YX 125cc Engine – Electric Start (Manual) – Kit 1


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The new generation of 125cc engine from the YX factory. With the factory fitted big valve upgrade and aluminium cylinder, the factory claim 12bhp at the flywheel from this engine. The YX 125 engine is one of the most reliable learner legal horizontal lay flat engines on the market.

Being the top spec 153fmi engine model, this engine has the extra power from the bigger valves, fitted as standard with the YX140 type alloy head, alloy cylinder barrel, wide ratio gearbox for increased top speed and long term reliability also complimented with easy starting with both kick and electric start.

Why are our engines different to other sellers engines? 

Other seller engines-

Engines are sold boxed, un-opened and unchecked and with no adjustments carried out which if left unchecked could cause potential problems and furthermore serious damage.

Our engines- 

We carry out a full inspection to ensure all components are present and make all adjustments  "Which are always required" to timing and valve clearance settings. We drain the transport oil which is not suitable to use for running your engine.

What does this mean for me?

This means your engine can be fitted straight into your bike with the peace of mind that a professional technician has set it up to run perfectly for its breaking in period, which is the most important point of the engines life....... just add good quality 10w/40 semi synthetic motorcycle oil and away you go.

Engine can be used to upgrade the following-

Pit Bikes, Honda Dax, ST, SS, CUB, Monkey, Z50, Mini Trail, Chaly, ATC 70, ATC 90, the list goes on and on!

Comes complete as follows:

-Complete Genuine YX 125cc engine 12 HP
-4 speed manual gearbox - 4 up (N-1-2-3-4)
-Removable side cases
-Output sprocket

Complete with:

-Starter motor wire
-Inlet manifold with spacers, gaskets and bolts
-Kick start
-Gear selector lever
-Mikuni VM22 (26mm) carburettor
-Twin foam 2 stage air filter
-Performance red ignition coil
-5 pin CDI
-Wiring loom
-Kill switch
-E start switch
-12v rectifier
-Starter relay
-Key ignition
-CNC oil cooler with oil cooler adaptor plate

These engines are 440mm long, 280mm wide. Top mounting is 93mm wide with an 8mm bolt hole, Rear mounting hole is 82mm wide with an 8mm hole. They also have the 4 M8 threaded holes on the underside which are 88mm apart left to right and 44mm apart front to back, These are to hole centres.

Please note: All our engines need to go through a braking in procedure.

Please follow the engine installation guide we include as this will helps you in setting up and getting the most from your new engine.

Here is a message from a happy chappy who purchased one of the Honda clone engines for a near 2000 mile European trip.

Just thought I’d let you know, I have just completed an 8 day tour of Europe on my Honda Cub fitted with one of your YX 125 4 speed engines. It ran perfectly for the 1,939 miles of the trip. Speeds were mainly between 43-50mph. It is still as quiet as a mouse and used no oil (I did have an oil cooler fitted). Countries visited, in order, were :- France, Belgium, Luxembourg, France, Germany, Czech Republic, Germany, Austria, Germany and finally France. Was I worried it wouldn’t make it…YES, am I worried now….No. Another YX engine also made it, one of your 150 manual clutch jobbies. Thanks for a great engine…Bogger”


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