Engine failure - seizing - what happened?

4Z · Post by 4Z » April 18th, 2011, 9:23 pm

What does the top of piston look like? i.e. wash.
Post up a pic.

Post by **AlisoBob** » April 18th, 2011, 10:49 pm

None of the comments explain the wrist pin galling.

I dont care how expensive that Motorex oil is...... it sucks.

Bomberpilot · Post by **Bomberpilot** » April 19th, 2011, 12:51 am

plug looks ok - it's brown and near perfect jetting - a little on the fat side.
I didn't close the throttle totally and I played with the gas - not only one position. But as the sound appeared BEFORE I changed the throttle position (I accelerated at WOT) I guess it is more a heat problem than a lubrication problem.
But you guys are right - I really should find the reason, otherwise I will blow the next topend too. I have to look at the water pump.

any suggestions how I could clean out the bottum end without disassembling it? there could be some aluminum flakes from the piston in it...

is the clearance that I am using ok and normal? (9/100mm, 0.0035")

I guess this failure would not have been happened with an aluminum sleeve - then the heat would have come out of the engine. what do you think?

britincali · Post by **britincali** » April 19th, 2011, 1:00 am

AlisoBob wrote:
That thing is fudged up.....

My last one...

Heat yes, galling no.

Check out all the 927 and VP red pooled on the skirt

2T500 · Post by **2T500** » April 19th, 2011, 1:28 am

I'm running a trailtech vapor with the temp sensor inline with the rad hose a couple inches from the head, I know that an engine can fail due to a heat seize before I picked up an over heat but the chances are I'll see it if its trending to run hot, this thing keeps the max temp recorded so at least that is something to look at after a failure.. running a weisco 90mm at .0035" with 39.5 pwk and 180 main, motul 8002t 40:1, mild comp squish, I did have some over heating from shit in the cooling system, still don't know where it came from - seemed to turn up during real hot weather and riding a bit harder, temp gauge got to about 110c and the rads started pushing the water out, the trailtech had a red flashing light and I took notice, probably saved the top end which still looks mint, stripped and checked with no signs of over heat, caught it in time, took the rads off and flushed everything including the engine, cleaned/checked water pump etc and water temp runs around 70-90c now depending on speed etc, over heat seems to be a thing of the past, the temp gauge doesn't reed rill about 38c so I usually warm it till it reads and don't go WOF until its at about 70c.

YMMV but could save this happening again.

craigf40 · Post by **craigf40** » April 19th, 2011, 1:51 am

your clearance is fine ....the fact that it seized both sides intake and exhaust says it a lube problem ...the top of your piston should tell you if it overheated...just a thought perhaps your cooling system is to good and cooling you jug down to much then your piston clearance is to little just a thought...i still think its oil

Gmbond · Post by **Gmbond** » April 19th, 2011, 4:22 am

Any chance you could have grabbed the wrong gas can and put straight gas in?

Bomberpilot · Post by **Bomberpilot** » April 19th, 2011, 12:22 pm

no chance for the wrong gas - but I will check again (it is still in the tank).
I have to make a picture of the piston from the bottum - will do that tomorrow. The top looks like the following:
Please note that I have opened the engine a few rides before the engine failure happened. But I didn't clean the piston top - looked all the time like that. I polished the dome of the head and this looks also still fine (will post a pic of that, too).

I definately had no water or dirt in the carb.

@craigf40: interesting thought, but I am using that cooling system for quite a long time now, never had any problems before. Now, after the modding the engine blew up.

Thinking about everything, then the strange noises - which where the loudest shortly before the engine blew up - started after:
-polishing the exhaust flange and widening up the exhaust port (but not in the sleeve, just the rest of the casting)
-adding the 41 PWK
-INSTALLING THE HIGH COMRESSION HEAD.

I guess the adding of the head is the key. The squish height is very small and the cc of the head also much less than stock. But there was no pinging, thats whats confusing me... But the higher compression is putting alot more heat in the system, right?!

britincali · Post by **britincali** » April 19th, 2011, 1:18 pm

I'd put my money on the PWK being jetted a little leaner than the other carb.

Rhino89523 · Post by **Rhino89523** » April 19th, 2011, 2:00 pm

I'm with Brit, I'm going with too lean...when these things ping it can be pretty dam loud!

Bomberpilot · Post by **Bomberpilot** » April 19th, 2011, 2:29 pm

Yeah, I had the PWK 39 before. Then I changed to the Sudco PWK 41.
Before I had a 195 main and 50 pilot. I read alot of numbers in the 17X area and also that the 41 doesn't demand a bigger jet than the 39. So I went down to 190 and 52 pilot.
I am taking a picture of the spark tomorrow too.

Post by **AlisoBob** » April 19th, 2011, 2:36 pm

AlisoBob wrote:None of the comments explain the wrist pin galling.

I dont care how expensive that Motorex oil is...... it sucks.

Bueller? Anyone?

Rhino89523 · Post by **Rhino89523** » April 19th, 2011, 2:52 pm

Yeah I guess running lean alone wouldn't cause a pin to look that hashed out.

100hp honda · Post by **100hp honda** » April 19th, 2011, 4:59 pm

AlisoBob wrote:
AlisoBob wrote:None of the comments explain the wrist pin galling.

I dont care how expensive that Motorex oil is...... it sucks.
Bueller? Anyone?

most bikes wont even run with a 195. even at see level i cant see a reason to have that big....... unless theres airleak somewhere. maybe on the base gasket or seal. this scenario combined with the engine wide open would seize the piston and fudge the wristpin.

thought he said it was making strange noises prior to this ? probly had a leak for a while but just didnt push the motor past the breaking point. airleak doesnt cause instantaneous seize, especially if its small leak and the engine only runs at low rpm.

one of the ktm had almost the whole base gasket blown out when i bought it, definatly ran erratic. knew right away what the problem was but would of siezed if you ignored the early warning signs. not to mention there was a strange vaccum sound

britincali · Post by **britincali** » April 19th, 2011, 5:34 pm

Its gotta be the oil or an airleak, 190 is retarded big for a main.

My AF has a 170 and the nitrous bike has a 175.

riverman · Post by **riverman** » April 19th, 2011, 6:15 pm

I'm not an expert. But have been around 2 strokes for a long time. It looks like lack of lube. An air leak caused a lean condition or lack of oil in the gas. Or as I have been told by builders and seen first hand you never let off the throttle all at once when wide open. The slide closes and you have no fuel charge going to the bottom end. Running WOT the piston makes many cycles before you get back on the throttle and you have a hot dry cylinder and bottom end. It starts to seize up. Happens more often on fresh tight top ends.

Just my 2 cents

100hp honda · Post by **100hp honda** » April 19th, 2011, 8:44 pm

brit is that a boat anchor wiseco ? skirt seems flimsy. nervous about using the one i have. thinking about the new version. probly take the coating off first though

britincali · Post by **britincali** » April 19th, 2011, 9:14 pm

No its the old style machined one.

Bomberpilot · Post by **Bomberpilot** » April 20th, 2011, 11:53 am

Now I took some more pictures.

Guess what bout the wrist pin: the holes look good, but the pin can not be pushed through the hole in the piston by hand

this could explain the exessive galling and temp. signs! I tried both sides of the wrist pin with both sides of the piston!

I checked the fuel and it looks ok and red because of the two stroke oil.

I guess my next steps will be after the gasket kit has arrived:
- checking the water pump
- trying to see if the bottum end is ok (there could be some aluminum flakes from the piston - no clue how to get rid of them...

)
- installing the new cylinder and piston
- measuring the cc of the head (I have used here and that I want to use again)
- measuring the compression
- making a leak down test (building first the tools that I need for that)

PS: my next piston/cylinder kit got only a clearance of 6/100mm or 0.0025. I am afraid now - do I have to?

Post by **AlisoBob** » April 20th, 2011, 12:03 pm

That piston has never seen much heat....

Look at Brits....

or mine...

Thats what a good running CR500 piston should look like.

Heat = Power

Post by **AlisoBob** » April 20th, 2011, 12:06 pm

100hp honda wrote:..most bikes wont even run with a 195. even at see level i cant see a reason to have that big.......

Yup....

britincali · Post by **britincali** » April 20th, 2011, 1:15 pm

Bomberpilot wrote:
Guess what bout the wrist pin: the holes look good, but the pin can not be pushed through the hole in the piston by hand

Mine never come out by hand, they have to be beaten out,

Post by **AlisoBob** » April 20th, 2011, 1:23 pm

Do a google search for:

"Britincali"

"Come"

"Hand"

and

"Beat"

....scary.

But even so, after you beat yours out Chris, they dont look like they spend 5 minutes tumbling around in the garbage disposal?

100hp honda · Post by **100hp honda** » April 20th, 2011, 4:26 pm

now im thinking the problem was the new head. caused too much heat and the oil flashed off. looks in the pic someone shaved off a ton

http://www.youtube.com/user/500bigbore · Post by **Roostius_Maximus** » April 20th, 2011, 4:43 pm

I'm jsut catching up here
theres a huge main?
the head has had .070+ cut off it, not had the squish modified,
I bet the big main jet helped the detonation because it was killing the ping with quantity not quality.
If it had race gas it'd ahve taken like 8 mains smaller probably.

BannedCR500Riders.com

Engine failure - seizing - what happened?