Tagged: Rotax Exhaust
November 12, 2013 at 3:18 pm #15418
For any of us racing late into the fall, warming the kart on the stand before hitting the track is unavoidable. I just completed my second season karting, and noticed that my exhaust packing burns off after one race day in this cooler weather. I know this is a consumable item, but Rotax suggests 6-8 hours of use before replacing the packing.
I picked up on the trick of putting a sticker at the beginning of the stinger chamber to show when the packing is starting to burn off, but I am curious if anyone has advice on a warm up procedure. I change my jets for the weather conditions, and mix 3.5 oz of oil per gallon of gasoline as recommended by KartSport.
Typically I run the kart on the stand for a few minutes, revving it up and using the brakes to put the engine under some load. This seems to be the common practice in the pits, but I am wondering if there is a better technique. Any suggestions?
November 13, 2013 at 5:18 am #15445
Other than completely covering the radiator while warming up the engine on the stand not much else. I get mine to 115 or 120 on the stand and then shut it off and put on ground get dressed and wait for grid release to go on track. fire it up and go easy 1st lap with rad flap down and maybe my hand over the front. I try to run enough tape to maintain 150 min with flap down.
I don’t think this has anything to do with packing blow out. Are you sealing the header with the RTV? use doubled up springs.
November 13, 2013 at 5:30 am #15447
Joe – thanks for the response. My issue is with the exhaust packing burning up, not blowing out, but you do raise another interesting topic. Is there a benefit to using RTV around the header flange other than keeping the back side of the engine clean?
November 13, 2013 at 11:08 am #15494
It is power lost if oil and gas is escaping. I would also pose the question does the pipe get hotter with an air leak? It’s all about building as much pipe pressure as you can.
Something else I thought of while not working today and watching World finals from my desk. We tend to run these motors WAY leaner than what Rotax recommends in thier fancy charts in the operators manual. This would definately burn out the first 2″ of packing. I pretty much open and inspect after each race weekend.
November 13, 2013 at 1:41 pm #15512
Lean makes power though. I don’t understand how you are going through exhaust packing in one race. You are talking colder than fall temperature if that is the case.
November 14, 2013 at 4:33 am #15555
Fall temperatures in North Carolina starting in the 40s and warming up to mid to high 50s.
November 14, 2013 at 6:46 am #15568
Man I need to move out of FL then, lol.
Any noticeable oil usage other than the normal, or leaking? I know my old YZ125 used to burn oil through the exhaust and I would go through packing faster because of this. It already gets hot, add oil to the mixture you get the idea.
Just trying to help with my 2 stroke 125 knowledge moreso than my lack of kart knowledge.
November 15, 2013 at 5:11 am #15669
I agree, I am sure the exhaust packing is loading up with oil and burning up when it gets hot. Like I mentioned, I already adjust my jet size for the weather conditions, so the fuel/air mixture should be good.
My exhaust packing is only burning up in the colder weather when we have to warm up the kart on the stand excessively, starting with a water temp of 70 and working towards 110 before we hit the track.
Anyone know of a place to buy bulk exhaust packing that is Rotax legal?
November 15, 2013 at 5:33 am #15671
Exhaust packing is Exhaust packing, there are 4 different types. I don’t really for see how it could be deemed illegal exhaust packing.
1.) Continuous Bulk Fiber
4.)Pre-formed glass, or Glass/steel pillows
The pre formed glass will last you the longest, will be the easiest to install, but will also cost the most.
Again I don’t see how exhaust packing can be dubbed illegal, as long as you stay under the DB threshhold (assuming there is one)
November 15, 2013 at 7:08 am #15704
Everything Rotax is legal. Are you racing local stuff or RMAX series. Ask your track for a ruling.
November 15, 2013 at 7:38 am #15711
I am just running in the TaG division at GoPro Motorplex in North Carolina. I am not looking for an exhaust packing alternative, but if I could buy 3 yards of exhaust packing material and cut it to size myself it would be more cost effective than buying an $18 pre-cut piece of exhaust packing each time.
Really my question was to see if anyone has had similar issues with exhaust packing burning up in a single day, or if they knew of some things to either try or avoid.
November 27, 2013 at 2:04 pm #16672
Thanks for the response Ayrton, you are right in assuming that we warm up the karts much more in the cooler weather. I don’t know of a way to avoid it and I only warm the kart up partially, say 90F. I already use tape on the radiator and cover it with my hand on the warm up lap. I see everyone else in the paddock warming their karts on the stand, and it looks like they use a similar method.
Regarding the steel exhaust mat, from what I have found online, this is for the micro max class only. I don’t currently run the Rotax series, I run in TaG, but I want my kart to stay Rotax legal incase I switch back. Has anyone used different exhaust packing for a Rotax engine ?
November 27, 2013 at 4:40 pm #16680
The Steel Exhaust Isolating Mat is legal for all Rotax senior so do not worry about that. I think this has been the case since the 2012 season. You said you race in the TAG class so you probably see the Leopard powered karts get warmed up rather aggressively on the stands and think you better do the same! In PA we have similar weather or even colder sometimes. All we do is add two or three strips of tape on the radiator, Start the kart about 3 or so minutes before rolling off the grid and we get it to temp with in a lap or so. This is sometimes in weather cold enough that we add latex gloves inside the regular gloves to keep feel in the fingers! I am assuming that you have the new radiator with the flap to modulate airflow. You are at MMX yes? I love that track! Talk to Eric Jones, he will help you plenty and keep you Rotax legal.
November 28, 2013 at 8:22 am #16700
Thanks for the good advice Ayrton. We actually bought our karts from Eric and Brandon Jones so I’ll have to get in touch with them, we have some things to replace during the off season anyways.
What track do you race at in PA ? I moved down from Buffalo, New York a few years ago to South Carolina for work and that is when we got into karting.
November 28, 2013 at 2:09 pm #16721
Pittsburgh International AKA Pitt Race and formerly known as BeaveRun. Great track! Give it a go sometime you will enjoy it.
November 26, 2013 at 3:32 pm #16624
Given the way you have described the condition, I come to the following conclusion. In warmer weather you do not warm up your engine on the stand, therefore; the packing last longer. Yes? In colder weather, you warm it up on the stand and in so doing unburned fuel is dumped into the exhaust pipe soaking the packing. When you finally go full tilt, it burns it.
Solution: Try using/adding the Steel Exhaust Isolating Mat. Also, if you start your engine about 2 minutes before you roll out, you should be up to temp within a lap especially if you put your hand over the radiator. If too cold, add tape. Starting it on the stand should then be for making sure all system are a go.
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