA Three wheeler and that used to boil till it was flushed out. The water ways on my Scott are only about half a mm or less and I was surprised how much grit came out of the spare  just by shaking.

[PhilCrowder]

If your engine still overheats , then the radiator might be being asked to do too much and the mixture strength might be a bit weak. Heat transfer also depends on ambient , so warmer days will affect it. All my other  two strokes are air cooled and two do have an under the plug bimetal  heat sensor so head temperatures can be monitored. Quite interesting when the reading  gets high!!!!

[Colin Gunn]

Thanks Phil I will try the flushing….

[Colin Gunn]

Hi

Sorted it turned out to be a small weep from the overflow pipe which would not allow the expansion to take place

[BRIAN MARSHALL]

Another point to watch out for is trapped air in the shoulder of the radiator that is the other side to the filler neck. Gases expand far more than liquids as they heat up and so displace the coolant out of the overflow. Always ‘burp’ that air out by leaning the bike well over so that the trapped air escapes over to the filler neck side. Perhaps a two-man job if it is a heavy bike ! Don’t top up coolant to the level of the overflow pipe as you will only lose coolant as it expands. Keep it a 1/4″ or so lower.

[Stan Thomas]

Following on from Brian’s point – some radiators had an air balance pipe across both header tanks -most did not.

Remember that if you change the domed end caps, as it only requires a short piece of small-bore pipe soldering across the highest point of both header tanks.

• This reply was modified 3 years ago by Stan Thomas.

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