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I think I see the bump

#1

PTmowerMech

PTmowerMech

But after checking the push rods, which were straight, adjusting the valves (.005/.005), and jumping with a good battery it's still acting like the compression release is bad. The view is from the camera laying under the head facing up. Turns til the compression stroke then barely moves passed it.

BTW, I also jumped straight to the starter.





#2

I

ILENGINE

After watching several times I don;t think it is decompressing correctly. Hard to tell with the uneven turning which kind of give a false feel of it being there. Where the bump off should be just don't look right.


#3

PTmowerMech

PTmowerMech

After watching several times I don;t think it is decompressing correctly. Hard to tell with the uneven turning which kind of give a false feel of it being there. Where the bump off should be just don't look right.

Sometimes it would bump, sometimes not. I'm thinking the times it did, was after letting go, the flywheel would stop and turn back just a hair. Making it look like a bump.
I put a fully charged batter on it, a new one in fact, and it still stops, then eases over the compression stroke. I rechecked the valves, and they're still set at .005 each.

When I get back out there, I may put the big drill, with a socket to it and rerecord the video. Because some rotations looked like it was bumping. And some didn't. Seems they all would've bumped.


#4

L

Luffydog

I never saw the bump. Make sure that it's tdc and on the compression stroke set at .004 and retry.


#5

L

Luffydog

I would also check to see if there was gas in the oil to rule that out as well


#6

T

Tinkerer200

Spring on Compression Release may have broken or come off giving those intermittent results.
Walt Conner


#7

TylerFrankel1

TylerFrankel1

It does seem pretty iffy as to if it's bumping or not. Before you tear it apart make sure the connection is tight at the starter. Take off the positive battery lead from the starter, then tighten down the nut that is left on the standoff. Then reattach and tighten the battery lead to the starter. If that doesn't work, and you have a bit of time on your hands (and 10 bucks for a new sump cover gasket) I'd tear it down and check the compression release on the cam. See if it's sticky or damaged.


#8

I

ILENGINE

If I was the OP and opened the engine us to check the compression release I would have a new cam ready to drop in. Seen too many of them with somewhat iffy operation over the years, and for the time it takes to get to the cam it isn't work the effort to have to do it a second time.


#9

PTmowerMech

PTmowerMech

Starter & battery connection's cleaned. Valves adjusted to .005 (which is fine) nothing but oil in the oil.


The spring is to keep the CR closed on low rpms, correct?

Customer can't afford the repair. Says they'll just put a stronger battery on it. Even after explaining about the broken CR fragments probably still lying inside the engine. And the damage they could do.

Repair on the cam. Plus a ton of other stuff. Drive and deck idlers, spindle bearings.


#10

TylerFrankel1

TylerFrankel1

The customer is making a mistake, not uncommon. A bigger battery isn't gonna solve the busted metal or likelihood of it getting worse.

Spring holds the compression release so that it bumps the valves until centrifugal force overpowers the spring at high RPMs and flattens the compression release hump. Taryl does a good job explaining this at 8:24 of this video:


#11

TylerFrankel1

TylerFrankel1

Starter & battery connection's cleaned. Valves adjusted to .005 (which is fine) nothing but oil in the oil.


The spring is to keep the CR closed on low rpms, correct?

Customer can't afford the repair. Says they'll just put a stronger battery on it. Even after explaining about the broken CR fragments probably still lying inside the engine. And the damage they could do.

Repair on the cam. Plus a ton of other stuff. Drive and deck idlers, spindle bearings.

You said you replaced the drive idlers. The ones on my tractor all spin freely but noisy. I have been reluctant to take the pulleys out because I have to drill a hole in the floor of the tractor to get at a nut. I was wondering if it would be ok to procrastinate more as long as I spray them with wd-40 and make sure they aren't seized each use. Also if I take them out and pop out the dust guard things, is it ok to just re pack the grease and go about my day?


#12

B

bertsmobile1

You can not remove the dust seals from the idler pulleys because the pulley is captive .
From memory yours should be plastic and are cast into the pulley so not replaceable .
You can after removing the pulley & cleaning them inject some grease into them with a syrenge but as this is a very temporary life extension & requires removing the pulleys to do there is little point in doing it unless the pulleys are not available right then .
As previously mentioned WD 40 is not a lubricant and should not be put anywhere near a bearing .
WD 40 is a good dewatering fluid, OK penetrant & temporary lubricant while it is wet .


#13

StarTech

StarTech

IF this is a Briggs 280000, 310000, or 330000 it is a good bet that the ACR is broken in pieces. The 793880 camshaft is prone to this. So much so that I keep one on the shelf at all times.


#14

T

Tinkerer200

"Customer can't afford the repair. "
I would not recommend it but I know of one case where the person put 2 head gaskets on lowering the compression enough the starter would turn the engine, He said he could not tell any difference in performance. Besides efficiency the head gasket problem they already have would be questionable. Others have added a manual compression release valve.
Walt Conner


#15

PTmowerMech

PTmowerMech

You said you replaced the drive idlers. The ones on my tractor all spin freely but noisy. I have been reluctant to take the pulleys out because I have to drill a hole in the floor of the tractor to get at a nut. I was wondering if it would be ok to procrastinate more as long as I spray them with wd-40 and make sure they aren't seized each use. Also if I take them out and pop out the dust guard things, is it ok to just re pack the grease and go about my day?

LOL.. I didn't get to work on this one. The cost of everything went above their heads. I suppose it'll sit at their house, out in the weather, until it's not even worth savaging. That's the way it goes with some folks.
I offered to buy it from them, cheap. But they didn't want to sell it.

I have a feeling that sometime during the mowing season they'll be calling and asking if I have an engine for sale for that mower.
And I probably will. But it'll be about the cost of the cam they don't wanna replace now. LOL


#16

PTmowerMech

PTmowerMech

"Customer can't afford the repair. "
I would not recommend it but I know of one case where the person put 2 head gaskets on lowering the compression enough the starter would turn the engine, He said he could not tell any difference in performance. Besides efficiency the head gasket problem they already have would be questionable. Others have added a manual compression release valve.
Walt Conner

There's still the bits and pieces of the CR inside their engine. It's just a matter of time before something gets caught up between the cam & crank gear.


#17

TylerFrankel1

TylerFrankel1

You can not remove the dust seals from the idler pulleys because the pulley is captive .
From memory yours should be plastic and are cast into the pulley so not replaceable .
You can after removing the pulley & cleaning them inject some grease into them with a syrenge but as this is a very temporary life extension & requires removing the pulleys to do there is little point in doing it unless the pulleys are not available right then .
As previously mentioned WD 40 is not a lubricant and should not be put anywhere near a bearing .
WD 40 is a good dewatering fluid, OK penetrant & temporary lubricant while it is wet .

Sorry, I made that comment before I saw your response to the other. I will just replace them. I do know WD-40 is only temporary but I've used it before to keep junk going (I have a cheap surface cleaner on a pressure washer with no zerk or way to grease it, and it seizes after about 1 hour of running. So every 30 minutes I spray it with WD-40 and it keeps limping along. lol!)


#18

TylerFrankel1

TylerFrankel1

IF this is a Briggs 280000, 310000, or 330000 it is a good bet that the ACR is broken in pieces. The 793880 camshaft is prone to this. So much so that I keep one on the shelf at all times.
I have a Briggs 31p777 sadly. I'm waiting for it to blow up! I thought it was blown up when I got it because it wouldn't turn over, and went through the mess of disassembling the engine, only to find it in-tact, and realized my valves were adjusted wrong and the connection to my car battery via jumper cable sucked. When the day comes I know what to do though.


#19

TylerFrankel1

TylerFrankel1

Sucks that they won't fix it. Perpetrator of Lawn Mower Neglect and Abuse. I'm working on a tractor right now (that Bronco) that was probably a similar case. It wouldn't crank, they probably assumed it was more severe than it was, and then it rotted in the yard. It's probably not worth salvaging either but I've mostly done it anyway. Just needs the new pulleys and belts now. As long as whatever sludge is left in the transaxle case holds up for a while I'm set. Even the dryrotted tires hold air somehow. Do y'all ever regrease the transmissions? I know they're sealed with no drain plugs but it pains me to think about what's in there after many years. (I'm talking manual and fake automatic, not hydrostatic of course)


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