1987 CR250 oil Ratio

[bazza]

Just bought a 1987 Cr250 honda, 1st outing ran at 37/1 with Motul 800. Have read few people saying there running at 25/1, any opinions?

[Hoony]

i run 50:1 Motorex Cross power 2T in my 1986 CR250, 1985 CR500 and 2005 KTM 300.

its a great oil compared to what i used to run in my 1986 CR250 which was Castrol TTS @ 40:1 for 19 years previous to 2005 when i bought the Kato ( KTM recommend Motorex Cross power 2T so that's what i used for all 3).

oils and ratios are a personal preference, in my experience with both oils above i never had a failure due to oil or ratio.

let the opinions begin........

[Momus]

Just bought a 1987 Cr250 honda, 1st outing ran at 37/1 with Motul 800. Have read few people saying there running at 25/1, any opinions?

My humble opinion is that for a given bike, the higher the duty cycle it is seeing, the more oil it needs; ie is it being ridden by a 22 year old Pro or a 55 year old wobbler?

What that precise amount, and brand, of oil might be is the good question.

[pokey]

Kind of like a broken clock being right twice a day.

The answer is up to you. The ratio is different for you riding it and anyone else as the load and environment changes. The type of oil and so many variables and this is only on the one machine . Then multiply it by different years , size.  manufacturer and ambient temperature and humidity. Each of those effect what is required of the oil.

If your bike is loading up. drop some oil. if it getting hot, add some oil.

[skypig]

In the ‘70’s and ‘80’s 25:1 was common. As synthetic oils became more common the ratios became leaner.
I wonder if the 60:1 KTM were recommending for 125cc was because the oil is so good, or the engine design/materials is ok, (or it was to disguise some jetting issues with the change to Mikuni.)

Unless someone is wearing out at least several identical engines, under identical conditions it is very difficult to draw conclusions about wear. All the “I run X at xx:x, and I’ve never had a failure” experience probably just shows how good modern oils are.

One interesting claim I’ve come across more than once is: peak power on 2 strokes keeps increasing as you go richer on the oil. Provided jetting is adjusted to suit. (more oil, leaner fuel/air mix without jetting change.). This is due to better ring seal. Doesn’t mean that it doesn’t run less “cleanly” lower down the rev range, or cause other issues.

HRC recommends 30:1 synthetic oil for road racing in late ‘80’s NSR250 (V twin 250cc)
I use this in my 1981 Suzuki RM125 as well as my NSR250. (Motul 800 personally)

[Butcher]

castrol tts @40.1 been using that for 20 plus years. Goes in ktm 300/200 JR80 TY250 chainsaw whipper snipper,leaf blower, haven't had a failure yet

[Momus]

Coated bores, water cooling, retard curve ignitions, piston and ring design and metallurgy improvements, universal silver coated big end cages and thrust washers, boost porting giving improved under piston crown cooling, power valves, combustion chamber design understanding, have all made a big contribution to 2 stroke reliability.

If anything, oils have only incrementally improved (perhaps as much because a more affluent market is willing to pay for stock that was available, but unaffordable 40 years ago) but overall not really become much better because of decline in the use of Castor bean based product.

[sleepy]

I've been doing re-bores and crank overhauls for over 25 years and my favorite question to the owners if I have direct contact with them(a lot come from shops) is what type of oil and mix ratio do you use and from what I can see there is a direct relationship to wear rate and mix ratio. Most of the 50:1 advocates swear they have never had a blow up but from seeing the evidence first hand I am convinced that running more oil means less wear. Even in bigends it is obvious they last longer with plenty of oil around.
I'm not going to rubbish any particular brand of oil but there have also been a trend with one of the more expensive synthetics being noticeably worse for wear especially in air cooled 125's.   

[Nebo]

 As  Two stroke oils go TTS and Motul 800 are both good oils. Have a air cooled KDX 200 it has done a lot of hours under hard racing conditions .  Still has Original Big End and the Electrofusion Bore is still like new.
Has run TTS at 32-1 since new.

We had a YZ125 that was raced by 3 different riders over 4-5 years. The bike clocked up to many hours to remember.
 Replaced 2 Cranks and several Pistons . Also one Barrel.  Out Factory of Spec.
Used Motul 800 at 32-1.

Maico VMX Air cooled 250 Square barrel ,250/400 Radial and Magnums. These things run very hot when ridden hard . 
Motul 800 35-1.  Minimal Engine wear.
Running 25-1 will gum up the Exhaust and the Power Valve in more modern bike. Also may cause other issues.

Victa mowers ran 25-1 and Motor Oil.

[skypig]

Some good advice, based on experience here.
(Unlike most “Oil Threads”)

[sleepy]

I said I wouldn't talk about brands of oil but one has bee mentioned a bit that I'm not a fan of. Motul 800. Had quite a few 80 and 125 cranks come here with bigend failure while using M 800 and swapping to something like Castrol 747 fixed the problem. Also remember a couple of guy's back in the early 2000's bought 2 brand new KX125's to go dirt track racing, first race meeting both had piston seizures. They had been sold Motul 800 with the new bikes as the salesman told them this was the best oil(most expensive) that you can get, also told them to mix it at 50:1. After returning to Kawasaki for warranty they were told no warranty as they had ignored factory recommendation of 32:1. After a lot of yelling and threats of legal action the bikes got fixed and from then on mixed at 32:1 with one of Kawasaki's recommended oils. At the time Kaw recommended a Kawasaki oil, Castrol A747, Rockoil K2 and a Shell product.
The problem with the use of most full synthetic oils in bigends over 13000 RPM is that fact they are to slippery which can make the roller slip instead of turn and that causes a very rapid over temperature leading to failure. These failure appear like they have had no oil at all in the fuel with the rollers melting into the cage and everything going blue from the heat. Castor based oil is the fix for those engine and is good in Gokart engines to over 20K RPM.
My recommendation for your water cooled CR would be 32:1 but I can't recommend Motul 800 if it was air cooled I wouldn't go over 25:1 for a race bike.   

[PeterC]

Well spoken Sleepy. You have told the facts without fiction.

[Momus]

24:1  927 -castor based- or Castrol R30 in my small bores. 125 cc down.

Younger bike guys, especially  millenials (born 1980s early 90's)  era seem to think that 24:1 is ridiculously oily despite being the factory recommended ratio for most older smokers.

It is instructive for some that the boat racing 2 stroke guys think nothing of 16:1 and go down to 10:1

My Taipan, at 1.5 cc is 5:1 (running methanol and 5% nitro).

[skypig]

Do the “Modern” castor based oils like 927 cause the issues we used to get with “Shell M” (Mixed with Shell A - fuel).
Like “Jelly” in the carb if allowed to stand. More “gumming” in the engine. (No power-valves in the old days)

[Momus]

927 burns cleanly in my opinion. I think they have cleaned it up. The contemporary Castrol R seems cleaner as well.