Rex's Tech Support

Rex's Tech Support

Rex's Tech Support


For us quality is paramount so along with carefully selected products from other suppliers, we offer our own range of products manufactured here in the UK, products you can depend on, from a simple voltage warning light to a complete charging and ignition system. All of our electronics are subject to on going quality testing in our own workshops to ensure ease of use, first class performance and long life. As designers have the equipment and knowledge needed to fully check and develop systems and system components. Should you need help with one of our products you will find a range of helpful guides and advice sheets below* If you need further assistance e-mail  the technical team and one of our technicians will be able to answer your enquiry. To avoid mistakes being made in the workshops our techs are not immediately contactable by telephone. 

(New) e-mail address:

We are one of the UK's premier motorcycle generator rewinding and electrical repair resource, our workshops offer a unique and wide range of specialist and bespoke electrical and engineering services for customers around the World. If you have a question or would like a quotation please e-mail us on the address above. A brief description of the fault you are experiencing is all that is required to get a fast estimate of costs, feasibility and what's involved in a repair. Our techs will ask you if they need detailed accounts. 


Pricing guide for rewinds & repairs (click on picture, downloads PDF guide)



Help sheets, articles & advice - free to download stuff.

Below is a selection of trouble shooting guides, useful background information and fitting guides that you may find helpful. The documents are free to download.

Our publications must be used in conjunction with the manufacturer's workshop manual and do not override any safety precautions the machine's manufacturer give. Some documents may go in to greater detail through our experience of in-depth strip down of components, we provide this data to make fault finding more accurate.

Our fitting guides do not set out to teach you technical skils,  instead guide you through a process that is either poorly explained or not covered in the shop manual. We give many tasks a technical rating to help you decide if you will need professional help:


Good working knowledge and technical understanding are necessary

A basic mechanic's tool set is all that is normally needed

Suitable for the home mechanic who is happy doing routine servicing such as oil changes and minor adjustments following the manual.


An in-depth working knowledge and good technical skills are required.

A good tool kit and some special tools will be needed

Suitable for those who can carry out all servicing and many repairs such as bearing replacement, top end rebuilds plus being able to use engineering tools such as micrometers or a DTi.


Expert level, good problem solving, extensive knowledge and experince.

Comprehensive tooling, possibly access to an engineering shop.

Suitable for those who could fully strip and rebuild an engine, fabricate new parts from raw material or experienced engine tuners.


Technical Publications & Useful Information

Feb 2018 

We've noticed that some guides were written quite sometime ago, we are up-dating many of the testing guides with more concise information to aid the professional mechanic and home mechanic alike.

Increasingly we are being given voltage readings taken when kicking the bike over. These are meaningless tests as there is no way of telling a good reading from a bad one. This is no way to test a stator. Such tests are not approved so may invalidate warranties on new parts - something not mentioned on the forums! Worse, some systems generate surprisingly high voltages, even an un regulated alternator can give an extremely nasty belt as it may be producing 100 volts or more with the engine running. Again something not considered by those who give poor advice with no thought of the safety of others. The reason manufacturer's don't tell you to do such testing as it can expose you to dangerous voltages!

We have improved on the information given in the workshop manual in all testing guides dated 2018 on, we are getting to the others and will be adding more very soon!

The tests we prescribe will not invalidate warranties and will keep you safe.

Important Service Bulletins for PME Products

XL5 & XR5 - Problem with non Genuine Honda manuals

Connecting Euro H4 Headlamp plugs to Yamaha XT/DT wiring

General Information

Rex's "Dual Power" System explained

Capacitor discharge ignition - how it works and what the shop manuals don't tell you.

Battery eliminators. What are they and how do they work?

DT250/360/400 12 Volt Conversions

Before you decide to purchase our kit, we explain what's involved here:

DT, IT, & MX 250/360/400 12 volt conversion information page

Useful background information:

Yamaha Service Bulletin M6-058

Pre 1977 wiring DT250/360/400 - Generic example

DT250 wiring diagram

DT250E wiring diagram

DT360 wiring diagram

DT400B wiring diagram

DT400E wiring digram

12v Conversion troubleshooting guide

XT250/500 12 Volt Conversion Trouble Shoooting

XT 12v conversion trouble shooting guide

TY250 12 Volt Kit/Lighting Upgrade

Fitting guide

Standard TY250 Wiring Diagrams

TY250 - 434

TY250 - 493

TY250 - 516


Notes on Setting 2-stroke Ignition Timing & Timing Curves

2-stroke ignition guide: Basic information.

How to set up & adjust flywheel CDi ignitions (2-stroke) using your own timing marks


Yamaha Ignition Trouble Shooting Guides

Yamaha SR400/500 Ignition Trouble Shooting Guide

XT500 G & H Factory Fitted CDi Trouble Shooting Guide

SR500 Low Speed Pulser Adjustment (Yamaha Publication)

XT500 & SR500 Oil Pressure Check (Yamaha Publication)

DT/IT/MX/YZ 250/360/400 Ignition Trouble Shooting Guide


Kawasaki Trouble Shooting Guides

KH400 with factory CDi trouble shooting guide


Honda Trouble Shooting Guides

CB250N & CB250T Testing the generator for ignition faults


Suzuki Trouble Shooting Guides

Suzuki SP/GN400 Ignition Testing Guide


Rotax Engines Trouble Shooting Guides

Rotax Ignition Testing (CCM, MuZ and MT350 & 500 models)


British Bikes

Lucas Rita Tests and Checks

Connecting Twin HT Coils (positive & negative earth)

Fitting an electronic dynamo regulator - PME DYNA-REG Fitting Guide

6 Volt Solid State Regulator Rectifier Unit - 2 & 3 Wire Alternators

British bike alternator information, upgrades and options

Lucas wiring diagrams for many common British Bikes equipped with an alternator

Improving output from Lucas altertanators & testing

Lucas E3L, E3LM & E3N dynamo manual

Options on converting 6 Volt Lucas Dynamos

Fitting Guides

All Rex's fitting guides must be used in conjunction with the OEM bike manufacturer's manual for that model. It is the responsibility of the person fitting the parts to ensure they have the correct technical data, tooling and test equipment. No part of any PME guide over-rules any safety precaution given in an OEM manual.

"RMK" Electronic Ignition Kit Fitting Guides

Background Information:

Dual Power - Why we use two source coils

TY175 Electronic ignition: RMK-1 

TY175 Electronic ignition fitting guide

TY250 Twin Shock Electronic ignition: RMK-3 

TY250 twin shock electronic ignition fitting guide

TY250 Mono Shock Electronic ignition: RMK-5 

Coming soon

Source Coils 

You will need a 40 watt soldering for points magneto and lighting coils. Order number 40W-SRN. Note this comes with UK plug. Please read through the guides and check you have all the tools and consumables you need.

SC-1 (Kawasaki KH400) Fitting guide

SC-2 (Suzuki GT250/500) Fitting guide

SC-3 (XT500 Points Magneto source winding) Fitting Guide

SC-4 (XT500 Electronic ignition source winding) single source coil kit fitting guide

Lighting Coils

LC-1 XT500 Lighting Coil

Setting Generator Clearances

TZ & MX Internal rotor type generators

Generator clearance adjustment KH400 & Suzuki GT250/500

Wiring Looms (Non Standard)

NEW TT5 Wiring loom Pre-sale information.

Guide to help choose parts to build up your 'bare bones' TT500 or XT500 wiring system.

TT500 Wiring Loom Fitting Guide

Indicator Fixes

LED Indicator Fix 1 - Incorrect Flash Rate

LED Indicator Fix 2 - All 4 Indicators Lighting Up At Once

Regulators & Rectifiers

Fitting an AC regulator

Dynamo Regulator Fitting Guide

6 Volt solid state regulator rectifier

12 Volt regulator rectifier (including converting a 6V alternator to 12V)

12 Volt 3 phase solid state regulator wiring

Japanese bikes

12 Volt single phase

12 Volt 3 phase


CDi Units - (where wiring is different from standard)

Kawasaki KX125, KD175, KE175, KX250 CDi unit fitting guide


H4 headlamp to Yamaha wiring Guide 

Speed Shop Custom Wiring Diagrams


Stripped down looms for cafe racers, specials and track bikes. Be aware that building a wiring loom takes considerable time and experience. We do not offer tehncal help on free to down load schematics.

XJ600 Race bike wiring 1984-92 models.

SR500 Stripped Down Wiring Loom

SR500 Stripped Down Loom With Indicators

SR500 Ignition Only (Complies with UK Day Light Only MOT Regs)

Corrected Yamaha XT500 American G & H wiring diagram.

The commonly published diagram for the G & H models contains several errors. This version has been re-drawn and correct by Dan Duncan of the XT500 forum and is published here with permission.


Standard Wiring Looms

RD250 E Wiring Diagram

Suzuki GSF600 Bandit 1996

Suzuki GN400 Wiring Diagram

Suzuki GT250A Wiring Diagram

Kawasaki KLR650 Wiring Diagram

Harley MT350 Wiring diagram

Yamaha XT500 Late type

©Powder Mill Electronics Ltd  2010 - 2018. All rights reserved. These documents may not be republished by any means without our written consent. This includes re-posting on internet forums.