Perfect! Thanks Clayton
That’s what I was thinking, since I got the kart like that. But how do I know if the 165 is better than the 175 for me?
You will have to test them on the track. The correct one will depend on your engine, fuel, temperature, altitude, and humidity level. Start with a big jet and go smaller. You will know when you go too small the engine won’t rev all the way at the top or hesitate out of slow corners.
The Rotax has a very big carburetor with a large float bowl. It would be very hard to go too small/lean and damage the engine. It will just lose performance before that happens.
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Perfect! Thank you very much Clayton
So, if I see any gaps, I can start by trying with a 175 jet and then reduce to the right jet, without danger for the engine. Can the color of the spark plug tell me some information on the right jet, because I have not yet managed to have a chocolate brown on the spark plug. I will see tonight with my hose cut how my rotax is doing.
I personally do not look at the spark plug color. Every different fuel has additives that can effect the color on the spark plug. Even if I get regular premium gas from the same gas station days apart.
I look to see that it is not “wet” that is a good quick check to see if you are too rich.
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In my previous experience using the pre EVO Rotax, the proper jetting was anywhere from 158-168 depending on conditions. The 168 jet is also used as the rich jet when breaking in a fresh engine. Here in SC, I usually ended up with a 162 main jet most of the time. Hope this helps.
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Perfect! Thanks Clayton
So, if my spark plug is wet, it’s because my rotax is too rich, therefore too much gasoline. So I should lower the main jet. Because on the air/fuel screw side, it is at 2 turns, and having tried at 2 and a half turns tonight, the spark plug blew after not much time. Sorry for all my questions, I understand better and better and I will make a post of general thanks for the new developments.
Thanks Jason
Yes, it helps me a lot and I feel lucky to have all this help.
(So I have a 165, if I put a 162, I’m leaner, less fuel. If I have misfires when accelerating, that’s what I should do. Richer is safer, but less efficient.
Well great news tonight, a very happy guy, who was a little discouraged, and by my mistake, I went to do a test with my MAX, hoze cut, and hurray, it works wonderfully. There will still be adjustments to be made of course, but that was really the problem. No need to put the choke, no more lack, it even turns well at idle. I turned about twenty laps without problem. Finally, and thanks to you. A Special Thanks to Stamatis, Clayton and Bjørn, who were the first to tell me about it with my photos. Now I am at the stage of adjustments, jets, etc. Big Big Thanks
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Yes, but if have a very slow finally lap and pull into the pit with the engine running it can look like there is too much fuel and the spark plug is wet. You have to run a hard final lap and turn off the engine when you enter the pits and just let it roll with the engine off.
Again, it is very hard to tune with spark plug color or if it looks wet. We shouldn’t care on exactly what the spark plug looks like, but how the engine feels on the track.
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Perfect! Thanks Clayton, I’ll take note of that.
Small problem, I couldn’t ride today because I didn’t have a spare spark plug and mine burned out again. Even though I left my air screw at 2 turns, I don’t understand why after each session, the next day, I restart, the engine turns a little and poof, the spark plug is burned out.
And is it true that my clutch repair could unbalance my chainring, even when everything is mounted. I don’t think so, since the bands are not all the same and there is some looseness, but the people here, not karting people, yes.
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Old type of clutch on the fr 125 rotax is a small mess . Always had peoblems with that .
Since i get the upgraded system from the evo witch is not a cheap one yes . But its somewhow bulletproof and with no springs inside it …
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The pre EVO clutch was quite error prone, springs failing, clutchshoes failing, the hub failing.
The EVO clutch is not completely bullet prof but do last a long time, we still see issues when people starts reving the nuts off it on the stand.
A complete upgrade kit to the EVO clutch is In the 350euro ballpark, but im not sure its worth using that much on a pre EVO engine just for the clutch.
Generally a lot of issues was solved with the EVO kit.
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Thanks! Stamatis, I’m thinking about buying the new EVO, but it doesn’t tell me if my repair can cause a problem.
ok! Thanks Bjørn, I’ll think about all that.
But can my repair cause problem. Sorry, I have to translate, maybe I don’t understand everything. And I was also wondering, why I burn candles almost every time I go out. My air screw is always at 2 turns.
Air screw shouldn’t effect the spark plug life. There is probably something else causing that.
Please post a picture of your bad spark plug.
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Perfect! Thanks Clayton, here are the spark plugs, the last one is on my rotax and I even have a burnt Denso IW31, the first one. Basically, a spark plug that burns every time I go out. Either at the start of the start or during my go out. 5 spark plugs, 5 go out.
Those do look brand new. What makes you think they are bad? The engine just stops running or it won’t start again? Loss of power?
What is the spark plug gap set at? Evo engines work best right around 1mm.
Maybe try the Rotax recommended NGK plug. They are expensive, but I haven’t had issues with them.
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