Aprilia Sprag Clutch

[ZAMR]

Hello all,

The University of Oklahoma is starting to get into cold weather tuning with the Aprilia, and I was wondering if anyone else had problems with the sprag clutch at cold temperatures.

At below 40 degrees F, the starter motors seems to spin for a while on its own and then suddenly engage, then disengage, then engage again. When we bring the dyno back inside and let it warm up a bit it works fine.

I was just wondering if anyone had similar issues.

Thanks,

Zach Moorhead-Rosenberg
Sooner Racing Engine 09

[ZAMR]

Hello all,

The University of Oklahoma is starting to get into cold weather tuning with the Aprilia, and I was wondering if anyone else had problems with the sprag clutch at cold temperatures.

At below 40 degrees F, the starter motors seems to spin for a while on its own and then suddenly engage, then disengage, then engage again. When we bring the dyno back inside and let it warm up a bit it works fine.

I was just wondering if anyone had similar issues.

Thanks,

Zach Moorhead-Rosenberg
Sooner Racing Engine 09

[gregjohno]

Hi,
I have had a problem starting my bike since the weather turned cold here in the UK.
On cold days in would'nt start, if it was warmer it would.
now when I try and turn it over it makes an awful noise and wont start at all.
a machanic now tells me the sprag clutch is had it, the repair will cost around £500 ouch.
so I would keep yours warm as I think if it starts it will get progresively worse.


Greg

[Wesley]

Zach, I've been thinking. For about 15 bucks we can get a heating pad and just slap it on the motor to keep the starter motor and clutch warm before we start it...

[ZAMR]

Thanks Greg,
Ya, our sprag has gotten progressively worse as you describe it. It started working for a while, but rocky starts in cold weather have completely trashed it.

Wes, we should try that heat pad this week sometime...

Zach Moorhead-Rosenberg
Sooner Racing Engine 09

[Erich Ohlde]

these starters make some strange sounds sometimes.
when you say "the starter seems to spin for a while on its own and then suddenly engage", have you verified this from the ecu rpm trace?

[Wesley]

No, we haven't, but I don't need a graph to tell me if an engine is turning over or not. Though I'll likely check it now, just to satisfy the curiosity.

[Tim Gornik]

True, but you do need recorded values to tell you if the battery voltage is droping (too much) therefore decreasing the cranking RPMs or if the starter is simply wearing out, where too the avg cranking value is substaintally lower. Due to the high compression of this engine, it is sometimes to much for the starter to overcome the compression stroke as the starter gets weak.

[Erich Ohlde]

Wes or Zach. Any progress on this?

[Yellow Ranger]

Yea, we are actually we're taking it to the tulsa dealer tomorrow, he said he could swap it out for us. If you didn't take so long machining your stuff http://fsae.com/groupee_common/emoticons/icon_biggrin.gif , you could here the thing and tell the starter wasn't engaged- it spins way too fast and way easily, we should have it fixed tomorrow and be able to get back to you...

[Erich Ohlde]

cool. yeah, it did take forever! oh well had to get the cob webs out sometime.

[Wesley]

So while we're talking about it, these engines have decompressors on the cylinders, to aid with starting effort... how do they work? Haven't done a lot of research, but if anyone knows off hand...

[Erich Ohlde]

its a spring loaded weight. pull a valve cover. its a very simple mechanism thats hard to explain but easy to see what it does.

if you can get the engine to idle right a 2000rpm you will here a bunch of noise from the decompressions opening and closing as the engine rpms fluctuate.

[Wesley]

Ah, got it. We pulled off our first cover today. Hopefully we didn't let any magic smoke out of the motor.

[ZAMR]

A man. If you guys could see the sprag clutch when we pulled it out. It was mighty effed up...

[Erich Ohlde]

pictures? what happened?

[ZAMR]

I didn't have my camera when we took it apart, and I left the spring in Tulsa, but the spring was all torn up and bent, it looks like the weights had tiny shears in them, like the spring came out of its groove somehow. All of the surfaces were chewed up as well.

The mechanic said he had people come in with sprag problems, but none this bad...

[ZAMR]

Also, curiously the engine did not turn over when I tried Saturday at 9:00 in the morning. When I got it to Tulsa around 11:00, after it had been sitting in a warm car for 2 hours, it turned right over.

I still don't know whats up with that...

[Wesley]

Both of the races were galled horribly, I haven't seen anything that bad since a crank bearing spun.

[Erich Ohlde]

pics?

[MalcolmG]

you guys need a team forum http://fsae.com/groupee_common/emoticons/icon_razz.gif

[Drew Price]

But then their guys might get together and start going for cargo ships off Somalia....



http://collectingtokens.files.wordpress.com/2007/09/pirate_jack_rackham.jpg


http://fsae.com/groupee_common/emoticons/icon_biggrin.gif http://fsae.com/groupee_common/emoticons/icon_biggrin.gif http://fsae.com/groupee_common/emoticons/icon_biggrin.gif http://fsae.com/groupee_common/emoticons/icon_biggrin.gif http://fsae.com/groupee_common/emoticons/icon_biggrin.gif http://fsae.com/groupee_common/emoticons/icon_biggrin.gif http://fsae.com/groupee_common/emoticons/icon_biggrin.gif http://fsae.com/groupee_common/emoticons/icon_biggrin.gif http://fsae.com/groupee_common/emoticons/icon_biggrin.gif <---- [ 1 x 9 ] * Happy

Best,
Drew

[Wesley]

The '09 frame rules make these cars $10 worth of caulking away from a boat anyways.

http://fsae.com/groupee_common/emoticons/icon_biggrin.gif