BOILING

[peter Whitwell]

Help!
The Silk has been running well but the last 2 trips the water boils very quickly and coolant streams out the overflow like a kettle boiling - rendering the bike almost to seizure with excessive heat

I am using Rock oil Kool XL engine coolant rather than water

it has been suggested its the head gasket but before I start pulling it apart im sure someone knows the answer

HELP!

[hendred]

Suggest you drain the system down and try just plain water, preferably soft water before taking anything apart.  I use
water from Cornwall which is virtually calcium free and hence no scale.  Two things affect the performance of the coolant in the system, the viscosity of the coolant and the thermal capacity of the coolant.  Ethylene glycol is more viscous than water and without a pump to circulate it the fluid will circulate more slowly in a thermosyphon system.  Ethylene glycol has a lower thermal capacity than water and will take heat away less effectively than plain water.  Add the two together and you may have a problem in high ambient temperatures.  The specification for Rock Oil doesn't give the percentage of glycol but I suspect it is quite high.  There is a previous thread about Evans Waterless Coolant, which is basically pure ethylene or polyethylene glycol, if you read the specification in detail it is not recommended for thermosyphon systems for these two reasons.  It also needs a sealed system which is not the case with a Silk.  So try the bike on plain water and see off the problem is resolved.

[peter Whitwell]

Thankyou for your help much appreciated I will try your suggestion in the next few days.

[peter Whitwell]

Good Evening Hendred

I flushed out the Rock coolant as you suggested - I  replaced the 5 pint contents with water with  blue freezer  additive 3+1 and all is well I went for a 50 mile ride after 10 miles the level of water adjusted with a very little amount from the overflow then  another 40 miles  examined the  overflow not a dribble  happy days all is well!!!!!!! bike ran beautiful.

Thats fortunate as apparently there are no head gaskets available - unless others no different?

Thanks for your Help much appreciated.

[hendred]

Good news.  Modern technology doesn't always work well in our old bikes.  On head gaskets, I thought solid copper ones were available.  Last time I spoke to Clive the problem was the price and quality of the original type.  Could be wrong on this though.

[Smokey_Paul]

Absolutely correct yes I use filtered water and a touch of oatmeal coolant the water less coolant works wonders in a pumped car type system either a large rad but an absolute no in bikes.

If the head gasket does go I have a few left for emergency