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2003 CRF450R Complete Rebuild

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Posted (edited)

I finally got some time to tear into the motor of my bike,  a bit of history I bought the bike cheap after it was dropped in water running.  The previous owner never was able to get the bike started again.  I broke the motor down and inspected everything.  Here's what I am thinking of doing, i'd appreciate any input or guidance on something that I might be overlooking. 

- Complete bearing replacement, Crank bearings look fine, some on the transmission side are a bit rough, but since it's split I will replace all of them. 

- Current Crank is within serviceable limits, no play up/down.  slight side to side, within limits.  I do not know hours but the internals aren't beat up so i'm figuring it's not super high hours. 

- Cylinder hone & inspection by machine shop.

- Clutch looks fine.

-2004 OEM Piston Kit, slightly higher compression than 2003.

-2008 Big Bore Thumper Complete Head - Head is pretty nasty, its worth it to me to spend a bit more $$ and have the better heads that will last longer.

- 1 new shift fork, the 4L Shift fork was bent pretty bad, all gearing was OK.

- Manual Cam Chain Tensioner.

-14 Tooth Front Sprocket - This bike is street legal, i'm not doing anything over 55 mph. 

- Engine Ice with higher pressure Cap. 

So am I missing anything? Do I have the correct years for Piston & Heads? 

Thanks in Advance!

Edited by CThumper
Updated List of Parts to Replace

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I wanted to add, I won't be racing this bike.  I'd like to set it up for trail/sand dune riding with some calm (less than 15 min per trip) street time.  I live near the beach in FL and thought this would be a fun bike to ride around the beach roads near me and hopping over to friends houses, no roads over 45 MPH.  I think the sprocket & engine ice/high pressure cap will help.  Is there anything else you'd recommend? 

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I wanted to add, I won't be racing this bike.  I'd like to set it up for trail/sand dune riding with some calm (less than 15 min per trip) street time.  I live near the beach in FL and thought this would be a fun bike to ride around the beach roads near me and hopping over to friends houses, no roads over 45 MPH.  I think the sprocket & engine ice/high pressure cap will help.  Is there anything else you'd recommend? 


Just a couple things, as far as a street legal bike goes, not entirely sure why you would want to up the compression ration and go with an 08 head. Realistic not going to gain any power or any more longevity out of either of those. Higher compression just means shorter service intervals and as far as the head goes, I’ve owned many 02 and 03 450r and the heads were never the problem. The problem was the soft titanium valves. The 02 had a terrible airbox design that was prone to leaking where the air box joined to the air boot which did not help the valves. That issue was corrected for the 03 model year but titanium valves were still used. People that didn’t clean their air filters properly contributed to the notion of the 03 having bad heads which just isn’t true. You can put stainless valves in a 03 head and have no issues with the head or valves. But the heavier valves does take a little bit of power away. It just seems very unnecessary to really do any major engine modifications like that considering the 03 made 55.7 horsepower and can be opened up to 60 horsepower mark with an exhaust, cam, and some jetting. In comparison, the 2018 CRF450R is making 59.3 horsepower and weighs in almost 30 pounds heavier. I’d also look into installing a fan set up to go with your engine Ice.

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I figured if it's an OEM piston (2004) it would be a similar service life I could do the 2003 but i figured I'd like a bit more power.  From what i've read some people say it makes more, some don't. I could go with the 2003 piston if it doesn't add that much power it might be cheaper. 

As far as the heads.  So could I expect similar reliability say sending the head to MX Time and having them redo the head (cut Valve Seats, SS Valves)? that is $150 cheaper.  I guess I could go with that route, maybe use that $$ on an exhaust. 

Is there an airbox fix that I could look into or just a better air filter? 

 

Thanks for the input!

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Sorry to say Big Bore Thumpers is out of the 08 head. No ETA on restock. I finished rebuilding trans, bottom/top end today. I sent the head to Pro 1. Charlie did a good job replacing the valve seats, cutting new ones and replacing the valve guides. Be careful honing the cylinder. If the cross hatch is still good I wouldn’t. I used to hone the cylinder every top end until the Nikasal started flaking off.

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I attached a few pictures of the cylinder, the vertical marks don't feel like scratches, I can't feel anything with my fingernail.  Maybe it its OK to skip the hone? I just want to do everything right while I have it broken down. 

I'm going to call MX Time tomorrow or Monday to see if they can do my head for me.  they are ~$150 cheaper than Big Bore Thumper.  Can I expect the same reliability out of my rebuilt head with SS Valves as Big Bore Thumpers? 

Thanks all! 

-Carl

IMG_20190106_003432820.jpg

IMG_20190106_003359322.jpg

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On 1/5/2019 at 2:00 PM, CThumper said:

I figured if it's an OEM piston (2004) it would be a similar service life I could do the 2003 but i figured I'd like a bit more power.  From what i've read some people say it makes more, some don't. I could go with the 2003 piston if it doesn't add that much power it might be cheaper. 

As far as the heads.  So could I expect similar reliability say sending the head to MX Time and having them redo the head (cut Valve Seats, SS Valves)? that is $150 cheaper.  I guess I could go with that route, maybe use that $$ on an exhaust. 

Is there an airbox fix that I could look into or just a better air filter? 

 

Thanks for the input!

You don't need a fix with the '03 airbox, it was the '02 that was junk. Re-seal it and run it. Twin Air makes a good filter but I'm sure others are fine. :thumbsup:

PS: Clean off the old glue and use 3M Weatherstrip Adhesive (comes in yellow or black). Find it at Autozone.

Edited by HRC27

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Looks like the Nikisal is flaking off your cylinder. You can see the cross hatching is missing in those areas. It can be repaired for slightly less than a new cylinder. Do a search on this forum for stainless steel valves. There’s lots of information and opinions on the best route to go. Yes you could expect the same longevity out of a cylinder as long as the seats are cut. The most important factor is keeping your filter clean.

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 So I dug into the head today with a friend who's a auto mechanic. It looks like the heads are fine. The valve guides are really tight and the seats look great, I can clearly see the 3 defined faces/2 cuts. I know the valves have never been replaced and only shimmed once. I'm just going to clean up the head and use it. I'm going to go with SS valves/springs and lap them. 

Can someone answer this question, are the original exhaust valves stainless steel? Only the intakes are titanium? 

 

Thanks

 

9 hours ago, HRC27 said:

You don't need a fix with the '03 airbox, it was the '02 that was junk. Re-seal it and run it. Twin Air makes a good filter but I'm sure others are fine. :thumbsup:

PS: Clean off the old glue and use 3M Weatherstrip Adhesive (comes in yellow or black). Find it at Autozone.

Ok I'll grab a new air filter,  what would I apply the weatherstripping to?

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Between the boot lips and under the steel filter base. You'll see Honda's half ass job. Clean that off and reapply, just do a better job. It's weathstrip adhesive not weatherstrip.

Wear gloves, it's sticky/nasty stuff.

036_l.jpg

Edited by HRC27

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11 hours ago, HRC27 said:

Between the boot lips and under the steel filter base. You'll see Honda's half ass job. Clean that off and reapply, just do a better job. It's weathstrip adhesive not weatherstrip.

Wear gloves, it's sticky/nasty stuff.

036_l.jpg

Thanks! I'll add this to the list!

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