Compression readings....


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leakyroof58
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Compression readings....

Post by leakyroof58 » Fri Mar 09, 2018 5:53 pm



My '87 Aspy only shows 135 PSI in all cylinders.
Should I not worry (runs/starts great) or should I
dump it for another GW ???



DaveO430
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Re: Compression readings....

Post by DaveO430 » Fri Mar 09, 2018 7:02 pm

Did you check it with the engine warmed up and the throttle wide open? If it runs good why worry?

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julimike54
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Re: Compression readings....

Post by julimike54 » Sat Mar 10, 2018 10:39 am

Also if the bike hasn't run in a while the compression will read low. If they are all even there is a great likelyhood it is fine.
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brian.peters
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Re: Compression readings....

Post by brian.peters » Sat Mar 10, 2018 1:00 pm

compression readings are affected by many things, WOT is really not one of them but temp and cranking speed absolutely are. Not sure what the spec should be but they are even and if the bike starts fine when cold I would not worry a bit.

DaveO430
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Re: Compression readings....

Post by DaveO430 » Sat Mar 10, 2018 2:59 pm

brian.peters wrote:
Sat Mar 10, 2018 1:00 pm
compression readings are affected by many things, WOT is really not one of them
Have you tried it both ways? I have.

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AZgl1800
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Re: Compression readings....

Post by AZgl1800 » Sat Mar 10, 2018 3:09 pm

.
took it all out....................
Last edited by AZgl1800 on Sat Mar 10, 2018 4:20 pm, edited 1 time in total.
~John

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brian.peters
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Re: Compression readings....

Post by brian.peters » Sat Mar 10, 2018 3:44 pm

Wow lots of sarcasm here. Yes I have tried it both ways and it makes zero difference. Done more compression checks than I can count on everything from a hot rod big block to a chain saw.

But then again I've only actually done it not been educated about it so I guess experience is meaningless.

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leakyroof58
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Re: Compression readings....

Post by leakyroof58 » Sat Mar 10, 2018 5:02 pm

Thanks to all who replied. Guess I won't worry
right now, just that 135 is a lot less than the 185
spec. Then again, its 30 YO. Bike DOES start
quick and run like a top, so I guess all my carb
work and rebuilds helped a lot. Still amazed at
the smoothness of these things......maybe I
won't sell it now.......once again, thanks to all....
leaky

DaveO430
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Re: Compression readings....

Post by DaveO430 » Sat Mar 10, 2018 5:47 pm

brian.peters wrote:
Sat Mar 10, 2018 3:44 pm
Yes I have tried it both ways and it makes zero difference.
My experience has shown the opposite.

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Aussie81Interstate
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Re: Compression readings....

Post by Aussie81Interstate » Sat Mar 10, 2018 6:22 pm

I would expect a slight difference with WOT or not - but probably not measurable enough to read on your gauge.

I would try a dry and wet test with all plugs out and WOT - and doing that on a warmed up motor as well - cold motor is not really indicative.

You might want to set your valves if the readings are a bit on the low side - might improve the readings as well.

Hopefully no sarcasm in that reply.. :)

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julimike54
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Re: Compression readings....

Post by julimike54 » Sun Mar 11, 2018 10:06 am

leakyroof58 wrote:
Sat Mar 10, 2018 5:02 pm
Thanks to all who replied. Guess I won't worry
right now, just that 135 is a lot less than the 185
spec. Then again, its 30 YO. Bike DOES start
quick and run like a top, so I guess all my carb
work and rebuilds helped a lot. Still amazed at
the smoothness of these things......maybe I
won't sell it now.......once again, thanks to all....
leaky
Had the bike not been running for a while? If so put a few hundred miles on it, then recheck. When they have been not running for a while (how many years?) they will have sticky rings that will free up with use. I would ride it and observe whether it smokes and what the fuel mileage is like. These can indicate the health of the motor. If the rings are really not good, find a long downhill run; start at whatever speed the road is posted; coast downhill with the throttle closed; at the bottom of the hill open the throttle to add acceleration; at the same time look in the rearview mirrors and see if you have a cloud of blue smoke (may just want to have someone follow you for the observing part) then the rings would be the number one suspect.

On another forum another person had similar low readings. They put close to 700 miles on and use Marvel Mystery oil, the readings were up to spec. after that. The user was on a 1200 that hasn't any adjustable valves.

Just fyi :)
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paneled
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Location: kansas city mo
Motorcycle: 1986 Goldwing 1200 aspencade sei

Re: Compression readings....

Post by paneled » Sun Mar 11, 2018 8:45 pm

being an auto mechanic for 30 plus years, when I do a compression test
I look more for one cyl considerably lower than the others, if all cyl are
within 10% I call it good, as long as I get reading higher than 100 lb.
I had a mechanic working for me that would do a comp test and only
let the compression stroke hit 3 time and then take that reading,
when I was in auto shop the process was to crank till the needle
quit climbing then use that reading.
So I let the compression stroke hit about 8 or 9 times.
somtimes i open the throttle all the way but most times i dont
but never only on select cyls, open for all or none the key is consistincy.
i personally would not worry about 135 on all cyls. when you get one that
only pumps 80 then we have an issue. hope this helps


86 aspy sei
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