What just happened?

English · Post by **English** » Wed May 25, 2011 9:12 pm

I was just riding my Rattler 110. It's a very hot day here in Atlanta. I was WOT. Suddenly, the engine tone changed dramatically, and I lost all power.

I instantly thought: "Oops, there goes the piston rings at the very least."
I pulled into a store car park, and started to make plans to get the scooter home.
I'm not sure why, but less than a minute later, I tried to start the scooter again.
It leapt into life and rode all the way home as if nothing had happened.

I can tell no difference with performance or top speed now, as to before this happened.

Have you guys any idea what may have happened? Could it just have overheated and lost compression?

SteveK · Post by **SteveK** » Thu May 26, 2011 12:04 am

I would guess vapor lock. Did it feel/sound like it ran out of fuel and sputter? Vapor lock can be a two stroke killer.

I'm not Professor Fancy Pants either though.

Good Luck!

English · Post by **English** » Thu May 26, 2011 12:16 am

Thanks. Not vapour lock though. There was a definite mechanical sound that accompanied it. At the time, I was convinced it was top-end carnage (rings, piston, etc...).

It had me so convinced it was a seizure that (being a full-size bike rider) I instinctively pulled in the "clutch" to stop the rear wheel locking up. Of course, all that achieved was nearly locking the back wheel up.

. Funny how old instincts kick in at times like that.

B02S4 · Post by **B02S4** » Thu May 26, 2011 2:17 am

English wrote:...I instinctively pulled in the "clutch" to stop the rear wheel locking up...

The auto clutch will auto release if the motor seizes...

English · Post by **English** » Thu May 26, 2011 2:22 am

B02S4 wrote:

The auto clutch will auto release if the motor seizes...

Well, that's good to know. Thanks!

B02S4 · Post by **B02S4** » Thu May 26, 2011 1:27 pm

Which oil were you using?

English · Post by **English** » Thu May 26, 2011 1:53 pm

B02S4 wrote:Which oil were you using?

Oil? You have to use oil? Just kidding.

I can't remember the exact type, but it's Motul two-stroke oil from the local scooter store.

I'm not sure if it's a coincidence, but the low oil reservoir light came on a couple of times on the ride home.

Keys · Post by **Keys** » Thu May 26, 2011 2:55 pm

Perhaps your oil pump is having issues?

When my top end fried, the auto clutch did NOT let go immediately. The engine wound down to an RPM where that was possible, but it took a few seconds.

--Keys

Lotrat · Post by **Lotrat** » Thu May 26, 2011 3:50 pm

English wrote: I'm not sure if it's a coincidence, but the low oil reservoir light came on a couple of times on the ride home.

It's probably not a coincidence. The scoot was telling you that you are low on oil and you ran it WOT? Come on, you knew what happened. That's why you assumed the worst. Fill it up and see how it feels. Damage is done, see if you can still hit top speed like before and go from there.

B02S4 · Post by **B02S4** » Thu May 26, 2011 5:48 pm

Keys wrote:
...The engine wound down to an RPM where that was possible, but it took a few seconds...

If that happened then in your situation it wasn't a hard-seize, as the crankshaft was still spinning...

SteveK · Post by **SteveK** » Fri May 27, 2011 12:25 pm

Oh, you forgot to mention the oil light thing....

I think I'd do a tear down immediatly. If for nothing else than the fun of it..

Good Luck!!

English · Post by **English** » Fri May 27, 2011 3:08 pm

Lotrat wrote: The scoot was telling you that you are low on oil and you ran it WOT? Come on, you knew what happened.

Thanks for the vote of confidence, but no, I'm not that stupid to run WOT after the low oil light was on. If you read the post again, you'll see that I said the oil light came on briefly a couple of times after this happened, and on the way home. It hasn't come on again.

English · Post by **English** » Fri May 27, 2011 3:37 pm

I just checked the oil reservoir and, although it's not full, I can put my finger in the hole and come out with finger tip covered in oil.
The oil light, although still working, is not coming on yet - except at odd times going downhill. This is all as normal at this stage between oil fll-ups.

Wheelz · Post by **Wheelz** » Fri May 27, 2011 4:58 pm

The Rat oil light is very touchy, it goes on and off when you get about half a tank of oil. It will come on when you throttle and when your going up/downhill, it's just the oil is not hitting the sensor. Not a problem unless it stays on. It's just an early warning that your getting low.
I've blow my rings on my rat and it didn't start at all afterward. Have you run a compression test? That was the best advice given to me and it really determined I had done something drastic to the engine, well with a 2t it's not so drastic or uncommon from what I gather.

English · Post by **English** » Fri May 27, 2011 5:06 pm

Thanks Wheelz. Yes, everything seems to be running exactly as normal. I haven't run a compression test yet as my tester is at my other house.
Do you know what the compression should be?

As all seems to be running exactly as normal, I'm thinking (hoping) it simply overheated. It was a very hot day, and I was running it hard.

SteveK · Post by **SteveK** » Fri May 27, 2011 6:14 pm

Is that really possible though? Overheating will stop the engine with no catastophic failure whatsoever? It sounds like a great addition to an otherwise normally operating engine to just shut off based on temperature instead of popping.

This high temperature is why I thought vapor lock. Not suction in the tank, but the real vapor lock which can happen to any normally aspirated engine when super hot.

I'm real interested in what you find English....will stay tuned.

English · Post by **English** » Fri May 27, 2011 6:26 pm

I just spoke to a friend of mine who is very knowledgeable about scooters. He used to own a scooter store in town, and has worked on scooters for many years.

He said it was almost certainly a "heat seize", where the piston expands at a greater rate than the other components and partially seizes in the cylinder.

He said that there is likely some scoring of the cylinder, but otherwise should run for 85% of its life fine. Suggested richening up the mixture some, or running a colder plug in the summer.

B02S4 · Post by **B02S4** » Fri May 27, 2011 11:01 pm

a/k/a "soft" seize...& was the oil synth or dino?

Lotrat · Post by **Lotrat** » Sat May 28, 2011 4:48 pm

English wrote:
Lotrat wrote: The scoot was telling you that you are low on oil and you ran it WOT? Come on, you knew what happened.
Thanks for the vote of confidence, but no, I'm not that stupid to run WOT after the low oil light was on. If you read the post again, you'll see that I said the oil light came on briefly a couple of times after this happened, and on the way home. It hasn't come on again.

Ah, ok. You're off the hook for ignoring the idiot lights.

I overheated my old XS650 one. I was climbing up a mountain with a passenger. She just popped and died. I let it sit for an hour until I could kick start it. Ran fine for years after. I have no idea how much damage was done, but I ran it anyway. My "seat of the pants dyno test" told me it wasn't too bad.

SteveK · Post by **SteveK** » Mon May 30, 2011 1:56 am

I'm glad you got to speak with someone in the know. But there seems to be a few of these same symptoms on this board including one of mine that certainly was not super hot. 2 miles into a lame and tame ride it did just what yours did.

This problem could be many things so it appears from reading here:

Gas cap venting
Evap cannister
Overfilling of gas tank
CDI
Clogged jets
Lack of Seafoam

I don't know now, but I hope your problem is gone.

English · Post by **English** » Mon May 30, 2011 2:15 pm

Steve. I think I've experienced the vapour lock before. With this, I'm pretty sure I remember the sound of the engine changing in a very "mechanical" way, just before it happened.

It's not easy to explain, but it just felt, and sounded like a mechanical issue, rather than a fuel, or ignition issue.
I've been riding bike for 33 years now, and have one or two have top-end issues while riding. This just felt like that to me. I'd be very pleased to find I was wrong though!

I'll try to pick up my compression tester this week, and see what that gives.

trackpete · Post by **trackpete** » Tue May 31, 2011 7:31 pm

Soft seize is likely, I'd check the compression if you're really paranoid.

Here's another really weird possibility that happened to me on my trip to Alaska:

I got some really bad gas in a suspect area in Canada and ended up having rapid carbon buildup. Flecks of carbon would come off and hammer into the plug, messing with the gap and causing all sorts of "engine failures."

I had a number of what I thought were soft seizes before we realized it was carbon buildup, but I'm not convinced that these were caused by flecks of carbon blocking the spark long enough for the engine to die, then shaking loose when I'd kickstart it.

So, check the plug for any sign of damage and maybe run some cleaner through the engine.

re: oil light on the rattler... it comes on WAY early. I've driven mine for quite a distance with the light on and plenty of oil in the reservoir.

B02S4 · Post by **B02S4** » Wed Jun 01, 2011 1:27 am

trackpete wrote:...re: oil light on the rattler... it comes on WAY early. I've driven mine for quite a distance with the light on and plenty of oil in the reservoir.

My experience also, & the feed line is on the bottom of the tank. It lights up with PLENTY of reserve.