2 smoke, except no smoke :(

"Jake - Has Bad Luck So You Don't Have To" (murdersofa) 09/14/2020 at 09:40 • Filed to: None

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Photo: me

Any two-stroke enthusiasts here? I’m having trouble. Got mine reassembled, verified spark after I put a new condenser in it though the spark seems a bit weak (new coil, plug, condenser, tested resistance on the points and it seems in spec). Kicked it over a crapton and not even a cough. Took the carbs out, gave the reeds a check. Reeds look good, carb looks slightly crusty. Soak it a bit, blow it out with carb cleaner, all the passages and jets look clear. Reassemble it, forgot to put the plug in the bottom of the bowl (oops). Clean up fuel spill, put plug in bottom of bowl (at least fuel is making it into the bowl). Kick bike over a crap ton more times while playing with the screws on the carb and choke, none if which I have any idea the actual function of.

Nothin. Not even a cough. Even tried starter fluid (which is a no-no, cuz no lubrication). Maybe my weak spark? The plug didn’t seem very wet when I pulled it. The bike feels like it has compression and the internet wisdom suggests that “if it feels like it has compression, it has enough to at least sort of run”

jminer > Jake - Has Bad Luck So You Don't Have To 09/14/2020 at 09:59

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How hard is it to kick?

Two strokes are usually more difficult to kick start than a comparable gas engine.  If it isn’t harder to kick than a gas bike it might be low on compression.  Could also be a crank seal.  Probably need to do both a compression test and a leakdown test.

Jake - Has Bad Luck So You Don't Have To > jminer 09/14/2020 at 10:04

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Hard enough to absolutely waste me after 20 kicks.

jminer > Jake - Has Bad Luck So You Don't Have To 09/14/2020 at 10:12

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That’s a good start.

You mentioned changing the condenser. Did you clean the points and set the timing on them?

Jake - Has Bad Luck So You Don't Have To > jminer 09/14/2020 at 10:16

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I cleaned them. Left the timing as-is since the bike supposedly ran when parked. Doesn’t even look like there’s enough adjustment in them to make the bike not at least sputter. Need to look back in the service manual and see what the timing settings are like.

Which, by the way, FUCK yamaha. I wanted to test my coils and such so I went in there for resistance specs but there are none, just “here’s how to set up our super special diag tool! if it says “replace part” then replace the part!”. No specs, just use their proprietary tool. Fuckers.

Darkbrador > jminer 09/14/2020 at 10:37

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Seconded. If you have air, gas, compression and spark , the timing must be off. 

Thir-STi > Jake - Has Bad Luck So You Don't Have To 09/14/2020 at 10:38

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I farmed out a lot of the engine/running issues on my DT360, but not knowing much I’d say to try a hotter plug maybe. Has the carb been rebuilt/refreshed? I had to change the floats and a few other rubber pieces. Its a lot of mix and match with carb kits. I wish I could tell you more but when I started on my own to learn it kept revving to the moon the second it would start so that stopped me pretty quickly (if that happens turn the choke on). the carb on mine is super finicky it took awhile to get it to run pretty decent.

Also the knob on the carb with the spring retention is the idle screw, setting idle is a whole ordeal but for now just make sure its not closed.

MoCamino > Jake - Has Bad Luck So You Don't Have To 09/14/2020 at 10:40

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I only know enough about two strokes to keep my weed eater running, so I could be off the mark here.  On my trimmer, the coil has a gap measurement between the coil itself and the flywheel.  If it’s not as close as it should be, the spark is weak and it runs like crap.  As deep as you are into it, you’ve probably already checked that.  Only other thing I can think of is maybe the new coil had a bad wire on it?

Pickup_man > Jake - Has Bad Luck So You Don't Have To 09/14/2020 at 10:48

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When you say the spark looks a bit weak, how so? What color is it, more of a yellow or blue? If it isn’t even firing on starting fluid I’d think either weak spark or timing.

One other less likely possibility is that your crank seals are bad and it’s pulling in a bunch of air making it too lean to fire. I’d still expect it to fire on starting fluid though, but when it does it will rev way up and not idle down. I’m going through this right now with my RX50. 

jminer > Jake - Has Bad Luck So You Don't Have To 09/14/2020 at 10:48

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There are probably resistance specs on a forum somewhere.

I do hate when manufacturers put in maintenance tasks like that involving special tools.

Pickup_man > Thir-STi 09/14/2020 at 10:51

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That revving problem tends to be caused by bad crank seals letting air into the case , I’m going through that right now on my little RX50.

Jake - Has Bad Luck So You Don't Have To > jminer 09/14/2020 at 10:56

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Annoyingly there were a million revisions of these bikes and the later CDI ones dominate the search results. 

Jake - Has Bad Luck So You Don't Have To > Pickup_man 09/14/2020 at 10:57

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It’s just not a particularly bright or large spark. I did gap the plug to spec. The spark is strong enough to bite me through the boot when I accidentally let my thumb touch the frame.

Akio Ohtori - RIP Oppo > Jake - Has Bad Luck So You Don't Have To 09/14/2020 at 11:07

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When I get something like this on my motorized bikes the problem is almost always an air leak.  Seems like it doesn’t take much to make these refuse to play.

Pickup_man > Jake - Has Bad Luck So You Don't Have To 09/14/2020 at 11:10

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Sounds like it’s decent spark then, enough to at least light it off once . I’d lean towards timing then, maybe something slipped or moved when you pulled the flywheel? That should be a pretty easy bike to time, can’t imagine things would get that far off but you’ve got all the ingredients it sounds like.

Maybe for shit’s n giggles throw a compression tester on it too, a t the very least it’ll be comforting to have a compression number that checks out.

Jake - Has Bad Luck So You Don't Have To > Pickup_man 09/14/2020 at 11:31

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Yeah. Frustratingly my compression tester broke so I’ll have to go back to harbor freight and buy another one. I don’t have a compressor for a leakdown test which is annoying.

cmill189 - sans Volvo > Jake - Has Bad Luck So You Don't Have To 09/14/2020 at 14:28

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You aren’t going to hurt anything by using a little starter fluid. Kicking it over a million times without much fuel would have done far more damage, if any at all.

If you've kicked it that much and the plug is barely wet, the carb is not drawing fuel. It's usually pretty easy to flood a two stroke.

Jake - Has Bad Luck So You Don't Have To > cmill189 - sans Volvo 09/14/2020 at 16:15

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That’s what I thought, but the bowl is full and the jets are clear so... what the fuck?

cmill189 - sans Volvo > Jake - Has Bad Luck So You Don't Have To 09/14/2020 at 18:17

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Do you have a base setting for the idle and mixture screws? Start with that, give it some starting fluid, and try again. You could close up the gap in the plug a little just as an experiment.