2nd Ride And Broken Skirt Blown Motor

[mskarl]

After getting it running this is what happened. For specs etc look at this post.

http://www.bansheehq.com/forums/index.php?act=ST&f=4&t=28249

 

 

Ok we started out with running really rich. 310 main and on middle clip on the needle. It's stock carbs with KNN's.

 

Pulled the plugs and they were really wet and lost of oil.

 

The only other jets we had were 290's and that's what we put in. Then after riding 1hr or so in sand it over heated on a cool day 55deg and raining. My brother was riding it and he said that he was about 1/2 throttle most of the time and then it died and it boiled over a little. He waited about 20 min and kicked it over. Seamed to have a little less compression. Got it running and rode it approx 1/4 mile and then he heard a ping sound and died. The engline was froze. When we pulled the spark plugs they weren't horrible. We pulled the heads off last night and found out that on the right piston the skirt broke. We pulled the piston off and felt the crank. Up and down is tight but side to side has about a 1/4in travel. Also something else that is confusing is that it's still really hard to kick over even with the head off but you can move the pistons. Is that maybe because the Clutch barring went south? If so can you check that without pulling off the side?

 

Lots of questions!!!!!! Thanks in advance

 

 

Questions.

Is there anything we can do about the head? Or just get new?

Why would the skirt break? becasue of the over heating?

Is there too much play in the crank?

 

 

Doesn't this side look good?

Edited May 26, 2004 by mskarl

[mskarl]

another pic

[mskarl]

another pic

[mskarl]

Is there anyway to save this head?

Edited May 26, 2004 by mskarl

[mskarl]

Here is a pic of the plugs I know it's hard to tell the color sorry.

[fixitrod]

It won't kick over because there is metal in the crank bearings.

Edited May 26, 2004 by fixitrod

[SDD]

What size bore? What kind of pistons? The piston crown looks like it suffered some detonation. You said it was recently rebuilt.... who bored/honed the cylinders? The pistons probably broke because of clearance issues. Did you check ring end gap and the piston in the bore when you put the motor together? Who cut the head? They didn't cut the squish band which could have lead to the detonation.

Edited May 26, 2004 by SDD

[MULLET~BOY]

the pistion looks like that because when the skirt broke metal got on top of the pistion and started mashing into it

[mskarl]

I understand that part about why this piston looks like that buy why did it break?

[MULLET~BOY]

just fualty pistions

[Justintoxicated]

The end of the plgus look like you may have been lean but you need to look inside at the porclin and see if there is a ring at the bottem. the tops look lean although they are not the best indicator. They look like a charred grey...But again can't really tell...But if it is overheating you either have an air leak or your too lean...Perhaps the head gasket had a leak in it and was pushing air into the collant and making it boil over onto the pipe?

 

Check the head to make sure it is level COMPLEATLY...I believe you can use fine sand paper and a pice of glass to test.

 

How much compression were you running (look like a milled head? if so how much is it milled?) Maybe you were haivng detonation? Is your timing advanced?

 

Your going to have to split the cases again to clean out the crank case and hopefully you did not damage your new crank!

 

If you were using forged pistons were you sure to let it idle untill warm before riding?

 

If you had an air leak, or coolant leak (small coolant leak let coolant into the cylinders etc) this could probably cause that. (washes lubercation away).

 

Or it could be a combination of these things. You put the C lip on the pin that holds the piston on right? (Dumb question but my friend fergot this once)

 

Or it could possibly just be faulty pistons

 

 

I think your going to need to have the topend re-done, get a new head, and split your cases to clean the crank case. You can get a head pretty cheap, I have a compleatly stock one if your interested, or it would be a good time to get a Cool Head.

Damn man I'm sorry your having all this bad luck.

Edited May 26, 2004 by Justintoxicated

[svtkid78]

I agree you either have some serious clearance issues, or you leaked some coolant and got some hydrolock, especially looking at where it broke. good luck

[SDD]

I don't think he had a leaking gasket. If you look at the sealing surfaces of the head you don't see any blow by burn't look any where. You do see a little oil but that looks like it came from spilling it onto the gasket. Show us the inside of the cylinder and take a better close up look of the piston crown.

[Blacksmith]

As for the head, you could sand down the high areas and reuse it, but I would'nt because this can lead to small hot spots and can cause detonation in marginal situations. You can get a new one on ebay for next to nothing. In fact, I have one I would let go pretty cheep if you need it.

As for why it is hard to turn over, I would bet that you have some babit in the crank bearings. You need to split the case and check out the bearings really close. This answers you question about pulling the side off, yes you have to.

I doubt that you had coolant in the cylinder, if so we would be able to see some sign of it on the top of the piston. I also don't thint that you were jetted lean, as the head looks really good on the other side. Now having said that, you can be lean on only one side if you have a problem with one carb and not the other. However, as both plugs look pretty much the same, I don't think that is your problem. As for detonation, that is also unlikly as it effects both side in most cases. I think that you either had an air leak or you got a bad piston that did not respond well to you getting the bike hot, or your bore was cut too big giving you execess clearance leading to piston slap.

Because the motor is already apart, it is too late to check for an air leak so I would not worry about that until you put it back together. You can measure the bore if you have the correct tools, or get it measured at a shop if you do not. However, I would not take it to the place that cut it to get it meausred. As for a bad piston, that is pretty much a guessing game. Sometimes you can tell by looking at the break and sometimes not. It might help it we know what kind of pistons you had in there. Also, I would like to know if you tightned the base gasket nuts on each cylinder before you torqued the head on you last rebuild. Did you use any type of sealant on the head gasket?

[Nightrider]

That looks like some serious detonation and the fact that you mentioned he was at half throttle leads me to believe that was the case even more.

 

Alot of the guys here who had piston crowns look like that also said they were running the engine at a moderate pace when the engines failed.Too high of compression/timing or too low of octane combined with a possibly lean mix.

 

Do a search,maybe you'll find some old pics and threads.