We run these type of engines a lot in Sweden, and Motul 2t is our no1 choice. 6% mix
Excellent result and wear.
1h 40min in this one
Thanks ! I have been suggested to use castor oil. Have you used this product? Sorry to clarify your response i dont understand the meaning of 6 % mix ? Could you clalify on feul to oil ratio please. Thanks sorry about my ignorance but i am very new to these old school air cooled 2 stroke motors. Cheers
Castor works as well, but often times burn more dirty.
Motul is proven to work and highly praised in 2 stroke communities
6% mix, so 1l to 16l of fuel. 1:16
I mix in small quantities, 320ml to 5l fuel
Thanks Lucas ,
I will use that mix , another question maybe you could help me with. The orginal carburetor is a tillotson HL 334 A . I was trying to source a brand new one but have no luck for they have been discounted. I bought a tillotson HL 334 AB which i was told is the same carb with a bigger venturi. Would you know the best High and Low needle settings on this carb where performance would be optimal with this engine.
Cheers
Sweet, I basically run all my carbs at L: 1turn and H: 1.5 turn
In my tryton HB27 I run L:1.1 and H: 1.50
Castor is good for air-cooled engines but they leave carbon inside. If you don’t mind cleaning it it’s a good option too
Lucas thanks your insight and knowledge is a super help. I seen some pics of your engine rebuilds which are wicked. Obviously your a expert at these older air cooled 2 strokes. Another question about my motor , its been sitting for some time probably years. I haven’t started it yet…New fuel filter, fuel lines , new carb , proper 16:1 feul , new plug anything else i could do to ensure i dont damage motor.
These engines are very sensitive to carburation… at least for optimal performance.
For most Tillotson models 1 turn out on the low and 1.5 on the high is the starting point. It should land you on the rich side.
“Optimal” will likely be leaner than this on a given day (or even time of day) but of course the leaner you go, the greater the risk of seizing the engine… along with the rear wheels.
These engines are a tricky way to start karting. Push starting is an art in and of itself. But they are very rewarding and there’s some good experience here that can help. There’s few vehicles you can drive that will turn 19,000 RPM.
If it’s been sitting for a few years, at the very least you will want to replace the crank seals as they harden over time.
Anything other fresh parts in it can be a risk between possible rust on bearing surfaces and parts with unknown time on them.
For now I would say do the crank seals, visually inspect internals and see if you can get it to fire up.
As James said.
Personally I’d fully disassemble it and check crank, change all seals and bearings.
Then check rotary plate and ignition
If things are not in order it could take many things with it when it blows
All depends on budget and what you want to achieve 
Is this the DSB? Ran these when I was a kid/young adult in America(late 80’s, early 90’s) . Ibea slide carb, direct drive, wonderful!!! Not to hijack the thread, I would Love to own one now, if anyone has leads pls DM me!!
Derek , I was wondering myself what exact Rotax model engine i have here ? On the block has GMB 85 and on the bottom of cylinder head is Made in Austria GMB 83. I have tried to find information on this exact motor with no luck. So, any help identifying this exact motor would be great.
Lucas and James you guys are awesome, and are invaluable in helping me with this kart. Next question would be where can i source crank seals and bearings for this particular motor.
On cylinder head one side Made in Austria GMB 83 , on the other side 6213 Rotax 660. The block has GMB 85 212780 Rotax . I have reseached to find this model with no luck. Any help again is awesome ! Great community of guys on Kart Pulse …Thanks
Going by the head it’s a DSB. Most of the internals stayed the same or similar for decades. It wouldn’t surprise me if KA100 seals and main/crank bearings fit. The rod bearing and piston would be different though. I’m not aware of a US supplier @Andy_DiGiusto might know someone?
I buy basically all my stuff on Mondokart since I’m in Europe.
As for seals and bearings it’s just read what you current ones says or measures. It’s often stamped on both seals and bearings
As for conrods, just avoid the cheap ones
I buy mines from a reputable source in Italy and we have very good success with them. Just make sure the rod moves freely in the casing. Sometimes we machine the crank halves to open up 1mm because of aftermarket parts
