The Trailworthy Honda CR85R Project Bike

There are many in the off-road industry who don’t have a good trail bike to ride. Why? There are plenty of great new and used trail bikes out there on the market. KTM has a good number of off-road bikes, and of course, with years of CRFXs and WRs out there, we know there are a multitude of choices available.

However, there is still a large void for those trying to get their little man (or girl) out on the trails riding an appropriate bike. Those who are 10-14 years of age can find themselves too small for – and perhaps a little intimidated by – a heavy, full size bike (like a KTM 150 XC, KTM 200 XC-W or CRF250X). So the real options currently available are the TT-R125LE, the CRF150F and the CRF230F. These bikes are great for entry-level riding; however, they do not lend themselves well to serious single track. They are wide, weigh a lot and have low ground clearance.

We would love to have a good trail bike like a CRF250X or a KTM 200 XC-W in a big wheel CRF150R chassis. Until then, we are left wanting. For those with kids in this category, the time in this “void” is relatively short, so we can either make do with a TT-R-type bike or get them on a lowered full-size trail bike sooner than they really should.

The Solution

The CR85R on the TrailWe decided to create our own solution – to convert an old MX bike into a trailworthy machine to hold off our young trail master for a year or two. We started with a good, cheap 2005 Honda CR85R. First, we needed to add larger wheels (supermini) to the bike, and we were able to find a swing arm and wheels via Craigslist. With the larger wheels in place, we had Race Tech set up the suspension to match it and make a good trail setting.

Making It Rip

For the motor, we wanted the bike to be fast enough to handle tougher trails and hills but also be a bit easier to ride than a full motocross CR85R. The first step to do that was to add a flywheel weight from Steahly Off Road. This makes the bike less “pipey” and gives it a bit more chug. We also had TMR mod the cylinder and head to help bring out the full potential of the CR85R. A Vertex Piston from Italy was used for reassembly with new Cometic gaskets. With the VForce3 reed cage added and the FMF pipe and Turbinecore 2 silencer installed, we looked at the jetting. The bike ran very well with close-to-stock jetting and only seemed to need the needle leaned out at higher altitudes.


To be good on the trail, there are some crucial things we needed to look at. First of all, all young riders are going to crash and drop the bike. Good wraparound handguards (Tusk D-Flex) are a must so there is no damage to the levers or throttle tube when things get tough. The ability for Dad to easily grab and lift up the bike can also be a huge help. Tugger has great lift straps for the front and rear of the bike. Being able to go on long rides is a must, and the large IMS tank takes care of that. With the IMS fuel tank, the CR85R can stay with the big bikes all day long on a tank of fuel. The IMS larger Pro-Series pegs also allow for better grip and more confidence while staying planted to the bike.

Keeping Your Cool

On the trail, it can be very common to overheat. For MX bikes that do not come with overflow catch cans, it can be a bad situation. We added an overflow bottle from Motion Pro; it was a great solution. It’s usually possible to find a good spot for something like this.

Finishing It All Up

We added new Polisport plastics, an Attack Graphics kit, Renthal bars and Renthal sprockets. They all helped to finish off a great trail bike.

The CR85R on the Trail

Does It All Work Well?

Well, of course! We would rather that one of the big five bike manufacturers provide a purpose-built trail machine to fill this void, but until then, this bike is a great option. The bike is easy to start and light enough for a growing rider to pick it up and move it around when stuck on the trail. It has the power it needs, but the main downside is that since it is still a motocross bike merely converted to trail use, it doesn’t have the type of power band best suited for good trail riding.

Check out this video to see more about the bike.


Interested in doing something similar with a bike of your own? We have the products included in this build listed below.

Tusk D-Flex Handguards Renthal Aluminum 7/8” Handlebar Renthal Factory SX Crossbar Pad Renthal Dual Compound Grips – Half Waffle
Tusk D-Flex Wraparound Handguards Renthal Mini 784 Bars Renthal Crossbar Pad Renthal Grips
VForce3 Reed Valve Steahly Heavy Flywheel Weight Vertex Piston Kit Standard Cometic Top End Gasket Set
Moto Tassinari VForce3 Reed Valve Steahly Off Road Heavy Flywheel Add-on Weight Vertex Pistons Complete Piston Kit Cometic Top End Gasket Kit
Klotz R-50 2-Stroke Oil IMS Fuel Tank Uni Air Filter Renthal Works Chain
Klotz Synthetic Lubricants R-50 2-Stroke Pre-Mix IMS Large Fuel Tank Uni Filter Two-Stage Air Filter Renthal Works Chain
FMF Gold Series Pipe, “Fatty Moto” FMF Turbinecore II Silencer Renthal Front Sprocket Renthal Rear Sprocket
FMF Racing Fatty Pipe FMF Racing Turbinecore 2 Silencer and Spark Arrestor Renthal Front Sprocket Renthal Rear Sprocket
IMS Pro-Series Foot Pegs CV4 High Pressure Radiator Cap Motion Pro Coolant Recovery Tank Works Connection Aluminum Radiator Brace
IMS Large Foot Pegs CV4 High Pressure Radiator Cap Motion Pro Coolant Bottle Works Connection Radiator Brace
Pivot Works Steering Stem Bearing Kit Pivot Works Linkage Rebuild Kit Dunlop MX51 Geomax Intermediate Terrain Tire Dunlop MX31 Geomax Soft Terrain Tire
Pivot Works Steering Stem Bearing Kit Pivot Works Linkage Kit Dunlop MX51 Front Tire Dunlop MX31 Rear Tire
Polisport Complete Replica Plastic Kit Works Connection Tach/Hour Meter Works Connection Tach/Hour Meter Mounting Bracket Works Connection Factory 4 Stand
Polisport Plastics Works Connection Hour Meter Works Connection Hour Meter Mount Works Connection Factory 4 Stand
Highline Recreation Tugger Lift Strap, Front Highline Recreation Tugger Mini Lift Strap, Rear Attack Graphics Custom Pre-printed Background Graphics Kits
Front Grab Strap Rear Grab Strap Attach Graphics Custom Graphics Kit

Other Mods

There were a few things that we had to outsource to get done at the level that we needed.

Tom Morgan Racing
We had a cylinder porting and head mod done by Tom Morgan Racing.

Applied Racing
Applied Racing’s CRF150R dual piston front brake carrier replaced the stock single-piston caliper with the dual-piston caliper from the larger CRs for increased stopping power. This required a Honda 250/450 caliper assembly as well. This carrier was designed for use with a Motomaster oversized 260mm front rotor.

Race Tech
Race Tech revalved the suspension to match the larger wheels and swingarm.

MotoSeat custom-made us a seat cover. They also cut the seat down slightly so we could get a little bit more distance there. It allows a younger rider to touch the ground just a little bit easier.

The CR85R on the Trail


This bike was built for a rider in the 10-to-14-years-old range. When our test rider first tried the bike, it was a new experience. He still preferred his TT-R125LE and the smoother ride afforded by its 4-stroke engine. However, once he got used to the CR85R, he has preferred its power increase and better ground clearance. Since then, it has been a huge hit.


Curious how this bike held up? Check out this follow-up video after some significant hours were spent on the bike.

What do you think of this trailworthy CR85R? What other mods have you seen to create an ideal trail bike to fill this void? Let us know in the comments!

Technician Disclaimer

By Jay Clark