tranny case pressure

[trxHRC450r]

my 450r is building pressure in the tranny case of the motor. it will hold pressure for days and it got me the last time i changed the oil when all the pressure blew out the drain bc i didnt remove the filler cap first. i went to a honda seminar and they sed they do build some pressure but they couldnt tell me how much. ive checked all the breather hoses and they r all clear. i think it might be internal and i want some feedback b4 i split the cases. anyone have this problem?

[400exBro]

ya make sure you don't over fill the tranny.... if there is to much oil there will be an increase in pressure....

[trxHRC450r]

yea i let it drain intil it stops dripping

[chad502ex]

look at in in-betweens of a case and take your guess. are you talking when you drain the tranny oil or the crankcase oil?

[trxHRC450r]

tranny oil it just holds pressure like a *******

[RedRaider]

I'm pretty sure there is a vent tube for the tranny. I've heard other people have this problem and it was because the tube was pinched off.

[roughrider01]

There is a vent tube for the tranny, its seperate fromyour crankcase breather. Its right behind the cylinder, then i think it kinda goes up by the carb. That should be your problem, i dont see how it could be holding pressure if the vent is doing its job.. its just not possible.

btw i did the same thing what you did when changing the trans oil when mines was holding pressure. I ended up with a crotch full of warm oil... nice.. lol

[chad502ex]

Originally posted by roughrider01
There is a vent tube for the tranny, its seperate fromyour crankcase breather. Its right behind the cylinder, then i think it kinda goes up by the carb. That should be your problem, i dont see how it could be holding pressure if the vent is doing its job.. its just not possible.

btw i did the same thing what you did when changing the trans oil when mines was holding pressure. I ended up with a crotch full of warm oil... nice.. lol


nice roughrider.

absolutely, there are two vent lines. one for the crankcase (the big hose) and one for tranny side (smaller hose towards rear of motor behind crankcase hose). the tranny vent hose goes upward and fits into the heat shield vent holder hole. remove this line and be sure it clear.

hope this helps

[chad502ex]

...

[hsr]

I re-routed my crankcase hose slightly and i accidentally cut the stock hose too short so i purchased some vent hose and some fittings (elbows, connectors) at a local hardware store that are of a smaller diameter than that of the stock hose. Is this going to cause more pressure or will i be ok with this setup??? It still breathes good when i blow into one end of the hose i can feel air blowing out of the breather filter that i installed at the other end.

[trxHRC450r]

i removed all the hoses and blew throguh em and they were all clear. yea that hot oil all over you is not a good feeling. i work at a dealership and if this becomes a problem im gonna yank the motor and get get paid to work on it bc i bought it there and it is under warranty

[roughrider01]

Originally posted by trxHRC450r
i removed all the hoses and blew throguh em and they were all clear. yea that hot oil all over you is not a good feeling. i work at a dealership and if this becomes a problem im gonna yank the motor and get get paid to work on it bc i bought it there and it is under warranty

Yah you should be able to blow threw that line pretty easily will the filler cap off, just like blowing thru a straw. Take it for a little 15 minute ride, park it and see if its still holding pressure. I mean, its hard for something to hold pressure if it isnt sealed.

Nothing wrong with getting paid to work on your own machine.. must be nice! ;)

[chad502ex]

Originally posted by hsr
I re-routed my crankcase hose slightly and i accidentally cut the stock hose too short so i purchased some vent hose and some fittings (elbows, connectors) at a local hardware store that are of a smaller diameter than that of the stock hose. Is this going to cause more pressure or will i be ok with this setup??? It still breathes good when i blow into one end of the hose i can feel air blowing out of the breather filter that i installed at the other end.

let me help with providing some insight on what i beleive is the reason the HRC kit includes the crankcase vent "T" in the HRC kit. As the piston is rotating downward into the case, downward pressure from the underside of the piston is pushed into the crankcase. This crankcase pressure must vent throught the crankcase vent tubing. if the vent tubing is reduced in any way (i.e size/diameter) the pressure in the crankcase has more resistance to exit the case. resistance reduces the downward speed of the piston which in a sense reduces rpm speed (hardly noticable tho). This is why HRC kit includes a bigger crankcase breather tube adapter "T" in their kit.

hope this helps shed some insight light.

my 0.02

chad502ex.com

[bobbo97f150]

I've also read of when people mess with their carb., they will plug the tranny vent line into the carb thinking it goes on it because there is a nipple on the carb which looks usable, and your vent line runs right next to. All this does is plug the line, the line is supposed to be free on the end, not plugged into the carb. With your filler cap off the tranny side, blow through the end of the vent line and see if air comes out the filler hole. If it does, there is no reason that thing should hold pressure. Unless something is plugging the vent line from inside the motor, which is unlikely.

[roughrider01]

Originally posted by bobbo97f150
I've also read of when people mess with their carb., they will plug the tranny vent line into the carb thinking it goes on it because there is a nipple on the carb which looks usable, and your vent line runs right next to. All this does is plug the line, the line is supposed to be free on the end, not plugged into the carb. With your filler cap off the tranny side, blow through the end of the vent line and see if air comes out the filler hole. If it does, there is no reason that thing should hold pressure. Unless something is plugging the vent line from inside the motor, which is unlikely.

Hey thats what i did.. lol. The carb on my DS650 that i use to own had two vents coming off each side of the top of the carb. Well when i rejetted my 450 i grabbed the tranny vent (didnt know it was the tranny vent at the time) and plugged it into the carb. Yup, so the vent was sealed causing pressure to build up. Im just surprised with that much pressure my tranny was holding that the vent didnt blow off the carb. Oh well, learned from my mistake i guess.

[chad502ex]

Originally posted by roughrider01
Hey thats what i did.. lol. The carb on my DS650 that i use to own had two vents coming off each side of the top of the carb. Well when i rejetted my 450 i grabbed the tranny vent (didnt know it was the tranny vent at the time) and plugged it into the carb. Yup, so the vent was sealed causing pressure to build up. Im just surprised with that much pressure my tranny was holding that the vent didnt blow off the carb. Oh well, learned from my mistake i guess.

Great to see you found the problem systematically like you did. great job! thanks for posting your find too!

chad502ex.com

[iceracer65]

i havent touched a thing on the hoses/carb...my hrc kit was installed by the honda dealer.

all breathers are clear and i still have some tranny case pressure...im not conserned...what can it hurt?

[bobbo97f150]

I've changed my oil many times and have never had pressure in either side. I always just crack the filler cap open to see if there is any after I let it warm up. If the pressure builds up too much, you could blow a seal. Just cause the dealer installed the kit doesn't mean they didn't plug the vent line into the carb. You may be surprised to find out how under skilled some of the mechanics can be.

[Live2Ride300]

Has anyone ever experienced oil coming up through the tranny vent line? I was out riding this past sunday, put 2 hours on the hourmeter and at the end of the two hours i noticed my motor was covered in oil. I brought it home and took the fenders and tank off and noticed that the tranny breather line was wet with oil. I'm not sure why this would have happened. The night before I went riding I changed the crank oil and tranny oil. I put the reccomended amount of tranny oil in as I always do. I've never experienced this problem before?

[K-Dub]

My tranny vent hose was plugged onto the carb when I bought it. I kept having pressure on the tranny side and my 2 friends Rs never did. Started looking and niether of theres was plugged to the carb.