Author Topic: compression testing thoughts (Read 2738 times)

DWS · « **on:** October 22, 2014, 05:05:02 PM »

Here are my testing results'
1st cylinder
cold-50
warmed up-100
wet-150

2nd cylinder[/color]
cold-60
warmed up-91
wet-145

3rd cylinder
cold-55
warmed up-92
wet-150

4th cylinder
cold-60
warmed up-93
wet-130

can someone help with the figures please
thanks
Duane

70CB750 · « **Reply #1 on:** October 22, 2014, 05:41:10 PM »

Sorry, you should say little more. Is it a fresh from the barn bike, daily rider you doubt or freshly rebuilt engine?

DWS · « **Reply #2 on:** October 22, 2014, 05:44:50 PM »

i bought it new in 78 but been sitting for the last 15 years i have restored everything but the motor it only has 15000 on it

calj737 · « **Reply #3 on:** October 22, 2014, 06:05:10 PM »

Depending upon the type of tester used (car vs motorcycle) then your psi is irrelevant. What is relevant is there consistency between cylinders. "Dry and cold" they appear low, but even. "Wet" indicates that the rings are currently worn. But that's inconclusive if the bike has been sitting for a prolonged period.

Are the valves adjusted properly? Did you have the throttle wide open when testing?

DWS · « **Reply #4 on:** October 22, 2014, 06:11:06 PM »

i need to check the valves, yes i did open the throttle all the way.
its an old cheap tester.
i'am at 5000 feet here also

calj737 · « **Reply #5 on:** October 22, 2014, 06:38:23 PM »

With an "old cheap tester" I wouldn't put too much stock in its measurements. I would double check the valves, and run the motor (ride if safe to do so) and get the motor up to a good, hot operating temp. Then test it. Many times compression comes back after some use if it's sat for a long while.

Of course, full service on the oil tank and pump etc...

DWS · « **Reply #6 on:** October 22, 2014, 10:20:01 PM »

Thanks ill try a good tool

dave500 · « **Reply #7 on:** October 23, 2014, 12:14:44 AM »

if the bikes been sitting as you say a few decent rides should see the compression come up,use the same guage as that's your baseline.

70CB750 · « **Reply #8 on:** October 23, 2014, 03:17:34 AM »

Quote from: dave500 on October 23, 2014, 12:14:44 AM

if the bikes been sitting as you say a few decent rides should see the compression come up,use the same guage as that's your baseline.

^^^ That. Very likely you will be happy with it after you put some miles on it.

Vinhead1957 · « **Reply #9 on:** October 23, 2014, 04:52:02 AM »

That bike needs the snot run out of it! Worry about compression when a problem running pops up. Otherwise ride!

DWS · « **Reply #10 on:** October 23, 2014, 02:46:22 PM »

Now that puts a smile on a guy!
That is what ill do.

Bailgang · « **Reply #11 on:** October 23, 2014, 03:24:35 PM »

Quote from: 70CB750 on October 23, 2014, 03:17:34 AM

Quote from: dave500 on October 23, 2014, 12:14:44 AM
if the bikes been sitting as you say a few decent rides should see the compression come up,use the same guage as that's your baseline.

^^^ That. Very likely you will be happy with it after you put some miles on it.

Most definitely +1.
I purchased an 83 gl1100 earlier this spring with a locked up engine due to the previous owner letting it set outside for 4 years and rain getting in the cyl's. It only has 34k miles which is chump change for a GL and I was able to free the engine without tearing it apart. At first it would smoke a bit on a cold start up but now it doesn't smoke at all and compression tests keep improving and I've only put maybe 1k miles on it so far but basically as Dave and 70CB750 pointed out what the engine needed more than anything was to be ridden.

TwoTired · « **Reply #12 on:** October 23, 2014, 04:04:15 PM »

How much "wet" volume did you add to the tiny cylinders?

But, I agree, run at least one hundred miles. What's the worst that will happen? A top end job? I'd rather do those later than sooner.

DWS · « **Reply #13 on:** October 23, 2014, 06:58:01 PM »

two pumps from a small oil can, 2 to 3 cc
I also adjusted the valves to .003 on every Valve and adjusted points.
I'll do the timing tomorrow.
What do you think that I should set the points at?
and advancement?

5000 feet here
1978CB750F3
Spark plugs- 24"
valves- .003"
Points- 14

Carb's 42A
stock air box
4 into 1
#35 slow jet
#110 main
2 turns out on the slow jet
4900 feet elevation
Timing is at --1&4 F mark now
advance, not sure what i was seeing timing light.

TwoTired · « **Reply #14 on:** October 23, 2014, 07:11:21 PM »

Quote from: DWS on October 23, 2014, 06:58:01 PM

two pumps from a smll oil can, 2 to 3 cc

That's fine for a car engine. The compression chamber is only about 13 cc on the 550. I expect a lot of your compression increase is due to the volume displacement change from the added oil volume. Changing from 13 to 10 cc is significant, as it is a smaller space to compress the swept piston volume into.

In general, you only want to use enough oil to wet the rings for a possibly better seal, not change the compression ratio.

There is/was a FAQ entry about this.

DWS · « **Reply #15 on:** October 24, 2014, 09:09:23 AM »

Good to know that, thanks

need to ride it i guess but need to sync the carbs but dont have the sync tool! can i make one or do they not really work?

strynboen · « **Reply #16 on:** October 24, 2014, 09:20:05 AM »

i just go for the lov kost 4 gauge type...they does the job easy and presise...
(.and are easyer then fluid and a lot of meters of gas lines..and spilled atf oil all over the place..sucking dirt up the next many years..dripping oil dovn the vall...until the day your vife throv it all aut)

DWS · « **Reply #17 on:** October 24, 2014, 09:34:59 AM »

Your probably right

garyS-NJ · « **Reply #18 on:** October 24, 2014, 10:09:47 AM »

like the others said, I'd be happy and ride if the motor runs OK and not blowing a ton of smoke. and 4 cylinders around 140PSI I'd be happy. If you're curious you can wet the rings with oil and blow the oil out putting your thumb lightly over plug hole and then test compression. the book says .002 intakes and .003 exhaust but some folks say .004 on both and others run larger clearance. for the Points use 0.015". find the shop manual online. I put a dyna in last year and happy with it.

DWS · « **Reply #19 on:** October 24, 2014, 10:25:03 AM »

i have mine set at .003 ex and in, from hondaman for this bike, he said that it will run a little cooler and lease tapping knock.
where did you get your info from?
my points are at 14 now
i have lots of different manuals plus hondamans book, just got the book after i'am almost done.
doesn't the manual say .002 and .005?
I would love to get the dyna.

thirsty 1 · « **Reply #20 on:** October 24, 2014, 04:24:42 PM »

Chop the hose off of that gauge and try it again. I'd also run that old girl and see what happens.

dave500 · « **Reply #21 on:** October 24, 2014, 05:36:00 PM »

no make it longer

then youll get this much compression

thirsty 1 · « **Reply #22 on:** October 24, 2014, 06:00:04 PM »

What gives Dave. The long hose will take up volume and chase a lower number.

dave500 · « **Reply #23 on:** October 24, 2014, 06:38:40 PM »

this has been gone over dozens of times,the hose has a one way valve at the spark plug end,itll still compress up just take a couple more pumps,for example fit a larger tank to your air compressor,itll just take longer to reach max.

thirsty 1 · « **Reply #24 on:** October 24, 2014, 06:58:07 PM »

Haha just checking your game.

. Pressures, Pressure. Pascals law. Cheers bud it's Friday!

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Author Topic: compression testing thoughts (Read 2738 times)