We have been
doing some VERY custom Head Mods to various Vintage MX Bikes.
Since 2 Stroke technology was literally, in its infancy in the
70's, the engine designs are a true reflection of how much was
NOT known about the 2 stroke engine at that time
We have found that the combustion chamber (Head) is one area
where HUGE performance gains can be realized on these Dinosaurs!!
In most cases, we have to weld the chamber in with special alloy
and then completely re-shape the combustion chamber to a design
that allows for a MUCH more efficient combustion process and
combustion chamber design.
After this mod
is finished, ALL of the Pro-Riders have been able to pull 1 gear
higher around the entire track!! Along with this added gear,
they have all realized easier starting and ,best yet, a Serious
increase in power throughout the ENTIRE RPM range!! This mod is
noting short of AMAZING~
Do not take
our word for it.. Search the internet on all the vintage forums
and see what the riders are saying about this awesome mod!!
We have PROVEN
chamber designs for ALL elevations and ALL octane requirements
for the following Engines:
1) Maico 490
2) Maico 440
3) Maico 400
4) Maico 250
5) Honda CR480
6) Honda CR500..
we also have a billet head for the 500 water cooled
7) CZ 400
RM250 (Full Floater)
RM400/465 (NOTE: We can not weld this cylinder due to it special
And the list
continues to grow as we get the engines in for testing!
COST? $275 if
we do the welding. If you are capable of doing the Welding, the
the cost is $175.00. Not much $$$ for the amount of added
performance you will obtain!
absolutely the BEST mod you can do for performance on your
Vintage MX Engine!
See below for
74 440 Maico
PVL # 2.1mm BTDC
Canadian Maico pipe
Eric Gorr cylinder
1980 440 single plug head
I received my RK modified head which they welded up and
machined into a true
hemi-head combustion chamber with a very interesting "fluting"
into the dome and squish band that starts at the plug hole and
to the gasket surface. According to Kelsey at RK they don't know
up) exactly why this pattern works so well, only that it does.
This head was
generically cut for a 440 radial on pump fuel according to
Kelsey and that he
had known I run 110 race fuel he'd have cut it a little
Head installation was straight forward and after some heating
and cooling cycles
the head was re-torqued to 18ft/lbs and a new plug installed.
was about 55F and the track was at app. 250-300msl. 3 different
WOT jetting runs
showed my installed jetting was good, plug was clean with a very
white brown/beige color on the insulator. Power seemed more
crisp and linear. As
a side note the bike definitely
started easier. I think I'm going to try going back to a 13t
sprocket and see how that works because this new head really
pulls good enough.
I've never had the power lift the front end going down a
straight in 3rd gear on
At the PIR race the bike ran really strong, coming off the
bottom end very clean
with a nice smooth transition into the mid range which is where
difference is that I noticed. Once in
3rd gear the bike just pulled and pulled down the back straight
so hard it had
me giggling. With my weight #240 in gear I still don't think I
can use 2nd gear
for the start and wasn't going to try it at a race.
After my first moto I checked the plug and found it to be a
darker color, most
likely due to the warmer ambient air temps and running the bike
at other than
WOT around the track. I think some jetting changes are in the
future and maybe
even trying some timing changes.
I've already sent RK my 81 head down to them for this mod along
with deck heigth
measurements, a new head gasket and a piston so that the squish
band can be
contoured to exactly match the piston dome.