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  • An Experience I Learned Firsthand (；・&forall... (POSH: Oversize Main Jet / Pilot Jet Set)
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【POSH】Oversize Main Jet / Pilot Jet Set Review
Oversize Main Jet / Pilot Jet Set POSH
POSH
Oversize Main Jet / Pilot Jet Set

Fits: YAMAHA SR400, YAMAHA SR500

Japanese Webike user
5/5

An Experience I Learned Firsthand (；・∀・)

When I bought SR400, British custom was the mainstream, and I also liked to install CABTON Exhaust System. Of course, I was young, so it does not correspond to Japanese Vehicle Inspection.
I had put it on without carburetor setting....
This is what happens.

Symptoms
Idling Rotational instability
I thought the ▲ sound was dull→Cool. (；・∀・)
▲ inadvertently stalls→ mistakenly thinking this is a taste (-_-;)
▲AfterFire a series of fires during embrasure
I would be ashamed of myself today.

Cause
The resistance of the Exhaust System changes against the intake from the air cleanerretc. and the adjustment of the Carburetor is out of setting.
→The point is that the balance of the combination of a good exhaust system + normal air cleaner is bad and the fuel mixture is out of balance.
It means that the mixture is thin.

As expected, I couldn't ride the car as it was, so I decided to try Carburetor setting (laugh).

Carburetor setting
The method of adjusting the ratio of air/fuel mixing (air-fuel ratio) in the engine. 。 If the air-fuel ratio is not right, the fuel cannot be burned properly and the engine will not be able to deliver enough power 。
In the worst case, it will lead to Engine failure.

The parts used in the Carburetor setting and their roles.
1:Main jet →Large action around Axel opening 50%~.

2:Slow Jet (Pilot Jet) →Engine hangs and affects running at low openings.

3:Air Screw (Pilot screw) →Since the scope of responsibility is covered by Slow Jet, if the Setting does not appear by adjusting Screw, the Jet is replaced, and so on.

4:JetNeedle clip step→Clip step up makes it thinner, clip step down makes it darker effect. 。 Adjust the sharpness of the blow-off from a physical point of view.

I thought I'd try 3 and if it didn't work, I'd try 2. →3 didn't work (laughs), so I tried 2.

Incidentally
What are the symptoms of a thin Pilot Jet? Throttle opening 1/8 to 1/2 →.
Breathing, Knocking, Stalling, Staggering, Lagging, Rattling, Poor acceleration Dark Idling Unstable rotation Light Idling Black smoke, Dull sound, Stalled after a while......just the way it is (laughs)

There are three types of Pilot Jet here.
・#48
・#50
・#52
The standard was 42.5 so I will try from the darker side.
Here's how each one turned out.
No afterfire or stalls.
... ##50→Engine takes, but Plug is completely Black.
... ##52→ Too dense to be Engine.
After that, when I ran, the explosion naturally eased up and I was in good shape (lol).

good point
◎Main jet:6 types from 165-190, Pilot Jet:3 types from 48-52:The number of component points that are in Set, so you don't have to worry about Setting with OEMcarburetor.
◎They are easy to obtain, which is helpful for Setting beginners. It is difficult to get Jet individually.

Point
You should check the number of OEM or current Main jet and Pilot Jet. It will give you an idea of what to do from the current situation.
It is better to have several plugs, because it is difficult to reuse a plug if it is too dark and too black, because the burn color of the plug confirms the Setting.

If it is a single cylinder, you can do it by yourself because it is only one carburetor. Especially if you have an external exhaust system and it is not working well, I think you should do the setting.

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