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Noassmblyrqired
03-31-2009, 08:55 PM
Here's some images of the failure from NJMP trackday. It went like stink until it shot me into the mud at 90mph!

http://farm4.static.flickr.com/3556/3403379944_b7e59d5f79.jpg?v=0
http://farm4.static.flickr.com/3558/3402571767_2fedbc4641.jpg?v=0
http://farm4.static.flickr.com/3540/3402572397_3ff615a08b.jpg?v=0
http://farm4.static.flickr.com/3590/3402571159_c130a6f135.jpg?v=0

ThisEndUp
04-01-2009, 06:14 AM
Ouch.....

Tough day for the RS125s' last Saturday. I would have been down with you if I hadn't fudged a gear shift and let you get away. ;) I was right on your tail.

My barrel will be off in the next couple of days......geez, 'can't wait to see what I find.

My RD350 was never this delicate. :rolleyes:

Hmmmm....I have a fresh RD engine in the basement....was the drive shaft on the left or right? :p:

ThisEndUp
04-01-2009, 06:33 AM
Me:
http://i203.photobucket.com/albums/aa266/ThisEndUp_photos/Metrack.jpg
http://i203.photobucket.com/albums/aa266/ThisEndUp_photos/MeTrack2.jpg

That fateful lap...two turns later....Noassemblyrequired in Mudville:
http://i203.photobucket.com/albums/aa266/ThisEndUp_photos/Track4.jpg

Noassemblyrequired still in good spirits, de-mudding himself:
http://i203.photobucket.com/albums/aa266/ThisEndUp_photos/TonyTrack.jpg

ThisEndUp
04-01-2009, 06:37 AM
'Still had a great time regardless of the engine giving up.

That little RS is one wicked little machine!

Gman2005
04-01-2009, 07:12 AM
what carb are you using? Before you put the a knew BBK on, get the port worked on. There shit when they come from Polini! But they can be really good. go to www.tjtuning.com and look for Patcho. Hes got the same BBK as you, but did some work on it. He can help you out, to stop this. PS make sure your using a 34mm carb. It just won't live very long on a 28mm carb.

Gman

ThisEndUp
04-01-2009, 07:15 AM
what carb are you using? Before you put the a knew BBK on, get the port worked on. There shit when they come from Polini! But they can be really good. go to www.tjtuning.com and look for Patcho. Hes got the same BBK as you, but did some work on it. He can help you out, to stop this. PS make sure your using a 34mm carb. It just won't live very long on a 28mm carb.

Gman

Noassem... had the cylinder worked a bit. 34 carb, etc.

Noassmblyrqired
04-01-2009, 07:20 AM
The motor had a 34mm delortto and a Jolly pipe on it. How could port work have eliminated this? I'm still not sure I know what happened... It appears to be thermal related to me since all the damage is around the exhaust ports.

I'm interested to see if the second RS125 had the same sort of failure. Get that head off!

Gman2005
04-01-2009, 07:38 AM
because the ports are shit. Compare them to a standard Rotax ports and you see the difference.

ladyrednb
04-01-2009, 09:20 AM
Clean Macro pics of the top and bottom of the piston please, remove wristpin for bottom pic. I suspect I know what happened but would like to be sure.

Sorry, did not mean for that to sound like an "order"...just I have a sneaking suspicion that it is a piston to bore clearance issue.

Micah...from GF's computer.

ThisEndUp
04-01-2009, 09:49 AM
The motor had a 34mm delortto and a Jolly pipe on it. How could port work have eliminated this? I'm still not sure I know what happened... It appears to be thermal related to me since all the damage is around the exhaust ports.

I'm interested to see if the second RS125 had the same sort of failure. Get that head off!

Yes sir.
Probably tonight....

Did I mention that my spark plug cracked pretty severely? Stock NGK plug (10).
(Giving some food for thought to Micah :cheers: )

Noassmblyrqired
04-01-2009, 01:15 PM
Is this macro enough?

http://farm4.static.flickr.com/3657/3405105170_8f406aeb12.jpg?v=0
http://farm4.static.flickr.com/3450/3405109158_d9191d8b18.jpg?v=0
http://farm4.static.flickr.com/3630/3404295457_453e4b9ebe.jpg?v=0
http://farm4.static.flickr.com/3591/3405107518_2be2ca86d9.jpg?v=0
http://farm4.static.flickr.com/3613/3404296969_fcce3d9111.jpg?v=0

Micah / AF1 Racing
04-01-2009, 02:46 PM
Sure are signs of detonation at the pistons edges, this increases the piston temp dramatically and results eventually in it being the same size as the bore it rides in...seizure.

I bet it ran like hell right up failure, they always kick ass right before they blow!

Steve / AF1 Racing
04-01-2009, 04:08 PM
Sure are signs of detonation at the pistons edges, this increases the piston temp dramatically and results eventually in it being the same size as the bore it rides in...seizure.

I bet it ran like hell right up failure, they always kick ass right before they blow!

Yep, looks that way.

Wonder if leaded fuel would have prevented this...

Noassmblyrqired
04-01-2009, 09:14 PM
I showed the cylinder to Eurosports today. They called it a classic 4 pint seize. They don't believe it was from detonation. The bottom of the piston was clean (not burnt) Piston edges were clean not beat up/melted. We think the low ambient temp of the track day high 50's low 60's over cooled the cooling system and didn't allow the cylinder to grow at the same rate as the piston.

I suspect ThisEndUp will find the same failure mode. I think mine gave up the ghost a session early only because of it's higher state of tune.

ThisEndUp
04-02-2009, 06:21 AM
Got the head off last night.

Piston head looks like new. No signs of detonation.

There's one wear spot on the cylinder wall above the exhaust port, where it looks like a ring may have grabbed a rough edge. It's not that bad really. Perhaps I can wet sand the slight roughness out a little.....then get new rings.

'Still.....I haven't taken the barrel off.

Sounds plausible....that different rate of expansion theory. Just standing around our paddock that day, I was shivering. At 90+mph , our cylinders were probably cooler than the pistons.
I have a water temp gauge that I intended on putting on the bike's radiator. Guess I'll stick that puppy on now....and carry more duct tape, in case we need to cover the radiator's surface area.

I'll get back to it tonight......and take pics.

Micah / AF1 Racing
04-02-2009, 08:17 AM
Do you guys use a thermostat in your cooling system?

Noassmblyrqired
04-02-2009, 09:48 AM
The stock thermostat was installed in the head, but It either wasn't keeping up, or failed because the motor temp dropped on me as my speed increased. 3 Bars showing warmed up on pit road, 2 bars light lapping on the yellow and dropped to 1 Bar under green. It may have gone to zero...but I was too busy roto-tilling the grass on the far side of the track with my RS to notice.

the brit
04-02-2009, 09:50 AM
Wow, that sucks to hear / see. Glad you're okay, and the off didn't appear to be worse!


When I woke up and saw the rain, I wasn't about to make the ride out to say hello but it sounds like it didn't hold you guys back too much.

ThisEndUp
04-03-2009, 03:01 PM
Pulled the cylinder off.

'Same exact damage as Noassemb..

Cylinder wall damaged above exhaust port. Piston rings on the exhaust port side shaved/melted into the piston wall. Intake side of piston has two wear marks...one below each ring junction. Pressure at the exhaust side pushed the rings open at the inlet side.

Piston shows no signs of detonation whatsoever. I could wipe the crown off and it could pass for new. (Just don't look at the sides :happy: )

Guess I had a hairline crack in the spark plug...and with heat it separated.
I did have a tough time starting the bike that day...thought it was just cold, like me.


--john

Dieterly
04-03-2009, 03:55 PM
John,

Do you have the 154cc kit?

ThisEndUp
04-03-2009, 03:56 PM
Do you guys in the U.K. tape up your radiators or change out the thermostat?

We were riding in London like weather :rolleyes: that day.

I'm referring to track time not street riding.

ThisEndUp
04-03-2009, 03:57 PM
John,

Do you have the 154cc kit?

No. I'm running stock.

ThisEndUp
04-03-2009, 04:04 PM
P'Med ya D.......

Dieterly
04-03-2009, 04:22 PM
John,

check your pm

Gman2005
04-03-2009, 05:16 PM
take the thermostat out if your racing. It will just make cold coolent into the barrel walls and fuck your engine, due to it cooling too quickly. Just have a warm up lap aswell to get everything nice and warm.

kanerdog1x1
04-03-2009, 06:18 PM
i run my bike without the thermostat, it takes longer to warm up, but is easier to keep warm like this as you dont get temperature spikes as the water travels round the system. at the moment 55deg/f ambient i have the central 3/4 of the face of my rad is taped up! and im keeping a beady eye on the temp bars, looking for 3 or 4, no less. i tend to run tape in the centre of the rad, to help keep stone chips from the tyre at bay.

ThisEndUp
04-04-2009, 06:44 AM
Ah....there we have it.

Cheers guys. :cheers:

Socket
04-08-2009, 05:59 PM
Mine did the exact same thing...track riding, cylinder/piston looked the same. Now I'm on a forged piston, and millenium did the cylinder new for me.

Gman2005
04-21-2009, 04:48 PM
are you increasing the amount of oil your use pumping?

Noassmblyrqired
04-21-2009, 06:13 PM
I was using premium pump gas and agip 2t oil in the resevoir. After a "strategy meeting" with the 2T engine builder at Eurosports (Bill Himmelsbach). We came to the decision to run VP C12 with Silkolene Race 2T Premix at 1:30. So premix plus leaded high octane should provide some extra protection. We played with the squish on the Polini kit. When assembled the stock kit had excessive squish clearance. They cut the squish down about half of what the as delivered kit was. The dyno charts showed good airfuel the whole way across the meaty portion of the rev range. Only going lean when power dropped off around 12.5K RPM.

Once the motor is back together we'll take the 32mm Dellorto with a 158 Jet in and try out a 165 on the Dyno and see how the airfuel looks. We also decided to remove the thermostat and come up with a "baffle system" (duct tape) for the radiator and try to keep a log on engine temp versus ambient temp. It was also decided that the stock temp gauge is useless and a proper gague should be fitted that reads in degrees C. Bill claims from dyno experience that most bikes make peak power at 60-70 degees C water temp and power falls off quickly when you are outside that range.

I also found a crack in the cylinder after the incident. The crack was between one of the booster ports and the powervalve port. Also indicating a severe thermal issue. The cylinder is now at Millenium getting a weld repair and a new lining.