Predator 212 backfire - won't start

[SparkyMark]

Hi All,

My Go Kart has a Predator 212 which looks fairly new. Only had the thing about a week and the engine is giving me fits. Engine will not run, and it's to the point where it will not start. It does however, backfire sometimes when pulling the cord.

I thought this would probably be a sheared flywheel key resulting in messed up ignition timing.... but I pulled the flywheel this morning and the key is fine. So I'm feeling a little lost now.

I am looking for suggestions for what to look at next. I have fiddled with the Idle screw so that is probably out of whack. Can a mis-adjusted idle screw cause a backfire?

Thanks for any help

-- Mark

 

[mckutzy]

No an idle screw is just that....
However, is the coil on tight and at the proper airgap.... A thickness of a buisness card does good...

Or take it back and get a new one if its brand new......

 

[SparkyMark]

No an idle screw is just that....
However, is the coil on tight and at the proper airgap.... A thickness of a buisness card does good...

Or take it back and get a new one if its brand new......

Thanks, I'll check that the coil is secure and I'll check the gap.

Sadly the engine is only new to me... it's probably a few years old. So can't return it.

-- Mark

 

[Hellion]

Is it backfiring or afterfiring? Most people use those words interchangeably but they'd be wrong to do so. Backfiring is back through the carb. Afterfiring is through the exhaust (and way more fun).

Tons of the same issues affecting our small engine community...

 

[SparkyMark]

Is it backfiring or afterfiring? Most people use those words interchangeably but they'd be wrong to do so. Backfiring is back through the carb. Afterfiring is through the exhaust (and way more fun).

Tons of the same issues affecting our small engine community...

Hi Hellion. I must admit I did not notice if the "backfire" was through the exhaust or carb. I (mistakenly) call any loud bang a backfire. I don't think I ever knew there was a difference - but it makes sense that it would be different based on where the valves are positioned when it occurs. So I will mend my evil ways now that I know there is a difference. I'll need to see if I can determine which it is for my case. At the time I simply noticed the loud Bang - didn't really notice where it came out of.

Thanks for the link to the videos - I will study those and see if I can get further along.

-- Mark

 

[SparkyMark]

More Info... I checked the coil and the gap. All seemed ok. I did loosen the bolts holding the coil and retightened them with a card in for spacing. When loosened the coil did scoot in a little closer to the flywheel.

I put everything back together and gave things another try this morning. What I really have is apparently afterfiring through the muffler. Still don't know why. Still investigating. When I try to start it will make a bang and I see smoke and bright orange particles on the muffler.

Earlier I had the valve cover off just to see if I could see anything weird with the valves - but I'm not really sure what I am looking for. The rocker arms go up and down. As I rotated the crankshaft slowly I could watch the rocker arms and valves moving. I was trying to visualize the Intake, Compression, Power and Exhaust stroke as I rotated things and observed the valves. At one point it seemed like the Exhaust valve was partly opening when I didn't really expect it to. I'll need to look again.

-- Mark

 

[cmmsr22]

Sorry, but how do I start a thread?

 

[MTNSleder]

Sorry, but how do I start a thread?

Find the Start new thread button...

 

[cmmsr22]

thanks

 

[Kleyny]

. At one point it seemed like the Exhaust valve was partly opening when I didn't really expect it to. I'll need to look again.

-- Mark

The cams on these have a de-compression leaver that works whilst you pull start it. That slight exhaust movement is the leaver doing its job.

I would be pulling the carb off and giving it a good clean, I'd also be checking gaskets whilst I was there.

Neil

 

[SparkyMark]

The cams on these have a de-compression leaver that works whilst you pull start it. That slight exhaust movement is the leaver doing its job.

I would be pulling the carb off and giving it a good clean, I'd also be checking gaskets whilst I was there.

Neil

Ahh, decompression... ok. When I double (maybe triple) checked this earlier today I had found that just as the intake valve was closing and the crank was passing the bottom of the stroke and beginning the compression stroke the exhaust valve would open slightly for a short bit (10 degrees maybe) and then close back up. So I guess this is not something I should worry about.

Ok, The engine is back on the bench, so I'll pull off the carb and clean it this week as suggested.

Is this the sort of decompression mechanism on a Predator 212?
https://www.youtube.com/watch?v=vU0QPhhpJ-E

Thanks,

-- Mark

 

[bob58o]

Heres a stock Predator cam.

At low rpm, it bumps the exhaust lifter.
At high RPMs, the arm swings open (which pulls the important part out of the way) and it misses the lifter.

 

[bob58o]

Hope the pictures do better explaining than I can. The exhaust lobe (closest to the gear) has a cutaway and a pivoting thing. Lol

 

[Kleyny]

^^^what he said lol

 

[SparkyMark]

Those are some mighty fine photos of the decompression mechanism bob58o... very helpful to see whats going on inside without tearing things apart. THANKS !!

-- Mark

 

[SparkyMark]

Yesterday I removed the carb and cleaned it. Everything "looked" really clean to begin with - but I gave all the passages a squirt of carb cleaner - and ran a soft copper wire through the jets and poked the tiny holes along the surface of the carb throat with a soft copper wire. I saw NO evidence of "gunk" while doing this.

Anyway, after putting the engine all back together it runs! WooHoo !! It didn't seem to run too well at first, but after 10 or 20 minutes it was running pretty smooth (maybe had to get all the carb cleaner worked through the system?). It does seem to stumble sometimes when attempting to accelerate. I need to read more and figure out if opening up the jets a little is something that might help with the stumbling. I'll probably put some run time on things as-is before tinkering with anything else.

-- Mark

 

[Hellion]

Carb cleaner isn't as mighty as people make it out to be; it's not the cure all, so poking all the holes, orifices and ports in the carb with fine wire is precisely what most mechanics recommend.

There's also something known as torch tip cleaners that you can buy, that are good for cleaning carb passages and jets.

Well, lo and behold, they make them specifically for carburetors now: https://www.amazon.com/Carb-Cleaner-Wire-Set/dp/B001DDMB2I... K&L Carb Cleaner Wire Set.

 

[bob58o]

Well, lo and behold, they make them specifically for carburetors now: https://www.amazon.com/Carb-Cleaner-Wire-Set/dp/B001DDMB2I... K&L Carb Cleaner Wire Set.

But the price doubles with the re-purposing/re-naming of the same product.
http://www.ebay.com/itm/311413289559

 

[Hellion]

Right you are. But you're robbing funds from Schlomo, the sly fella in the marketing dept who renamed and repurposed them!

 

[OzFab]

... & you get less for your money