Topic: FAST HELP Required CR750

[Bergi86]

Hello,

I´ve built a CR750 rep.
Next weekend is the first race meeting and unfortunately some probs occurred- which I´ve to fix soon!
So I need your help!

One of the problems is the one with the oil tank.
Does a tank like one from Mead Speed work without an breather box?
I did not install one because I thought that it will work without overmore I have no room for one... Now the problem is that it throws a lot of oil out of the breather line at the back of the tank.

So my question: Does it work without a breather box? How can I make it work without!

Thank you!
Cheers

[teebee67]

Mine has the breather tank inside the seat hump.

[Bergi86]

there is the battery

Do I really need a breather box?

[teebee67]

Well, if it's throwing oil out of the breather pipe, I would think you do.

[bear]

If your racing I'm assuming you have a catchcan for the engine breather, run a pipe to that for the time being.
Are sure you have not over filled the tank.

[Bergi86]

I have no catchcan- normaly this models do not need one...!?
The breatherlines from the engine and from the gbox goes into the CR oil tank. One pipe goes to the back of the bike to atmosphere...

Is it possible that the breatherpipes from gbox and engine puts so much pressure to the oiltank that it trow all the oil out of it? And maybe this also increases the pressure in the engine?
Since I´ve fitted the oiltank the engine loses a lot of oil....!?

Next question... who can tell me to which level I´ve to fill the CR oil tank? I actually have very less oil in it...

[Nose736]

If you have a replica oil tank such as the one from bartel, You must run the two oil lines from the motor into the oil tank and out of the oil tank into a catch can And be sure to run a single piece of hose out of the can just like a straw for a vent, Or else yes it will overflow the tank ,As for oil level3.5 litres,  I had your oil tank problem in 1996, No vent, filled the oil tank,pissed all over the rear tire pitched it at 80mph in a corner 1year of work.  Thanks Howard

[Don R]

 Can he vent the oil tank to the trans fitting and put a K&N breather on the rocker cover?  Just asking.
  Usually the factory puts on the minimum everything, if it's there, it's there for a reason.

[JohnN]

The original CR had a catch tank and I believe the Mead Speed replica tank matches the original setup. Transmission and cam tower hoses connect directly to oil tank, and oil tank vent connects to the catch tank (mine is also located under the hump). Be careful with this as it won't be a problem in neutral but 9,000 rpm under a load creates a lot of pressure and you could have oil all over your back tire! AHRMA and WMRRA require a catch tank; what club are you racing in?
John

[turboguzzi]

a catch/breather tank is a must have in all racing rulebooks, it will not pass tech check without

here is a good setup

http://forums.sohc4.net/index.php/topic,155235.msg1778505.html#msg1778505

built something similar in my supermono, including the very important back drain to the motor, no more problems with oil blow anymore.

in dry sump motors it seem more important to have the complete setup breather tank + oil drain back. my wet sump motors never needed more that a simple catch bottle which always remained dry.

[Bergi86]

Hey guys, thanks for all the answers!

I´ve now two questions.... Why do this system not work without a breather tank?? I don´t understand this... because my tank has a vent (a line which goes to atmosphere)- so the tank can´t be prssionized... or do I understand anything wrong?

So... my prob is that I have no room for a breather tank. Under the seat is the battery... What if I take the two lines which comes from the engine and just let them go to atmosphere.... and put a plug into the positions at the oil tank where they have been before... After this there would still be the vent at the oil tank (line to atmosphere)

would that work?

(pls do not think about the regelmantation while answering )

[Bergi86]

@ John.... not club racing... just some hill races in Austria! I´m no professional....

[turboguzzi]

the problem is that dry system constantly pressurizes the tank, that is because the return side of the pump has always more capacity than the pressure pump (to keep the sump dry )

the simple vent line you have can work ok in street use, but in racing, with lots of acceleration, braking and high revs, very good chances that it will spit oil too. oil on rear tire nicht gut. you dont need any room, just zip tie a bottle to one of the tubes in the rear. not cool looking, but better than oil on the tire.

[Bergi86]

Turboguzzi= German speaker??

[turboguzzi]

english, italian, spanish, hebrew i am fluent. deutsch, nur ein kleine  bisschen....

[Old Scrambler]

You could run the valve-cover vent to a catch-can.........but the line from the oil tank to the tranny MUST stay connected..........it actually DRAINS excess oil in the tank back to the tranny in extreme cases. Do you also have an oil-cooler? Who made your tank? You say it is LIKE a Meade-Speed unit. My friend and I also make CR-replica tanks...............internal baffles and deflector plates help to reduce foaming and excessive 'swirl' at high rpms..........especially when down-shifting.