Rotax DD2 starting problem

[Christopher Madia]

I have a rotax DD2 and i was practicing last weekend and after about ten laps the kart started to lose power and eventually died. When i went to try to restart it it did not make the normal clicking sound it does when trying to start. Instead it sounded like the engine wasn’t even trying to turn over but you can clearly hear the starter. I have a spark from the spark plug and fuel is the bowel as well as good compression. The only thing i did was change the jetting from a 175 to a 168 and changed the seals on the water pump. Like I said the kart ran fine for a little over ten laps then died. any help would be greatly appreciated. Thanks

[Eric Alexander]

First two things I’d check are fuel pump and battery.

Fuel pump: when the diaphragm wears out it stretches out and stops pumping fuel efficiently.  It shows up as miss-firing and hesitation on the track, and if unchecked eventually leads to the engine just dying.

But a bad battery will do the same.  If it will not hold a charge it will start out strong and quickly fail to run the kart out on the track.  Also a bad battery can have enough voltage to spin the starter but not engage the flywheel and therefore not turn the engine over.

After checking those two, I’d start looking at the wiring harness.

[Christopher Madia]

Yea i think the problem i am having is that the flywheel is not engaging. Any idea what the voltage should be on the battery?

[tony zambos]

Minimun of 12. 12.8 volts would be better.

A couple of things to remember. The Rotax is a total depletion electrical system, meaning the engine will drain the battery until it doesn’t run. If the battery charges back up to 12v quickly after being drained to the point where the engine doesn’t would indicate a bad battery.

LAD Specialties customer / tony kart / rotax / kt100

[Christopher Madia]

I just checked the voltage on the battery and it read 12.8 so i know its not the battery. Not sure why when i go to start it the flywheel isn’t engaging if I have sufficient voltage. Could it be a bad starter even though i can hear it winding when i start it?

[Steen Carstensen]

Your battery can show 12.8v but still be bad. Hook it up to a known GOOD battery, and see what happens. From your description of the engine starting to lose power and then die, I would bet you dime for $ that a new battery will fix your problem.

PS. The flywheel doesn’t engage, the starter motor does. That’s another sign of a poor battery, it has enough power the spin the starter, but not enough to throw the bendix  forward.

[Christopher Madia]

I just tried a brand new battery and it did not work. It made the same noise as the old battery did when trying to start. Any other options?

[Steen Carstensen]

Well, if it’s not the battery, it could be wiring. Make sure all your connections are clean and solid. This is a long shot, but I have seen the flywheel come lose on the crank shaft, so when you try to start, the flywheel spins, but does not spin the crank/engine.

[Christopher Madia]

I appreciate all the help, I think at this point I am going to try to find someone who will work on it. I live in Upstate NY Syracuse area does anyone know of any place i can bring it to be fixed? the local track i go to is not to familiar with the rotax motor so they were not able to help.

[Eric Alexander]

So another thought is the starter bushing wire has started to come undone.  It might even be touching the starter cover (which *might* short out the electrical system and cause the kart to stop running on the track).  If you only have a thread or two of the braided wiring in the bushing connected I could see that causing the starter issue.  And the bushing wiring is a known item that wears over time.  If anyone at the track has a spare starter you could try swapping out and seeing what that does.

If you race Rotax, a spare starter is a must for your spares kit.

[Martin Colligan]

Hey man do you have good compression ? Are you sure you did not blow the engine ?

168 main jet is kind of lean. Do you recall the motor heating in the last laps ?

 

If you got spark and Fuel it should start.

 

[tony zambos]

Have you made certain that the engine is not stuck? I’m guessing that if the spark plug is removed and it’s in gear, you can turn the rear wheels. The piston maybe stuck or the gears in the transmission are damaged.

Another guess would be that the ground wire is either broken or loose. That would cause the motor to shut down and not restart.

I’m assuming that the starter is not spinning, so the bendix is not being pushed into the flywheel. Or is the starter spinning and the bendix no engaging? At this point you might want to bench test the starter motor. But can’t see how a starter would have stalled the engine. There is an interruption of electrical power to the engine while shifting. Don’t have any idea if the interruption includes power to the starter.

If you have a voltmeter, check the on/off and start switches.

LAD Specialties customer / tony kart / rotax / kt100

[Steve Libretto]

Make sure to check the ground wire. If the gound wire has loosened up, it could cause this. I’m not sure of the technicality behind why, but I had the same EXACT issue with a leopard, and all it ended up being was a loose ground wire.

[Christopher Madia]

I appreciate all the help and responses. I ended up dropping the kart off at my local rotax repair shop. I will let you all know what the verdict is.

 

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