Honda Makes Changes to GX390 Engines
When the new management team took over MMRA in 2002, one of our goals was
to keep the rules for engines as consistent as possible from year to year.
We have been fortunate that we have been able to do this for four years, but
there is a necessary change being made for the 2006 season.
Honda Engines has changed all their GX line of small engines from K1 to
U1, representing a new country of origin for the engines. While they
are basically the same, there are two differences to note. The crank
and rod design in the new U1 motors are different from the old K1 motors.
An "old" and "new" crank are pictured below:
Rob Stambaugh is a member of the MMRA Competition Committee
and he also works closely with QMA. Rob confirmed that all GX engines
have changed to the U designation and QMA is also being forced to modify
As such, the MMRA Competition Committee voted to allow new
U1 motors, and to allow racers with the old K1 motors to replace their crank
and rod with the new U1 crank and rod if they so choose. This is not
required, it is just a legal option for racers with old engines.
In the great tradition of MMRA, here is a FAQ (Frequently
1. Do I have to upgrade to the new crank and rod?
No - it is optional. Check with your engine builder to
see if they recommend the new crank and rod for performance or durability
2. Why is MMRA allowing this new crank and rod?
There is no other option. All new engines are coming
this way. If we outlawed the new crank and rod, we would force new car
buyers to find an old engine for their car. Eventually, these old
engines would run out and we would stop any potential growth in the sport.
The best we can do is to minimize expense for existing racers by allowing
them to just replace their crank and rod instead of buying a whole new
3. Can you tell the difference from outside the
No - the only way to tell which crank and rod an engine has
is to take the engine apart.
4. Are there other rules changes for minicup motors
No - this is the only change approved by the MMRA
Competition Committee. If you are ready to get your engine freshened,
you can send it off now to get ready for next season.
5. When will the new 2006 rulebooks be posted?
They will be posted late this year.
6. What would changing my crank and rod cost?
In the EES Catalog, cranks cost $241 and rods cost $87.05 -
the total cost to changeover will depend on the amount of labor involved.
Also, other engine builders may charge more or less than these figures.
7. Is there a way to save money on this?
Tim O'Brien of Extreme Engine Systems will be at the
Awards Banquet on November 5 in Nashville, TN. If you bring your motor
to the banquet, you can give it to Tim for freshening and/or sealing with
MMRA Approved seals. This will save you shipping costs.
8. I have a different question.
No problem - please send an e-mail to
mmra@MMRAracing.com and we will get
you an answer.