What goes where?

[OMEGAMAN]

 

I ran my newly built Tzr/XT640 race bike at Snetterton a few weeks ago & it seemed to run fine?, except for a mystery oil (not leak!) covering of the rear/under oil tank & shock area. On investigation my first thought was an overfill of the FULL oil tank giving too much pressure & blowing through to the catch bottle & out?  I sucked  the excess  out through a straw (YUCK!) until the level had gone down & went out again. Same happened again, & I assumed the tank was still too full & removed a lot more until the tank was half filled, went out for the last race & came in with oil all over the same area yet again!. Checked all hoses, checked the tank etc etc etc but still could not see where it was coming from, checked the tank level & it was EMPTY! It didn't surge out of the catch bottle as I had wrapped a clean white piece of rag around the top of it & that was still clean & dry?

It's got me baffled??

Have I got some pipes connected wrong?  the bike seems to run ok, just keep losing the oil over the shock area?

If I describe the basic set up, perhaps somebody can put me right (if i'm wrong?)

This XT engine has three breather pipes exiting, the main large crankcase breather, a smaller one just in front of it (under the cam chain adjuster?), & this race engine has a small breather exiting from the rear tappet cover.

Where should they go???

The oil tank has the inlet & outlet at the bottom front & about half way up the front.
It has a small outlet/inlet? on the top at the front with another similar size one set slightly higher on the top at the back

[guest27]

Not really and answer....

I had similar problems with the Jawa 500 - I think it was 'misting' out from somewhere rather than leaking - no matter what I did I had a lubed rear... tyre. 

Breathers need to go somewhere and if they do not hold over 640cc - probably each - they will be carrying air/oil in and out of the engine on each stroke.  I routed the rotax ones into the air filter - made some difference, but personally I feel a one way valve on breathers - letting air out but not in is a good idea, have even seen breathers (small) connected to the inside of the top exhaust bend - where there is a vacuum to pull the air out of the cranks.

Just some basic thoughts if not answers

R

[Steve H]

How does the oil tank breathe? . The SRX has a breather on the front which is connected to the small engine breather, on the crankcase, below the cam chain adjuster. The scavenge pump has a greater pumping capacity that the pressure side, so in theory the engine cases could be completely emptied into the oil tank, hence the need for an overflow. If your oil tank breather is vented to air it could be coming out of there.

[Steve Lake]

As steveH says, the small crankcase breather vents to the pipe at the top of the oil tank, the larger crankcase breather vents to the airbox between the filter and carbs...and there is no breather from the rocker box on the standard SRX
On my tzr/srx600 track bike...the larger crankcase breather vents to a catch tank, the rocker breather (must be something either added by tuners, or standard on xt's?) vents to the oil tank
and the smaller crankcase breather goes somewhere....but i can't bluddy remember, and Andy230's got the machine right now.....so if he can go and have quick look..all will become clear......whats worrying is why you are getting so much oil loss, hopefully it is only a mist, and if routed to the oil tank or vented to the catch tank..all will be ok

[andy230]

steve,

will check your racer and post.

john, what about your shock leaking??  I suppose its (WAAAAY!!) too much oil for that...

speak soon,

a

[OMEGAMAN]

 

Thanks all, will try re-routing the pipes as suggested over the weekend & fire it up. I'll post the results?

Hope to take it out at Mallory on Wed. for some MUCH needed practice (before the big Snetterton meet on July 13/14 & 15th)

Ps. definatly not the shock leaking Andy!

[peterj]

When I rebuilt my SRX with TT cases, there was no small spigot in front of the main breather on the TT cases. The XT/TT manual I have shows the small breather coming from the cambox, and it looks like the SRX head has a blank boss at this point. Maybe you have an SRX motor with an XT/TT head?

[OMEGAMAN]

 

It's definately a pure XT motor (for racing only?) but has had the rear (Oval) tappet cover modified so that it can breath thru a small tube.

[Steve Lake]

Interesting.....my track bike is mainly XT....(magnesium cases) and the cam box breather is plumbed directly into the cam box casing somewher between the front and back tappet covers...i guess that means about in the middle :-)

[OMEGAMAN]

 

What do you mean by "cam box"

& who get's up at 7:59 on a Sunday morning?

[Steve Lake]

 , was up at 6.....weak bladder + 5 pints last night

for cam box read the top of the camshaft cover