J’s Dirty 30 north truck

[WickedFog]

If you pull the plug after trying, is it wet? Is the plug firing?

You don't have a vacuum leak anywhere do you?

 

[J’sCrawler]

If you pull the plug after trying, is it wet? Is the plug firing?

You don't have a vacuum leak anywhere do you?

The plug always looks wet, if I lean or go rich. Only dry if I literally start at only half turn out.
I have pressure tested the carb and didn’t see leaks. I swapped the Teflon gasket/insulators for some paper gaskets.
Seems like it really only starts when cold. Then once warm or I’ve been mucking with it for hours it will eventually die and never start again regardless of lean or rich..?
Yes the plug is firing, I have been doing a spark check on every plug I swap to. It has spark.

 

[WickedFog]

Have you pulled the needles to make sure they aren't damaged? How does the timing and spark control on that motor work? I am used to small engines, but not that one. Like, how does it generate spark? Like with a magneto? Have you checked the gap on it? These are all just basic things my dad would check first when he was working on engines. Sorry I can't be of more help.

 

[Tunedfrog]

Are you holding your TX in while trying to start it? Sometimes it just takes a little throttle. Sounds like it fired but not getting enough fuel.
I wouldn't mess with the needles until you get it started because it takes a few seconds for the engine
to start responding to your needle adjustments.

 

[J’sCrawler]

Are you holding your TX in while trying to start it? Sometimes it just takes a little throttle. n't mess with the needles until you get it started

Have you pulled the needles to make sure they aren't damaged? How does the timing and spark control on that motor work? I am used to small engines, but not that one. Like, how does it generate spark? Like with a magneto? Have you checked the gap on it? These are all just basic things my dad would check first when he was working on engines. Sorry I can't be of more help.

I have not pulled needles. It’s a new carb and I’ve been gentle.
It’s a pickup coil with a business cards width gap against the flywheel.

Are you holding your TX in while trying to start it? Sometimes it just takes a little throttle. Sounds like it fired but not getting enough fuel.
I wouldn't mess with the needles until you get it started because it takes a few seconds for the engine
to start responding to your needle adjustments.

I do hold the throttle lever on the carb when I don’t have the camera in my hand. It helps sometimes.
i let this thing sit for awhile and started it just now. No idea where my set screws were at. It ran till it warmed up. Now it won’t start.
I had to mess with needles just to start it. I hear what you are saying now after taking a break from it

 

[Weezel]

Woes for the past 3 days.

Why did you set the idle screw so it just barely touches butterfly throttle arm? It should be adjusted when the engine is at operating temps. What happens if you hold throttle open when trying to start, does it try to run?
Old timer trick: Holding throttle wide open will help unflood a 2 stroke engine.

Another possibility if it starts easy when cold but won't restart when hot can also be a symptom of a bad coil. Nice dark blue spark or white?

Like @Tunedfrog mentioned, the needles should only be adjusted when engine is at operating temps.

 

[J’sCrawler]

Why did you set the idle screw so it just barely touches butterfly throttle arm? It should be adjusted when the engine is at operating temps. What happens if you hold throttle open when trying to start, does it try to run?
Old timer trick: Holding throttle wide open will help unflood a 2 stroke engine.

Another possibility if it starts easy when cold but won't restart when hot can also be a symptom of a bad coil. Nice dark blue spark or white?

Like @Tunedfrog mentioned, the needles should only be adjusted when engine is at operating temps.

I started adjusting needles when it quit running. I have tried the wide open throttle to clear it, and sometimes it starts up with a little throttle but doesn’t stay running.
I have set the idle so there is no simulated vacuum leak.
It appears to be a blue spark.

 

[Weezel]

If you're sure you are getting fuel and spark the only thing left is compression. Either cylinder compression is low or crankcase has an airleak. If you don't have a compression tester there's another trick for testing. Put a small amount (~1/2 teaspoon) of oil down sparkplug hole while piston is up. What it does is seals scratches, worn rings temporarily for a few strokes. Try starting and if it makes a difference you have low compression.

An airleak somewhere will cause hard starting. Either crank seals, intake, somewhere in the case halves, or cylinder base gasket. An airleak is the hardest thing to find without tools.

 

[J’sCrawler]

If you're sure you are getting fuel and spark the only thing left is compression. Either cylinder compression is low or crankcase has an airleak. If you don't have a compression tester there's another trick for testing. Put a small amount (~1/2 teaspoon) of oil down sparkplug hole while piston is up. What it does is seals scratches, worn rings temporarily for a few strokes. Try starting and if it makes a difference you have low compression.

An airleak somewhere will cause hard starting. Either crank seals, intake, somewhere in the case halves, or cylinder base gasket. An airleak is the hardest thing to find without tools.

Yea I suppose I better take it apart and see. I need a new pull start anyway, the spring broke inside. I was a little rough on the few pulls before it broke. I was frustrated

What should the compression be?

 

[Weezel]

I'm not sure what they are supposed to be. A quick search revealed Zenoah goes by compression ratio.

When I was working on my small engines, chainsaws to snowmobiles, I would want over 120psi before thinking of a rebuild.

I wouldn't go out and buy a compression tester as they are not that great for these tiny engines. The oil trick works better.


You can pressure test the engine yourself to test for leaks if you really want to get into it. You would seal up the exhaust and intake then hook up air hose to sparkplug hole (~5psi) and check block and seals with soapy water.

 

[J’sCrawler]

I'm not sure what they are supposed to be. A quick search revealed Zenoah goes by compression ratio.

When I was working on my small engines, chainsaws to snowmobiles, I would want over 120psi before thinking of a rebuild.

I wouldn't go out and buy a compression tester as they are not that great for these tiny engines. The oil trick works better.


You can pressure test the engine yourself to test for leaks if you really want to get into it. You would seal up the exhaust and intake then hook up air hose to sparkplug hole (~5psi) and check block and seals with soapy water.

I actually have that tester.

 

[J’sCrawler]

Plenty of compression, a little bit of oil makes it feel hydro locked.
This engine starts just fine cold, yesterday it hit about 123 degrees when it started to run like crap. I’m stumped, don’t know if it’s lean or rich! It’s really hard to get this on video

 

[Weezel]

I think there's something more than a simple tuning issue going on. When it's running you can check for lean vs rich with the choke. When it's starting to act up you can add 1/4,1/2,etc choke to make it richer without touching jets. If it runs better it is lean. If it's makes it worse then it's rich.
Another possibility could be your fuel system isn't vented good. It's creating a vacuum. Opening the gas cap when it starts running like crap would diagnose this. Does your fuel cap make a hissing sound when opening it?

I'm still wondering if your coil could be the issue or maybe something like the failsafe. Never messed with a failsafe so I don't know how they actually work or could fail. You could always disconnect it and test truck on a stand (or tires off it)

 

[J’sCrawler]

I think there's something more than a simple tuning issue going on. When it's running you can check for lean vs rich with the choke. When it's starting to act up you can add 1/4,1/2,etc choke to make it richer without touching jets. If it runs better it is lean. If it's makes it worse then it's rich.
Another possibility could be your fuel system isn't vented good. It's creating a vacuum. Opening the gas cap when it starts running like crap would diagnose this. Does your fuel cap make a hissing sound when opening it?

I'm still wondering if your coil could be the issue or maybe something like the failsafe. Never messed with a failsafe so I don't know how they actually work or could fail. You could always disconnect it and test truck on a stand (or tires off it)

I have a DDM vented cap, but I never hear it hiss when I unscrew it, I have tried it.
I have not tried the choke idea while it’s running.
Disconnecting the fail safe is a bit of work…. I guess if I have to.
The truck is down again because the pullstart is acting up. The spiral spring inside keeps coming out of its little holding groove, causing it to not retract. I’m going to have to find something better, or get a replacement and use a better rope. The stupid rope has snapped twice on me. I’m not even pulling hard.

 

[Weezel]

Just had a thought. Could the receiver battery be weak? Between when it dies and when it cools off and restarts did you happen to put it on charge?

They are a pain to me too. Its always just before I finish coiling, it always seems to slip out of the groove. Then I have to start all over.

 

[J’sCrawler]

New pullstart came.

I doubt the battery is too low, I do have telemetry on this so I can see where the voltage is at. It doesn’t matter if I toss in a fresh battery. Once it hits that point it just won’t run.
It got up to 123 degrees last weekend when it did its thing. Then I broke my second pull start string, repaired it with new stuff but the spring kept dislodging so that ended.
I’m waiting for some RTV to cure so I can start it up. That will be tomorrow maybe.