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1955 Model 150D - Petrol and oil mix

Technical help for all early models, A, B, C, LC, D, LD, E & F models

1955 Model 150D - Petrol and oil mix

Postby Big Al » Thu Apr 29, 2021 4:45 pm

Could someone please advise which grade of petrol I should use in my 150D, and which 2 stroke oil would be best for the mix?
I have seen various percentages given. My old book suggests 6.25% (16:1) but others suggest 4% with a Rock Oil SAE 30, or 3% with a Rock Oil PP2 Semi-Synthetic solution.
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Re: 1955 Model 150D - Petrol and oil mix

Postby jbcollier » Fri Apr 30, 2021 2:56 pm

Back when these were new, there was no 2T mix like we have today. They literally used plain old motor oil. This did not mix well, stick to metal well or burn completely so it had to be used in large quantities (6%+) in order for it to work. This meant lots of burnt oil (coke) which plugged up everything. It was very common to have to remove the head and exhaust and clean things out every 1500miles.

Now we have specially formulated 2T mixes that blend (and stay blended) with the gasoline, it's also designed to "stick" to metal parts and burn more completely. This means less mix can be used and regular de-cokes a thing of the past.

These engines have a plain bush for a little end bearing. Some replacement cranks have a needle bearing little end. If you are running a plain-bush little end, use 4%. If you have a needle-bearing little end, then you can use 3%. I highly recommend the best fully synthetic oil you can afford. I use Amsoil Dominator Racing 2T. There are plenty of other excellent options from Mutol, etc.

As to gasoline to use, I use the highest octane I can find and I don't let it sit around. Use it up within three months! Today's fuels go "off" quicker and may have additives (such as ethanol which phase separates) that cause issues over time. I live in a dry climate so I drain old fuel and leave my tanks dry, If you live in a humid climate, that's not a good idea, Instead ask at your local shops for their recommended wonder-additive and store your scoot with a full tank of fresh fuel mix and the wonder-additive.
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Re: 1955 Model 150D - Petrol and oil mix

Postby Big Al » Fri Apr 30, 2021 3:27 pm

Thanks again John.
I'm not sure about the crank, so I will go for the 4% with a fully synthetic 2T oil and the highest octane petrol.
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