Snap Crackle Pop, Power Drop?

[Toadmund]

Sorta backwards but had to rhyme.

Went for a good 25K or so burn with high WOTtage, we'll at least as fast as I could go, normally I can get to about 60kmh, but I am struggling to reach 55kmh lately.
Then about 10k's in I have a power drop, then bleeeh.....dead, then I restart and it hesitates, then slowly comes back to life.
So then on my way back home I have shuddering stalls and I slow drastically when the engine cuts, then further on heading home, I get the snap, crackle, pop sounds like it's going to backfire, so I shut' er down, looked it over, took it easy, then increased speed until I got home.
Spark plug is tight, gas cap I loosened to see if venting is a problem, no; cap on plug was a bit loose (not that), wire connections good (Should check for corrosion)

I am thinking my CDI unit is dying, if it is I made my own from the 'Roll your own' thread, and am waiting for an Ignition coil, so we'll see.

Whadda you guys think?

 

[Toadmund]

Well, I guess I am going to take a look at the magneto later today, good place to start I guess, check and maybe resolder some stuff, see what the ohm'age is.
See what's causing misfiring, I wonder if fuel build-up can cause the sound like it's going to backfire?
Can't wait until my ignition coil gets here!

Oh, and bump.

 

[fatdaddy]

I hope it is something simple like electrical and not a piston starting to seize. Also, make sure the head gasket isn't blown. That will also cause power loss and backfiring.
good luck bro.
fatdaddy.

 

[Toadmund]

No leakage from the head gasket, I took off the magneto cover, everything is tight and looks normal and the piston moves freely when I turn the magnet by hand.
I think I'll go read up on CDI issues.

 

[Kioshk]

I see that you checked the head-gasket, but it sounds like classic gasket-failure/loose-head-bolts behavior. Try lapping the mating-surfaces of the head and cylinder. May also be a loose spark-plug/worn threads? Anybody?

CDI: I rolled my own and didn't notice an appreciable difference. Although it's a fun project, I spent way more in parts and my time than it was worth. I say pick up a couple of cheap ones on eBay. I have never had a CDI just start to go bad, they work until they stop working in my experience.

 

[Toadmund]

Well, they are already lapped, and I have no signs of gasket leakage, and I just torqued them two weeks ago.

It may even be something like my stock connectors, those double barrel types, with the bullet type male parts.
I'll have to check those.

And when it misfires, perhaps I got unburned fuel exploding in my muffler?

 

[a_dam]

I have a Toro snowblower (ccr 2000?) with an ignition module going bad. It's about 15 years old. It runs great for about 20 mins (about enough to do 2/3 of the driveway), then it starts bogging and I know I've got about 2 minutes until it dies. Then it won't start for about 10-15 mins. The colder it is outside, the quicker it cools off and restarts. There are areas I have to hand-shovel, so I just do those spots while it cools down.

For some reason that module is like $150, if you can even find it. A lot of people online have this same kind of problem.

I know this has nothing to do with your problem, but at least some ignitions can work fine until they get hot; then increasingly run like crap; then work fine again when cool. I would love to have that Toro motor on a bike if it didn't act up like that.

 

[Toadmund]

Hmmm. yeah, seems mine started to act up once at full operating temp.
But can't say for sure.
Another problem I notice is that when I am having these issues, instead of idling it dies unless the throttle is milked. (weak spark?)

My magneto appears OK.

Today I disconnected my stock connectors (CDI/engine) sanded the connecting points, re-crimped the female ends, put them together, shrink tubed them, wrapped in sticky rubber tape (my new favourite stuff!)

My spark plug is the perfect milk chocolate brown, like cinnamon, but I re-gapped it to 0.030" which I converted to 0.762mm and then using my cheapass vernier caliper found out a Canadian dime is about that almost exact to 0.762mm. The dime fits tight.
I am hoping the larger gap may reduce pre-detonation according to a theory that I have read here.

If those things don't fix my issue, I will have to assume the problem lies in my CDI unit, or in the stock plug wire (but not the boot itself which is a decent aftermarket chainsaw boot)

 

[KCvale]

Did you cut your white off at the magneto? You should, put your kill button across the CDI.
A flakey kill button can cause wired thing, test with out of circuit.

And try an NGK BPR7HIX Iridium plug, you will actually feel the difference.

 

[Toadmund]

Using a Bhp6s NGK right now, But I will try iridium when the time comes.

My white wire is not connecting any ground.

The thing about the kill switch though is that it is normally open anyway, the engine doesn't need that wire to run, so that wouldn't be the issue IMO.

Wait a minute, you are right, if it's abnormally closing, that would be an issue indeed, another area to check.
As a matter of fact, I have some nice normally closed/normally open switches that I could use to cut the electrical flow instead of the short circuiting stock kill switch.
I will look into that if my problem persists.

 

[crassius]

kill switch wire can throw a spark if it is too close to metal (they've bitten my finger a few times when insulation was nicked)

 

[Toadmund]

I haven't tested it yet, but I suspect the problem is....Drum roll please..............A dirty air filter.

I couldn't go top speed, like I lost 20km/h, it wouldn't stay idling, bogged out, sounded like BYOOOOooooooooooooooooooo

I figured that it sounded really restricted, I figured that the foam piece I put in my old NT carb may have got sucked into the carb and clogged the muffler, nope, air flow good.
I looked into the exhaust port and I saw a puddle of gas there, well that explains the backfiring type pops, snaps and crackles a few days ago (fuel exploding in muffler) and that situation arises because of restricted air sucking in excess gas (or simply because it didn't burn off, one of those scenarios)
Then I took off the RT carbs filter, looked at it, seemed a bit dirty, stuck it in a peanut butter jar with varsol in it, the varsol got pretty dirty and now my air filter looks new again!

So I guess I am going to try again tomorrow to see if that was the culprit.

 

[Toadmund]

Well not a dirty air filter, but quite related, I believe my problem was some sort of dirt that got into my carburetor, probably through the choke lever slit on my RT carb.
I will show you people why I was having the problem I was reporting, I have found the cause, here are some pics:

 

[Toadmund]

The cause was not my small end bearing, it must have been something that entered my engine from outside.
More pics:

 

[crassius]

from the pics, it looks like you were also leaking at both the head gasket and base gasket - even one mounting stud has a burn on it

 

[Toadmund]

Well I really had no problems with the head being tight, the scorch marks may be from being so close to the edge of the gasket, or just how the head compressed on the gasket.
The bottom gasket may be wet from gas mix that poured out when I tipped it, the top end is dry.
My plug was the perfect colour of cinnamon powder.

I poked a telescoping magnet thing to the bottom of the case and pulled out a bunch of metal shavings.
I have side to side play of 5mm's of the edge of the piston, from left to right, could that be a sign of a toasted large end piston rod bearing?
Could grit coming into the motor (of which there was some) destroy a bottom end bearing, or start the cascading effect of destruction?

Good night, I'm going to bed, I shall further disassemble my motor tomorrow, and see the extent of the damage.

 

[Toadmund]

I think people should start storing their valuables inside these motors, because I think they are harder to crack than a safe!

After trying to pry off the magnet, not getting anywhere I finally found some large carriage bolts and used the rounded ends under the magnet, levered them and there I go, magnet off.

Here is where it gets super frustrating, try to take off my small gear, put the extractor in (all the way), put a sock into the gears to stop them from moving, started turning the wrench, it's coming out, nope, the threads on the extractor are coming OFF! $#@$%.
So I think I will unscrew the screw bolts, start to unscrew, nope, the PHILIPS head screws are too friggin soft and are stripping, managed to loosen one with the vice grips, cut a slot into the next one, and I got a bunch of other tight ones that are countersunk, I think these screw bolts must be 70% lead for crying out loud!

Where does a person buy a small gear extractor that wont strip?

This is nuts, and frustrating beyond belief, I just want to see what bearing destroyed itself, so I will know if I can fix it economically.

 

[crassius]

you'll need an impact driver for the screws, and I always dress the threads of my puller with a thread file before every use (pulled over 1000 clutches, drive sprockets and drive gears with it over the last 3 years)

 

[Toadmund]

What surface do you use your impact driver over, I suppose carpet and a 2 x 4 is not the best surface, too much bounce?
The motor is on a carpet with a 2x4 propping the motor up to clear the various protrusions sticking out, like the driveshaft for instance.

 

[crassius]

try fitting an extension onto the impact driver