Welcome to Underbone Tuner

Underbone tuner is a free online magazine for Underbones, Scooters, Backbones and occasionally we might squeeze in a big bike or two . We have been covering small motorcycles modifying culture for over 8 years already and still counting. We have the latest updates/news on motorcycle racing events from all over the country such as circuit, motocross, flat track, endurance, trail and supermoto. We cover motorshows from all over the country. We cover the latest bike launches and the latest trends in bike modifying culture.

But at the core of Underbone Tuner is the bike modifying / customizing culture. We scour the country for the best motorcycle builders/modifiers. We feature the owners of these amazing bikes and the talented teams and individuals behind these bikes. We give you the story behind those builds and hopefully we inspire others to keep this fascinating culture alive.

This website is dedicated to all motorcycle enthusiasts, this our life, this is our passion, this is who we are. We may be riding different bikes but we share the same fascination and love for motorcycles. We are all brothers in two wheels.

Sunday, June 1, 2008

The Importance of Breather Systems for Underbone Race Engines

The Importance of Breather Systems for underbone Race Engines.


A tuned underbone engine undergoes at lot of stress and pressure than
stock condition. The common pitfalls of newbies is they do not
consider the additional parameters involved like more pressure in the combustion
chamber or higher temperature levels for the engine. Having a bigger piston
( last bore ) on a 110cc engine, dramatically increases the stress demands on the
engine, this in turn increases the wear & tear and structural demands on your machine.

To make things easy just imagine containing a fire cracker explosion within a small can,
a lebintador might not affect it but if you put a super lolo, it will rip the can to shreds.
Thats the same effect it does on your engine. The bigger the piston, the bigger the bang.
So how do you compensate for these additional demands on your engine?

First we have to learn about "blowby" all four stroke internal combustion engines
produce at least some amount of "blowby" due to the relatively high pressures occuring
in the combustion chamber during the compression and power strokes of the engine while its
operating. While the piston(s) is/are normally reasonably well sealed by means of their compression
and oil control rings, there will nevertheless always be some compression and combustion pressure
which escapes the combustion chamber(s) past the rings and ring gaps, and finds its way to
the crankcase of the engine.

The turbulence within the crankcase, due to the spinning of the crankshaft and its throw(s)
with the lower end(s) of the connecting rod(s) attached thereto, along with the spray of return
oil from various components in the engine, results in a considerable amount of warm oil vapor being
contained within the crankcase during engine operation. This blowby gas, with its oil vapor byproduct,
must be released from the crankcase in some manner, in order to prevent the blowing out of
crankshaft or other seals within the engine. This is where the breather system comes in.


The breather system serves to capture oil vapor which has been expelled from the crankcase along with
blowby gases from the crankcase. The crankcase communicates with the oil catch tank/collector/container by
means of a tube, with the container also having a filtered outlet thereon. Blowby
gases and oil vapor mixed therein enter the container with the relatively heavier oil vapor
collecting in the bottom of the container and lighter blowby gases passing through the filter to exit
to the atmosphere. Oil may be drained from the container periodically by means of a petcock or drain
valve in the bottom of the container. The filter also serves to prevent unfiltered air from entering
the system when the engine is shut down.

So before you rebore to get the big D, dont forget what happened to the can. Invest first
on a good oil breather system.

by: Underbone Tuner

Images from:
Asian Concept Co., Ltd. : Tel (66)32.321.614 Fax (66)32.310.814

Motorcycle depot


Frances Azhelia said...

san po me makakabili ng oil breather for 110cc,dito po me sa batangas at magkano po?
eto po # ko 09498368498

Frances Azhelia said...

san po me makakabili ng oil breather for 110cc,dito po me sa batangas at magkano po?
eto po # ko 09498368498

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