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I only know Rotax, but I’ve never found them to be spectacular below, oh, 7k RPM. Of course, all I’ve ever tweaked has been the main jet.
The needle clip governs how high the needle sits in the carb. There are multiple grooves the clip can sit in on the needle… The higher the groove, the leaner you are at partial throttle. At wide-open throttle, the needle is out of the picture regardless of clip setting, so it doesn’t really do anything for “low-end power.” The Rotax manual actually explains it pretty well (but then again, I’m a Mechanical Engineer, so take that with a grain of salt :loony: ).
Conventional wisdom is to leave the clip in the highest groove, maybe 2nd highest, but otherwise it impacts operation only occasionally (how long do you keep it at 1/3 throttle?).
@Garrick wrote:
Buy it from the track.
Lest there be any confusion, I meant “the track where you’ll be running.” Not “The Track” per se, although that’s the only place I have experience buying racing fuel.
Buy it from the track. Regardless of how it’s sold, you’ll need your own plastic jug for mixing the oil with the fuel and for storing mixed fuel. If you haven’t already, get a Ratio-Rite or similar mixing cup to make dispensing the right amount of oil a snap.
Last time I was at Centennial, they were only selling 5-gallon jugs (you’ll need VP93 for your Rotax). The jug was 50-ish bucks, but that was last month… 😯
That Bernie is one wacky guy. Actually, he strikes me as a very shrewd politician. Still, every so often he lets loose with gems like this, commenting on Danica Patrick’s 4th place at Indy in 2005:
“She did a good job, didn’t she? Super. Didn’t think she’d be able to make it like that. You know, I’ve got one of these wonderful ideas that women should be all dressed in white like all the other domestic appliances.”
I’ll probably be out there testing this weekend… Will there be a chance to walk the track? What about putting down some traffic cones to mark apexes (apices)? That first downhill hight-hander (in the “downhill” configuration, leading down to the chicane) messes me up.
I got an Interstate BSL1075, but I have an older wiring harness that presses on to two male spades at one end of the battery. I dunno about the newer-style harness with screw-on terminals located on opposite ends of the battery.
It’s a crap shoot… I’ve been using an Interstate battery with good results (knock on wood). I’ve also heard of the spec Rotax Max battery giving up quickly.
I haven’t had to service my starter (yet), but I understand the starter is the same as that for the Leopard engine, even if it’s mounted a bit differently. The Leopard manual has a procedure, including helpful hints on retaining the brushes during rotor replacement and securing the brush wires with silicone:
http://www.artkart.lt/championkart/manual.pdf page 35
On my starter, which AFAIK is still functional, I get 0.5 Ohms between the power plug and a randomly-chosen bolt head on the engine (hey, I’m a Mechanical Engineer, not Electrical, OK?). Dunno if that’s a significant difference, considering how beat-up my multimeter is. Is there any sign the starter is even trying to turn? Is the reducing gear seized up with gunk? The one time my starter wouldn’t crank, the fix was a new battery and dielectric grease on the terminals. I know you say your battery is new, but stranger things have happened… Consider getting a spare battery (you should have one anyway) and try it or someone else’s “known good” battery before doing any serious teardown.
@jibco wrote:
Do I need to turn down the obscuring time to below the shortest sector time? I think that is what I was missing.
Bingo! Obscuring Time set to x = “Ignore all inputs for x seconds after the last signal was received.”
Premium pump gas “will work” in a Rotax. The first year I had my kart, that’s all I put in it (well, a dash of oil too :rotate: ).
The oxygenates in pump gas may affect your jetting, in turn requiring a bit of experimentation on your part, and I’ve heard racing fuel is just way, way more consistent. However, if it gets you seat time, I say go for it.Late to the party, but oh well. All I’m going to add as a fellow n00b who doesn’t have a MaxJet is…
- If there are other Rotax runners at the track, ask how they’re jetted that day. Over time, you may find what works for others works for your engine too, or you may need to consistently go one way or the other.
- Keep notes of what jet you ran, the temperature at the time (I look up the hourly observation at Centennial Airport (KAPA) on my phone), and what RPM you were able to reach on the front straight.
- If you’re not sure you’re jetted correctly, go up or down by one jet and see the difference.
- Learn symptoms of running lean or rich. I’m still working on that myself… There’s the infamous “lean pop” at high RPM, but sometimes you can pop when rich too, I’m told. Look at your spark plug for excessive oil (rich) or a whitish, “cooked” appearance (lean).
- Personally, I release the throttle fully under braking, but I don’t slam it open or shut. Works for me, anyway.
I have just enough sessions under my belt to know that a little jet adjustment on the Rotax can make the difference between a sweet ride and a lead sled. That, and you were running an enormous gear! 🙂
@Franco wrote:
…and i want somthing that will good enuff for racing after i get practice in.
That depends on what classes are offered at the track(s) where you would be racing. You’d need to buy a kart that was capable of meeting the class requirements. If you’re looking at TAG, then basically you have a handful of engines from which to choose (go to tagracing.net for the complete list… the Parilla Leopard and Rotax FR125 are the most common in these parts, with some Motori Sevens and PRD Fireballs as well, plus there’s a lot of talk about the new crop of 4-stroke TAG engines), and the tech rules for club racing and the CSC are at coloradokartracing.com. The bigger task is getting the driver/mechanic “good enuff for racing.”
The trick about telling you “what to look for” is that every kart is a slightly different package. My advice would be to get whatever fits your budget and learn how to drive and maintain it. Many modern chassis have most of their basic features in common. The main thing is to avoid getting an “ugly duckling” chassis that you can’t get certain parts for, but there are a lot of parts that are pretty much interchangeable. You’d probably want a 50 mm axle. You’d probably have to replace some parts off the bat, like the chain and sprockets, and find a seat that fits you.
Karts were meant to be driven hard, and no two used karts have the same history. Even a new-looking, shiny kart can be crashed or bent. On a used kart, look for cracked welds, tubing that’s flat-spotted on the bottom or bent, and signs of neglect. Pick up the front end of the kart by the center of the front bumper, and the front tires should lift off the ground at about the same time if the chassis isn’t twisted. Spin the rear axle to see if it turns smoothly (binding could indicate a bent axle or toasted bearings). See if the seller would be willing to meet you at the track for a test drive… At the very least he should start the engine for you!
There are plenty of n00bs besides me who have gone through this exercise recently and posted questions here. You’ll need a means for transporting a kart, tools, spares, safety equipment, the list goes on and on. Still, for getting into honest-to-goodness 4-wheeled motorsport, karting has got to be the best bang for the buck.
Ah, where to begin… Where are you located, so we can give you info appropriate to your area? How mechanically-minded are you? Are you willing to turn some wrenches? Do you have prior motorsport experience, or maybe rode motorcycles in a prior life? Info like this will help us offer suggestions without wasting your time or insulting your intelligence! 🙂
Have you visited and/or driven rentals at the local tracks (see list of links on home page) yet? You can learn a lot by hanging out at the track, and rentals give you at least a small taste of what the action is like. Get to know the local shops, too, to see what they sell and service and to learn what to look for in terms of mechanical bits. You missed a great series of seminars put on last winter by Doug at Shockwave in Arvada.
If you’re starting from square zero, get proficient in the rentals first, then if you’re really hungering for more after that, take the plunge and get a used kart, then get out to the track whenever you can to get seat time. Some people start club racing right away, others (like me) do lots of Test & Tune sessions to try to get lower (and CONSISTENT) lap times.
Everyone will have his own opinion of what class you should enter. Personally, I think the TaG (Touch and Go) single-speed, electric-start karts are a smart place to begin, and this type of kart you can pretty much operate and service solo (my pregnant wife hasn’t expressed a desire to work on the kart). There’s enough to learn without having to worry about shifting, and you learn to carry speed through corners when you don’t have the option to grab a lower gear. Whatever you do, hang out at the tracks, ask lots of questions, and you’ll get a sense of what constitutes a good deal on a used kart. I lucked out and found a great deal on a used Rotax TaG package that serves me quite well. Ownership costs are a world apart from just doing rentals every so often, but a racing kart offers a lot more smiles per mile.
As with other esoteric endeavors, you’ll get out of karting what you put into it, and it takes a lot of self-motivation. I haven’t regretted for a moment getting my own kart, but for me half the fun seems to be working on it. These are not low-maintenance toys! I enjoyed my Saturday morning overhauling my brake caliper, but had a blast at Centennial today. I guess the “afterglow” from that session is what compelled me to write this novel…
Get an air tank from Harbor Freight… You fill it via a Schrader valve (same as car tires), so you can charge it at any gas station. A bike-tire pump works in a pinch.
My pressure gauge is 0-30 psi and has 1/2-psi increments. The cool feature you won’t find on garden-variety gauges is the bleed valve. It’s a small button you press to release air from the tire a little bit at a time. You over-fill the tires a bit and then bleed them down to the desired pressure. I don’t remember the brand, but I got it for $30-ish at IMI.
Ditto what Troy said about testing in order to hit the optimum pressure (13 psi for MG Yellows) at the right time.
@He who assembled the registration form wrote:
Arrive & Drive GT-4 _____
4 Drivers minimum per team. No Max.Unlimited number of drivers and no wear and tear on our own karts, eh? Hmmm… I envision a rag-tag team of 12 drivers, up to two-ish hours on the track each, for $300 a head… :look
Sounds like a real hoot as long as “Team Test ‘n’ Tune” avoids being punted by a shifter… After a while the track will look kind of like this: :jump
Seriously, I’d be interested in being part of an enormous team for this.
