Hard Starting 6.0 B&S Intek

Hi everyone,

New user here, found this place by Googling for a problem I'm having. Got a weed trimmer with a B&S 6 HP Intek (Model #121607-0018-E1) that often binds up on the compression stroke when trying to start it. I can start it with the rope; sometimes it spins OK, but many times the resistance is so hard you could just about pull your arm out of the socket. The electric start can't overcome the compression at all. Once it starts it runs great but you about kill yourself to get it going. The motor is about 1997 vintage. I've been the only owner. It has sat for a few years, but I would guess it has about 50 hours on it.

Here is what I have done, trying to get this thing going reliably so I can cut down the weeds I really need to cut down.

1) Replaced the battery.
2) Cleaned and overhauled the carb
3) Checked the valves and set the valve lash to .005. The specs I can find say .004 to .006.
4) Changed oil and all filters.
5) Replaced the spark plug with a new one of the correct type. (Champion RS12YC IIRC) Don't know why it had the wrong plug in it, but with the right one it does run much better WHEN it runs.

At one point I thought there was too much oil in it, so I drained ALL the oil out and the problem persists. I believe there was too much oil in, but as I said, with all oil drained it was just as hard to pull when it hit the compression stroke. It now has the correct amount of oil in it according to the dipstick.

Any ideas?

Thanks for all suggestions!

-- Jason

https://www.briggsandstratton.com/na/en_us/support/results.html?searchrequested=121607 page 19 in operators manual

engine cold, intake & exhaust valve clearance 0.004-0.008

mechanic mark said:

https://www.briggsandstratton.com/na/en_us/support/results.html?searchrequested=121607 page 19 in operators manual

engine cold, intake & exhaust valve clearance 0.004-0.008

Click to expand...

I see that. Thanks!

So, after adjusting valves to the required specs (.006 - center of range) the engine runs nicely but is no easier to start. I can get it started fairly easily with starting fluid and the pull rope after which it runs fine, so that is what I will do. Possibly the electric start is shot, but at the price of a replacement it will have to be what it is.

A youtube video from a fellow I like to watch suggested checking valve adjustment after a few hours running. I did that and what I found is that the valves do not stay where adjusted, usually becoming loose. Yesterday I readjusted and the starter work once and then the valves were out again.

After some research I have found that this engine is an "early-production". In the intervening time the rocker arm adjuster has been totally redesigned and now uses part 694543, which has an adjustment screw and a locking nut, which is the arrangement for every other intek I see. Mine just has a locking nut and no screw. I am guessing the lash was originally set at the factory and then lock-tited. However it worked, the "locking nuts" don't stay locked and the lash wanders around.

Is it possible to replace these "early-production" rocker arm adjusters with the current part? I am assuming that is what a repair shop would do if the part needed to be replaced, right?

They all have a locking screw.
people get confused because the screw in the middle is the locking mechanism and the nut is the adjustment.
A lot of ewe-tube shaved monkeys have this backwards.
There are a few variations of the grub screw.
Slotted, hex ( allan head ) and torx.
The size of the pivot nut has also changed.
So you adjust the pivot nut then lock it in place with the little grub screw in the middle.