We have been doing some VERY custom Head Mods to various Vintage MX AND STREET 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 utilizes our Patented 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
8) Suzuki RM500
9) Suzuki RM250 (Full Floater)
10) Suzuki RM400/465 (NOTE: We can not weld this cylinder due to it special alloy)
11) Suzuki TS500
12) Suzuki GT 750 (water buffalo) We mod your stock head to accept billet inserts
And the list continues to grow as we get the engines in for testing!
COST? $375 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!
This is absolutely the BEST mod you can do for performance on your Vintage MX Engine!
See below for 1 review...
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" pattern machined
into the dome and squish band that starts at the plug hole and radiates outward
to the gasket surface. According to Kelsey at RK they don't know (or wasn't
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 different.
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. The temperature
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 light almost
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 countershaft
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 the big
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.