[Ismail]

Hi

I would like to know if you guys could help me since you have experience with the Comer motors.
I'm from South Africa & my son (10 yrs) races in the junior class. We are new to karting & we have done 6 races.

The guys here say the carb settings should be H: 1/2 turn & L: 2 & 1/2 turns out.
I think that on the L 2 & half turns is too much but im scared of blowing the motor so I always leave it.
Since the weather in Durban is quite similar to you guys I was Hoping that you guys could assist me with any info you might have.

We use the Wildkart chassis.

Pls help with any info to help us.

Many thanks
Ismail

[JohnKing6]

Hi

I would like to know if you guys could help me since you have experience with the Comer motors.
I'm from South Africa & my son (10 yrs) races in the junior class. We are new to karting & we have done 6 races.

The guys here say the carb settings should be H: 1/2 turn & L: 2 & 1/2 turns out.
I think that on the L 2 & half turns is too much but im scared of blowing the motor so I always leave it.
Since the weather in Durban is quite similar to you guys I was Hoping that you guys could assist me with any info you might have.

We use the Wildkart chassis.

Pls help with any info to help us.

Many thanks
Ismail

Ismail,

I haven't got much experience with the Comer but I've raced in ZA many years ago and now in Malaysia but actually it doesn't make much difference. The theory is simple - set the carb to what the manuafcturer says and the listen to the engine and check the plug. If the engine is "4 stroking" - so only firing very 2nd stroke (and blowing smoke) down the straight, slowly lean it out until it stops doing it. The absolute safest situation to have is that it starts to 4 stroke just as you start to brake. With the plug, if it's dark then the engine's running too rich, if it's light, then too lean. The problem is that the very best setting depends on the temperature, humidity etc so you have to adjust it. Basically you son needs to learn to do it on the track. When we use carbs with driver adjustable jets, I'll adjust mine a bit 2 or 3 times a race 0 lean it out a bit to try to pass someone and richen it up if I'm running on my own.

Ultimately it's always a balance between performance and safety - to rich give less performance but won't seize the engine, lean is fast but fragile.

Good luck!

[Ismail]

John,

The manufactr says the L shoud be 1 & quarter turn out but the guys here says that it doesn't
work & the motor will heat up & we should keep it at 2 & 1/2.
I have a CHT & the temp goes up to about 220 degrees celcius if I keep it at 1 & 3/4, is this
normal?
Thanks for the advice.

Regards
Ismail

[gp8]

We raced the Comer engine very successfully for 2 years in Australia. We ALWAYS set the low speed jet on the dyno and then NEVER changed it until its next rebuild and check on the Dyno. The optimum setting was more than half a turn different between our 3 engines. The dyno charts were quite different for each engine we had, even though the achievable lap time with each was within a tenth. They dyno readings allowed to better match gearing to each engine. One was quite the revver, usually geared to max at around 12,500, whereas another enginewas a tractor which we usually ran to a max 10,800. With a dyno reading you know your engine.

High speed jet was set and tweeked during the race for a maximum cylinder head temperature of 225 degrees C (taken under the sparkplug). We always made sure that we ran between 215 and 225 degrees for optimum performance. We used Maximo 927 castor oil at 20:1 and the only engine based retirements we had were due to ignition module failures (2 over the 2 years). The ignition modules seem to start to go off after about 50 hours or so of racing.

One other thing worth mentioning - except in the very hotest and most humid conditions, we used to blank off one intake hole into the airbox. This appeared to have better draw through the airbox due to reduced turbulence within the airbox. Possibly irrelevant for Durban (and Malaysia), but when it's quite cold (less than 10 degrees ambient) we found that standard unleaded fule worked better than the premium unleaded as the engine simply couldn't advance the ignition or suck in enough air to fully exploit premium.

I trust that this helps.

[Ismail]

Hi,

Thanks for the info, just a few questions:
Is 225 degrees not to high, the guys here say they keep it to max of 200 (under spark plug)?
How many turns did you keep the high & low jets turned out to?

Unfortunately I don't have access to a dyno.
I use Shell Advence X & the ratio is the same 20:1.

Also can you tell me how long can you keep the mixed fuel before you throw it away?

Thanks
Ismail

[gp8]

Temperature first.

We have always used a Mychron 3 Plus Gold. We ran 2 heat sensors on the Comer initially, an under sparkplug thermocouple and an exhaust temp thermocouple tapped into the barrel. The under sparkplug temp is quite dynamic, rising and falling quite quickly with revs as it really only measure combustion chamber temp. The exhaust temp thermocouple tapped into the black provided us a much more stable (and reliable) temp reading. Eventually we only used the barrel temp. and the engine was tuned to max 225 degrees C barrel temp and always within the range of 215 degrees to 225 degrees.

These temperatures may prove too high if you are using a fully synthetic oil in the Comer. Nearly everyone in Australia runs castor based oils in these engines (either Maxima or Shell M) as the oil seems to resist breakdown a little better. The Comers don't appear to nip up a piston anywhere near as much running on castor.

Before we get into tuning I suggest that you get a very good engine shop to have a look at and measure up your engine port positions and especially check to see if the bottom of the barrel and the mating face on the bottom end casings are perfectly perpendicular to the cylinder bore - most 60 and 80 cc Comer engines are not. IF it is possible to machine these surfaces so that they are perfectly perpendicular to your piston bore without ending up with an "out of spec" port timing, then do so. Peak revs from this simple "blueprinting" will be plus 300 - 500 revs with a much healthier top end. Check your local engine regs carefully first and discuss with an engine builder before you start and work to ensure that this is legal under your competition regs.

If you have your engine properly set up, with the bore, barrel mating faces and bottom end bearings all aligned and properly set - and the port timing optimised to the homologated template for your engine, then your tuning should work out as follows:-
1. Ideally - with a dyno
Engine set to run max temp no more than 225 degrees C with the high speed jet at 1/8th turn. Temp adjustment on the dyno is via the low speed jet setting. Once set we used to plastic tie the jet into position

You then head to the track and run laps, keeping an eye on the barrel temp. If it edges above 225 tweek up (richen) the HIGH SPEED jet. If it doesnt make 215 after 4 or so laps lean off the HIGH SPEED jet.

2. No dyno
Similar process. You set the High Speed at 1/8th turn and fiddle with the LOW SPEED jet until you have 215 - 225 steady between lap 6 - 10 or so. Once you have achieved this - pretty much forget about the LOW SPEED jet and only adjust the HIGH SPEED jet for tempertaure. Effectively you will always have the high speed jet set in the range of 1/16th through to maybe 1/2 turn. This is the range within which ours always ran - from ambient temps of 4 degrees through to 44 degrees... It will prove to be about 95% right.

We mix fuel on demand using an Accu-mix container. Unused fuel goes into a tin marked "practice pre-mix" and it gets used first the next time we are at the track doing practice. Fuel for a race is always fresh, mixed just before going into the kart tank. Unmixed unleaded that remains unused at the end of a track days goes into my wife's car. I never throw away fuel and this works out quite well. After all - Happy Wife, Happy Life.

[DMmotorsport]

Dear Ismail,

I sent you a PM ! with some small information ...


Ciao, Kristof

[tmskarting]

Hi,

If you are using the tryton carb, I think you will find that the low jst should be 45 to 65 mintutes, or between 3 three quaters of a turn and just over one turn. Please find below a link to a set up sheet.

http://www.zipkart.com/downloads/Tryton ... -Guide.pdf

Thanks

TMS

[DMmotorsport]

Hi There !

At this moment (a few months after Ismails post... His already learned a lot about the carb, as give him some tips,
As Ismail and his son allready did good results in the SA championshipd !

congrats again, anyway

Ciao, Kristof
DMmotorsport