Castrol R40 is available. Contains castor oil. No other oil is available in my country. Distributors do not have it on offer. Polish engine builders use Motul 800V or Kart Grand Prix. The person who built the engine for me also recommends it. Unfortunately, it will not help me set the carburetor because it will land on the other side of the country.
Just to say that Castrol R40 ,R30 and Shell M, all castor based were the only oils used in UK for the cast iron linered 100cc engines.
6% mixture.
I have been using the Motul Gran Prix 2T from the first time I fired it up and every time after that. I always run it 6.25% (16:1). At one point I had a temp alarm go off for Water Temp above 140 F. Water Pump Belt broke. I idled back into the pits. Let the engine cool down and checked the piston and sleeve. No damage. Hung a new belt and was back in action for the next Session. Nine months later had Top End rebuild (Piston & Ring). Engine builder said everything looked good, just normal wear. Mindful, I did not know how many hours were on engine from last rebuild and builder said it was halfway through sizing options for rebuilds.
I do not think the Oil is the issue, but I would increase your % mix. Breaking in a motor is a mix of temperature and loading. You have to get enough heat into the engine for things to expand to their proper fit and progressively load the engine for mating parts to seat.
Forgive me if you already know this process. It may be helpful for those who do not.
This is the procedure my builder gave me to use in 8-10 minute sessions:
Note* Low Needle at 1.25 -1.50 TO, High Needle at 1.0 TO. (IAME '09 Leopard w/ HL334AB carb)
1st. Warm on stand with throttle cracked. Can use a folded piece of paper behind throttle stop to the point wheels slightly spin. Keeps water flowing. Watch temp gauge until reaches ideal operating temp. Stop engine and let cool to ambient air temp. You may have to adjust needles slightly for atmospheric conditions. Usually only the low side.
2nd. Warm engine again to 105 F (water temp) on stand then drive on track. Gently accelerate to 25% throttle until engine RPM peaks for given input then let off throttle for same duration. Every session on track, never allow engine to remain at same rpm for more than a few seconds. Idle is okay, but better if always changing RPM. Repeat this for an entire session. Let engine cool to ambient air temp again.
3rd. Repeat step 2 but while on track, accelerate to 50% throttle and decelerate for same duration. Remember to let engine cool after each session to ambient air temp.
4th. Repeat step 3, but only accelerate in the corners and decelerate on the straights. If you have a long straight, you can treat the middle of the straight like a corner, but allow enough off throttle time for clutch to disengage before next corner. Let engine cool after session.
5th. Like step 4, accelerate in corners only, but increase to 75% throttle. It is okay if extends onto a straight. Let off throttle until clutch disengages and repeat for the remainder of the session. Let engine cool.
6th. Now you can begin to accelerate on the straights. First half of the session to 75% throttle and Second half of the session to 100% throttle. As you approach peak RPM choke the intake slightly to enrich the fuel mixture just before letting off the throttle. This will provide extra oil and cooling to the engine before throttle closes and starves the engine. Let engine cool.
At this point break in should be complete, but you can repeat step 6 if you want. Things to keep in mind. Always gently warm the engine to minimum operating temperature before each session and always allow engine to cool to ambient air temperature after each session. This is sometimes called Heat Soaking. It gives the components a chance to expand and contract several times. Progressively load the engine. You never let the engine spin up too quickly during break in. By loading the engine in stages, you allow those moving parts to expand at similar rates. If you were to rev too high too quickly, then the iron sleeve would not expand as fast and would pinch the piston and ring. The sleeve has much thicker walls and takes longer to expand than the piston. This is more so in a water cooled engines where the water jacket surrounds the sleeve dissipating heat more quickly. That is another reason to use tape on the radiator to retain a little extra heat during break in. During the first few sessions it is not likely engine will get to full operating temp due to lower revving. Being mindful of Temps, you can remove some tape from the radiator during each session as needed to reach full temp. Bring extra spark plugs. During break in, the fuel ratio should be more rich than racing conditions. It my foul the spark plug. Check plug after engine cools down and replace as needed.
If anyone has anything to add, please chime in.
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Thatâs a lot of valuable information, thanks! Could you please give an example of L and H needle settings after engine run in, giving the air temperature? Are you using the Jetting App? I have HL334a carb
The following in taken from E.C. Birt. A carburetor guru that is well known for his work with Tillotson Carbs. It gives good tuning instructions on how to find optimal settings for the HL and HR carbs. It can also be found on the ECcarburetors website at the bottom of the page under E. C. Birt Archives:
âYour Tillotson carb earned the reputation of being âuser
friendlyâ because if you got anywhere close to the above
information you carb will work for you. Track side there are a
few simple steps to follow on finding the right tune of your
carb. 1) Set the low side needle at 1 1/4 turns out from bottom
and the high side needle at 1 turn.
Now youâre ready to start the engine. Set the kart on the
starting grid and have it pointed at the race track. Pointed at
the privy or someoneâs pick-up just could lead to major problems.
Never get into the kart without being dressed to race. Put
yourself in the kart, hit the throttle a couple of times and watch
the linkage of the carb. Make sure that it is going from full
throttle and have your handler put the starter into the starter
nut and spin the motor over. Watch the fuel come up the fuel
line. As soon as it disappears into the carb, count to two and hit
the throttle. The motor should fire.
lf the clutch is set up right, youâre still in the pits. lf not,
youâre on your way to the track. Now you know why you didnât
point your kart at the privy. Hold the brake on and throttle the
engine a few times to get the clutch to hook up and move out
onto the track. lf the motor is loady, give it a chance to clear
out by itself. lf it wonât, you may have to take a touch of the low
side away. Turn the needle in a little bit at a time until the motor
cleans up. As soon as the motor cleans up brings the low side
needle back out where it was. Give the kart a couple of laps to
warm up. Once the motor is warmed up, come down to parade
lap speed then stand on the throttle. lf the motor bogs, it could
be on the lean side. Open the low side needle lust a touch.
Keep coming out with the low side needle in steps of 1/8 turn till
the motor pulls hard from the parade lap speed.
Now youâre ready to find the tune for the high side. On the
longest straightaway, bring the high side needle out till it goes
rich in the middle. This rich sound will be a splattering sound
or irregular firing. Better known as 4-cycling. Once you tind
this spot, start taking the high side in till it runs clean all the
way to the end of the straightaway and just 4-cycles at the
point where youâre going to lift for the turn. Once you have
found this spot, take the high side needle in lust a touch more.
Now go back to parade lap speed and make sure it pulls off the
bottom clean with no bogging.
Next check the feel ol the motor as you just come off the turn
after a high speed straightaway flat footed. lf the motor 4-
cycles here, the low side is just a touch on the rich side. Take a
little away from it. (Turn the needle in.) Watch your temperaturegauge. Anything over 350â F is starting to get too hot. lf you
donât have a temperature gauge on your kart and the stickers
start to melt off the side of your helmet, that is also a good sign
that the motor is running on the hot side.
Once you are comfortable that the motor is tuned right,
come back into the pits and check the position of the needles.
lf you find that the high side needle is out more than the low
side needle you missed it somewhere out on the track. When
youâre tuned at the optimum, the low side needles will be out
just a touch more than the high side. Once you have found this
place for the needles you can start f ine lining the tune by the
plug color and temperature of the motor. Plug color will be a
light tan to brown color. Motor temp 250* to 350* F max on a
control. A lot of people tell me that a TS-40 or US-820 has to
run 500" plus to make good power. Try 375â and put your stop
watch on it. Just maybe 500" is not the hot tip after all.
ODDS AND ENDS;
Never mix up any more fuel than you need for race day.
Dump left over fuel into your race hauler. Never use left-over
fuel for parts wash.
Service carb after every race meet. When pumps get
stretched, replace them. Stretched pumps make for a richer
running carburelor.
On real hot day set the pop-off pressure a bit higher. This
will let you run the needles out f urther and help coolthe motor
off without being too rich on the top end.
Cool weather, good air, high A.D. Set the pop-off just a
touch lower. Carb can stand to be a touch richer.
When setting pop-off pressure never have carb dry. Wet
everythng with WD-40 for safety factors.
When putting in new gaskets, wet them with your 2-cycle oil.
This way, if you have to pulla track side service you wonât have
gaskets stick and tear on you.
Pop-off pressure must pop then drop a touch and hold. lf it
doesnât hold carb will not perform right. Will always be on the
rich side. Cure: reclean needle and clean seat with Q-tip (cotton swab) and
wD-40.
Always carry a spare cap, fuel screen and cork with you. lf
carb starts acting lean, pull cap and check screen. lf trash is in
it, replace with brass screen and hope that none of it gets to the
needle, causing it to leak.
Torque carb pump plates like you would a cylinder head.
Every other one till tight. Any leaks here will cause lots of
tuning problems. lf lap times are not fast, itâs always easy to
blame the problem on the carb. But just maybe you will find
that faster lap time by tuning the driver or the chassis.
Keep your fuel dry and have a good time at the races."
- E.C. Birt
(Minor edits for points of reference, i.e Q-tip = Swab & Degrees in F not C)
2 Likes
Thanks a lot !!! I read it, very interesting and maybe that will be what I missed. Maybe this will allow me to finally enjoy the ride. I just need to understand the technical text, itâs not all clear. Thank you very much 
Let me know if you have questions about any of the details E.C. writes about and I will try to answer with different words that are easier to understand. I know some things do not translate well into other languages.
My flex coupler is new, and Iâm using an exhaust strip
fiberglass, metal wire for assembly. The glass fiber tape is very quickly covered in oil, I also gave some motor silicone but it did not give me a good result.!