Oil Mixture

[b40rt]

Although I do respect your opinion and what you are stating, this last example would not be average use by normal folke. I do believe the P.O.U. must be kept in mind.

For putting about and occasional revving, I feel safe with 80:1. For harder running or a road trial at higher(moderate) revs for long duration, I may go 50:1, and for extreme usage as in idiot use, well this may require a bit more such as 36:1 or so, thus I choose to stick with what works for my average use. And that is not extreme, thus the ratio.

So if you average out your recommendations, you end up with ? 50 : 1

[breagh]

I wonder what mix they use in the SSDT?

Do they mix up different ratios for different bikes?

Probably the hardest most bikes will ever run.

[taffe]

I wonder what the daytime temperature is in the SSDT, Can't see them bikes overheating in a hurry. Merry Christmas all. Taff

[copemech]

So if you average out your recommendations, you end up with ? 50 : 1

You know that does make perfect sense for your average idiot!

I consider myself far below average, thus the lesser requirement I suppose, although I have done some tough testing trying to blow them up!

Too lean on the jets will give you a lot quicker result that you may not like!

[0007]

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

[b40rt]

I wonder what mix they use in the SSDT?

Do they mix up different ratios for different bikes?

Probably the hardest most bikes will ever run.

In the past they only had 2 stroke petrol in one ratio, but when the copemecs of this world demanded a certain ratio they just agreed with whatever they said.

[b40rt]

copemecs got it covered !

[dadof2]

0007 and others - I will do a lengthy post when I have a bit more time. The information is commercially sensitive as it involves warranty claims so I can't give too much detail

Briefly, yes, the engines are smaller than typical trial engine and I should perhaps have downgraded RPM to give comparable piston speed.

The engines were electronically limited to well short of 12,500 RPM yet suffered ring failure as a result of inadequate lubrication. Tests using control fuel, recommended oil and 50:1 ration show that these problems should not occur under 12,500 RPM. The suspicion is that variable fuel quality may be the cause or something about the fuel was degrading the oils ability to lubricate adequately

[0007]

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

[copemech]

copemecs got it covered !

I am just an average mechanic, so I never see anything until it breaks! Been riding and racing 2T for several decades now, so seen a few! I work on cars and trucks for a living, bikes are a disposable pastime now.

There are some brite fellows on here as well, and they probably know all about the oil migration cycle within a 2T motor.

The lads with the small kart motors of 100 cc run plenty of oil as it gives them power!

Cabestany posted up once stating they were getting over 13K on his bike, and he uses it! Although briefly.

If I were to guess, I would think the standard mix for SSDT would be 50:1 all considered, yet even then the lads cannot take too much chance of overheating on the roads due to cooling capacity. Some may push it, some may fail!

Edited December 18, 2013 by copemech

[b40rt]

I think 50:1 as you say is a reasonable figure, using good quality 2 stroke.

The SSDT bikes can have real overheating problems due to the radiators getting blocked with mud etc. Riders are advised to put a mud flap on the front mudguard, and constantly check and clean the radiator shroude. Specific SSDT preparation can be read here. hhttp://www.trialscentral.com/news-archive/scottish-six-days-trial/13143-ssdt-the-beta-survival-guide

[lewis cosgrove]

[zippy]

[guys]

[taffe]

What a varied MIXTURE of ideas, anybody changed their fuel/oil mix?? I'm looking foreword to page 3..........not.