what would cause this?
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Joined: Jul 2012
Posts: 95
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From: Lincoln ne
what would cause this?
Running a steady 80mph when the back cylinder dropped. Then I found this... what would cause this? Keith black hypereutectic (or however it's spelled) pistons. Happened after 1200ish miles of running fine
Last edited by Schulte94; May 22, 2014 at 01:28 AM.
Road Captain
Joined: Aug 2012
Posts: 625
Likes: 102
From: New Albany, Ms.
Detonation
By the way, I'll never buy another set of Keith Black pistons.
Ride Safe,
Harold
Club Member
Joined: Jun 2007
Posts: 45,429
Likes: 2,898
From: Bedford UK
Ouch - that doesn't look nice! Funny thing about KB pistons. The indy who built my 89" stroker would only use them because they were the only brand he could get that were dimensionally accurate and consistent and would also hold up in his drag bikes! They were fine for me, pre-107" days.
Seasoned HDF Member
Joined: Nov 2006
Posts: 12,878
Likes: 5,449
From: la la land jerzey
K black pistons have always been a money maker for them as they dont work and people buy them anyway
first as said above the timing was probly wrong too much
the fit is too tight piston to wall ( the spec they give you ) and the alloy they are made of is for water cooled motors soooo
plus you bought the 10 to 1 set and with that small cam the static compression was way over the top ( again the timing was wrong )
put a flat piston in it and use cometic 020 steel base and the .030 head gasket and drive it 50,000 miles trouble free
anything else with the gas we now have you will be doing it again the end of this year
first as said above the timing was probly wrong too much
the fit is too tight piston to wall ( the spec they give you ) and the alloy they are made of is for water cooled motors soooo
plus you bought the 10 to 1 set and with that small cam the static compression was way over the top ( again the timing was wrong )
put a flat piston in it and use cometic 020 steel base and the .030 head gasket and drive it 50,000 miles trouble free
anything else with the gas we now have you will be doing it again the end of this year
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Outstanding HDF Member
Joined: Oct 2010
Posts: 2,706
Likes: 14
From: Near Frankenmuth, MI
I wouldn't be so quick to blame the piston. I'd pin it on the mechanic who replaced those pistons.
At 1,200 miles you should not have all the scuff marks and blow-by that I see in the picture. I'm going to lay the blame on not precisely checking bore against piston dimensions as it looks like the piston rattled in the bore and that cause the top segment to crack.
My Indy just installed these based on experience and previous use. He was very certain that the machinist had the most precise matching there could be. I just rolled over 1,200 mile on the new rebuild and pray I don't ever see this.
There are so many "precise" factors needing to be addressed. Experience is the greatest teacher! We had to wait for machinery and my jugs to be at a proper temperature before boring. We did the rebuild over last year's extremely cold winter and waited for the temps to do the job. Also the strict method of break in started with my Indy doing warming cycles starting at 30 seconds runs to properly seat the two different metals used. He did many "runs" like this before I was even allowed to have the bike back. And my break in was strict too. Nothing over 3 grand for almost 500 miles and an oil change. Then another 500 limited to 4 K rpms and under. I just hit the first 1K and have now been giving it full throttle and running it out to the limiter. At 30 over and 9.6:1 bump it's impressive with the EV27. Carb and pipes next on my list.
And best wishes getting your ride back on the road!
At 1,200 miles you should not have all the scuff marks and blow-by that I see in the picture. I'm going to lay the blame on not precisely checking bore against piston dimensions as it looks like the piston rattled in the bore and that cause the top segment to crack.
My Indy just installed these based on experience and previous use. He was very certain that the machinist had the most precise matching there could be. I just rolled over 1,200 mile on the new rebuild and pray I don't ever see this.
There are so many "precise" factors needing to be addressed. Experience is the greatest teacher! We had to wait for machinery and my jugs to be at a proper temperature before boring. We did the rebuild over last year's extremely cold winter and waited for the temps to do the job. Also the strict method of break in started with my Indy doing warming cycles starting at 30 seconds runs to properly seat the two different metals used. He did many "runs" like this before I was even allowed to have the bike back. And my break in was strict too. Nothing over 3 grand for almost 500 miles and an oil change. Then another 500 limited to 4 K rpms and under. I just hit the first 1K and have now been giving it full throttle and running it out to the limiter. At 30 over and 9.6:1 bump it's impressive with the EV27. Carb and pipes next on my list.
And best wishes getting your ride back on the road!
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Dirt don't hurt
Joined: Jan 2011
Posts: 21,065
Likes: 4,561
From: Haslet Texas
Ouch - that doesn't look nice! Funny thing about KB pistons. The indy who built my 89" stroker would only use them because they were the only brand he could get that were dimensionally accurate and consistent and would also hold up in his drag bikes! They were fine for me, pre-107" days.
I have a friend that has put 100k miles on his 9.5-1 KB hypereutectic pistons.
