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CV461S Stopped running.

#1

J

joea99

Was running and shut off. Would not restart. When cranking, seemed to "over speed" and would "backfire" occasionally.

There is spark and starting ether would not fire it.

Did a compression check, which was near zero, but reading the engine manual, there is an auto compression release, so that is useless. Trying to hunt up a leakdown tester now.

Anyway, figured to check valve lash and adjust, so pulled the valve cover and plug and find the exhaust valve clearance is "a lot" and the intake is "nothing". Went through several engine rotations and the rockers move normally.

Looked for a way to adjust lash. Found none. Reading the manual, again, (what a concept), seems these engines have hydraulic lifters and there is no adjustment.

So now I am not sure what to think. is the Zero intake clearance part of the compression release, or does it indicate a problem?

How to proceed?


#2

Mower King

Mower King

joea99 said:
Was running and shut off. Would not restart. When cranking, seemed to "over speed" and would "backfire" occasionally.

There is spark and starting ether would not fire it.

Did a compression check, which was near zero, but reading the engine manual, there is an auto compression release, so that is useless. Trying to hunt up a leakdown tester now.

Anyway, figured to check valve lash and adjust, so pulled the valve cover and plug and find the exhaust valve clearance is "a lot" and the intake is "nothing". Went through several engine rotations and the rockers move normally.

Looked for a way to adjust lash. Found none. Reading the manual, again, (what a concept), seems these engines have hydraulic lifters and there is no adjustment.

So now I am not sure what to think. is the Zero intake clearance part of the compression release, or does it indicate a problem?

How to proceed?
Click to expand...
The compression release, ACR, on most all mowers are on the Ex valve


#3

I

ILENGINE

With a hydraulic lifter type system you shouldn't have noticeable valve clearance because the oil in the lifters will keep the clearance to nothing. I would be looking at the exhaust valve to make sure it has closed all the way and the seat hasn't came out and holding the valve open..


#4

J

joea99

ILENGINE said:
With a hydraulic lifter type system you shouldn't have noticeable valve clearance because the oil in the lifters will keep the clearance to nothing. I would be looking at the exhaust valve to make sure it has closed all the way and the seat hasn't came out and holding the valve open..
Click to expand...

I suppose the only way to know is to pull the head? I have a cheap "bore scope" but can't really see anything.


#5

J

joea99

mower king said:
The compression release, ACR, on most all mowers are on the Ex valve
Click to expand...

Might that cause the apparent excess exhaust valve lash? I've no idea how the ACR works.


#6

Fish

Fish

Can you put up some pics?
Like a pic of the rocker arms?


#7

Fish

Fish

But would guess a loose valve seat.


#8

J

joea99

I could post some pictures if I know what you wanted to see. Top view, side, open, closed?

Rather than pull the head, HF has a leak down test kit, pretty cheap. That could tell the tale.


#9

Fish

Fish

joea99 said:
I could post some pictures if I know what you wanted to see. Top view, side, open, closed?

Rather than pull the head, HF has a leak down test kit, pretty cheap. That could tell the tale.
Click to expand...
Just take a few, especially at tdc.


#10

Mower King

Mower King

joea99 said:
I could post some pictures if I know what you wanted to see. Top view, side, open, closed?

Rather than pull the head, HF has a leak down test kit, pretty cheap. That could tell the tale.
Click to expand...
You don't need a "leak down" tester just to find if compression is leaking from a valve, just make sure both valves are closed or looks closed....remove rockers just to be sure, and put air in the spark plug hole....if a valve is stuck open, you will hear the air coming out, THEN you must pull the head to see why!


#11

J

joea99

mower king said:
You don't need a "leak down" tester just to find if compression is leaking from a valve, just make sure both valves are closed or looks closed....remove rockers just to be sure, and put air in the spark plug hole....if a valve is stuck open, you will hear the air coming out, THEN you must pull the head to see why!
Click to expand...

I can give that a try to confirm what I just saw. I put the scope barely in the spark plug hole and managed to see the exhaust valve. To be certain, I put a lever in the valve lash gap and could see the valve moving as I levered it. Never closes completely apparently.

I'll check the price of a new head vs getting a new seat installed, before I do anything else.


#12

Fish

Fish

At tdc, both valve stems should be at an even height, generally.
Pull the head before ordering anything.


#13

J

joea99

There are a lot of used head on ebay, that match the part number, but list for different engines. Some of them look good, some are pretty groady. Same rockers, etc? Safe to use old head bolts, or get new?


#14

J

joea99

Proceeding to remove head. Found an astounding amount of debris packed into the cooling fins. Apparently just blowing it out once in a blue moon is insufficient, when mice build a winter home in there.

Anyway, I suspect more serious problem may be found. Of course a "random" thunderstorm has interrupted my labors, but, when I get the head off, are there any tell tale signs in the cylinder wall or piston top I should look for, besides obvious heat discoloration and scoring?


#15

Fish

Fish

Look for scrathes, streaks, and if it has a noticable "lip" around the top.
You will likely readily see the problem, I still predict a loose seat.


#16

J

joea99

Fish said:
Look for scrathes, streaks, and if it has a noticable "lip" around the top.
You will likely readily see the problem, I still predict a loose seat.
Click to expand...

So, if it is just a loose seat, is there a reliable and economic way to repair that, or just go with a clean looking head from ebay?


#17

Fish

Fish

I would look for a good used one if it was me.


#18

J

joea99

Having a VERY hard time removing the top two head bolts. They do move a few turns, with difficulty. Tried the usual things such as penetrating oil (Kroil) and threading in and out to loosen things, soaking again, etc.

The head is loose so I can actually soak the threads where they go into the block, but, feels like the want to gall, or are galled already.

Not sure if heat might be the answer, or, as has worked a few times in aluminum, using Break Free as a helper might. So far I have not tried an air impact, going gently forward and reverse and hesitate to do that, having sometimes been badly fooled by soft bolts.


#19

J

joea99

Well. Fish was right, a loose seat. Intake, not exhaust. Cylinder looks good, still has crosshatch pattern plainly visible and only a small arc on piston top where the it touched the seat.Mostly just wiped the carbon. Buuuut . . .

Broke the two reluctant bolls. I can drill them out, I suppose, but suspect the threads are well galled. Could do a Time Sert repair but the kit for head bolts runs over $400. I suspect there are very new around for rent and that the "not for head bolts" kits will not suffice,


#20

B

bertsmobile1

Drill em out then pop the engine / mower on a trailer and pop dowwn to your friendly Mower mechanic ( not a glass front retail shop ) or even a motor mechanic.
Make sure you have the new bolts in hand.
Most will do a helicoil on the spot while you wait.
I charge $ 20 each ( aus ) for helicoils ( any size ) and $ 40 for solid inserts cause they are a bit tricker to do.


#21

J

joea99

Those kinds of shop tend to be few and far between in this part of US. Australians seem to be a bit more willing to fix what they got than here.

If helicoil will hold for this repair, I see kits on Amazon that are fairly inexpensive. For the solid inserts, do you use the Time Sert "head bolt" kit, or their normal kit? Or something else? I have a couple of the cheaper timeserts but not in this size.


#22

B

bertsmobile1

I have about a dozen different brands of inserts
In solid I have time certs' lock certs, new thread E-Z Loc , Fastenal and a couple of bronze kits with no brand name on them
Some have the locking keys some don't.
For metric I am going to towards a things called a threadnut which has a small hex in the top so you drill & tap either 1 or 2 sizes larger then thread the insert in with an allan key & some loctite.
A lot easier system and you don't need expensive custom taps or insertion tools
Down here every service station mechanic will have a full set of metric & Unified helicoils at least.
As for mower repair shops go to be around 30 who post regularly on here.
Mind you 30 across the entire continential USA would be a bit thin on the ground.
Heck we even have 2 mobile thread repairers and a mobile electro errosion van for removing broken bolts
Surely in the land of the entrepreneur you must have some over there
The thread man charges $ 90 call out + $ 10 for each additional insert .
Called him in to do plug inserts on the rear holes on the shadow & while he was there he did about 1/2 dozen motorcycle heads


#23

Fish

Fish

A long while back in Lexington was a shop that could blast out the metal, and leave the old threads intact. I cannot remember what the machine was called.


#24

J

joea99

bertsmobile1 said:
I have about a dozen different brands of inserts
In solid I have time certs' lock certs, new thread E-Z Loc , Fastenal and a couple of bronze kits with no brand name on them
Some have the locking keys some don't.
For metric I am going to towards a things called a threadnut which has a small hex in the top so you drill & tap either 1 or 2 sizes larger then thread the insert in with an allan key & some loctite.
A lot easier system and you don't need expensive custom taps or insertion tools
Down here every service station mechanic will have a full set of metric & Unified helicoils at least.
As for mower repair shops go to be around 30 who post regularly on here.
Mind you 30 across the entire continential USA would be a bit thin on the ground.
Heck we even have 2 mobile thread repairers and a mobile electro errosion van for removing broken bolts
Surely in the land of the entrepreneur you must have some over there
The thread man charges $ 90 call out + $ 10 for each additional insert .
Called him in to do plug inserts on the rear holes on the shadow & while he was there he did about 1/2 dozen motorcycle heads
Click to expand...

I don't see a way to find those shops on this site.

Anyway, ever used helicoil for head bolt holes and have them hold? The only hex drive inserts I find are made for use in wood.

If I can't do the entire repair for $100 USD, or so, time to scrap it. An old mower I've already rebuilt the deck twice. Sadly, just this spring.


#25

J

joea99

Fish said:
A long while back in Lexington was a shop that could blast out the metal, and leave the old threads intact. I cannot remember what the machine was called.
Click to expand...

I'll give drilling and extracting a try. But I think there is a lot of aluminum bound up in the threads. I guess it is possible I can get them out and have enough thread left to clean up and get a good bite on.


#26

Fish

Fish

I have carefully drilled them out just a hair smaller, and picked the metal out of the block's threads. But I was a lot younger with a steadier hand.


#27

J

joea99

Fish said:
I have carefully drilled them out just a hair smaller, and picked the metal out of the block's threads. But I was a lot younger with a steadier hand.
Click to expand...

I heard THAT. I'm more concerned about any aluminum that comes out with the bolt. Right now we've have thunder boomers rolling around making it unbearably humid to work outside.

Now, I'm assuming the head bolts thread into aluminum and not inserts, from the factory.

Do you know if heli coils only come in one length? McMaster-Carr shows up to 20mm length for 10x1.25


#28

StarTech

StarTech

Yes I would rework the threads as the galled threads will not hold to spec torque.

Do you know if heli coils only come in one length?
Click to expand...
They come in several lengths. The M10-1.50 helicoils range from 10 to 30mm in 5 mm steps. Tool kit not too bad at $50 but it only comes with 15mm inserts and you would need to order the desire length inserts but the tool kit only has a thru hole tap, if you need the bottom tap (closed hole) that is another $40. Of the prices are from my source of the Helicoil items.

I waited ten years before getting my first Helicoil kit but I already use it 3X this year; but of course, it is a 5/16 version.


#29

J

joea99

StarTech said:
Yes I would rework the threads as the galled threads will not hold to spec torque.


They come in several lengths. The M10-1.50 helicoils range from 10 to 30mm in 5 mm steps. Tool kit not too bad at $50 but it only comes with 15mm inserts and you would need to order the desire length inserts but the tool kit only has a thru hole tap, if you need the bottom tap (closed hole) that is another $40. Of the prices are from my source of the Helicoil items.

I waited ten years before getting my first Helicoil kit but I already use it 3X this year; but of course, it is a 5/16 version.
Click to expand...

Looks like I could get away with the regular tap. Still struggling to get the bolts out, but drilling through one of them shows there some kind of gap at the end of the threaded hole. At least the penetrating fluid I spray in there flowed out the "blind end". That was a desperate last gasp attempt to use an extractor on the bolt. Bits of it did break off and came out, but some remain in there.


#30

J

joea99

Finally got around to drilling out the broken bolts. I had to 3d print a "guide" to help me drill as "square" as I could. Spend about 20 minutes using a HF drill bit on the first one. Only got part way through went it stopped cutting. Went to Lowes and got a Dewalt bit.13/32 and was done with both in under 5 minutes. Like cutting in wood,

Anyway,the Helicoil kit I'm getting has 15mm inserts. I wonder if those are long enough, or if I should go with 20mm or longer?

Edit - I just made an attempt to determine the length of the threads on the remaining bolt holes and they seem to be about 30mm long, starting about 6mm below the block surface. Should I go that long? Come to think, can I actually sink the helicoils below the block surface, or will the tool not allow that? Do I resort to drilling out the first few threads?


#31

B

bertsmobile1

Rule of thumb
Std bolts get a std insert which is 1 diameter
Medium strength bolts use 1.5 d
High tensile bolts get 2 D
When used in alloy go up one lenght .


#32

J

joea99

So, a head bolt, in an aluminum "block" would bit a 2.5 or 3 diameter? That is 25 or 30mm?


#33

B

bertsmobile1

d = diameter of the bolt
so for an 8mm head bolt 3D = 24 mm
Getting a 3D insert in is a lot more difficult that many would believe
It has to be shorter than the threaded section of the original hole by 1 thread top & bottom ( if hole is through ).
I mostly use 1.5's and 2's on push mower head bolts


#34

J

joea99

bertsmobile1 said:
d = diameter of the bolt
so for an 8mm head bolt 3D = 24 mm
Getting a 3D insert in is a lot more difficult that many would believe
It has to be shorter than the threaded section of the original hole by 1 thread top & bottom ( if hole is through ).
I mostly use 1.5's and 2's on push mower head bolts
Click to expand...

These are 10mm x 1,5 bolts. The measured (roughly) original thread length is 30mm with about 10mm unthreaded past that. Suggests I can just use the standard tap. I have my concerns about the longer lengths, mainly just the ever increasing torque needed to thread them in. Maybe that is not really a problem.

This is a ride on mower, single cylinder. as you probably know. I think then going with 2.5 D max would be the ticket here?


#35

B

bertsmobile1

Yep, 2.5's or even 2's will do you fine , 3's will be too long .


#36

J

joea99

Just to close this out, the inserts installed fine. I went with the 25mm coils.

The used head I got on Ebay turned out to have a warped exhaust valve, discovered when I decided to "lap" in the valves prior to installing it. I used the valve from the head with the dropped seat and it lapped in nicely.

Installed, with very few left over parts . . . . and it seems to be running fine. Though it did give me a scare as it warmed up and began billowing smoke. Panic set in until I remembered how much penetrating fluid I had used trying to get the head bolts out to begin with.

All in all a learning experience, having never done heli-coil before. Thanks for all the tips.


#37

B

bertsmobile1

Thanks for the close out and well done.


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