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| *Vultures Knob>>>Dirt Bike |
Any info on the net for old time 2stroke dirt bikes 1979 YZ125? |
fuel to oil ratio?reference materials and so on tnx To tell you the truth, Roger Decoster of team suzuki pointed something I remember years ago and I've lived by it sucessfully. People used to mix a quart of oil to five gallons of gas, which is 20:1 ratio. Decoster says its better to run a good oil at 40 or 50:1. The reason is that oil burns at a higher temperature than the gasoline and therefore more oil is worse on your engine! wierd but true. Maxima 927 at 40:1 always worked good in my two strokes. i would run 32:1 I used 50-1 castrol "r" in my H2R,H1R,and F9R never had any problems. Tons of info on the net . AHRMA.org-go to Yamaha links you will find vintage Yz and some others. Your bike ai a YZ125F model designates the 1979. It is eligible for for AHRMA's post vintage Grand Prix class -for bikes from 78-81. The real hot rod 125 of this class is the 1980 model RMs,Crs, and YZs-the 80 KX125 so a toad-though the air cooled and visually identical 81 model was a rocket-go figure. Anyway the 81 125 which are water cooled have to compete in the Ultima class. Still, the reality is that a YZ125F is as good as anything else in its class. Now, the oil..factory recommended Yamalube R aT 32:1. It is a very good oil-I used it for years. Now the general rule with air cooled two strokes is the smaller the bore-the more oil-and the larger bore somewhat less. At high engine speeds a 125 often benefits from a 20:1 ratio-giving added protection. This as mentioned creates more heat-so you may experience accelerated wear compared to the 32:1 ratio. Then you must consider modifications-such as you likely have not a stock cast piston(hard to find) , but an aftermarket Wiseco forged piston. A forged piston will expand more with heat than a cast piston, and while considered stronger-requires slightly more clearance. Also, using any of todays pump gas(and many blends of race gas) you are using oxygenated fuel. It will burn hotter-and in some cases require richer jetting and/or retarded ignition timing. Also, when mixed fuel(oil and gas) sits-the gas evaporates while much of the oil does not. I have found this to be exagerrated with oxygenated gas. Other factors you may consider for oil choice and ratio are the use of the bike and how much maintanence you will perform. In the case of my 440cc Maico I have come to use Vp c-12 race gas-as it has the octane level I need-is not oxygenated-and is consistent.I mix at 40:1 withKlotz Be-Nol-a castor oil. Now I would not suggest you to use a castor if you are new to this-as most castors separate from fuels with a specific gravity less than .700 (many race fuels) and /or temperatures below 45 deg or so. I found the klotz to be the most tolerant. I do like the 927 castor as well, but occasionally a VMX race in Tx takes place on a cold morning-and it separates. Why do many use castor-and put up with all this plus it leaving more deposits than a petroleum or synthetic? It gives the best protection-period-and even has that great sweet smell. That said, I would recommend you use premium pump(fresh from a major brand busy station)-and Yamalube R at 32:1 to start with. You will find as many opinions on two stroke oils as politics- not all are applicable to your bike/use-nor is there one correct or magic answer. Remember, as you add oil to the mix, you lose gas, so a 20:1 ratio is leaner than a 50:1 ratio for tuning(yes, I know a 20:1 ratio is richer in OIL than a 50:1 ratio). |
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