Mikuni Jet from china clone GX200.

[chados]

Hello, I write from Russia, through Google the translator, excuse for it mistakes.
In Russia it is a little developed completion of clone gx 200 motors, there is no information, there are no councils.

I have lifan 168f2 karting, a compression ratio about 10, channels are chiseled polished, an exhaust of 30 mm a pipe, the limiter is dismantled. I want to improve work as the carburetor of a mikuna of 22 mm. 5000 RPM more I won't allow to twist my maximum turns 5500 RPM. What jets are necessary for this carburetor, for the moment in the lower RPM?

Above 5500 turns it is impossible, I try to hold a resource. I want to achieve stable engine performance and response to overclocking.

Thank you,
Max.

 

[bob58o]

Try a mikuni jet size 120-125 if your altitude is around sea level.
Advance the spark timing to 32 degrees Before Top Dead Center

 

[chados]

Try a mikuni jet size 120-125 if your altitude is around sea level.
Advance the spark timing to 32 degrees Before Top Dead Center

Thank you!
What's the standard the spark timing ???

 

[bob58o]

Thank you!
What's the standard the spark timing ???

22-24 Degrees Before Top Dead Center.
Advancing the ignition timing by 8 degrees is fairly standard.
Oh!!!!!
VALVE SPRINGS!

You need stiffer Valve Springs to turn faster than 5400 RPM. Stock valve springs are 10.8 pound springs and limit RPMs to 5200-5400 RPM. 18-22 springs will allow the engine to spin faster.

If you change the springs, there is a chance the connecting rod and / or flywheel may break, which can be very serious and dangerous. ARC RACING makes a billet aluminum connecting rod and flywheel many like to use.

Valve float isn't good for the engine, but over-revving is not good either. Valve Float prevents the engine from turning faster. In general, the valves will float before the engine spins fast enough for connecting rod or flywheel to break.

 

[bob58o]

Lets try Russian (also from Google)

 

[chados]

22-24 Degrees Before Top Dead Center.
Advancing the ignition timing by 8 degrees is fairly standard.
Oh!!!!!
VALVE SPRINGS!

You need stiffer Valve Springs to turn faster than 5400 RPM. Stock valve springs are 10.8 pound springs and limit RPMs to 5200-5400 RPM. 18-22 springs will allow the engine to spin faster.

If you change the springs, there is a chance the connecting rod and / or flywheel may break, which can be very serious and dangerous. ARC RACING makes a billet aluminum connecting rod and flywheel many like to use.

Valve float isn't good for the engine, but over-revving is not good either. Valve Float prevents the engine from turning faster. In general, the valves will float before the engine spins fast enough for connecting rod or flywheel to break.

Thanks again! So far, we do not have the opportunity to purchase the details, now this is expensive for us, the dollar rate is very high to the Russian ruble. But in the future, we will definitely buy these details. We have a hobby club for children, there is no financing, we buy everything for our money. For now, we will limit the bar of revolutions in 4500-5000 RPM to save the motor.

 

[bob58o]

For safety.... At this forum, we usually tell people DO NOT CHANGE VALVE SPRINGS WITHOUT A BILLET CONNECTING ROD. Other forums say DO NOT REMOVE GOVERNOR (LIMITER) WITHOUT A BILLET FLYWHEEL.

A broken rod might put a hole in the engine block. An exploded flywheel 7000 RPM at might kill someone.

That being said, some race go karts at 6500 RPM with a "prepared" stock rod... And Jody from ARC RACING said he doesn't feel billet rods are needed, but with rule changes (porting allowed) the engines will turn higher RPMs and he's afraid billet rods will become necessary. He says these engines (for stock racing) are too expensive already.

---------- Post added at 12:05 PM ---------- Previous post was at 12:02 PM ----------

0.07 - 0.08mm oil clearance between the connecting rod and crankshaft journal is recommended.

 

[chados]

Thanks, we for safety, will be искатьть a finansorovaniye and sponsors to buy necessary materials and spare parts. Safety most important.

Now on karting I as much as possible do 35 MPH, with 4800 RPM, and I don't untwist any more. My reducer with oil and coupling has a gear ratio 1\2, I want replacement by the dry coupling not to lose turns to receive on 4800 RPM speed in 50 MPH and to leave safety.

 

[bob58o]

I think that says the engine has a 2:1 reduction on it and you want to get rid of the reduction unit on the engine to go faster.

An easier method might be to put a smaller sprocket/gear with less teeth on the rear wheel or axle.

Or get a bigger clutch sprocket with more teeth.

 

[chados]

I think that says the engine has a 2:1 reduction on it and you want to get rid of the reduction unit on the engine to go faster.

An easier method might be to put a smaller sprocket/gear with less teeth on the rear wheel or axle.

Or get a bigger clutch sprocket with more teeth.

Yes, I understand you, stars 12\27, and plus a reducer 1\2 now.
I would like dry centrifugal clutch and a star 8\27, so we will achieve bigger speed on smaller turns, and the maximum speed will increase. I need not to lose acceleration, the route short yet, it is necessary the maximum acceleration for small sites.
Correct me if I am not right, I am a beginner in this case

 

[chados]

Hello! Today I installed a china clone 22mm mikuni, a 0.9mm jet, I'll set the tachometer output and adjust it.

0.9mm, how much performance did not measure, do you think it's normal?
can there be a hole diameter measurement on the 120/125/130 jet?

 

[bob58o]

http://www.jetsrus.com/FAQs/FAQ_mikuni_vs_dynojet_vs_keihin_sizes.htm

https://www.google.com/url?sa=i&rct...aw1Mos6JjdIMkNjegq8reXrh&ust=1529694508196203

125 mikuni jet might be around 1.45mm hole diameter.
0.9mm might be around an 85 Mikuni Jet.

 

[chados]

Hello dear forum users! on my gx200 clone I installed a Chinese carburetor 22mm. Standard Jet 0.75mm on it, the engine stably starts and accelerates and turns 6000 RPM. I increased the jet to 1mm as advised here, the motor does not work stably, does not raise above 3000 rpm, shoots exhaust, can not be adjusted, what could I do wrong?

Foto in attach.

 

[bob58o]

What is the elevation above sea level at your location?

I'd put the 0.75mm jet back in if it performs better.
If you search the internet for "How to read a spark plug" you can get an idea if running rich or lean. But it sounds like you already know it seems to be rich. (too much fuel, not enough air).

 

[chados]

What is the elevation above sea level at your location?

I'd put the 0.75mm jet back in if it performs better.
If you search the internet for "How to read a spark plug" you can get an idea if running rich or lean. But it sounds like you already know it seems to be rich. (too much fuel, not enough air).

0.75 mm, gives a bad mixture, after an hour of racing, the spark plug has a white tint - a small dosage of fuel. Can I correct by raising or lowering the needle?

 

[bob58o]

Raising the needle (by lowering the clip) should make the engine run richer in the 1/8 to 3/4 throttle range.

At wide open throttle, it is usually just the main jet that determines the fuel mixture.

 

[chados]

My spark plug with 0.75mm Jet.

 

[bob58o]

Spark plug with 0.75mm Jet

I am not very experienced in reading spark plugs, but it looks good to me.

 

[Joe-405]

Did you pull that plug when it was idling or did you hit the kill switch at wide open throttle to check it until it fully shut off ?

 

[chados]

Did you pull that plug when it was idling or did you hit the kill switch at wide open throttle to check it until it fully shut off ?

This spark plug after 1 hour of a race (45-50 km a distance), from 0.75 mm a jet.