Please Help Extreme Crank Case Preasure

[Batavia's450r]

I own a 05 Honda 450r with a 13.5 to1 wiseco gas ported piston with gapless rings... it has a Hotcam and headwork done... exhaust etc...

it gets extreme crank case preasure inbetween races i need to losen it to releave the preassure... if i take the check oil level bolt it spews oil five feet!!

I constantly change my oil on both sides of the motor after every race and i recently put a new clutch in it... it did this before the new clutch was installed and still does... the breathers are not blocked off they flow freely any help please would br more than appreciated thank you

[Nick110]

Do you have an HRC breather T or drill out your stock one. I heard that T relives crankcase pressue.

[watts16]

Does it have pressure in both sides or just the engine?

[ss440ex]

Read the manual..
Does`nt it say to loosen or remove the fill cap first,before the drain plug or the smaller over flow screw!

On the trans side....

[d3ktrix]

Originally posted by ss440ex
Read the manual..
Does`nt it say to loosen or remove the fill cap first,before the drain plug or the smaller over flow screw!

On the trans side....

That just so the tranny can drain faster because the opened fill hole acts as a vent to let in air.

Has nothing to do with the abnormal pressure he has building up.

[250RXCrider]

I had that probelm once, make sure all of the vent tubes are clear and flowing air. I have heard of people accidentally taking the vent hose and plugging it into the side of the carb.

Originally posted by 250RXCrider
I had that probelm once, make sure all of the vent tubes are clear and flowing air. I have heard of people accidentally taking the vent hose and plugging it into the side of the carb.

I agree i have seen it too. When people do a rebuild they see that hose and the open spot on the cab. It fits perfectly so people plug it in. It should be hooked to the hole in the plastic piece under the gas tank.

[Batavia's450r]

all breathers are free and clear and when i blow air threw them they flow nicely... its been doing that since i bought the bike a year ago.. runs good and is still fast as hell i took it to the local honda shop because i have the extended four year on it and they cant figure it out... but its only on the trainy side and the thing exploids when i loosen the fill plug it gets tons of preasure

[400exrider707]

Originally posted by Batavia's450r
all breathers are free and clear and when i blow air threw them they flow nicely... its been doing that since i bought the bike a year ago.. runs good and is still fast as hell i took it to the local honda shop because i have the extended four year on it and they cant figure it out... but its only on the trainy side and the thing exploids when i loosen the fill plug it gets tons of preasure


Obviously there is a vent plugged somewhere or a vacuum line plugged, how else would it build pressure like this? The best thing to do would be get a buddy with the same quad and put them side by side and look at every tube and connection.

[watts16]

Originally posted by 400exrider707
Obviously there is a vent plugged somewhere or a vacuum line plugged, how else would it build pressure like this? The best thing to do would be get a buddy with the same quad and put them side by side and look at every tube and connection.
You may have been overfilling it. Drain in and put enought in so it barley comes out the check hole. Mine was doing the same thing.

[Batavia's450r]

impossible for it to have any vents plugged... they have all been tested... as for to much oil its all put in to specs... i was thinking possibly a center seal but it never loses oil from the crank side.... im confused... motor builders are confused and so is the honda shop but she runs soo damm fast!!

[ss440ex]

Did ya ever find the problem???