Hard to pull/crank predator 420

[CartMan007]

Hey everyone. I need some help.

I have been running my predator 420 fine for a bit. When I do the electric start it will start and run, but it takes a few attempts as it will not fully crank sometimes almost like there’s a dead battery. But then I turn the key two more times and it will start (with choke). After this it runs fine, idles fine. I have done a valve lash adjustment in the past to address backfiring and it was needed. While I had some time, I figured I would check to see if it needed another adjustment so I took the cover off, but even with the valve lashes fully open, the pull start is extremely tough.

So then I took out the spark plug. That was the only way the pull start is actually smooth. I understand there needs to be compression, but should the spark plug be the reason the crank is so difficult? Is there another issue I’m missing?

I have:
stock 420 predator
NGK BPR6ES spark plug (stock replacement to have a resistor to prevent stereo interference)
aftermarket flywheel with magnets for the 26amp charging unit

 

[Hellion]

Could be valve lash and you need to verify that it is correct . The only time I have ever had a starting issue of the kind you describe was with a large bore OHV engine that sees a lot of use (riding lawnmower). Had trouble starting the old girl and it turns out the valve lash was way wide or loose. Made me think the starter/battery was weak when it was the valves.

I used to "help it" through a few revolutions by turning the flywheel with my hands.

 

[CartMan007]

Thanks and that makes sense. But if I loosen both valve lashes completely, shouldn't the pull be easier?

 

[Denny]

No, your not relieving compression with the valves opening like they should.

 

[panchothedog]

When the valve lash is too loose, that is what makes it harder. Set both valves at
.003" with the engine cold. Make sure to go past the secondary bump on the exhaust valve right after it closes. That is the compression release on the cam.
If they are too loose, the compression release doesn't engage, and makes it harder to start.

 

[CartMan007]

When the valve lash is too loose, that is what makes it harder. Set both valves at
.003" with the engine cold. Make sure to go past the secondary bump on the exhaust valve right after it closes. That is the compression release on the cam.
If they are too loose, the compression release doesn't engage, and makes it harder to start.

Ok I’ve been adjusting and it seems to be getting better but I’m still a little confused about the best point to set the lashes. My untrained eyes are having are hard time seeing the secondary bump on the exhaust side. After this secondary bump, should the intake valve still be fully compressed? And are you saying I set both lashes at that point?

 

[Hellion]

Do you mean spring compressed?

Uh oh. Set the valve clearance on both valves when they are closed (valve springs relaxed), with the piston at top dead center--is a good rule of thumb.

Use a wooden pencil, eraser end in first, stuck into the spark plug hole and then you can pull the engine around manually (in the normal direction of rotation) and watch the pencil move in and out to determine top dead center. Otherwise there are copious videos showing the process on Youtoob. Avail yourself of these videos, watch a few of them.

 

[CartMan007]

Do you mean spring compressed?

Uh oh. Set the valve clearance on both valves when they are closed (valve springs relaxed), with the piston at top dead center--is a good rule of thumb.

Use a wooden pencil, eraser end in first, stuck into the spark plug hole and then you can pull the engine around manually (in the normal direction of rotation) and watch the pencil move in and out to determine top dead center. Otherwise there are copious videos showing the process on Youtoob. Avail yourself of these videos, watch a few of them.

Ok another dumb question. you all have been saying the normal rotation of the engine. Forgive my stupidity, but if I’m using the pull cord to turn, is that not the normal rotation? Maybe that’s also my issue.have I been going backwards the whole time?

 

[Hellion]

Ok another dumb question. you all have been saying the normal rotation of the engine. Forgive my stupidity, but if I’m using the pull cord to turn, is that not the normal rotation? Maybe that’s also my issue.

Yes, normal rotation via the pull cord. I wasn't sure if you had the recoil starter installed or had the flywheel exposed while doing this.

There are no dumb questions. The only dumb one is the one you don't ask and naturally assume you already know the answer (or something like that).

 

[CartMan007]

Yes, normal rotation via the pull cord. I wasn't sure if you had the recoil starter installed or had the flywheel exposed while doing this.

There are no dumb questions. The only dumb one is the one you don't ask and naturally assume you already know the answer (or something like that).

Ah I see. Going to keep going and will report back. Thanks!

 

[CartMan007]

I think I’m close. The starter motor is able to turn with key crank mostly easily now. I was getting some backfiring though. I’m wondering if I’m not setting them at the proper point. When I was at what I thought was TDC, the lashes were not loose at all. Is the feeler gauge supposed to just have a little drag or be pretty tight?

I did forget to mention this is the Hemi version if that matters.

 

[Hellion]

With your feeler gauge between the rocker arm and the valve end, it should fit snugly (not tightly) with a little bit of drag. Are you using the right feeler gauges? Most feeler gauges have both metric and decimal inch printed on the gauges. Make sure you are using the right ones for your engine.

Did you watch any videos? Try one of the small engine guys, maybe Taryl Fixes All or Donyboy. Or heck, that drug-addled Red Beard fella.

I will tell you, if you don't set valve clearances every other day, it can be a hassle what with the inner lock nut, the outer nut, and trying to run a feeler gauge through the rocker and the end of the valve. It's like you need three hands.


Does anyone know if CartMan007's engine has a "bare end" on the end of the valve stem or is there a valve cap?

 

[panchothedog]

The exhaust valve has a lash cap. The intake is just the valve stem. No difference in setting either side. Pull the spark plug, loosen the upper small lock nuts, back off the larger 14mm adjusters. Now pull the engine over ( with the starter rope ).
Slowly tighten the 14mm adjusters by hand until you see some valve movement.
Pay attention. Continue to pull the engine over. Familiarize yourself with how the valves open ( spring compressed ) and when they are closed ( spring relaxed, taller ). When they are relaxed and the rocker arm feels sloppy ( no tension ) this is the position when the lash ( clearance ) is set. Don't be in a hurry. Even after you set the lash with the 14mm, when you tighten the 10mm lock nut, it can change. It will take a few tries before you get it right.

 

[Hellion]

I would ensure the lash cap is still there. I remember my 17hp Briggs had one for each valve stem.

Even after you set the lash with the 14mm, when you tighten the 10mm lock nut, it can change. It will take a few tries before you get it right.

Kaboom! Seconded. The clearance(s) will inadvertently change as you tighten/loosen the nuts CartMan, and you have to hold the outer nut (with a box end wrench, probably the best way) precisely still while you’re holding the feeler gauge and while you tighten down the lock nut. If you’re slightly frustrated while doing the procedure, then you must be doing it right lol.

 

[CartMan007]

With your feeler gauge between the rocker arm and the valve end, it should fit snugly (not tightly) with a little bit of drag. Are you using the right feeler gauges? Most feeler gauges have both metric and decimal inch printed on the gauges. Make sure you are using the right ones for your engine.

Did you watch any videos? Try one of the small engine guys, maybe Taryl Fixes All or Donyboy. Or heck, that drug-addled Red Beard fella.

I will tell you, if you don't set valve clearances every other day, it can be a hassle what with the inner lock nut, the outer nut, and trying to run a feeler gauge through the rocker and the end of the valve. It's like you need three hands.


Does anyone know if CartMan007's engine has a "bare end" on the end of the valve stem or is there a valve cap?

You're absolutely right. I did it last summer and it's "simple" but the smallest movements and often times locking the nut to realize the clearance changed makes it tedious. I originally purchases mm in the summer but I have inches now which is what I used.

I watched a bunch of videos and even found some old threads on this site. The issues is so many do it differently. Some say TDC and some say absolutely do not use TDC haha. Some say the exhaust clearance should be .006 and the intake at .004. Lots of variation out there.

I ran it again this morning and it seemed strong. I will put the muffler on to see if that fixed the backfiring and report back before rechecking clearances.

 

[CartMan007]

The exhaust valve has a lash cap. The intake is just the valve stem. No difference in setting either side. Pull the spark plug, loosen the upper small lock nuts, back off the larger 14mm adjusters. Now pull the engine over ( with the starter rope ).
Slowly tighten the 14mm adjusters by hand until you see some valve movement.
Pay attention. Continue to pull the engine over. Familiarize yourself with how the valves open ( spring compressed ) and when they are closed ( spring relaxed, taller ). When they are relaxed and the rocker arm feels sloppy ( no tension ) this is the position when the lash ( clearance ) is set. Don't be in a hurry. Even after you set the lash with the 14mm, when you tighten the 10mm lock nut, it can change. It will take a few tries before you get it right.

Thanks I actually used your explanation from the first response which helped a ton. My confusion is the comp release bump. I think I might not be seeing the right bump. I set it after that extra bump which is what I thought you were saying.

 

[CartMan007]

Update: backfiring complete stopped once I put the muffler on. 8/10 electric starts turn easily (before it was 2/10). No pinging/knocking while it’s running. I can settle for good enough?