Barrell cylinder ever crack?

concours

concours

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Or is it an illusion?
Barrell cylinder ever crack?
 
My stock 750 cylinders cracked on the lower backside at .040" over and started smoking. Running alum Maney cylinders now.
 
Is that dye, did you highlight it, or am I looking at what appears to be a verticle crack by the hold down hole?
 
MikeG said:
Is that dye, did you highlight it, or am I looking at what appears to be a verticle crack by the hold down hole?
Click to expand...
Highlighted. Just above the yellow highlight, there appears to be a horizontal line.


Gonna dye check it later
 
Does not look like it to me, looks like a flaw in the mould similar to the vertical one on the boss below the left stud. All depends how much material was taken off by the milling cutter that cut the recess as their could be a depression there that is below the cut taken by the milling with a casting flaw in the depression.
 
Scratch some of the black paint off to see if the iron is indeed cracked. I had a 750 barrel crack at the base flange…looked like this. I recall a few decades ago this was discussed a lot regarding 750 barrels. The bike in my avatar was the offender.
 
That does look concerning...but I have a feeling its a casting flaw as previously mentioned...fingers crossed....mind you if I keep magnifying it could look like the East African rift...:)
 

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concours said:
Puzzling.😵‍💫

The Yamaha XS650 breather has worked perfectly for 10 years.
Before that the vacuum check valve from power brakes worked fine. 🤯
Click to expand...
I've never tried 650 valve they are popular. I used a some Australian type pcv valve that came with a bit of plumbing for most brit bikes...( forget the brand)but was like farting in the wind compared to the sump reed valve breather
 
concours said:
Puzzling.😵‍💫

The Yamaha XS650 breather has worked perfectly for 10 years.
Before that the vacuum check valve from power brakes worked fine. 🤯
Click to expand...
Hmmm, do you use an anti wet sumping device? Maybe years of starting with sump full could cause it even with a better breather.
 
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