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B&Stratton Cam Mystery..looks Good but didn't work

#1

tackleberry

tackleberry

I have a OHV Single cylinder 17.5 B&S engine that exhibited classic signs of camshaft compression release failure...engine would bump 1/4 of a turn on attempting to start. When I opened the engine, the camshaft and compression release device was intact. No visible signs of undue wear on anything, the cam lobes barely showed any wear at all. The valves, I had checked before pulling the engine and valve lashes were within spec, I replaced the Cam with an OEM B&S cam, and the engine started and ran normally after that. So, My question is, is everything was intact on the cam I pulled out, what is the indicator or target on the old cam that would tell me its bad? The spring seemed free and the little lever for the compression release looked like it would be in the correct position to bump the valve on start, then swing away properly once the engine started spinning...any clues?

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#2

ILENGINE

ILENGINE

I have come across an occasionally camshaft with what I will refer to as a lazy compression release. Everything seems normal but just doesn't seem to work for one reason or another. Part of the reason I have a policy of if I am opening an engine for a suspected ACR failure I am installing a camshaft out of principle. Just not enough time to mess with what could be a faulty camshaft.


#3

tackleberry

tackleberry

at 80.00 plus for a OE cam...I hate replacing something that aint broke...you understand that...but i'm mystified with this one...I've got another in work (a 28N707-0526-A1) doing the same thing, I do not see a bump out of the valves, and it will not revup upon starter application, so its going to get a new cam. Has Briggs and Stratton ever addressed this massive design failure? The design is is good, but apparently the materials are not up to the task with this many failures...If the Chinese want to make a zillion dollars just on this part, fix this part to work 1000 hours. They make em, but they aren't any better and maybe worse than OEM, from what i've seen and heard so far. For myself, I'd go with a Aftermarket and just fix it if it breaks...I cannot put that part in as an aftermarket and then sell the mower..won't do it to someone knowing that aftermarket won't last even a year or even to the next startup.


#4

ILENGINE

ILENGINE

tackleberry said:
at 80.00 plus for a OE cam...I hate replacing something that aint broke...you understand that...but i'm mystified with this one...I've got another in work (a 28N707-0526-A1) doing the same thing, I do not see a bump out of the valves, and it will not revup upon starter application, so its going to get a new cam. Has Briggs and Stratton ever addressed this massive design failure? The design is is good, but apparently the materials are not up to the task with this many failures...If the Chinese want to make a zillion dollars just on this part, fix this part to work 1000 hours. They make em, but they aren't any better and maybe worse than OEM, from what i've seen and heard so far. For myself, I'd go with a Aftermarket and just fix it if it breaks...I cannot put that part in as an aftermarket and then sell the mower..won't do it to someone knowing that aftermarket won't last even a year or even to the next startup.
Click to expand...
I understand about not replacing something that is not broke. But in some cases that has to be wieghed against having to do the job a second time if you put it back together and still have the issue. Briggs has not fixed the ACR issue. But you need to keep in mind that we may see what appears to be a lot of failures but in reality that failure rate is probably less than 1% of the engines in use.


#5

H

hlw49

Probabaly got a cam where the lobes have slipped on the shaft. They will kick back violenty and not start and you may think it is a compression release but it is not. Briggs single inteck is the sorries engine on the market. It is not is the cam is going to fail but when. Sorry design.They also blow head gaskets.


#6

Tiger Small Engine

Tiger Small Engine

hlw49 said:
Probabaly got a cam where the lobes have slipped on the shaft. They will kick back violenty and not start and you may think it is a compression release but it is not. Briggs single inteck is the sorries engine on the market. It is not is the cam is going to fail but when. Sorry design.They also blow head gaskets.
Click to expand...
The compression release mechanism simply does not break that often. I get tired of hearing online on forums, etc. about what a POS Briggs engine is because of this, this, or this. It isn’t that bad of a job to replace a camshaft to solve the problem. I have done (1) in the last five years. If you are going to go to the trouble of removing engine from mower and opening it up, even if the compression release is still physically on the cam, replace the cam if the bump isn’t happening.


#7

H

hlw49

I robibaly get 4 or 5 a year. but will say they seem to be on the older units. maybe they have help the problem.


#8

StarTech

StarTech

Now I have replaced about 20 of the 793880 camshafts in the last 14 yrs. Matter of fact I just replace four last year and one yesterday. Please avoid those Chinese aftermarket ones as the ones I got were junk. They only lasted a season before there ACR broke off. The pin would snap off due it being constantly rocked back and forth.

I still got a couple of them in stock and only use them on the el cheapo customers' engines. Down to one OEM camshaft now. Not ordering another $100 camshaft until I use the last one here.


#9

B

bertsmobile1

I do about 100 jobs a year at the moment
Usually 3 to 4 Intek head gaskets a year & 1 to 2 cams
The cams are just about the only engine out of the mower jobs I regularly do


#10

H

hlw49

I get a lot of pan gaskets on the Briggs Inteck V Twins and the Kohler Twin Commands. Have a lot of head gaskets on the older Commands. Matter of fact have one in the shop now.They have a tendency to blow out side the cylinder and they whistle at you on start up and shut down. The Kohler Command is a really good engine they run forever, know of one with over 8,000 hours on it and still going strong. Single cylinder Command is the best single cylinder engine ever built. They just don't give any trouble other than and occasional carb issue. Too bad they stopped building them but I guess they just cost too much to build today.


#11

H

hlw49

These old Dixie Choppers never sease to amaze me. Just worked on two that one an '02 model guy spent over $2000.00 on. Another one '04 model spent over $1000.00 on and were happy to get them fixed. They still have some of the orignal idlers on. These are commercial mowers used daily. Have no idea how many hours they have on them since orignal hour meters died a long time ago. i have worked on both of these mowers myself for just over 15 years. Hsve another one guy just put a new Brigg 36 HP Vanguard on it for just over $4000.00. These guys love their old Dixie Choppers.


#12

F

Forest#2

I've seen similar valve lift issues and the cam appear ok to the eyeballing.
What I started doing is set the valve lash at very minimum .003 and leave the plug wire off or ground the kill wire. If compression is still too much for electric crank through I just inset .002 feeler gauge to take the valve lash to .001. If still won't crank and I know the electrical system is good I then quickly know no need in trying to adjust valve lash.
I've seen all kinds of compression release issues with those Briggs engines,
Worn lift pins, cam lobes worn out to where could get a compression release but the valve lift when running was not enough, broken stuff. Sometimes have to set the valve last below minimum (.0015 -.002) even with a replacement cam to get good crank through.


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