Hello! guys. I would like to understand why my rotax max, goes well for a while and after a while, it gets wad, almost wants to stop, and I have to open the choke a little, a bit, to get it back correct and then remove it to do another good bit. I did everything and thank you for all your advice, gasoline ok!, 50/1, Motul oil, carburetor completely cleaned, fuel pump redone, compression #1 and spark plug #1. Air screw at 2 turns, 2 and a half turns and did all possible screw tests.
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check your carb float height adjustment . i had some problems with those after some quick laps .
and the last time one of those had a small hole , and kept fuel inside of it
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Check float height, check the fuel filter In the carb(and remove it).
I would go a bit up on oil, maybe 2 1/2 to 3%.
Is it the same place it does it, same RPM`s?
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Ok! thanks, but the carburetor has been completely disassembled, the floats are #1, no holes and the height has been checked and adjusted.
Thanks! I think the height of the floats is adjusted well, the fuel filter in the carburetor had been removed and the one in the line near the tank is new. I was driving at 2.5% (40/1) at the start and it was worse and my rotax was smoking at the end of a straight line. Much better at 2% (50/1). Right now, I’m practicing on a fairly large square and turning clockwise, and I drift a little bit coming out of each curve. I’ll try it next time, to see if it changes anything.
Are my jets to blame?
you need to have a small cut on the green hose that goes from the one side to the other side from the upper of your carb … from breather hole to hole . do you have the cut ?
also those 2 exits has to be cleaned
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Ha! well, no I don’t have a cut. This pipe was broken when I bought it and I put a new one in thinking it was ok!. I don’t really understand how I do that. Here is a picture I took when I cleaned the carburetor. It shows how the pipe is right now. Thanks!
yes it can . had some problems in the past with those
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Yes the carb needs to “vent” and equalize with atmospheric pressure to work. You need to add a similar cut to your green tube.
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That could verywell be the issue, it will have a hard time working without the Cut In that line.
I really would recommend that you go higher then 2% In Oil, if its smoking its not because of the ekstra oil, We use 2 1/2 - 3%.
Regarding the jets, it must be a pre EVO engine else the jetting is way of
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To add to what’s already said…. Smoking is not necessarily a bad thing. Especially at idle and part loads, much of the fuel (along with its oil) escapes out the exhaust port. This can trick you into running less oil than you need while also causing your engine to run richer
Although Rotax’s recommendation is 50:1, it does seem that most people deviate from this and run more oil.
To summarize: Snip a small break in the breather hose and verify your jetting against your oil ratio and whether you have an evo or “prevo” engine. The new ‘24 cylinder may also be a factor but I’ll leave it to people with more direct experience on that to chime in.
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New cylinder hasn’t effected jetting much for me.
I run 1:50 on race days and 1:40 on practice days. To stay well on the safe side.
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Perfect! Thank’s Stamatis
Can’t wait to try this!
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Thanks Clayton and for this info
Thanks! James I’ll do a test with this mix at 2%, and my hose cut and then, noted, I’ll go back to 2.5% if all goes well.
I don’t really know how to tell if my main jet is correct. But if you have any info or the other guys, I’ll take all the advice I can get.
Prevo engine, Fr125 2013
Thank you! Bjørn Noted and for the oil.
Yes, a pre-evo, Fr125 2013. You tell me which jet is best, if mine is not ok! There I have a 165
That sounds close. What I’ve heard is 165-175 works for pre evo engines.
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On the subject of carb venting - I currently have the two vent hoses venting separately to atmosphere - would it be better with one hose running from one vent to the other with the cut vent in the hose?
I don’t think it matters as long as it’s venting. I just think the single hose looks cleaner in my opinion and to race the Rotax series it has to be as the factory supplied the carb.
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