 Re compression
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Joined: Jan 2007
Posts: 331
Adjunct
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OP
Adjunct
Joined: Jan 2007
Posts: 331 |
Has anyone done a compression test on a stock 865 America with the efi. If so can you give me an idea of what they should be for a engine in good condition. Thanks Kent 
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Re: Re compression
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Joined: Feb 2007
Posts: 23,134 Likes: 52
Fe Butt
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Fe Butt
Joined: Feb 2007
Posts: 23,134 Likes: 52 |
less than a 10% difference between sides.
I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!
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Re: Re compression
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Joined: Jan 2005
Posts: 4,931 Likes: 1
Loquacious
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Loquacious
Joined: Jan 2005
Posts: 4,931 Likes: 1 |
10%????? they use the metric system down there.
we should do this every weekend!
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Re: Re compression
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Joined: Apr 2008
Posts: 3,937
Loquacious
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Loquacious
Joined: Apr 2008
Posts: 3,937 |
If one is 10% higher than the other, you're ok. If one is 10% lower than the other, YOU'VE GOT PROBLEMS!!!  
And you may see me tonight
With an illegal smile
J. Prine
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Re: Re compression
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Joined: May 2010
Posts: 5,720
Check Pants
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Check Pants
Joined: May 2010
Posts: 5,720 |
Most healthy gasoline engines run somewhere around 170 Lbs. per square inch, compression, 10%(170)= 17 Lbs. Personally, I would rather see a deviation of no more than 10 Lbs between cylinders, as 17 Lbs. is a huge imbalance on a two cylinder motor. Agree, disagree, chime in, as that's what forums are all about.
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Re: Re compression
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Joined: Jan 2007
Posts: 331
Adjunct
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OP
Adjunct
Joined: Jan 2007
Posts: 331 |
I had thought rightly or wrongly that the comp would be about the 130-140 psi mark for these engines. A mate has just bought a you beaut compression gauge kit with all adapters etc. Thought I might do a comp test on my 08. Runs well but would be good to know for the future. 
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Re: Re compression
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Joined: Apr 2007
Posts: 3,053 Likes: 6
Loquacious
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Loquacious
Joined: Apr 2007
Posts: 3,053 Likes: 6 |
If you want to know what the compression of a good engine is, check tthe engine dry to get a base reading, then add a bit of oil to the cylinders, spin the engine over with no plugs, then test. The compression should go up a bit, indicating how much wear has taken place. The wet compression test is usually a bit higher than the manufacturer's recommended numbers.
Oh and by dry I mean with no oil in the cylinders for those of you that might have thought I was referring to the crankcase.
12 Rocket Roadster
03 Bonneville America
69 BSA Firebird Scrambler
73 Yamaha TX 750
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Re: Re compression
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Joined: May 2010
Posts: 5,720
Check Pants
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Check Pants
Joined: May 2010
Posts: 5,720 |
Quote:
If you want to know what the compression of a good engine is, check the engine dry to get a base reading, then add a bit of oil to the cylinders, spin the engine over with no plugs, then test. The compression should go up a bit, indicating how much wear has taken place. The wet compression test is usually a bit higher than the manufacturer's recommended numbers.
Oh and by dry I mean with no oil in the cylinders for those of you that might have thought I was referring to the crankcase.
#1, That's the basically the procedure I was taught, you add enough motor oil to encircle the perimeter of the piston, if the compression reading goes up, that is a indication of ring wear. If no change, when dealing with a lower than desired pressure reading, than the cylinder degradation is most likely in your valves, and of course, if you get good initial numbers, (using Gregger s protocol) and both cylinders are in the same range, don't fool with it and ride on. Now I have to go check my bikes compression, 'cause this will bug the sh!t out of me, until I do.
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Re: Re compression *DELETED*
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Joined: Jul 2011
Posts: 2,212
Oil Expert
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Oil Expert
Joined: Jul 2011
Posts: 2,212 |
Post deleted by edmspeedmaster
2007 Speedmaster and miss it!
2013 T-Bird Storm and Luvin it!
Catching a yellow jacket in your shirt at 70 mph can double your vocabulary
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Re: Re compression
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Joined: Jul 2007
Posts: 6,060 Likes: 6
Worn Saddle
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Worn Saddle
Joined: Jul 2007
Posts: 6,060 Likes: 6 |
You guys forgot one important thing. Hold the throttle open. You can't compress air that can't get to the cyclinders.
Fidelis et Fortis
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Re: Re compression
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Joined: Jan 2005
Posts: 4,931 Likes: 1
Loquacious
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Loquacious
Joined: Jan 2005
Posts: 4,931 Likes: 1 |
thats why you fill the cylinders up with mercury!
we should do this every weekend!
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Re: Re compression
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Joined: Feb 2007
Posts: 23,134 Likes: 52
Fe Butt
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Fe Butt
Joined: Feb 2007
Posts: 23,134 Likes: 52 |
I would guess 150psi is probably about normal for our engines give or take.I never tested one though. I got the 10% difference from working on V8s, as stated above maybe a bit much for a twin.
I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!
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Re: Re compression
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Joined: Jan 2007
Posts: 706 Likes: 1
Adjunct
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Adjunct
Joined: Jan 2007
Posts: 706 Likes: 1 |
Quote:
I had thought rightly or wrongly that the comp would be about the 130-140 psi mark for these engines. A mate has just bought a you beaut compression gauge kit with all adapters etc. Thought I might do a comp test on my 08. Runs well but would be good to know for the future.
hey Kent dont you go playing with that bike now Buddy
after all imbill is only 2 weeks away and you dont want to be missing that i'm sure
if i dont catch ya befor hand....will see you their 
04 yellow&black Speedmaster+the Money Pit{xj jeep}
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Re: Re compression
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Joined: Apr 2007
Posts: 3,053 Likes: 6
Loquacious
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Loquacious
Joined: Apr 2007
Posts: 3,053 Likes: 6 |
Quote:
You guys forgot one important thing. Hold the throttle open. You can't compress air that can't get to the cyclinders.
You're absolutely right Rich. Easy to be fooled with low comp numbers because the intakes are closed off with the throttle.
12 Rocket Roadster
03 Bonneville America
69 BSA Firebird Scrambler
73 Yamaha TX 750
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Re: Re compression
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Joined: May 2007
Posts: 6,432 Likes: 1
Worn Saddle
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Worn Saddle
Joined: May 2007
Posts: 6,432 Likes: 1 |
Quote:
You guys forgot one important thing. Hold the throttle open. You can't compress air that can't get to the cyclinders.
Yah, you gotta prop the slides up on CVs as there's not enough vacuum to lift them clear.
A positive attitude may not solve all your problems, but it will annoy enough people to make it worth the effort. Herm Albright (1876 - 1944)
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Re: Re compression
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Joined: Jan 2009
Posts: 1,228
I live in the sun downunder
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I live in the sun downunder
Joined: Jan 2009
Posts: 1,228 |
He,s frightened that he might have worn it out trying to catch up to the Harlies on our trip to Mount Perry for lunch. 
FrankW
Ex Speedmaster rider, went to the Dark Side now riding an America.
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Re: Re compression
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Joined: Apr 2007
Posts: 3,053 Likes: 6
Loquacious
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Loquacious
Joined: Apr 2007
Posts: 3,053 Likes: 6 |
Quote:
He,s frightened that he might have worn it out trying to catch up to the Harlies on our trip to Mount Perry for lunch.
Hey you old f_rt....how yah been? I've been waiting for all the typical Aussy banter about winter coming...snow...blah blah blah.
Too bad you didn't wait to purchase a trophy instead of that 1930s technology. I hear everytime a Harley owner goes on a trip, they have to rebuild their engines because the engine can't handle all the extra weight in tools required to keep the bucket of bolts running..... 
12 Rocket Roadster
03 Bonneville America
69 BSA Firebird Scrambler
73 Yamaha TX 750
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Re: Re compression
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Joined: Feb 2007
Posts: 23,134 Likes: 52
Fe Butt
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Fe Butt
Joined: Feb 2007
Posts: 23,134 Likes: 52 |
Quote:
He,s frightened that he might have worn it out trying to catch up to the Harlies on our trip to Mount Perry for lunch.
Was that running back for parts for the Hardleys then catching back up to the lumbering beasts?
I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!
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Re: Re compression
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Joined: Jan 2009
Posts: 1,228
I live in the sun downunder
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I live in the sun downunder
Joined: Jan 2009
Posts: 1,228 |
Quote:
Quote:
He,s frightened that he might have worn it out trying to catch up to the Harlies on our trip to Mount Perry for lunch.
Hey you old f_rt....how yah been? I've been waiting for all the typical Aussy banter about winter coming...snow...blah blah blah.
Too bad you didn't wait to purchase a trophy instead of that 1930s technology. I hear everytime a Harley owner goes on a trip, they have to rebuild their engines because the engine can't handle all the extra weight in tools required to keep the bucket of bolts running.....
Hi Greg, Have a look in the other bikes section. I couldn't resist mentioning your oncoming winter.
Hope you are well and give my best wishes to your family.
We are OK down here, 30c yesterday and summer is a month away. We have bush fires burning all over. Makes a change from last years floods.
Keep safe and no doubt we will talk again, even if it's about bashing my Harley.
FrankW
Ex Speedmaster rider, went to the Dark Side now riding an America.
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Re: Re compression
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Joined: Jan 2009
Posts: 1,228
I live in the sun downunder
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I live in the sun downunder
Joined: Jan 2009
Posts: 1,228 |
Quote:
Quote:
He,s frightened that he might have worn it out trying to catch up to the Harlies on our trip to Mount Perry for lunch.
Was that running back for parts for the Hardleys then catching back up to the lumbering beasts?
Hi Ian, It's whatever floats your boat.
My lumbering beast gets me where I want to go, as did my Speedmaster.
The comfort of riding the Softail compared to the Dyna I sold ia amazing. Also with the short inseam I have my wife feels a lot safer now that I can get both feet flat on the ground
FrankW
Ex Speedmaster rider, went to the Dark Side now riding an America.
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Re: Re compression
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Joined: Jan 2009
Posts: 1,228
I live in the sun downunder
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I live in the sun downunder
Joined: Jan 2009
Posts: 1,228 |
Quote:
10%????? they use the metric system down there.
57/64 ths. shouldn't be a problem. 
FrankW
Ex Speedmaster rider, went to the Dark Side now riding an America.
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Re: Re compression
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Joined: Feb 2007
Posts: 23,134 Likes: 52
Fe Butt
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Fe Butt
Joined: Feb 2007
Posts: 23,134 Likes: 52 |
Glad you are happy and comfortable with your newest ride Frank but you know I gotta yank your chain some.
I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!
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Re: Re compression
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Joined: Jan 2009
Posts: 1,228
I live in the sun downunder
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I live in the sun downunder
Joined: Jan 2009
Posts: 1,228 |
If you didn't yank my chain from time to time Ian, I would be thinking nobody loved me. 
FrankW
Ex Speedmaster rider, went to the Dark Side now riding an America.
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