US Praxis PRX90 - User Manual

Questions and Answers

M
Madison WatsonJul 30, 2025
Why is my US Praxis Grinder engine gutless and running unevenly?
- D
  Dale SmithJul 30, 2025
  If your US Praxis Grinder engine feels gutless or runs unevenly, it could be due to several reasons: * A clogged air filter: Clean or replace it. * Improper fuel: Ensure you're using the correct fuel, not a 2-cycle oil mix or diesel. * Choke issues: Open the choke valve. * Carburetor problems: Clean the tank, sludge reservoir, and empty the carburetor. * Spark plug issues: Replace the spark plug with the correct type, check the electrode gap, and clean it.
C
Cynthia YoungAug 5, 2025
Why is the belt coming off my US Praxis Grinder?
- M
  michaelgibsonAug 5, 2025
  If the belt on your US Praxis Grinder is coming off, engaging late, slipping, or not staying tight after adjustment, it could be due to several factors: * Misaligned pulleys: Adjust the belt tension. * Insufficient belt tension: Tighten the belt as described in the operator’s manual. * Damage to axle, pulley, or key: Inspect these components for damage and ensure the setscrews are properly tightened.
M
matthew32Aug 10, 2025
What to do if the cutting wheel does not rotate on my US Praxis Grinder?
- L
  lgutierrezAug 10, 2025
  If the cutting wheel on your US Praxis Grinder does not rotate, it might be due to: * Pulleys not aligned: Adjust belt tension. * Insufficient belt tension: Tighten the belt as described in the operator’s manual. * Damage to the axle, pulley, or key: Check for damage and ensure setscrews are tightened. * A worn clutch: Replace the shoes, springs, and/or clutch bearings. * Insufficient engine speed: Ensure the throttle cable is working correctly.
P
Paul WilsonAug 14, 2025
Why does the cutting wheel continue to rotate on my US Praxis Grinder?
- A
  Allen WebsterAug 14, 2025
  If the cutting wheel on your US Praxis Grinder continues to rotate, it could be due to: * Insufficient engine speed: The engine speed is not under 1000 rpm, which is required to disengage the centrifugal clutch. * Not enough tension on clutch shoes: Inspect springs on clutch shoes. If tension on clutch shoes is not enough to pull shoes back, replace springs and clutch shoes.
G
Gregory ArellanoAug 19, 2025
What to do if the parking brake is slipping on my US Praxis Grinder?
- S
  Stephanie WilliamsSep 12, 2025
  If the parking brake is slipping on your US Praxis Grinder, consider these potential causes: * Insufficient brake tension: Adjust the brake tension in the manner described in the operator’s manual. * Damage to the brake rod or lever: Check these components for any signs of damage. * Worn brake pads: Inspect the brake pads for wear and replace them if necessary.
P
Pamela DiazAug 25, 2025
What to do if my US Praxis Grinder engine runs unevenly due to a short circuit?
- J
  James ConradAug 26, 2025
  If the US Praxis Grinder engine is gutless or runs unevenly, and there's a short circuit or faulty ignition unit, contact an authorized service workshop.

Summary

Introduction to the Stump Machine

Use of the Stump Machine

Explains the primary function of the Stump Machine for grinding tree stumps.

Machine Insurance Guidance

Advises obtaining comprehensive insurance coverage for the machine.

Service and Support Information

Details the availability of service and support from authorized dealers.

Serial Number Identification

Guides on locating and identifying the machine's serial and engine numbers.

Safety Instructions: General Use

General Use Safety Guidelines

Provides general guidance on safe operation and understanding the manual.

Important Safety Information

Stresses reading the manual and using authorized service providers.

Stump Grinder Danger Warning

Warns about potential dangers and serious accidents from improper use.

Machine Modification Warning

Prohibits unauthorized modifications to the machine design.

Operational Safety Guidelines

Regulatory Compliance, Training, and Service

Emphasizes following regulations, training users, and using authorized service.

Safe Operation, PPE, and User Restrictions

Covers safe operation, required PPE, and user age/training restrictions.

Operator Focus, Supervision, and Emergency Preparedness

Advises maintaining concentration, supervision, and having help nearby.

Operational Safety and Hazard Warnings

Engine Cooling and Burn Prevention

Warns about hot engine parts and the need for cooling before touching.

Vibration Exposure and Health Risks

Discusses potential health risks from vibration exposure and symptoms.

Machine Condition and Expert Assistance

Advises against using damaged machines and seeking expert help.

Work Area Preparation

Stresses clearing the work area before starting operation.

Pre-Operation Safety and Personal Protection

Pre-Operation Preparations and Checks

Lists essential checks and preparations before operating the machine.

Personal Protective Equipment (PPE) Requirements

Details required PPE like mouth protection, gloves, and protective clothing.

Footwear and Head;Eye Protection

Mandates protective footwear and recommends head/eye protection.

Protective Equipment Details

Selecting Appropriate Protective Equipment

Advises consulting dealers for appropriate protective equipment selection.

Required Personal Protective Equipment List

Lists specific PPE items required for safe operation.

Safe Operating Practices

Safe Operating Procedures and Grade Limitations

Covers safe operating practices and restrictions on slopes.

Operator Fitness, Ventilation, and Footing

Prohibits operation when unfit, indoors, or on unstable footing.

Moving Parts, Body Positioning, and Fire Hazards

Warns about proximity to moving parts, body positioning, and fire prevention.

Post-Impact Inspection, Parking, and Child Safety

Requires inspection after impacts, proper parking, and child safety vigilance.

Transport and Storage Safety

Child Safety and Visibility Awareness

Reinforces child safety and advises caution around visibility obstructions.

Movement and Transport Procedures

Provides instructions for moving and safely transporting the machine.

Storage Guidelines

Outlines proper procedures for storing the machine.

Fuel System Safety

Proximity to Open Flames and Fuel Handling

Prohibits storing or operating near open flames and advises fuel handling caution.

Gasoline Flammability and Fuel System Operation

Warns about gasoline's flammability and provides fuel system operation guidelines.

Maintenance Safety Protocols

General Maintenance Safety and Shutdown

Lists safety precautions for maintenance, including stopping the engine.

Spark Plug Disconnection and Component Checks

Mandates spark plug disconnection and checks component tightness.

Operator Training, Governor Settings, and Safety Equipment

Warns against unauthorized service, altering governor settings, or modifying safety equipment.

Fire Risk Reduction and Maintenance Warnings

Advises removing debris to reduce fire risk and highlights muffler hazards.

Machine Controls Overview

Engine Components and Controls Identification

Identifies external engine parts and their associated controls.

Throttle and Starter Mechanism Operation

Explains the function and operation of the throttle and starter.

Control Specifics

Starter Handle and Fuel Valve Operation

Details correct starter handle usage and fuel valve function.

Choke Control and Air Filter System

Describes choke control for cold starts and the air filter system.

Control Components Details

Air Filter Maintenance and Spark Plug Service

Covers air filter cleaning/replacement and spark plug service.

Muffler Precautions and Oil Dipstick Check

Warns about muffler heat and explains oil dipstick usage.

Fuel and Oil Management

Engine Oil Drainage and Disposal

Describes oil drain location and emphasizes proper disposal methods.

Fuel Tank Capacity and Safe Fueling

States fuel capacity and provides guidelines for safe fueling practices.

Clutch and Brake Systems

Centrifugal Clutch and Throttle Engagement

Explains centrifugal clutch engagement and throttle control.

Brake Operation and Safety Warnings

Details brake activation and warns against operating with a defective brake.

Operating the Machine

Pre-Operation Checks and Safety Preparations

Lists essential checks and preparations before starting machine operation.

PPE, Familiarization, and Guard Checks

Ensures proper PPE, understanding of procedures, and guard functionality.

Work Area Safety and Bystander Exclusion

Ensures a clear work area and establishes a safety zone for bystanders.

Starting the Engine

Engine Starting Procedure and Fuel Valve

Guides on performing daily maintenance checks and opening the fuel valve.

Choke Control and Throttle Setting for Start

Explains choke usage for cold/warm starts and sets throttle for starting.

Engaging the Cutting Wheel

Safety Presence Grip Bar and Starter Handle

Explains the function of safety grip bar and correct starter handle usage.

Throttle Control for Cutting Wheel Engagement

Describes how throttle movement engages the cutting wheel rotation.

Stump Grinding Operation Steps

Positioning, Brake Setting, and Engine Start

Guides on positioning, setting the brake, and starting the engine.

Grinding Technique: Sweeping and Depth Control

Details the sweeping motion and depth control for effective stump grinding.

Advanced Grinding and Shutdown

Stopping the Cutting Blade and Clearing Chips

Instructs on disengaging the blade, waiting for it to stop, and clearing chips.

Normal Shutdown Procedure and Blade Warning

Outlines safe shutdown steps and reiterates the rotating blade danger.

Final Shutdown Procedures

Activating Brake and Closing Fuel Valve

Details activating the brake and closing the fuel valve.

Final Safety Checks Before Completion

Advises releasing the safety bar and confirming blade stoppage.

Maintenance

Maintenance Schedule Overview

Presents a schedule for required maintenance tasks.

Maintenance Safety Prerequisites

Lists essential safety conditions before performing maintenance.

Cyclone Filter Cleaning

Cyclone Filter Cleaning Steps

Provides detailed instructions for cleaning the cyclone filter.

Cyclone Filter Reassembly Precautions

Offers crucial advice for correct reassembly of the cyclone filter.

Air Filter Maintenance

Air Filter Replacement Procedure

Details the steps for cleaning and replacing the air filter.

Paper Air Filter Cleaning Restrictions

Specifies what not to do when cleaning the paper air filter.

Sludge Reservoir and Idle Adjustment

Sludge Reservoir Cleaning Process

Provides instructions for cleaning the fuel system sludge reservoir.

Idle Speed Adjustment and Safety

Guides on adjusting engine idle speed and warns about carbon monoxide.

Ignition System Maintenance

Ignition System and Spark Plug Service

Focuses on the spark plug as the main maintenance item for ignition.

Spark Plug Tightening Precautions

Advises on correct spark plug tightening to prevent overheating or damage.

Cutting Blade Maintenance

Cutting Blade Importance and Wear Assessment

Highlights the critical role of the cutting blade and its susceptibility to wear.

Installing New Cutting Blades

Provides a step-by-step guide for installing new cutting blade sections.

Cutting Blade Sharpening

Cutting Blade Sharpening Preparation

States that blade sections must be removed before sharpening.

Carbide Cutting Teeth Sharpening Steps

Details the specific steps for sharpening carbide cutting teeth.

Brake, Cleaning, and Lubrication

Brake Adjustment and Two Minute Rule

Explains brake adjustment and the time limit for tipping the machine.

Machine Cleaning and Bearing Lubrication

Recommends regular cleaning and lubricating cutting blade bearings.

Drive Belt Maintenance

Drive Belt System and Safety

Describes the drive belt system and safety precautions for inspection.

Belt Tension Adjustment and Checking

Details how to adjust and check the drive belt tension.

Troubleshooting Engine Starting

Engine Wont Start Issues

Addresses common causes and solutions for engine starting problems.

Fuel System and Spark Plug Problems

Lists issues related to fuel systems and spark plugs and their remedies.

Troubleshooting Engine Performance

Engine Gutless;Uneven Running Causes

Diagnoses causes for poor engine performance and uneven running.

Exhaust Color and Ignition System Issues

Interprets exhaust colors and ignition system faults related to performance.

Troubleshooting Mechanical Issues

Belt Related Troubleshooting

Provides solutions for belt coming off, slipping, or tension issues.

Cutting Wheel and Brake Problems

Addresses issues with the cutting wheel not rotating and brake slipping.

Storage & Technical Data

Winter Storage Preparation

Outlines procedures for preparing the machine for winter storage.

Long-Term Storage and Service

Long-Term Storage Preparation Steps

Details steps for preparing the machine for extended periods of non-use.

Indoor Fuel Storage Warning and Service Recommendation

Warns against indoor fuel storage and recommends annual service.

Machine Specifications

Machine Specifications (PRX90 & PRX130)

Provides detailed technical specifications for both models.

Service Journal Entry

Indicates where to record service actions and dates.

Delivery and Initial Service

Delivery Service Checklist

Details the actions required during delivery service.

First 20-Hour Service and Journal

Outlines maintenance for the first 20 hours and service journal entries.

Parts List Overview

Chassis and Engine Assembly Parts

Lists parts related to the chassis and engine assembly.

Chassis and Engine Assembly Diagram

Chassis and Engine Assembly Components

Identifies components within the chassis and engine assembly diagram.

Handle Assembly Parts

Handle Assembly Parts List

Lists parts specific to the handle assembly.

Handle Assembly Diagram

Handle Assembly Components

Identifies components within the handle assembly diagram.

Blade and Shaft Assembly Parts

Blade and Shaft Assembly Components

Lists parts for the blade and shaft assembly.

Blade and Shaft Assembly Diagram