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Do you modify aftermarket over-sized fuel tanks? 

We don’t sell the over-sized tanks that have been modified as of right now. We are working on a way to be able to offer modified over-sized tanks.

Can I use the 05-08 CRF450R conversion kit to modify my 02-04 CRF450R chassis? No, our 05-08 CRF450R kit will not work to modify the 02-04 CRF450R. The lower rails on the 02-04 CRF450R are rectangular and the 05-08 CRF450R are square. We don’t currently have any plans to create a kit for the 02-04 CRF450R.

Does CP500 have instructions to do the conversions? Yes, we have created instruction manuals for most of our conversions in a PDF format as well as a videos on our YouTube Channel. Click here to view our conversion manuals.

What if my CR500 engine is NOT a 1989-2001 engine? If you use a CR500 engine from a 1989-2001 CR500, no modifications to the engine are needed. You can also use an engine from a 1985-1988 CR500 engine but three issues need to be considered. 

The earlier engines have a coolant hose that goes from the water pump up to the top back of the cylinder. This hose interferes with the newer exhaust pipe that you will need to use in the aluminum frame conversion. You can simply find a coolant hose at your local parts store that has the right shape to go straight up from the water pump then curves left around the back of the engine. If you search the aluminum frame conversion forums on you will find suggestions for hose part numbers that have this shape. 

Another issue is that the bushings in the rear of the engine case where the swing arm bolt passes through have a smaller diameter on the older engines. One work around that we suggest is to have your machinist bore out the bushing that comes in the older engine case. You should leave the bushing in the case while it is bored, they will be relatively thin when it is done but should fit the swing arm bolt. Provide your engine case and swing arm bolt to the machinist and ask that the bushings be bored out to give a slip fit between them.

One final note to consider is that the cylinder intake is a little different so the carb may be a bit more difficult to get to line up correctly if you use an earlier engine. The intake is longer on the older engines.  This forces the carb to sit further back on the bike and it may hit the shock, depending on which chassis you are building. There are a couple of ways to handle this.  The first way is to shorten the inlet boot so the carb sits closer to the engine. This is just a matter of trimming the boot.  Before cutting it, verify that it will move the carb enough to clear the shock. The second method is to change the angle of the inlet so that the carb moves away from the shock.  This method only works if your reed valve cover on the inlet is metal which most of the older ones are. Check out these photos to see how Ross M. handled it on his 2005 CRF250R conversion.

Do I need to heat treat my frame? It is up to you whether you want to heat treat your frame. We haven’t heat treated the frames that we have modified and have never had any issues. This is a decision you would need to make. I would recommend asking others that have completed a conversion to see what they have done and how it has worked for them.

I am having issues getting the Y-piece to align perfectly, it is slightly off. What did I do wrong? How can I fix this? Because there are so many variables on how the conversion is completed (where exactly the frame is cut, where the headstays are placed...etc) you may need to heat/bend the lower frame rails to get the bolt holes of the Y-piece in the correct location to line up with the front mount of the engine. Also, it is typical for the frame rails to be too wide or too close together to line up with the Y-piece. This is a typical "problem". To get the lower tubes to align with the Y-piece properly, they may need to be heated and bent slightly. To adjust lower frame rail alignment with the Y-piece, apply pressure near the cut end of the tube in the direction you need the tube to move while heating the tube in the area that you want it to bend. Apply light pressure while heating. Be patient! It can take 15 minutes or more of heating to get it hot enough to bend. You want it to bed primarily due to softening instead of the force you are applying to avoid stresses in the tube once it has cooled back down.

Which chassis’ are the easiest to modify? Each conversion does have a different difficulty level. In our experience, the 02-07 CR250R, 04-05 CRF250R, and 06-09 CRF250R chassis’ are the easier conversions to complete.

Can I send my frame to CP500 for the modifications and welding to be completed by CP500? We are no longer offering in house modification and welding services. We recommend reading our conversion manual completely and talking to a experienced welder for welding services.

Which type of welder do you recommend or can I do it myself if I am familiar with welding? We recommend finding an experienced aluminum TIG welder. Even if you know how to weld aluminum we strongly recommend that you have an experienced professional welder do the welding. Make sure he is a skilled TIG welder (MIG welds are ugly) and ask him to show you some of his work on aluminum. Aluminum is not easy to weld unless you have a good deal of experience and the right type of TIG equipment (the little $1500 TIG you bought for hobby work in your garage will probably not do very well.) Welding usually only costs about $70-150 when done by a professional. That will be the most worth-while money you spend on this project.

Is there anything I should know before taking my frame to the welder? It is least expensive if you complete all the modifications before going to the welder because it will be less expensive to have him do all the welding at once.

I want to do a 02-07 CR125R (CR500 Engine) conversion, is there anything I will need to know? Yes, below are some facts about this conversion.

  • This conversion makes a very fast and light bike that handles extremely well.  
  • The CR125 chassis is almost the same size as the CR250 chassis, but it has a steeper fork rake for better tight track handling. 
  • The CR125R chassis are cheaper and easier to find.  You can usually buy a whole bike then sell the engine, carburetor, exhaust, and electronics on eBay to recover most of the cost of buying the bike.
  • The swing arm bolt and spacers are the perfect width, so you don't have to modify anything with the rear engine mount or swing arm spacers.
  • The gas tank has a nice cavity in the bottom of it in just the right place to clear the spark plug and coolant hoses, so you don't have to modify the fuel tank at all.
  • The only thing you have to do to make the airbox work is to replace the rubber boot with a boot from a 2000 CR250R.
  • This conversion does require a significant pipe modification to allow enough clearance for full compression on the front wheel.

I want to do a 02-07 CR250R (CR500 Engine) conversion, is there anything I will need to know? Yes, below are some facts about this conversion.

  • This is the easiest chassis to convert to accept the CR500 engine.
  • You don't have to move the lower engine mounts.
  • Uses the existing airbox and boot.
  • Replace the swing-arm spacers with spacers from a 02-07 CR125 to make the sprockets line up perfectly.

I want to do a 04-05 CRF250R/06-09 CRF250R/04-12 CRF250X (CR500 Engine) conversion, is there anything I will need to know? Yes, below are some facts about this conversion.

  • These chassis are fairly straightforward to convert and offer newer and better performing chassis designs.
  • The airbox does need to be modified. You will need the airbox from the chassis as well as a boot and the metal airbox frame from a 1998-1999 CR250.
  • The fuel tank needs to be modified.  The bottom of the tank must be pushed into the tank to make clearance for the spark plug and wire. We are now selling modified tanks. Check out our store for details.

I want to do a 05-08 CRF450R/05-12CRF450X (CR500 Engine) conversion, is there anything I will need to know? Yes, below are some facts about this conversion.

  • These chassis’ hold the large CR500 engine well and again offer newer generations of chassis.
  • The head stays/brackets on the CRF450s are different than the CRs and the CRF250s. There is no mount on the back bar of the frame for the head stays. The kits now come with a shaped head stay block and head stays that can be used for the build. Just weld the block in the right place and attach the head stays.   
  • The airbox needs to be modified. Our 04-05 CRF250 adapter works well.  You may need to trim it a bit for fit and finish.
  • The fuel tank needs to be modified. The bottom of the tank must be pushed into the tank to make clearance for the spark plug and wire.

Can't find the answer to your question? Feel free to send us an email