2002 CRF450R rebuild questions

So I picked up this pile of a bike for a couple hundred bucks and I'm starting to get through rebuilding the engine. Looking for some help on anything I should look out for on the 02 model specifically. 

Goal is to do full engine rebuild and have a fun/reliable backup to my 06 crf450r. I only ride trails and dunes, no track. 

Some quick questions, I've heard many people are scared of the auto cam tensioner (especially the early crf tensioners). I do NOT want a manual one, are there any options for a better auto tensioner? (as in a newer crf tensioner that would fit) 

Piston options, would prefer oem. Can I fit/should I fit a piston from a newer crf? What years work and with it fit properly with an oem 02 head with stainless kibble white valves? 

Planning on having the head done by fast heads with stainless valves and already have a brand new oem crank and a clean oem cylinder. Also have an 03 or 04 airbox already and a full yoshi exhaust. Any other hints or issues that I should fix that are specific to an 02 I'd appreciate! I'm plenty mechanically inclined just lacking in knowledge of this particular bike. 


If not manual, you're only option on a cam chain tensioner is OEM but use an '03.

'02 to '08 pistons fit your bike.  I wanta' say in '04 the piston went to 12.1:1.

The '02 airbox is junk with it's flush mount boot and screws that went into the airbox and made it difficult to get a good filter seal.  They fixed it in '03.  They went back to a double lip boot and a steel filter base.  Good stuff.  If that mounts up, that is the box to use. If not, drill out the nubs (I'll get you the bit size) and use the boot, etc, from the '03 airbox.  Seal it up and you're good.

That bike had understeer problems, we found that a good sand tire up front helped.

Edited by HRC27

Here's some pics that you might find helpful if you have to mod the '02 box.  Pics are of a CR250R airbox that I modded for a 500AF.  Honda never corrected the CR250R airbox from '02 to '07.  Maybe not all will apply but perhaps they'll help.

The drill bit size is shown.  11/32".

Hopefully, the '03 airbox is a direct fit for you. :thumbsup:






Thanks for the reply! I already have the 03 box and it fits well, I resealed  the boot to the box on it too just in case. 

Why dont you want to run the manual tensioner? You'll pay less attention to it than you will any other part of the bike, I can guarantee you that. The Auto tensioners were junk, no matter what year they are.

I'd put a crank in it, replace the main bearings with OEM parts if your going to keep it. Cam chain too. And just get an 05 air boot. It had more volume. And piston wise, I'd put a 13.5:1 Wiseco in it. They can be had cheap. They're every bit as good as an OEM and the 02 cam LOVES a little more compression. The 02 also had some really funky jetting in it from the factory. The main jet was way bigger than it needed to be. I think they came with a 185, it only needs a 180 max at sea level. If you go to the 13.5:1 piston, it may want a 45 pilot, but if it's all sealed up well and the head is in good shape, the 42 usually works fine. 

I really don't like manual chain tensioners and at least on my 06 crf450r and my 05 trx450r I've had zero issues with the auto tensioners. Maybe it's because I don't ride hard that I haven't had issues? The bike isn't constantly hitting the limiter then dropping to idle when I'm out. The bike came with a low hour oem tensioner and a manual one, maybe I will just use the manual one that I've got. 

I am a fan of wiseco, are these bikes happy on pump at 13.5:1? Also, just realized while doing some teardown today that it has a stage 1 hotcam in it. I have a feeling I'd prefer the stock 02 cam but the goal is to keep the rebuild simple and use as much of what I've got as possible. 

I will be doing new oem bearings for the crank, very cheap insurance. 

That 13.5:1 piston and Stage 1 hot cam dont play nicely together. If you dont mind kicking like a damn fool to get it started, it pulls pretty hard down low, but Id never recommend it.

The stock post 04 piston is 12:1, which works fine with the stage 1. The OEM 02 Honda cam is very similar to the stage 2 Hotcam, which is why it really comes to life with the 13.5:1 piston.

The other thing you may want to think about is the entire crank, because the rods dont last forever. @280 bucks, it's pretty cheap insurance.

I've got an entire bucket of failed OEM cam chain tensioners. One only had about 4 hours on it. It's up to you, but I dont allow anything with my name it go out of my shop with the OEM tensioner in it. If the customer insists...I pull it after I start the bike for him and hand it to him. Let him stick that shot gun in his own mouth.

But, with a stage 2, or the stock cam, even with the stage1 and the 13.5:1 pump gas is fine because the head has a really good combustion chamber to start with. Another relatively cheap, very effective hop up tip is a later model ignition box. 05-06 were much more aggressive. You can probably get the 05 harness and box cheap on ebay. Adapting the crank and stator connection is a no brainer. The wire colors are the same. The connections are different but not terribly.

I do have a brand new oem crank so we're good there :)

I actually think I have a full spare ignition from my 06 crf but don't whether it works or not. 

Guess it's time now to order crank bearings and gaskets, try to get the bottom end cleaned and buttoned up. Then I'll forge ahead with a piston and shipping out the head for a rebuild. 

Throwing on a fresh pic of the bike since it got some new white side panels. Would have replaced them all but this is supposed to be a relatively cheap bike. Coming up soon should be engine teardown 


Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Similar Content

    • By aminem
      my kill switch is not working and i had bought a new one , My problem is that , i cant disconnect the OEM kill switch . is it a trick to disconnect it !? 
      plz Help
    • By Kevin from Wiseco
      Jeremy Martin Leads the Charge for Wiseco Riders at Daytona Supercross
      Christian Craig Turns in Career Best in 450 Competition
      MENTOR, Ohio (March 13, 2018) – Jeremy Martin showed the way for Wiseco-sponsored riders in Saturday night’s Monster Energy Daytona Supercross presented by Honda. In a season marred by bad luck and misfortune, Martin put together a near flawless ride to earn his first Eastern Regional 250SX Class podium finish of the season.
      Martin qualified eighth for the division’s annual visit to the World Center of Racing, finished fourth in his heat race, and came home second in the 250SX main event, missing his first win of the year by less than a second.

      “It’s Daytona, a real man’s track.” said Martin who sits fourth in points. “It was the toughest race of the year as far as fitness. I had to slow down a little bit, halfway through the main. I was getting close to (race winner) Jordon (Smith) and I was starting to think about where I could make a move on him, then I made some mistakes and he got away from me. Couldn’t quite get close again, but it’s good. We’re on the podium and in contention for wins again. That’s something I haven’t been able to say in supercross in a while. We want to get wins and now we know it’s coming.”
      Martin’s podium was a bright spot, but the rest of the event was rough for the GEICO Honda/Factory Connection squad. RJ Hampshire crashed hard in his heat race and had to be transported to a local hospital. He injured his back and ribs, but shoulder pain left him with the most concern.
      “I felt good on the bike all day,” said Hampshire via his Instagram account. “Had some pretty good speed and my foot just slid off hitting my shifter in those rollers during that heat race. After seeing the pictures from the crash I’m very thankful I didn’t take a shot to my head. I have some fractures in my T3/T4 in my back and ribs. Also have some damage to my lungs which is why I’ll be spending a couple nights in the hospital. I’ll be getting some more checkups this week on the shoulder also.”
      Cameron McAdoo, the third member of the team, was unable to compete at Daytona after being sidelined with a hand injury two races ago in Atlanta.
      Across the paddock, in the premier 450SX Class, Christian Craig got the call to fill in for Team Honda HRC. With the team’s regular riders Ken Roczen and Cole Seely out with injuries, it was up to Craig to carry the load for the factory team, and the upstart rider didn’t disappoint.
      The San Diego native was solid in both qualifying sessions, won his heat race and snagged the holeshot in the division’s main event. After relinquishing the lead to eventual winner Justin Brayton, Craig continued to show he was up for the challenge. The 26-year-old rider raced for second and third for most of the 20-minute-plus-one-lap feature before losing one more spot in the late goings to bring his No. 32 Honda CRF450R home fourth in the final rundown.

      “I had a great week testing with the team,” commented Craig. “They came down to Florida right after Atlanta and I feel like we really improved. Just getting more time on the bike and getting more comfortable was huge. I started off race day feeling really good. My qualifying position didn’t really show it, but overall I was happy with my riding. It’s all about having fun out there, and man, that’s what I did tonight. I was up front in the heat race, fell to third, but then the two guys in front took each other out so I ended up winning. You can call it luck or whatever, but I just put myself in a good position to capitalize on people’s mistakes."
      “I had a good gate pick and some confidence going into the main. I grabbed the holeshot and led for almost the first lap, but [Justin] Brayton got by me pretty quick. I stayed second for quite a while. I just rode my hardest and did my best. Unfortunately, a couple guys got by me so I ended up fourth. The track was so tough. This is only my second time racing Daytona and last year didn’t go well, so I really wanted to get some revenge this year. It’s better than the week before, but man, I was so close to a podium. I just need to keep putting myself in good positions and work on getting better each weekend.”
      Monster Energy AMA Supercross rolls on this weekend when the series visits the “Gateway to the West” for its annual race at the Dome at America’s Center in St. Louis. The 11th of 17 races on the 2018 supercross calendar will be televised live on FS1 Saturday, March 17, beginning at 8 p.m. Eastern Daylight Time, 5 p.m. Pacific.

    • By desert520sx
      I have a 03 450 that I just got and it runs great! I love my bike and am big on preventative maintenance. I have searched the threads on TT and have not found any descriptive threads on how to check valve clearance or adjust them. Just by looking at them, I can see that the intakes need to be shimmed and the exhaust valves can be adjusted quite easily unless one needs to be adjusted differently than the other.
      I tried to do it last night, and lined up the marks on each side to get the piston to TDC to check adjustments and could not get any readings on tolerances on either the intake nor the exhaust. I moved the crank a little bit forward and got a .011 reading on the exhaust valves. I read in a thread that the spec was .011" for the left one and .014" in the right for the auto decompressor. The spec I am using for the intakes is .006" Are these specs correct? :excuseme:The only issue is that the adjustment for the exhaust valves is one and the same. Different from my KTM where you can adjust each valve individually.
      No matter where the cam was on the intake valves, I could not get any readings. Does anyone have a thread, website, downloadable manual, or article on checking and adjusting valves in these beasts?
    • By Eric Schrader
      I am selling my 2007 Honda CRF 450-R which is set up for desert racing (Track/desert). It has an 18" rear tire with a heavy duty setup (see description for details). The bike screams and has a Tokyo mods carb mod with the 10x ignition mapping (currently set to a handlebar switch for smooth power and max power). Gas tank is a 3.2 gallon IMS dry break tank. V4 steering stabilizer included. Precision Concepts suspention, Bike is set up for 6'4" 175lb rider. Zero oil leaks and well maintained using a preventative maintenance method with the best new parts each time. Receipts for all items can be provided. About 20 hours on the rebuilt head. Carb just rebuilt. Starts cold in just 2-3 kicks. 100% reliable bike as long as you turn the gas on.  Current CA Red sticker and original title.
      Expand above to see details
    • By bigg_stevee
      I recently replaced water pump and seal after I noticed that my '02 CRF450R was spilling coolant on easy trail rides. After the water pump swap (which was successful), I noticed the same problem. It's interesting - the bike only spits coolant (I mean a LOT of coolant) after passing anything above 1/2 throttle. The bike makes this weird 'gurgling' noise, like trying to suck through a straw when your glass is almost empty. This is weird because I properly bled/ burped the radiators with coolant, and filled them to normal operating levels. The coolant spills through overflow hose. 
      anyways - I swapped the radiator because I thought maybe the bike was running hot. I purchased oversized radiators, bought a 1.6 radiator cap (with a temp gauge) and bought engine ice. The bike runs very very cool - the temp gauge allows me to see this. Still, the bike shoots coolant out of the overflow after going above half throttle, making the same weird gurgling noise when it does. Bike has all of its power, top end was replaced not too long ago. 
      I'm lost and don't know what is wrong with the cooling system in my bike. How do I make the bike stop shooting out coolant, and stop making the weird gurgle noise??? Any advice would help me!!! Thank you!