| Author |
Message |
    
Buelliedan
| | Posted on Monday, May 12, 2014 - 11:41 am: | 
|
I too feel is was due to a too lean or too much ignition advance condition. Looks like you used factory head gasket and those can go bad and cause it to go very lean quite quickly.
That piston does not look like a factory piston either, it looks forged. If it is they need more clearance that stock cast pistons which many shops do not understand when they install the pistons. This can also cause the scuffing we see on the piston skirts.
(Message edited by buelliedan on May 12, 2014) |
Rocket_in_uk
| | Posted on Monday, May 12, 2014 - 03:06 pm: |
|
Gone fishing 
(Message edited by rocket_in_uk on May 12, 2014) |
Screamer
| | Posted on Monday, May 12, 2014 - 08:56 pm: |
|
Rocket,
I think you miss-read. I stated it was NOT pre- detonation.
The intake valve has carbon, but not unusual for 26k. But,,,,,, the exhaust valve is white,
like the plugs, which seem to suggest a too lean condition.
I must be misunderstanding your other statement. The "cleaned" portion of the piston and the cylinder head is more towards the intake side of the chamber - not the exhaust. |
Rocket_in_uk
| | Posted on Tuesday, May 13, 2014 - 07:09 am: |
|
Whatever went on here I'm of the opinion the problem started with piston and cylinder overheating. This causes temperature in the combustion chamber to spike. This the detonation process at work but in the strict sense of my explanation I do not believe detonation caused this issue.
Piston slap and bore wear have lead to piston scuffing and cylinder wall damage, causing ring seal failure as the piston temperature increases, leading to oil passing into the combustion chamber. This process as confirmed by the owner has continued for sometime. Thus oil is burnt in the combustion process, combined with high temperature spikes, oil burns into the exhaust tract and onto the back of the valve due to the exhaust valve being open passed TDC on the firing stroke.
This would be my opinion based on what I can see, and experience. None of which should deter anyone from checking the basics and the necessary when diagnosing and repairing any engine problem. This one included. As I said from the get go. Check timing and fueling as a matter of course.
Rocket in England |
Buelliedan
| | Posted on Tuesday, May 13, 2014 - 11:19 am: |
|
Rocket is 100% correct. |
Kalali
| | Posted on Tuesday, May 13, 2014 - 07:50 pm: |
|
The English man speaks the truth...Call him Sir Rocket. |
S1owner
| | Posted on Tuesday, May 13, 2014 - 09:05 pm: |
|
Here is an option
http://minneapolis.craigslist.org/dak/mpo/44679894 73.html |
E30dean
| | Posted on Monday, May 19, 2014 - 02:19 pm: |
|
So I finally heard back from the shop and they said that the cylinders have already been bored to 30 over. According to my service manual it shows that is the last size. Im guessing for safety/reliability reasons I shouldnt go any bigger? Now I gotta figure out if I can afford a big bore kit or get the used set that s1owner posted. Im planning to sell the bike due to going into academy so either sell it as is/parts or pay someone to fix it and sell it. |
Lynrd
| | Posted on Monday, May 19, 2014 - 02:51 pm: |
|
Yep - if that is the last oversize - the bore walls in the steel liner are getting too thin. I have only seen a catastrophic cylinder failure once (on a knucklehead so cast iron cylinders) and it was impressive, but not something you want to experience.
Technically you can have them re-sleeved but I have not seen it be cost effective on a HD engine - parts are too cheap and labor too dear. That bike does not have nearly enough miles on it to be on the third overbore. Not nearly. now I'm wondering if the rods are true.
Hard call, but if you are planning on selling it soon, I think you would end up money ahead selling it now as is. There is a time investment needed to do the top end up right, and it doesn't sound that that would enrichen your life right now. At best, you will end up breaking even on the money.
Your call - just my opinion. |
Buelliedan
| | Posted on Tuesday, May 20, 2014 - 07:47 pm: |
|
time for a 1250 kit!!! |
Rocket_in_uk
| | Posted on Tuesday, May 20, 2014 - 11:18 pm: |
|
There's no point putting the engine back to stock for the cost involved unless you land lucky on a reasonably priced used cylinder piston setup.
You're left with the only option then of selling the bike as is.
Otherwise bite the bullet and go 1250.
Rocket in England |
S1owner
| | Posted on Tuesday, May 20, 2014 - 11:31 pm: |
|
Well I do not have mine anymore but 750 will get a 1250 kit or sell as is |
|
