Thumper Club Forum

Technical => Bike Problems/Questions => Topic started by: KungFooBob on March 22, 2009, 07:45:32 PM

Title: XBR rocker breather
Post by: KungFooBob on March 22, 2009, 07:45:32 PM

Hello all,

I'm building a XBR race bike to race with the Earlystocks Club in their single cylinder class.

To cut a long story short I've had the head to bits, replaced a valve, treated it to new rings and bolted it all back together with fresh gaskets.

Today was the day I decide to kick it into life having made a race loom and bolted on a 41FCR-MX carb.

it's still a work in progress so it didn't have an end can on it.... or any breather pipes.

It fired up and ran great, but after a couple of minutes I was getting quite a bit of pressure coming out of the the crank case and the rocker cover breathers.... the bit that worried me was the rocker breather started to blow a bit of smoke, it's not a huge amount, but not having ever run an XBR before with out the proper breather in place (iirc it vents back in to the airbox?)

Is this normal, am I being paranoid, should I give it a good run and see if it goes away?

I'm thinking at worse it's a valve guide letting exhaust/intake gasses into the rocker cover?

G

Title: Re: XBR rocker breather
Post by: guest526 on March 22, 2009, 10:41:04 PM

 
On a standard XBR the rocker cover breather hose goes back to oil tank,and the crankcase breather hose goes into the airbox.Hope that's not pointing out the obvious.

Keep us posted with your build,good luck :)

Title: Re: XBR rocker breather
Post by: guest295 on March 23, 2009, 09:19:10 AM

With new rings, it should smoke through the breathers. Put hoses on them and take it for a good run. Back in the day when 500 singles were raced seriously, the breather pipe was about 3/4" ID and ran back along the frame until it cleared the tyre. Try to avoid idling the engine until you get it worn in a bit.

Title: Re: XBR rocker breather
Post by: KungFooBob on March 23, 2009, 09:28:35 AM

Thanks guys, put's my mind at rest a bit.

I'll put a post in the projects section, let everyone know what I've done to the bike and see if anyone has suggestions for making it faster.

Title: Re: XBR rocker breather
Post by: guest27 on March 23, 2009, 09:35:22 AM

Who is the US tuner who claims that you get better power by warming the rebuilt engine and then thrashing it - cuts in the rings...?

Seemed to make a lot of sense to me - mind I like a nice bit of iconoclasm

R

Title: Re: XBR rocker breather
Post by: themoudie on March 23, 2009, 11:53:10 PM

Aye Rog,

This what you looking 4?

http://mototuneusa.com/ (http://mototuneusa.com/)

My regards, Bill.

Title: Re: XBR rocker breather
Post by: guest27 on March 24, 2009, 08:13:57 AM

That's the one

R