[tony zambos]

Sid,
IMO, the first thing you should do is contact the association that you’ll be running. There a many regulations covering the Rotax and you should me yourself aware of what you need to make this engine legal.
If your clutch has springs and shoes, you have an old clutch. If the clutch drum has holes in it, it is an old type. The new clutches do not have a vented drum and the clutch is one piece. A change in clutch drums came out a few years and all the associations I’ve race with require the new style drum. But upgrading to the new clutch also requires replacing the nylon gears in the crank case with metal ones. The new clutches are low rpm engagement and not adjustable.

You can manage with a single clutch drum as different size gears can be attached to it. But you’ll have to invest in purchasing a socket that fits the retaining nut and have the front of the socket cut flat to insure a good fit on the nut. For road racing, get yourself a 16t driver

Next, if your engine does NOT have the EVO upgrades, again check your racing association. You may not have to install any of the EVO grades or maybe just some. Some of the changes are replacing the wiring harness, new piston and rod, and a new carb.

The carb is fixed jet meaning that it can’t be adjusted on the track. If this is the first time with a carb like this, jetting software would be a very good idea. You’ll also need several jets, know how to change them out and how to set the floats

Make sure you know what you’re getting into with the Rotax. I’m not telling not to go with the Rotax. It is strong, reliable and probably a lot of fun at Mid-Ohio.

[tony zambos]

Sid,
What do you think are your options are for a Rotax clutch and what clutch do you have on the engine now?

[tony zambos]

In addition to Christian’s and Marks’s comments;
# Connect a piece of fuel line to the carb inlet. With the carb in its upright position, blow into the fuel line. If you can blow air into the carb, turn the carb upside down and blow into again. This time you should not be able to blow into the carb. If the carb passes this test, the needle valve should not be the issue.

# If the test above fails, with the carb upright, rap on the side of the carb with the handle of a screw driver. This should dislodge the needle valve if it was stuck.

# There is an internal fuel filter in the carb. Try cleaning that.

# If you’ve done all of the above and still having issues, check your fuel pump. It may have assembled incorrectly or the fuel lines are attached wrong.

Scour the internet for manuals and articles on the Rotax and the Dellorto carb That you can find. The first two are on me.
http://www.karting1.co.uk/new-ThePreparation&JettingoftheRotaxCarb.pdf
http://www.kartservice.nl/pdf/DOC_Handbuch_Dellorto.pdf

[tony zambos]

Dave,
Had two messages this morning. Tried to delete both, but one reappeared. I’ve left it in my inbox.
Have a good day, tony

[tony zambos]

Make sure you check with the organization that you’ll be racing with on the size of the weights that can be used and how they must be attached.
Another option to bolting the weights to the seat is weld on tabs such as this, https://cometkartsales.com/Weld-On-Lead-Weight-Tab-Steel.html. There uses to be a perch that was bolted to the chassis frame that you could stack weight on. But couldn’t one this morning.

[tony zambos]

Cheeseburger! Cheeseburger! Cheeseburger!
When that doesn’t work, bolt lead weights to the seat of the kart. You can buy them from kart shops. They’re available from 2 to 8 pounds. If you know of a local plumbing supply near you, they should have 5 pound lead bricks. You’ll have to drill them for a 5/8’s bolt and either double nut them or drill the bolt for a cotter key. On the 8 lb weights, you’ll probably be required to use two bolts. Most track I know of require the weights to be painted white.
You can move the weights up or down the seat for to help in chassis tuning.

[tony zambos]

I’m not sure if carb cleaner is a culprit. Brake cleaner is a definite no-no. I’ve always removed the needle valve before spraying the inside of a carb. If you’re stripping the carb completely down before putting it in the ultrasonic tank, you should be good.
Have you gone back out and do you have the same problem?

[tony zambos]

Mike,
It’s been a very long since I’ve had a JR and it’s going to be awhile until there will be another in the family, but here goes.
First off, don’t be hesitant on trying different setups. If nothing else, you’ll what not to do the next time. A couple of things to try besides tire widths: Moving the seat up will result in a higher center of gravity which will result more weight on the outside rear wheel. Is your driver leaning into the turns?
Try adding more castor. That will increase the jacking effect and again get more weight on the outside rear tire. Changing your tire could help as well.
If you are struggling and desperate, ask the people you race with. If there is a local kart shop that supports younger drivers, ask them for help.
Good Luck.

[tony zambos]

You should have not bent the float arms. This may have made your carb illegal. Check your associations rules. Your should have bent the tab that is in contact with needle valve. Remove the pin that holds the float arm and check the needle valve. The plunger in the needle valve is spring loaded. The spring may have broken or the valve may no longer be making a good seal against the seat. There also could be a possibility that the seat is not tight.

[tony zambos]

Matt is right. Make one. But Comet does sell one, https://cometkartsales.com/Mychron-Axle-Speed-Sensor-Bracket.html

[tony zambos]

Dave,
on the desktop version of EKN, there is an ad playing for $100 off on custom suits. It’s got an expiration of 10/1/15.

[tony zambos]

Dave,
Know all too well of making a change to one thing and seeing an adverse effect somewhere else. That goes for software and karts.

[tony zambos]

While you’re buying tie-rods, assuming they’re for spares, invest in a spare steering shaft.

[tony zambos]

Oops. Forgot to thank you Dave. When FS1 wasn’t broadcasting the race, had the desktop and the feed from IMSA.com. Got a lot done in my office during the race. ;)

[tony zambos]

When you purchase the tie rod, ask the vendor for the appropriate left and right hand threaded ends. There is one of each per tie-rod. Probably 8mm. Don’t forget to get a couple of left hand thread jam nuts.

[tony zambos]

What was the amperage rating on your last battery? Maybe you’ve been purchasing batteries that were not powerful enough. Suggest charging your current battery with a charger that’s not a trickle charger. Borrow one from a friend if you don’t have one or ask you gas station.
This might be a good time the consider purchasing a used Coleman mini-starter with a sealed battery. They’re about 18 pounds with the battery.

[tony zambos]

Tim,
race groups for CES are usually group by average group speed. The only issue you might have is the shifter and 4-cycle classes practicing and racing back to back. But CES has always been willing to work on these issues. Best advice is to call Dave Larson.

[tony zambos]

Tom,
First off, listen to TJ and Gary.

Second, this is a good time of year for you to look at maintaining your engine and clutch. If you have no idea how much run time is on the engine, get it looked at. Could prevent you from having a short weekend at the track. Since the stall speed was over the norm, check the clutch for being worn or warped.

Last, consider upgrading to a MyChron 4(4 or 4-2t), a Data Key plus a GPS module. Time at the track gets hectic. With the MyChron and Race Studio on a pc you can go back over your data at a quieter time. AiM does have seminars on Race Studio and they’re cheap. Only issue is that the closest one to you is a little west of Milwaukee.

[tony zambos]

Tom,
I sure some one will post up a gear ratio for your class. But having run the weekend at the track, you should be able to come up with a reasonable guess at the right ratio. Were you over revving the engine at the fastest part of the track or turning too few rpm’s in the corners? What was the clutch stall speed set to?
What’s going to be more important is your chassis setup. Nothing is going to kill your lap times more than a poor handling. My advice is to take to gear ratio that someone will graciously provide, and maybe add two teeth on the axle. Then work on the chassis until you can run with everyone else and knock off the extra teeth.
Good luck.

[tony zambos]

+1 on Peter’s comments. It seems that all your existing chassis needs is routine maintenance. Make sure your frame is reasonably staight. If you go traveling, it will be easier on a chassis you’re familiar with and the money you save could go towards extra spares and entry fees.

[tony zambos]

to the best of my knowledge, it’s legal to weld up cracks in a Rotax pipe. But I’d toss this one because it appears from the photo that you can’t get completely to both end of the crack.

[tony zambos]

I’m going to take a wild guess and say that most people don’t align their karts by using a string is because they never seen it done and have no idea as to how to do it. That simple.

[tony zambos]

Joe,
if you have an SMC axle clutch, I might be able to help.

[tony zambos]

Thanks Dave for looking into this. Didn’t receive the email notice of your last response either. tony

[tony zambos]

Mike,
the throttle stop keeping the butterfly from closing is not going to have an effect on the max rpm’s from the motor. While you have the air cleaner off, check that the butterfly is opening completely. Also check that the throttle pedal stop will not allow the throttle to try to get past full open. That will put undue stress on the carb. Are the other carb settings now the same as when you sent the engine in?

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