Grey is a weird thing and it doesn't mean anything to me
The only way to read plug color is on the trail, you cannot way any time period, it must be done hot
I prefer the burn pattern on the piston crown, if you can get a carbon spot in the middle of the piston that extends to within 6mm or so of the ring land you are getting good combustion temps
Sounds like interesting work, testing is more science than anything and science often wins
The other thing worth mention is high rpm use like spinning an engine fast while running down a road as opposed to full load dyno testing produces drastically different load on the ring (12g limited by electronics or 12g limited by a brake for instance)
Our bikes probably don't get over 7g give or take a bit and it's a rare occurrence to have full rpm and full load
I'm not sure our apples compare to those oranges
It's kinda like saying my trials tire will fail over 120kph, moot point
I have quite a bit of respect for Jon Stoodley - but it does not mean he is always right nor do other tuners always agree with what he says.
The comment about gearbox makes as much sense as ignoring manufacturers advice. Why spend a lot og £££s on a bike then risk damaging it due to lack of oil?
Some recent research has shown that at 50:1 a good / top quality synthetic oil starts failing to protect piston rings at about 12,500 RPM so in theory at typical trials bike revs an 80:1 mix should be fine. But then add in some variables like water droplets, a bit of engine wear, poor carburation, variable petrol quality etc and 80:1 looks nowhere near a safe bet.
I stripped a 2010 gasgas recently (gearbox fault). Run on Motul at 75:1. Rings, piston, barrel all damp with oil, some wear but still within tolerance. Quite a bit of oil in the bottom end but little end far too dry for my liking. The piston, bottom end and even the reeds were covered in dark brown deposits caused by blowby. It would seem 75:1 was providing adequate lubrication but nowhere near enough piston cooling and ring sealing.
There is a serious drawback to advising 80:1 - You do't know what sort of use the bike is going to have, I have seen a beginner stuck in a peat bog rev the bike till the exhaust glowed dull red just outside the barrel. Try that at 80:1 and see how long the piston lasts.
I'm curious what engine they were using to test with at 12,000rpm
the problem is a long stroke engine as opposed to a short stroke engine radically changes piston speed so testing different oils would always have to be with an identical spec engine but would not apply to other engines, our trials bikes would huck parts everywhere at 12g, and a 2 stroke revving that high is pretty unusual, probably an 85 or something, they have an incredibly short service interval due to their HP per Litre
Not applicable to our low hp per Litre bikes
Due to the sliding scale of usage, all anyone can say is "Average user = Average oil ratio"
Most of us could run from 60 - 80:1 and notice very little difference
Another note, large amounts of oil means leaner fuel air ratio, so saying 20:1 will save an engine is not really true as a clean running bike at 80:1 will be lean at 20:1, the safety would be in the fact that the engine HP is reduced if anything
Finally, engine builders reccomend very conservative jetting and oil ratios for a reason, it's protection / padding, it's often done during testing on pre production engines in a controlled environment on a dyno and with an oil manufacturers general recommendation
It's just not real world
Anyway, cheers, this question will never be settled on the internet, it's just fun to talk about
The only time I have a problem of the lever hitting my fingers is when I smack a tree with the lever..............come to think of it, that happens too often...........
LOL, ya, there is a good argument
Nothing like bumping the brake lever on something during a low speed maneuver
There is no Pre detonation, there are at least two forms of abnormal combustion
Pre ignition: where the fuel mix is ignited by a source other than the spark plug, this is similar to having incorrect ignition timing, it could be a glowing bit of head gasket or carbon etc, sometimes the fuel is ignited by both the plug and the other source and the flame fronts collide
Detonation: the fuel mix does not burn evenly from the spark plug out like it should, it explodes (no the mix is not supposed to explode), this is sometimes due to incorrect ignition timing but most often it's excessive compression or lean condition
It's kind of hard to tell the difference between the two but detonation is far more common
Does it happen only when the engine is full hot, does it only happen at partial throttle etc etc
Ya it's unburned oil that's coating the inside of the exhaust
When you get the pipe up to high temp such as hill climbing it basically cooks off the oil
As this is a symptom rather than a cause, cleaning it will not stop it from happening again
I think most trials bikes do this anyway, it's because we don't get the exhaust temp up often enough, you may be able to make it better but I doubt you can stop it completely
I kinda think it's not a worthless talent, it's all part of learning and feeling the balance point, how to put it there and not go too far, how to feel the bike react to throttle and weight placement
And ....it kelps you maybe react properly when it all goes wrong
And let's not forget that the CDI factor is high (Chicks Dig It), I think a wheely is about an 8.5, a stoppie is slightly higher
Spark Plug Colour
in Beta
Posted
Grey is a weird thing and it doesn't mean anything to me
The only way to read plug color is on the trail, you cannot way any time period, it must be done hot
I prefer the burn pattern on the piston crown, if you can get a carbon spot in the middle of the piston that extends to within 6mm or so of the ring land you are getting good combustion temps