Briggs 28 series Intek OHV, flat cam lobe.

[Arkie]

I do not know the history of the engine from a MTD lawn tractor.
283H07 197E1 030718Z
Stumbled into a briggs engine that was running rough and would not go to high speed when cold. Would idle ok warm or cold and start good. When warmed up it would eventually go to high speed but not smooth. Another carb had same results.
When checking valve lash I noticed the intake rocker not moving up/down enough.

Long story short the intake lobe on the camshaft is worn down by about .250 and almost flat on top. The lifters and push rods look ok.
The ACR is still in good shape.


Is this a very common thing with these engines for one lobe on the cam to wear down?

[KE4AVB]

Not too common but it does happen. I had in the recent year two 793880 camshafts with exhaust worn round. Broken ACRs are the common problem with these camshafts.

[Arkie]

Anyone ever tried replacing/exchanging just the ACR on a Briigs 84005207/793880 camshaft?

The reason I ask is I have one cam with a flat intake lobe and good ACR and another that has good lobes but the ACR portion is bad. (just the ACR pin is broke off)

[KE4AVB]

Can be done if the plastic retainer is still in good shape. Only done one here and the fellow died before much use was put on the mower. His took the mower and sold it to someone. No idea how well things lasted.

[Arkie]

Can be done if the plastic retainer is still in good shape. Only done one here and the fellow died before much use was put on the mower. His took the mower and sold it to someone. No idea how well things lasted.

I have a good plastic piece that is between the swivel part of the ACR and the gear next to the spring. It cannot be seen with the swivel part of the ACR in place. Is this the plastic retainer you are referring?
The c-clip retainer that holds the ACR in place on the shaft on these two cams is the steel type and removable.
Do you recall if you had to press the intake lobe out approximately 1/4 inch or so on the shaft to get removal clearance for the ACR then gently press the intake lobe back to it's original position?

I see that both the ex and intake cam lobes are a press fit on the shaft and maybe the ACR was installed on the shaft/ gear before the intake lobe was pressed into place?

[Arkie]

I went out and done a close inspection of the Briggs Cam's ACR's and their is NO plastic piece involved that you mentioned anywhere on the three that I have.

[KE4AVB]

Finally got a full day in the shop.

Sorry for the late reply as I was dead tired when 6 pm got here.

Sounds like they might have redesign yet again. Here is the ones I have here. The arrows are pointing to plastic piece I was talking about. On these you simple the pin out and back in.

[Arkie]

Thanks for the picture.
On closer examination these are plastic also, not steel as I indicated and they are Ok. They are a deep black hard plastic like used on the Toyota plastic hard body vec's.

This cam with the flat lobe and good ACR might be a generic because it does not look quite same as my other two that has the bad ACR's and good lobes.

The flat lobed cam does not have the washers pressed onto the exhaust lobe end of the cam.

I'll report back after weather warms about doing the ACR swap. I will have to gently press the intake lobe towards the exhaust lobe about 5/16 inch to slide the ACR pin assembly out and then carefully press the lobe back into place and cannot use any major warming heat on the lobe due to the plastic.
Since these are cams are already prone to failure this adds new meaning to the term "Whipping on a Dead Horse"
and or
"Fighting a losing Battle"

[Arkie]

I transferred the good Briggs ACR from the flat lobed cam to the other broken ACR cam yesterday with good results.
I had to use my otc bearing puller and move the cam lobe back on the shaft of each cam about 3/8 inch to make the transfer. I mic'ed all the spacing before starting so as I could re-set to previous locations.