OzVMX Forum
Clubroom => General Discussion => Topic started by: bazza on July 05, 2020, 12:13:27 pm
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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?
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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........
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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.
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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.
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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)
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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
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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.
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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.
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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.
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Some good advice, based on experience here.
(Unlike most “Oil Threads”)
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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.
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Well spoken Sleepy. You have told the facts without fiction.
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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).
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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)
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927 burns cleanly in my opinion. I think they have cleaned it up. The contemporary Castrol R seems cleaner as well.
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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)
this is the methanol doing the “Jelly” in the carb. i had a speedway bike (4T) for years, if i didn't drain the carb after the meeting this was the result.
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927 burns cleanly in NY opinion. Ithink they have cleaned it up. The contemporary Castrol R seems cleaner as well
The current castor based oils are much cleaner due to the additives mixed with the base castor oil. Every 2 stroke oil sold today has detergents added to help keep things clean even the Full synthetics. One thing to be careful of when deciding on a mix ratio is to not go outside the oil manufactures recommendations. It gets complicated but if you use an oil made to mix from 50:1 to 100:1 at 25:1 the concentration of detergent and other additives in the final mix may be to high to work and can even have the opposite affect causing very high carbon build up.
Other thing to think about with Ester based oils is that the oil is Hygroscopic and can cause internal corrosion so there is normally an additive to help stop corrosion. This was never a problem back in the old days of mineral oil. I've pulled apart motors that haven't been run since 1970 and the bearings once cleaned are as good as new but not case with the modern oils.
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We run a 73 YZ 125, 73 YZ 250, 77 RM 125, 81 YZ 465, 94 KX 500 all on Maxima 927 castor oil at 30:1. These bikes have never lost a race at Nats, Origin or Conondale Classic level. They are ridden flat out for the entire 3-4-5 laps every race by the two fastest guys in VMX with no issues.
So for anybody advocating 40,50,60,1000:1, keep it up. Just makes our job a lot easier????????
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Funny how nothing has been mentioned about the heat retention characteristics of the various oils.
I was told by an esteemed world class tuner (this is 15 y.o. info) that synthetic oils hold far more heat than mineral oils. The logic being that synthetics are 'plastic' and we all know how hot plastics can get. The result is more cooked big / little ends. Mineral oils hold less heat and so 'wash out' the heat more.
Anyone ever heard this theory?
Also, go-kart guys will tell you how small high revving 2 bangers gain better ring seal and more horsepower from a rich oil mix e.g. 16:1
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I agree with Ted. ( Not often ). That Maxima 927 is a very good oil.
But some of you are getting off the point of oil/fuel Ratios.
KX80/85,Go karts, and Road Racing Engines are really a different subject as the Engines are operated at much higher RPMs at long periods of time at full throttle.
A friend worked at a Kawasaki Dealer . He would rebuild KX80/85 Cranks some times 5 or 6 a week for the Junior A Grade Riders.
He stated that using Castrol A747 or Kawasaki Racing 2 Stroke made the Cranks last longer.
Honda HRC Australia used a Special Shell oil made in Japan to run in the NSR 250. It came in a screw top metal container and the writing was in Japanese. So i know little about it and if it was Mineral or Synthetic. It gave good Piston and Crankshaft life . It was never Sold Retail even in Japan. It was mixed 30.1.
Would not use Shell VX/VX2 2 stroke oil . Found to not burn clean and has a lot of smoke.
Castrol A747 has been used Road racing bikes for many years and still is. But it is expensive but so are engine Rebuilds.
When Belray MC-1 first came market it made may claims including low smoke,less plug folling and clean burning etc.
Clean burning was true . If run at 40/50-1 it burnt that clean not much oil was left when it got down to the big end.
It was recommended by our Maico Dealer and Maico USA to run MC-1 at 25-1. Used it for some time with no problems.
Then switched to Castrol TTS and used it for many years.
Someone brought up Bearing Skid. Have not heard this term for many years. I know it will happen if you use Moly grease on Taper Car Wheel bearings but as far as engines go i have not heard of it since i read a article from Alpha bearings UK.
The paper was written in the early 1950,s. They built a much improved crank and rod for the Villers engine with a bigger
pin and Caged rollers. Which helped with Bearing Skid and Clearance problems.
Just note the first thing a rider does when a Engine fails is blame the oil. It is has and can be caused by something
like Dirt/Dust , Dirty water, Air leaks, Spark Timing / Detonation etc. Or just worn out.
Another Point to think about is the oil ratio effects Combustion Temperature, Carburetor Jet flow and Changes the
Fuel Octane Level.