Sifus!!..Normally when you engine reach 50 hours of running time, it’s advisable to rebuild it. Correct me if I am wrong.

When they rebuild the engine, what parts that need to be changed.

Sorry for asking so many question in this forum. It might irritate someone I guess. I just try to picture my yearly budget for my new hobby. I should have my own 2nd hand 125cc rotax by end of this month...so many thing keep playing in my mind.

Well rebuilding youre engine I was in same situation when i started with everyone telling me different stories from every meeting to every 6 months and every year. I think it comes down to how much you want to spend and how competitive you want to be. I have run engines for the whole KKS and rotax season 11 races plus pratice without changing a thing and the wasstill on podium at end. After that it was pulled down and i changed a piston ring bearings and gaskets. I ran another engine to see how long it would go till it seized and that took 18 months and alot of hours. So unless you have alot of money to spend I dont see the any need to do it more then the rotax series which is only 5 races.

1st..congratulation to your podium finishes. Thank for the explaination bro.

i know of some who change piston every race and never see a podium. so...

Our two race engines are ex-Langkawi 2005 World Finals. We bought them early 2006 and rebuild them once a year, before the start of the season. We only change what is necessary upon inspection, e.g. our pistons are 2 years old. This year's rebuild cost us about RM2,300 per engine, inclusive of labour.

We open the race engines every two or three races for inspection. Sometimes we have to change the piston rings, sometimes we don't. In any case these inspections are affordable as the costs are mainly for seals and gaskets.

We also have a practice engine of unknown vintage. Even after two years of abuse it was only 0.5 sec slower than our race engines! We eventually rebuilt it at a cost of only RM1,663.

We all hear how reliable and robust the Rotax engine is so if this is the case to keep costs down why dont they make us run the engine for several rounds like formula one does, this would help keep the costs down and probably ensure closer racing. The engines are all sealed so I dont see why it would be difficult and just let the engine be rebuilt if it has seized.

As i said before I have been racing engines for the whole season without pulling it down and I have found my lap times were still improving through the season, maybe these engines perform better once they have got more hours on them.

Drivers don't all practice the same amount. If a driver did 20 hours of practice between two events he'd probably want to have the engine opened up fairly often.

In F1 they have a lot of engines they can use during testing.

The beauty of it is that there is no need for such a controls - because an engine rebuilt only at the beginning of the season will most likely be just as competitive at the last round as an engine that has been rebuilt after each race meeting.

The main thing that many rebuilds might assist in is improving reliability - which with the max engine is close to 100% already though - so the risk might actually go up with additional rebuilds because of possible errors when putting the engine together.

You will gain more performance by repackaging your exhaust 3 times a season than you would with 3 engine rebuilds... although it seems many only repackage their exhausts only once a year or even more rarely.

Oh i was told no gain on that part. guess i should try it. 3x per season is every 2 race?

how about airbox fitment? how ofen you change them. this i know have performance gain.

what about the powervalve rubber thingy. any performance gain here?

And what is repackaging exhaust actually..what do you do...

i've had people telling me to change the piston/ring every race.... if i was selling pistons i would do the same!

although they say how reliable these rotax engines the suppliers certainly dont advise against changing frings and pistons regularly after all it is there lively hood. Also i have also gone well over a season without repacking so maybe if i do that then i can take up a higher step on podium hi hi

I have not opened my engine from new - motor is 3 1/2 years old now.
It is still very strong and have no intention of any rebuild.
The only thing I had to repalce was the brushes in starter motor.

Biggest gain is from
1. Driver input/experience and
2. Chassis setup

I read with interest on the forum about the Rotax engine re-build. Changing pistons or rings after every race is excessive unless you import these items. As the Rotax distributor we also do not advise customers to do this. If your service guys ask you to do it then it is probably some other things he has in mind.

The most important thing when you do an engine check is to make sure your oil in the crankcase is topped up or renewed. I would suggest changing your oil every two race meeting. Check your hoses for leaks. Put your battery on charge mode when not in use. The charger cuts off when battery is fully charged. Rotax advise that the battery to be on charge all the time. Check your clutch shoes, springs and flywheel after every race. Problems always come from this area.

I am having a dyno installed in my premises in about a month's time and all owners can bring their engine in for a test to ascertain the power and what need to be done. In future we will dyno test all engines to make sure the power output is within the range acceptable. That will give everyone a level playing field.

James Leong