Hi to all, Just recently acquired a Bultaco 250 1978 198 and to be honest I dont have a great deal of experience or knowledge of the bike. Hopefully with time this will improve. My question is a simple one really, could some one give me the fuel/2 stroke oil ratio that I should be running with this bike. I have read 20:1 in an old manual, is this correct?

Please forgive such a simple question. Many thanks.

Marty Dunn

use castrol TTS at 50 to 1.

Twinshockdude, Many thanks for your reply. I have lots of questions I need to ask regarding this bike but I wont bother you just yet with them. Just one more if I may, what is the best way to clean out the exhaust system as I believe it will be full of oily goo - hence previous question. Thanks again, Marty

there are as many answers to that as there are owners !!

my prefered method is caustic,others set it on fire,others cut it open and clean manually

take your pick

Use a semi synthetic or castor oil NOT castrol TTS which is fully synthetic

and run at 40:1 not 50:1.

Use super unleaded fuel.

It is possible to avoid oily gunk depositing in the exhaust by running with very little oil in the fuel. Trouble is, it is not kind to the motor to run with so little oil. It will run fine but will wear out much faster than it would with adequate oil in the fuel. How little oil you mix with the fuel depends on what life you want to achieve from your motor. Because of this, you will find a variety of opinion about what is the ideal amount of oil to add. I use 40:1 semi-synthetic

If your M198 has a standard exhaust and you burn out the gunk, the main (first) muffler section will need repacking to run properly. It will run but not very well without packing around the inner tube. To repack the main muffler it will need to be opened and there are many ways to do this.

Edited September 14, 201015 yr by feetupfun

Please do NOT use TTS Fully Synthetic as it is to good for old boreable barrels, use a Castor based oil....

Like Castrol A747, caster based semi synthetic at 40:1.

That's 125cc per 5 liters of fuel!

Big John

Thanks guys for the advice. What about clutch oil - I have heard that Automatic Transmission Fluid is the stuff to use. What kind, quantity etc whats your advice on this.

Cheers

Marty

Thanks guys for the advice. What about clutch oil - I have heard that Automatic Transmission Fluid is the stuff to use. What kind, quantity etc whats your advice on this.

Cheers

Marty

ATF is OK for primary drive 300cc.

I'll try to reply to your PM as soon as possible, been a bit busy recently!

Big John