Is your Puch running poorly?

Follow the steps below to get it running right!

Many riders install a performance part and instantly expect more power, but instead get poor acceleration, low torque, or low top speed. A two stroke Puch engine only performs well when all parts are matched and correctly adjusted.

If your Puch runs poorly after installing a new part, use these six tuning checks to restore power fast.

How a Two Stroke Puch Engine Works

A two stroke Puch engine works as a complete system. The cylinder, carburetor, ignition timing, clutch, and exhaust must work together. If one part is not adjusted correctly, the Puch will run poorly.

Many performance problems start after installing a 50cc or 70cc cylinder because the carburetor jetting and ignition timing are not adjusted. Correct Puch tuning always starts with checking the basics before changing parts.

Step by Step Guide to Fix a Puch Running Poorly

Puch Tuning Step 1: Check for Air Leaks

Pro tip: Soak the engine with brake cleaner and look for air spitting from the engine while it’s running to identify air leaks.

A two stroke engine needs crankcase compression. Air leaks cause poor acceleration, overheating, and engine damage. Always fix air leaks before adjusting the carburetor or ignition. If you have an unusually high idle, you may have an air leak.

Check the crankshaft seals, carburetor connections, intake manifold, and cylinder gaskets. An airtight engine is the foundation of a well running Puch engine.

Puch Tuning Step 2: Adjust Your Carburetor Jetting for 50cc and 70cc

Carburetor jetting is the most important step in Puch tuning. A new cylinder always requires a larger main jet because the engine needs more fuel.

A fast 50cc cylinder with a 12mm Bing carburetor usually needs a larger main jet. A 70cc cylinder requires an upgrade to a 15mm or 17.5mm carburetor with a larger main jet and correct needle adjustment.

Correct carburetor jetting improves torque, acceleration, and engine temperature. Always check the spark plug burn colour.

Puch Tuning Step 3: Air Mixture Screw Adjustment

Pro tip: Warm your engine up first. Do not attempt to tune a cold engine.

The air mixture screw controls idle and throttle response by tuning the air/fuel mixture.

Start with the base settings and adjust from there. While the Puch is idling, fine tune in small steps until the engine responds correctly. Listen to the engine as you adjust.

You want to achieve the highest idle RPM purely by adjusting the air mixture and then adjust the idle screw to your desired RPM.

If the engine does not respond, the main jet size is incorrect or you have an air leak.

Puch Tuning Step 4: Adjust Your Ignition Timing

Incorrect ignition timing causes poor torque and slow acceleration. A faster cylinder requires earlier ignition timing.

A common base setting is 1.4 mm before top dead centre with contact points at 0.40 mm. Aftermarket ignitions like PVL, MVT, and HPI require specific timing settings from the manufacturer.

Correct ignition timing improves throttle response and overall engine performance. Make sure to always review the manual for your ignition.

Puch Tuning Step 5: Tune the Clutch for Better Acceleration

If the engine revs but the Puch does not accelerate well, the clutch setup is incorrect. Clutch adjustments may be necessary.

The centrifugal clutch controls how quickly power reaches the rear wheel. You can adjust clutch slip and engagement timing by changing spring tension.

• More slip / later engagement: Loosen the springs by turning the adjuster screws outward. The clutch grabs later and engages more smoothly. This works well on tuned engines that make power at higher RPM.
• Less slip / earlier engagement: Tighten the springs by turning the screws inward. The clutch grabs sooner with less slip, helping standard or low-torque setups pull away faster.
• Good starting point: Fully tighten the screws, then back them out 1.5 turns. Fine tune from there based on acceleration and takeoff feel.

If further adjustments are needed, you may need stronger clutch springs to achieve the engagement RPM you require and ultimately improve acceleration.

Heavier riders often need stronger clutch springs. Lighter riders can use standard springs. Proper clutch tuning makes a big difference in how a Puch accelerates.

Please note that the clutch must be removed to make these adjustments.

Puch Tuning Step 6: Choose the Right Exhaust

The exhaust has a large effect on engine performance. A standard exhaust gives smooth performance and low noise. A performance expansion chamber exhaust gives more torque and higher top speed.

Always match the exhaust to your cylinder and carburetor setup so the entire engine package resonates correctly and delivers the best performance.

Summary: How to Fix a Poorly Running Puch

A poorly running Puch after installing a new cylinder is usually caused by incorrect tuning or mismatched parts. The best results come from checking for air leaks, setting the correct carburetor jetting, adjusting ignition timing, tuning the clutch, and choosing an exhaust that matches your setup.

Whether you run a 50cc or 70cc engine, using the right carburetor, main jet, ignition, clutch springs, and exhaust allows all components to work together properly.

When tuned correctly, your Puch will deliver stronger torque, smoother acceleration, reliable running, and the best possible top speed.

Choose the right Puch parts, tune your engine carefully, and unlock the full performance of your setup.

FAQ

Why does my Puch run worse after installing a new cylinder?

Because the carburetor jetting, ignition timing, and clutch are not adjusted for the new cylinder.

What jet should I use for a 50cc Puch?

A 50cc cylinder usually needs a larger main jet than a standard setup. Always start rich and adjust down.

What jet should I use for a 70cc Puch?

A 70cc Puch typically needs a larger carburetor, larger main jet, and needle adjustment.

What is the correct ignition timing for a Puch?

A common base setting is 1.4 mm before top dead centre with 0.40 mm contact point gap.

How do I know if my Puch has an air leak?

Symptoms include high idle, poor acceleration, overheating, and inconsistent running.

Why does my Puch rev but not accelerate?

This is usually caused by incorrect clutch springs.