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6V C90's, oil coolers and stirring up a discussion (hopefully)
Posted by : Nut aka Neil (82.33.210.228) 
Inappropriate or SPAM?
On Thursday 23/07/15 at 21:31:01
Hello All. Ok let’s see if we can stir things up a bit, and get a bit of banter going again. 6v C90’s and oil coolers seem like an excellent place to start (we can move onto types of oil later lol).
Right then 6V C90’s. From personal experience they do not seize due to temperature, they seize because of lack of oil to the underside of the piston. Evidence of this is the fact that the small ends seize as often as the piston itself. Further evidence is that if you remove the barrel and piston whilst the engine is in the bike and then fill with oil to the correct mark on the dipstick, you will observe the crankshaft does not touch the oil and therefore cannot provide splash lubrication to the underside of the piston; essential to cool the piston and lubricate the small end. Cure: throw the C90 dipstick away and fit a C70 dipstick which is about 10mm shorter and then never let the oil drop below the top level…..problem solved.
Next oil coolers. You do not need an oil cooler on a std 12V C90, but fitting one will reduce the temperature and hence oil usage on long full throttle hauls such as dual carriageways and motorways. Because of this they soon pay for themselves and ultimately save you money if you do this kind of journey very often. If your engine is tuned then fit an oil cooler, I personally melted a 110 piston on a motorway and distorted 2-off C70 pistons racing at Wittering.
All experience is personal and practical so although opinions are welcome, don’t even think about telling me I am wrong unless you have personally (not your mate, or you read, or a bloke said down the pub) seized a C90ZZ, or used an oil cooler, or ridden full throttle from tank full to tank empty on a motorway.
Happy Tinkering
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