Wrench Rabbit Yamaha YZ125 Engine Rebuild Kit

By Michael Allen:

Although one of the main perks or being a part of Keefer Inc. Testing is getting to ride the latest and greatest bikes, there are times when you need to have your own bike. I needed my own bike because I was going to race the Los Ancianos Tecate Enduro that is run in Mexico and I needed to be able to show proof of registration. After a lot of looking around I found the perfect bike, a somewhat abused 2006 YZ 125. I raced it for two years in Mexico and would randomly ride it here and there when I wanted to feel like I was going fast. Here is where the embarrassing part comes in, this last winter we had an abnormal amount of rain in California, which was great, but I was admittedly a little lazy in the maintenance department.  I figured “it’s wet, how dirty could my air filter be getting”? Well after not checking my air filter for about three rides, my $1,800 Yamaha YZ125 decided to come to a quick stop in the middle of a snowy trail ride. As I was on the pipe climbing a sandy canyon the wheel locked up and I came to a skidding stop. I luckily was within pushing/coasting distance back to the truck, but when I got there and pulled the seat off, I immediately knew what happened and felt really stupid. You see when I got the bike I did the current plastic re-style kit from Polisport and when I re-installed the air box, apparently I didn’t do a good job with the hose clamp (that holds the air filter cage onto the air box). To my surprise my air filter and cage was just sitting in the bottom of the air box and I had been sucking dirt into the engine for who knows how long. Fail!

Needless to say when I tore the engine down there was grit everywhere from top to bottom. I knew if I wanted to do it right the whole engine would need to be rebuilt, but I also knew that replacing bearings, seals, gaskets, a top end, and crank with OEM parts would cost more than I purchased the bike for. After talking to Kris he mentioned that Wrench Rabbit sells complete engine rebuild kits and from what he remembered they weren’t all that expensive. After that conversation with Kris, I reached out to them and got the ball rolling on rebuilding my little 125.

The Wrench Rabbit kit (Part Number WR101-081) really does come with EVERY bearing, seal, and gasket you need to do a complete rebuild on your bike. To be completely honest I had done a bunch of top ends on previous two-strokes, but this was my first time splitting cases and doing my own rebuild. I took it slow and really tried to do good job of keeping everything organized when I took it apart. Upon disassembly it was then that I realized that it wasn’t as scary as I imagined it would be. When the engine was torn down I found that my issues were a scored piston (luckily the cylinder wasn’t bad enough that it needed to be re-plated or replaced), a blown out rod bearing, and main bearings that were ready to come apart at any time. The Wrench Rabbit kit comes with a brand new crank/rod from Hot Rods already assembled as well as new main bearings to go with it. In the past I had been scared to use aftermarket engine parts, but the quality of the Wrench Rabbit parts were very impressive and every part fit just as good as the factory parts that came out of the bike.

As I buttoned up the cases and slid the cylinder onto the new Vertex piston I was pretty excited to get my 125 running after looking at it sit in the garage for the past five months. I slapped the engine back into the frame at about 11pm and was so excited to get it running I ran to the gas station that night to mix some gas and wake up my neighbors. The child like smile on my 32 year old face said it all when it came to life on the third kick and I was able to take it down the street for an initial heat cycle a midnight. After a few more heat cycles I was able to moto down and I’m happy to report that my 125 runs better than ever. In fact, the rebuild is done just in time for me to head back down to Mexico in about a month for more trails, tacos, and beer.

I learned three main things from this whole process… The first lesson is to never be lazy about maintenance, no matter how well you think you know your bike. The second is to not be scared to do your own bike work, even if you have never done it before. With an OEM Owner’s Manual and a proper set off tools, you are more capable than you may think. I did go out and buy a Motion Pro case splitter (Part # 08-0605), a Motion Pro flywheel puller (Part # 08-0026), Motion Pro bearing driver set (Part # 08-0551), and some Yamabond Liquid Gasket (Part # ACC-BOND4-MC-00) to make the rebuild a little easier  The third and most important is to not shy away from quality aftermarket parts. After adding it up, I saved over $350.00 by using Wrench Rabbit parts. OEM parts are great, if you can afford it, but finding quality aftermarket parts are like riding a unicorn and by the looks and sound of my YZ125, I have found Pegasus. With all the parts supplied, the Wrench Rabbit kit only set me back $514.95. Reason #158 why I love two-strokes! So if you have either a worn out engine (no matter two or four stroke), or in my case are an idiot and blew your bike up because of negligence, give Wrench Rabbit a try, you won’t be disappointed. Also keep in mind that Wrench rabbit doesn’t just have kits for engines, in fact they offer replacement parts for all facets of rebuilding a motorcycle.  You can email me if you’re interested in ordering some parts and getting the Keefer Inc. discount. michael@keeferinctesting.com.

OR YOU CAN CLICK ON www.wrenchrabbit.com TO SEE WHAT PARTS YOU MAY NEED.

Yamaha YZ125 Wrenh Rabbit Kit Part Number WR101-081 ($514.95) includes-

• Vertex piston kit (standard compression piston, rings, pin and clips).

  • Premium quality Vertex piston.

  • Complete set of nitride coated or chrome-plated piston rings.

  • Fully case-hardened wrist pin.

  • Circlips.

• Hot Rods heavy-duty crank (stock stroke – includes wrist pin bearing for two strokes).

  • Factory assembled and trued to O.E.M. specifications, Hot Rods cranks will meet or surpass the O.E.M. in performance and durability.

• Hot Rods main bearing / seal kit.

  • Like other Hot Rods products, these main bearing and seal kits are built to the highest quality standards that meet or exceed those of the O.E.M.

• Hot Rods transmission bearing kit (includes transmission bearings, output shaft collar and sprocket lock washer).

  • A must-have for any new transmission or engine case installation or repair.

  • Includes trusted Hot Rods bearings for the primary and secondary shafts of the transmission.

  • Also includes the special needle bearing for the shift drum and the output shaft collar and washer (where applicable).

• Hot Rods counter balancer bearing kit.

  • A must-have for any new counter balancer or engine case installation or repair.

  • Includes trusted Hot Rods bearings for the counter balancer shaft of most modern 4-stroke engines (where applicable).

• Hot Rods water pump bearing and seal kit.

  • Hot Rods water pump repair kit includes water pump cover gasket or O-ring, water pump shaft bearing(s), and seal(s) to repair a leaking water pump seal and/or a failed bearing.

  • Precision micro-bearings provide O.E. quality and durability.

  • High pressure / temperature mechanical and rubber seals.

• Hot Cams cam chain.

  • Replacement cam chain.

  • Meets or exceeds O.E.M. specifications.

• Vertex complete gasket kit, including seals and O-ring kit (covers top and bottom).

Tools For The Job: 

• Motion Pro Case splitter Part # 08-0605

• Motion Pro Flywheel puller Part # 08-0026

• Motion Pro Bearing driver kit Part # 08-0551

• Yamabond gasket maker Part # ACC-BOND4-MC-00