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Old 08-10-2008, 06:33 AM   #1
Marc Miller
Birel & Rotax Specialist
Join Date: Jan 2008
Posts: 850
Exclamation RotaxMax discussions

Attention MRP Motorsport customers. We have added a Rotax section to our forums. This is to request technical information, MRP Rotax Challenge results and rules and to get more information about our Rotax program in general.
Marc Miller
Director of Brand Development
MRP Motorsport/Birel
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Old 08-10-2008, 04:58 PM   #2
Garry Lobaugh
MRP Motorsport - President
Join Date: Jan 2008
Posts: 1,780

I assume this will also cover technical questions with contributions from the famous Bruce Woodrow and others? Thanks for getting this up.
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Old 05-12-2009, 05:21 PM   #3
Junior Member
Join Date: May 2009
Location: Dakar
Posts: 1
Default Rotax Jr. for max torque

Hi, We have a karting club in Dakar (yes, famous city after which the Dakar rally is named). Our karting club has finally decided to change from a very old Comer 100cc air cooled to Rotax. Our track is not big so they chose the max jr- 20HP.

I am busy reading all the advice on carb settings, jetting, etc, etc.

What advice can you guys give for improving the torque on this little engine so that an 80kg guy can compete with a 50kg youngster?

I also want to order some starter jet kits, etc from the gorotax parts list. Which dealer will be closest to Washington DC? I have a friend going there on Monday.

PS- Our club rules are very soft. What is the maximum size piston available for the max jr? I see Gorotax list a 54.00.

Last edited by Erasmus; 05-12-2009 at 05:24 PM.
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Old 05-14-2009, 11:56 AM   #4
Chris Lobaugh
Birel Specialist / Engineer
Join Date: Jan 2008
Posts: 237

To increase torque you can do a couple of things:

Add a tooth or two on the rear sprocket to increase acceleration and low end power.

Try changing the clip position on the needle in the carb...move the clip down which raises the needle and gives the engine more fuel on the bottom end to help pull the heavier drivers out of the corner.

There are some internal changes that can be made especially with the base gasket which will produce more torque but will also affect top end power.

If you truly want to have one engine package for both Jr. and Sr. drivers with a large difference it weight you might consider having a spec gear for the lighter Jr. drivers and allow the senior drivers the option of a "free" gear ratio.

You could also do this with the jetting in the carburetor...spec jet for the Jr. drivers, free jetting for the Seniors. Obviously this will take a bit of testing to determine what is a fair and safe jet for the conditions that you are racing in.

In terms of the maximum piston size: 53.99 is the largest piston that we have in stock here in Michigan.

In terms of a dealer near Washington D.C. SSC East is located near Boston, MA. I don't know of any dealers in D.C.

Hope this helps
Chris Lobaugh
Birel Engineer & Specialist
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