How to tell when it's time for a rebuild?

[Matt Clark]

What are some signs it's time for a rebuild for a club racer? Anything in particular? Is there some part that fails more commonly than others if you run it too long past needing a rebuild? Just trying to get some ideas as I bought my engine w/ an unknown amount of hours on it, and would rather be proactive than run it too long and damage things and cost more $$$. Thanks guys!

Matt

[Nick Weil]

Run it too long and the connecting rod or the rod bearing will fail and that's not cheap since it usually destroys the cylinder. Any of the internal bearings can fail without too much warning due to heat and lack of lubrication over time.

We tell our customers to rebuild top end after a 10%-15% loss of compression over time. And if there's more than 20 hours on the top end, you're pushing your luck if you don't do the bottom end at the same time. There's no real magic number, but most racers will agree, they are the fastest the lap before they BLOW UP!
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Nick Weil
Authorized Rotax Service Center and Dealer since 2002
2004 Team USA Rotax Worlds Finals DD-2 Driver

Want to save money AND grow the economy? www.fairtax.org

[Russell Stevens]

Is your club requiring the rotax to be sealed? If not it is pretty easy to crack it open and check for wear. Top end can all be done with some basic tools, and the lower bearing can be checked for play once the jug is off. Replacing the lower bearings is doable at home, but you might want a press (or take it to a small engine shop and have them do it). Either way go through it yourself with the shop manual, or have it gone through and the bearings replaced by an authorised Rotax shop if you need it resealed. It will give you some peace of mind, and you will know how long since the last rebuild. If you aren't at the level of looking for the last % of power in your racing program run your premix with the maximum oil ratio you are comfortable with. I personally run Golden Spectro at 32:1 in just about everything, including my chainsaw, weed eater, 2 stroke ATV, Leopard, and Rotax. I'm new to karts, but stick with the oil and mixture ratio that has served me well for over a decade. I don't have carbon buildup issues, and rarely foul a plug.
I personally dont go north of 13k RPM for more then a millisecond every lap, so mine is a fairly low stress environment, I rebuild less frequently than someone who is banging the rev limiter halfway down the straight. If you have fairly open rules at your track get an adjustible main jet, and relocate the fuel pump. It makes living with a Rotax much easier, and allows you to richen the mixture on the fly. (Or lean it out and break stuff if you get greedy).
I guess my point is, rebuild time depends on how often and how hard you push the engine, how much oil you use, and if you tend to run it a little lean or a little rich. Have it checked over now so you have a known starting point. If you have to pay someone to check it over, might as well have the bearing replaced while you are at it.
Rusty

[Joe Brizzolara]

Go with the 50 hours as it states in the manual unless reving the piss out of it or competing at a high level and need to wring the last drop of horsepower out it it.

I've know people who are running nationally changing rings or piston and rings at 10 hours and doing the bottom end at 20 but I've gone just about 50 with no ill effects.

[Joe Brizzolara]

[Joe Brizzolara]

[Russell Stevens]

I love the adjustible main jet. It makes life easier. It allows me to tune by ear on the stand, and give the knob a twist if I feel like it's too rich or lean when I'm on the track (just like about every other karting carb out there). You have to relocate the fuel pump to allow the cable for the adjuster to exit the bottom of the float bowl and have a lose enough radius bend to allow the knob to turn it. Mine goes right through the hole in the stock fuel pump/airbox mount that is normally covered over by the fuel pump. I put the middle of the 3 jets from the Dellorto adjustible main kit and have had enough range so far.
Rusty

[Chris McGinley]

[jeremy shaw]

So what should the compression ratio be?

[John Savage]

[Ryon Beachner]

An easy way to monitor when it is time for a rebuild is using an hour meter. This takes all the guess work out of the equation.

We have these in stock ready to ship.

http://www.2wildkarting.com/pulse-engine-hour-meter.html
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2Wild Karting
www.2wildkarting.com
Shop: (949) 206-9906