Pre-Mix Ratio M91 Bultaco Sherpa

[no balance]

Ho no not this again !! Anyone know what the manufactures recommended for this model when new ? Given that I only use fully synthetic that's for pre-mix only I was thinking about 40 to 1, what ratio's are other's on this site using.

Regards No balance.

[hewson]

50/1 semi - synthetic -----100 ml oil per 5 ltrs petrol

[suzuki250]

I use 40:1 for my Suzuki Beamish (Castrol TTS) It runs very well at this ratio

[triple_x]

Hi

I run PJ1 Silver fire semi synthetic 50/1 as recommended by Bultacouk.

Old engines are not designed for fully synthetic, something to do with manufacturing tolerances.

Three years trialling with no deterioration of perfomance.

But it is up to you!!

Regards

Martin

[pschrauber]

Bultaco engines where designed to use 1% or 1:100 with synthetic two stroke oil back in the days. With standard mineral oil a ratio of 4% where recommended.

If the engine is "fresh rebuild and runned in" (and you use gasoline with less the 5% ethanol in combination with a synthetic oil that can be used up to 1% by the manufacturer), then - also today - 1% is possible.

I only used 1:100 / 1% when the two stroke oil made for Bultaco still was availalbe, (which was btw. completly synthetic):

Now as ethanol free gasoline is difficult to get and many other indegrents are enclosed in the gasoline I personal use IPONE synthesis at 1:75 mix ratio for trials in every bike SWM, Bultaco, Yamaha, (which is 1,3%).

For trails riding with longer routes on lanes up and downhill I use a ratio of 1:67 = 1,5%.

Here the front page of the Bultaco quick guide I still have:

I personal would use as less oil as possible as puttering around the trees in low rpm will clogg your motor interna and the exhaust very quick.

When the engine have already some wear the piston have got some carbon build up, here a good example,

old used Bultaco piston on the left, new one on the right side:

Many of the full synthetic oils including cleaning agents for the combustion chamber of the motor. When the engine has been

used a lot with standard oil I would stay with the oil which was used previous. Otherwise the cleaning agents of the new and different two stroke oil might remove the deposits which then can lead to piston seize.