CD-11’s compression issue

[Mumbles]

It came in a plain brown wrapper from Princess Auto.

http://www.princessauto.com/en/detail/d … -p8214082e

[bob-d]

Great, thanks Mumbles.
I am going to pick one up.

[jerry-ahrens]

It sounds to me like you need to try a completely different compression gauge. 60 psi is way to low for the 40 tiller, and it may not even run with that. Where do you have your high and low speed needles set at?

[fleetwin]

Skanders
It sounds like you are just changing the gage, but still using the same hose/valve/threaded adapter, am I correct? If so, you really need to swap out the entire setup. There may be problems due to a long hose, leaky valve or threaded adapter. Like all have said, 60PSI is way low for a 40hp, so this would back up our gage problem theory.
OK, you used a ball hone, so I am doubting you took too much meat off the cylinders, but it is possible. You say you didn’t rebuild all the powerheads, do the ones that were untouched run? If so, do they start and run OK? If so, then this would also back up our gage problem theory, these engines aren’t going to start or run well at all with only 30PSI.

[skanders01]

Thanks for the questions, fleetwin. Yes it is possible that there may be something wrong somewhere between the cylinder head threads and the compression gage. I am going to borrow a different one from Auto Zone tomorrow.

The ball hones didn’t spend more than the recommended time in the cylinders. Doubt that is at issue.
I did take my red and gray corded drill to the motors to spin them faster. The 40 HP Johnson came up to 82 PSI in each cylinder. The pressure in the little green one currently on the autopsy table didn’t change, HOWEVER, by spinning it faster with the bigger drill, I was able to get it to start and run after playing around with settings. Doesn’t want to idle down, but will run without too much trouble from "shift" position speed through full speed. A lot of smoke though. I think I ensured there was at least a 16:1 for initial starting.

Will report results with another compression tester tomorrow.

The one motor I did not touch the internals does start/run OK, but as mentioned before, it too read around 30 PSI.

I sure hope the problem is the compression tester for my sake, but for the effort of all you supportive troubleshooters out there, I hope it is not so your time and efforts were not wasted.

Kyle Anderson
Trempeleau, WI
skanders@triwest.net
920-764-0501

[Steve D]

Even if it does turn out to be the tester, I wouldn’t consider any time or efforts wasted. It’s impressive to see all the angles being worked and ideas being thought of and reading the explanations…anyone looking at a discussion like this has to be learning something. I know I am. Anything that doesn’t apply now can be tucked away for future reference.

[david-bartlett]

quote Steve D:

Even if it does turn out to be the tester, I wouldn’t consider any time or efforts wasted. It’s impressive to see all the angles being worked and ideas being thought of and reading the explanations…anyone looking at a discussion like this has to be learning a lot. I know I am. Anything that doesn’t apply now can be tucked away for future reference.

+1

[Mumbles]

Your compression tester should have a working check valve like these ones on the end of the hose.

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[necks]

The experience I’ve had rebuilding engines, I have three compression gauges. Two are the screw in spark plug hole like you are using. Never had any luck with readings. I went back to the old style rubber push in and hold, and get accurate readings 100% of the time.
The screw in type would read the same as the push in , except I would lose the reading do to gauge leaking

[skanders01]

So, time for an update for all of this issue’s followers.

1. Using my corded drill (850 RPM) I was able to get the last of my three rebuilt 5.5’s started and running. Like the others, it did not want to idle down below the "shift" point on the tiller position band, but I will worry about that common issue among all of them when my garage thaws out.
2. Borrowed a loan-a-tool compression tester from AutoZone. According to that gauges readings (if we are to believe that gage; I know it is a loaner probably rode hard and put up wet) my gage (hoses, fittings, and all) is reading around 10PSI low. 30-35 came up to 40-45 for the CD’s, the 6R79E that I am sprucing up to sell this spring read in the mid 50’s, and my 40 HP came up to 90/90. All readings in a 30 degree environment and no additional lubrication in the cylinders beyond the residual oil from their last run.

So, from here, when it warms up, I will borrow another compression tester from a neighbor who is currently out of town for a third opinion. Will also fix whatever the heck is wrong cheap but new compression tester in the warmth of my basement!! Also need to finish working on my fantasy of a control scheme to operate the three I choose to tripe up on my FD-6 (that is also awaiting warmer weather to get spruced up.)

Not a resounding definitive closure here, but progress is acceptable. If I we ( 😀 ) had completely resolved/repaired the issue I would have to go out to find more trouble to shoot!

My thanks again to all of the effort on my behalf. Promise to send an update and pictures in a few months.

Regards,

Kyle Anderson
Trempeleau, WI
skanders@triwest.net
920-764-0501

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