Question about 2004 Honda CRF 450 R

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My crf 450 is leaking engine oil from the air box when running. any ideas?

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Is the breather tube venting in the air box bud

Posted on Sep 30, 2009

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My 2005 450 is also blowing oil into the air box. I drained the oil and found it had a full quart in it. This is impossible. I always measure the oil. Could my Transmition be leaking into it?

The problem is with the balancer shaft seals and or bearings. This is the only place that oil can communicate between the two compartments. I have seen and repaired this many times.

Jul 31, 2012 | 2005 Honda CRF 450 R

1 Answer

My 04 crf 450 is leaking oil out of the air box breather

Hi, Jmattison21 and the usual suspects are:
1. Oil tank/system overfilled.
2. Faulty breather valve.
3. Engine breather hose bent, pinched, kinked etc.
4. Air filter has too much "pre-oil".
5. Crankshaft seal failure allowing transmission fluid to migrate.
6. Blow by drain tube cracked/split or filled to capacity.
For more information about your question and valuable "FREE" downloads that you will need please click on the blue links below. Good luck and have a wonderful day.
Engine Oil leaking out of my CRF 450 air Box
Oil coming out of airbox 2012 CRF 450
Honda CRF450X 2005 Service Manual
OEM parts for Yamaha
Honda CRF450R Owner Manual

Dec 22, 2010 | 2004 Honda CRF 450 R

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How much engine oil does my 2005 crf 450 R need when changing oil and filter?

Engine oil:
Fill the crankcase with the recommended oil. Capacity: 0.73 US qt (0.69L) at oil and filter change Tansmision oil: Fill the crankcase with recommended oil. Capacity: 0.62 US qt (0.59L) at oil change.

Dec 07, 2010 | 2005 Honda CRF 450 R

1 Answer

I have a 2006 CRF 450, at the track I noticed a

yes sir the seal hole should not be oblong, was the bearing bad when you took it out? sounds like the shaft has worn out the hole.

Apr 08, 2010 | 2005 Honda CRF 450 R

1 Answer

What type of oil should i use or a 2005 honda crf 450 x?

Use either the Honda 4-stroke engine oil, or any quality brand of automotive engine oil. In either case, make sure you select the viscosity that is correct for the temperature ranges in your area.

Mar 08, 2010 | 2005 Honda CRF 450 X

2 Answers

'06 crf 450 oil leak

There is an o-ring on the oil filter cover that might be foulty.. check it might have pinched it when installing the new oil filter. also the 2 bolts holding the cover on might need to be sealed with some sealer...

Mar 22, 2009 | 2005 Honda CRF 450 R

1 Answer

I am trying to replace the spark plug on my 2005 CRF 450 R has been sitting for about 1 yr without running and I am sure it needs to be replaced....Is there an easy way to do it or do I need to pull...

Hi jjb
To give you all you need to do change the plug, and swervide the bike, you can download a service manual for free from here. If the the bike has been sitting for a year, to look after the engine BEFORE you start it, you should do a few other things also. A quick list 
  1. The engine oil will need to be changed, 
  2. clean and check your air filter
  3. Drain any stale fuel from the tank and carb, refresh it, prime the carb
  4. Remove the plug, and put a dribble of 2 stroke oil into the chamber
  5. Crank the engine over a few times with the plug out.
  6. Fit the new plug
  7. Start it up, it may smoke a little initially, but this is ok. 
 Before you go for a ride, good idea to go through the manual and do all the service requirements. Thanks for using FixYa. 
regards robotek

Jan 10, 2009 | 2005 Honda CRF 450 R

3 Answers

CRF 450 Honda leaking oil through carburetor

it sounds like your valve/rocker cover to spark plug tube seal is folded over or something. My reason for saying this is, because the only place for oil to get into the plug tube is a bad seal to the cover or the spark plug isn't tight? and that hole is for expelling liquid so it doesn't cook the plug into the head

Dec 06, 2008 | 2005 Honda CRF 450 R

1 Answer


Hi there

You should not have oil leaking from the carby. If you have over filled it with oil, then it may be coming from the crankcase breather and then into the airbox, and appearing to come from the carby. If you have not over filled it, then the bike may have blowby problems with compression gasses passing the rings, and in a similar manner forcing oil out the crankcase breather. Not sure about the hole in the side of the cylinder... do you have a picture? Unless its pouring out, or gets worse, I would not be too worried. If you have over filled the oil, maybe time for an oil change to get the level right.


Dec 06, 2008 | 2005 Honda CRF 450 R

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