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Too Much Compression?

#1

Ivor_Wolf

Ivor_Wolf

I have an older ds craftsman riding mower with a model: 441777 type: 0785 E1 Code: 061011YG motor. My father has put in a new starter and new battery over the years and we keep having the same issues. It will start up and run but it does run a little rough. However, if you shut it down and then try to turn it on again the starter cant turns the engine. If I manually turn the engine past the compression stroke then it can turn on the engine. I checked the timing and it is good and I was gonna go look at a compression relief valve however I cant seem to locate one online for this engine and I've seen people talk about this specific engine not having a mechanical one. If anyone could toss me ideas as to the starting issue that would be great. We have been chasing this for years and wed love to get it fixed.


#2

I

ILENGINE

That engine appears to have a compression release on the camshaft. So could be broke.


#3

Ivor_Wolf

Ivor_Wolf

ILENGINE said:
That engine appears to have a compression release on the camshaft. So could be broke.
Click to expand...
I can't seem to find that part in the parts diagram for this model. Could you show me where you found it? I'm not exactly sure how to find the proper parts for this thing. The part I keep finding says there's just slightly larger lobes to hold the intake open longer vs an actual mechanical relief. I'm just kinda hoping to have a diagram 100% before I decide to pull the engine. I'm dreading it haha.


#4

R

Ron_AU

You found it, you just don't know what you are looking at.

A finger rides on the taller cam that holds the intake open longer, thus dropping compression.
Once the engine spins up, the finger pulls away and the rocker arm runs on the normal intake cam, giving full compression.

The finger can get stuck in the off position, giving full compression and difficulty starting.

The opposite can happen too - the engine doesn't run too well.

Pull it apart and have a good look at how it works - it's on the cam cog.


#5

R

Ron_AU

Ron_AU said:
You found it, you just don't know what you are looking at.

A finger rides on the taller cam that holds the intake open longer, thus dropping compression.
Once the engine spins up, the finger pulls away and the rocker arm runs on the normal intake cam, giving full compression.

The finger can get stuck in the off position, giving full compression and difficulty starting.

The opposite can happen too - the engine doesn't run too well.

Pull it apart and have a good look at how it works - it's on the cam cog.
Click to expand...
It is spring loaded and is meant to move under centrifugal force, unless it is stuck.

A commonly used decompressor mechanism, causing a common problem.


#6

I

ILENGINE

Ivor_Wolf said:
I have an older ds craftsman riding mower with a model: 441777 type: 0785 E1 Code: 061011YG motor. My father has put in a new starter and new battery over the years and we keep having the same issues. It will start up and run but it does run a little rough. However, if you shut it down and then try to turn it on again the starter cant turns the engine. If I manually turn the engine past the compression stroke then it can turn on the engine. I checked the timing and it is good and I was gonna go look at a compression relief valve however I cant seem to locate one online for this engine and I've seen people talk about this specific engine not having a mechanical one. If anyone could toss me ideas as to the starting issue that would be great. We have been chasing this for years and wed love to get it fixed.
Click to expand...
It is the weight and finger between the first lobe and the cam gear in this picture

1678016452208.png
But I am finding pictures of supposedly the correct camshaft and some show it with the compression release and some without even within the same multiple picture scholl.


#7

StarTech

StarTech

That is the new version (PN 797242) of the camshaft recently released. The older camshaft PN 790562 does not have an ACR.

1678018237784.png
1678018290749.png
Just another example of not fully researching things. In this case supposedly an improved camshaft has been created since the original camshaft was done.


#8

StarTech

StarTech

Note if you are logged into your account images are currently not appearing but do if you are not logged in.


#9

F

Forest#2

If not already done try adjusting the valve lash to minimum specs, especially the intake valve lash on both cylinders.


#10

S

SeniorCitizen

With a feeler gauge of the correct thickness to adjust the intake valve , insert it between the rocker lever and valve when he piston is coming up on compression stroke . Maybe this is one that the cam bumps the valve stem just before TDC to release just enough compression . The feeler will get tighter at that point .


#11

M

milliemar

#1 Make sure your battery/engine ground wire is clean and tight. #2 Intake valve needs adjusting.


#12

C

CWatters

I had same issue on a B&S. Definitely check the valve clearance is spot on.
Apparently the decompressor only opens the valves a tiny bit so if the valve clearance is slightly out they don't open and the starter can't turn the motor over. Adjusting mine totally fixed the problem.


#13

D

dbelcher1950

Before tearing into your engine, check the valve clearances. I have seen improperly adjusted valves cause the condition you described.


#14

LarsMunk

LarsMunk

Hi,
Have you checked if gasoline has found its way through the carb to the cylinder and into your oil?

Had the same problems because of that.


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