MicroMax engine temp 120

Markus Smith · Joined: 25 Dec 2011 Posts: 6

Need some help/advice/thoughts!

We have been testing our new micro max! I have changed jets, tried hotter plugs(rotax legal), tapped radiator ( even ran less water) but we can not get our engine temp over 115-120 during all lap testing. The only way I found to increase temp ( only 10 degrees) was to tighten up the chassis (lap times decreased)!

Mark

Marshall Martin · Posted: Mon Dec 24, 2012 4:59 am Post subject:

What is the air temp?

Try changing the temp sensor. Water temp in a Micro Max should not be an issue. The other problem could be your driver is not running the engine hard enough.
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Marshall Martin
LSR Motorsports
www.lsrmotorsports.com

marshall@lsrmotorsports.com

andy graham · Posted: Mon Dec 24, 2012 6:19 am Post subject:

duct tape works wonders...

Markus Smith · Joined: 25 Dec 2011 Posts: 6

Air temp was 77.

The radiator is tapped, only 2 inches of radiator exposed!

Marshall Martin · Posted: Tue Dec 25, 2012 6:16 am Post subject:

My first question is the accuracy of the reading. See if someone has an infared temp gun to verify the reading on the guage. Just does not seem correct.
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Marshall Martin
LSR Motorsports
www.lsrmotorsports.com

marshall@lsrmotorsports.com

Joe Ricard · Posted: Tue Dec 25, 2012 9:54 am Post subject:

Get your fuel / jetting correct 1st. Only by pipe color.

The only Micro max I ever seen was smoking fast. near as fast as a Mini Max

You could put an experienced driver on it and wind it up. Not to say you are not using one now.

My driver could not max out our Mini Max. I kept chasing tuning. finally swapped the motor for my sr Max and Holy crap!!!!!!! this thing is fast.
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Arrow AX-8/ Rotax Sr.

Markus Smith · Joined: 25 Dec 2011 Posts: 6

I was running 5.5 ounces of the xps per gallon. I thought about reducing the oil. How low could I go? Right now, the piston top is black but very wet, seems to stay the same even when I reduce the jet size.

Went to track again and put someone else in the kart. The only thing that changed was the max rpms went up 200. Still seems to be way rich, temp 121. How hot should thing get? What rpms should we be shooting for? ( 1000ft straight).

Marshall Martin · Posted: Wed Dec 26, 2012 4:10 am Post subject:

Way to much oil. Should be 50:1 (<3oz per gal). RPM should be 9000-9500. Temp should be 170-185.
_________________
Marshall Martin
LSR Motorsports
www.lsrmotorsports.com

marshall@lsrmotorsports.com

Brian Degulis · Posted: Wed Dec 26, 2012 5:41 am Post subject:

Sounds like your way to rich and it's not making power so it's not making heat. Share your jet size and needle clip position.

Brian

al nunley · Joined: 13 Nov 2006 Posts: 3032

Put a new plug in it and run 5 laps. Tell us what it looks like.
Check the compression pressure. Very good idea in all cases.
What is the air density? Once you get it running right, write down the density and the jet you’re using.
What size jet are you using? I have an Excel spreadsheet that tells you the area difference between different size jets. It gives you percentage differences down to .0001” size change. A 1% (or close) change in air density calls for a 1% (or close) change in jetting. Lots of other stuff in the spreadsheet.
Anunley@austin.rr.com
_________________
If the data does not support the theory, get a new theory. (Al Nunley)
All else being equal; Compression is the Holy Grail.
45 years, in and around karting

Markus Smith · Joined: 25 Dec 2011 Posts: 6

I completely agree that I'm to rich! The guys at OGP said to run 5 to 6 oz of oil. I will try closer to three but I really do not want to stick the motor,

Not sure of the air density, but after all the jet changes I ended up going back to a 128 with a pin setting of 1 ( top setting).

We are going to the track in a few days and will try to get closer.

william keyes · Posted: Wed Dec 26, 2012 10:20 am Post subject: Micro Max engine temp

We ran our final Micro max in October with the following:

118 Jet
3oz per gallon
170 degrees
9200 rpm
In Northern California at sea level

I think you are way to conservative...especially on the jet. As for the oil, that much you would think would make the amount of fuel lean by porportion but there is so much oil coming through that large jet that does not burn like fuel and leaves behind a wet mess and a cold cylinder.

Some one else can confirm this, but in the 7 years we have raced Rotax (micro, mini, junior and now senior) I have not witnessed a stick...ever, mine or anybody.

Brian Degulis · Posted: Wed Dec 26, 2012 10:34 am Post subject:

50;1 is the spec. Many run 40;1 which is around 4 ou per gallon so 5 is a lot but your problem is probably still mostly jetting assuming nothing else is wrong like air filter or a carb problem. Does it sound OK or is it 4 cycling or sputtering?

Brian

Markus Smith · Joined: 25 Dec 2011 Posts: 6

The little motor sounds good,we are turning 9800 rpm. Corners are not that tight so it does not bog down.

I will try the 3 oz of oil and a smaller jet.

We will be testing again in a few days, I will keep you posted.

Thanks for all the input!

Brian Degulis · Posted: Wed Dec 26, 2012 1:40 pm Post subject:

Look at your gearing also. If you way big on the axle the engine isn't loading. Could be a combination of that and jetting.

Brian