Rotax fuel ratio change

[Anonymous]

Anyone running Rotax might like to know that Rotax has changed its fuel ration requirements for the Rotax Maxchallenge as well as running the motor in general. They state that engine failures initiated these actions.

The recommended ratio was 50:1 it is now 33:1.

The link to the notice is http://www.rmaxchallenge.com/tech/newsflash/NEWSFLASH06232003.doc

Jocelyn

[Anonymous]

Your link doesn’t link to a newsflash

[Anonymous]

Thanks, it has been fixed.

Jocelyn

[Tom Dennin]

That news is old, 6/23/2003. It is now back to 50:1. Check the Rotax site.

Tom

PS –> I have never run at 50:1

[Anonymous]

Yes I saw the date but until you pointed out they changed it back I did not realize it was back at 50:1 (2/2004 rules primer). However it would be nice if they clarified what really is correct because the June 2004 Max Tech has the link to the notice from Rotax right there. So they are sending mixed messages.

If you never run 50:1 what are you running?

Jocelyn :idn:

[Doug Welch]

We are running as per the Rotax manual. We use VP MS93 with RS7 oil. For break in, we did two 15 minute sessions with rpm limits as per the book. We used 33 to 1. After beakin, we switched to 50 to 1.

[Anonymous]

I don’t understand why a rotax would be just fine at 50:1 when leopard require 16:1 (I always ran 16;1 in a cr125 also) They are esentially the same type of engine? Lack of oil or oil quality seems to usually be the culprit in bottom end failures. Do Rotax’s fail on the bottom end more thsn they should?

[Doug Welch]

Two years ago the Rotax engines did experience an unusual number of bottom end failures. It was traced to faulty bottom rod bearings. They have long ago changed to a better bearing and failures are now very rare.

I think the reason the Rotax can survive on less oil can be traced to the under stressed nature of the engine. The Rotax turns far less rpm and has a very low compresion ratio compared to the other engines. The Rotax is igintion limited to 13,800 rpm and delivers max hp around 12,500. It runs on 93 octane fuel. All the other 2 cycle enges run much higher rpm and much higher compression, so they need more oil and higher octane fuel.

I think we have a real challenge for us at Bandimere next weekend. Since we can not rev near as high, we will be at much lower rpm coming off the slow corners than the other 2 cycles.

[Anonymous]

I personally run closer to 35:1.

I was recommended to run a lower ratio at altitude because we are running smaller jets = less oil into the motor.

I would personally rather be on the safer side of things.

[Anonymous]

I run 32:1 except inthe Rmax races at 50:1.

[cgordon]

Where do you get VP MS93 in the Denver area? None of the tracks have it. Is RS7 available in the Denver area?

Thanks,
Charles

[Anonymous]

Charles,
from google -Redline Motorsports
http://www.cosportbikeclub.org/local/highoctane.html
hth,
Richard

[Bruce Boman]

You can get both VP’s MS93 fuel and RS7 oil at:

Big T High Performance
2577 E 79th Ave Unit B
Denver CO

(720) 872-2414

Good people, nice little performance shop, they sell by the gallon or drum. They also have all the other VP fuels too in case you need MS98, VP110, C12.

Bruce……….

[Doug Welch]

I use Big T, good guy who really works hard to keep his fuel clean and water free. He keeps it in doors, heated and air conditioned. During the summr, he flters it with a chamois to remove any condensation that may form in the barrels.

[Angie MacEwen]

Here is their web site.
http://www.bigtracingparts.com

Very nice people – Mark and Jennifer Thompson.

[Author]

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