general symptoms of a 2 stroke timing being out of whack? - Motorcycle Forum
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Old 10-23-2009, 10:02 PM   #1
mitchberry
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Default general symptoms of a 2 stroke timing being out of whack?

What are the general symptoms of a 2 cylinder 2 stroke motor's timing being way off?

i'm trying to figure out if my issues stem from my timing, or the piston rings.

It's really hard to explain this to people who haven't been keeping up with the issues i've had over the last few months, so i'll just address things as they come along.

the last few times i started the bike, it poured smoke from the right cyl only.

i mean POURED smoke; which could have been from the countless times i flooded the motor while working on it and trying to fire it up.

But in my opinion, it may have been that the piston rings were bad from sitting for 36 years.

last night i rode it around a little bit and tried to get up to "speed" (45mph or so) and it seemed like that was pretty much as fast as the bike wanted to go, but may have had a little more in it. it's supposed to top around 70-80 depending on various things.

the carbs have issues, apparently the electrical has issues, etc, but it's hard to diagnose things when every time i fix something, i get another issue popping up.

anyway, it backfired a few times when i would down shift to come to a stop, but nothing bad.

Today, i rode it around a little more and it ran fine. in fact it even idled like it was supposed to once it warmed up, but there's still somewhat of an off sound to the motor like something isn't quite in sync. i didn't try to go fast, just fast enough to test it out before making more tweaks, but in all, it ran fine aside from smoke that for whatever reason comes from the front of the motor, which may be oil that's burning off, or it may be a gasket seal in the heads or a leaky exhaust gasket.. i really don't know.. ALL of those things will cause errors.

I went to take it out a few minutes ago, and i couldn't get it to fire up at all.. it would run fine for a second, backfire and die. this repeated several times until i gave up and came here to get more opinions on the matter...

for the record, earlier today when i was riding it, it wasn't pouring smoke out of that cylinder. in fact it wasn't smoking much at all compared to past times.

what could it be now?

Once Paul Miller actually sends my carb kits i think i'm going to suck it up and have one of the local shops look at this bike. kind of tired of messing with it and i'd rather be riding it than screwing with it.

-----------------------

heh... ok... i figured out something weird and i don't know how to fix it per say..

2 cylinders. they are both getting spark at the same time..

cyl 1. big spark little spark big spark little spark
cyl 2. little spark big spark little spark big spark


condensers???????

This would definitely cause it to misfire and backfire...

Last edited by mitchberry; 10-23-2009 at 10:19 PM..
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Old 10-24-2009, 10:15 AM   #2
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Do you have dual fire points and condensers and coils?
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Old 10-24-2009, 10:23 AM   #3
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Quote:
Originally Posted by mitchberry View Post
heh... ok... i figured out something weird and i don't know how to fix it per say..

2 cylinders. they are both getting spark at the same time..

cyl 1. big spark little spark big spark little spark
cyl 2. little spark big spark little spark big spark


condensers???????

This would definitely cause it to misfire and backfire...
This indicates that one coil is able to discharge through the other. Do you have a dual condenser, one with a wire to each point set, and a common case? If so, either the ground to the case is questionable, or the condenser needs replacing.
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Old 10-24-2009, 11:09 AM   #4
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i have 2 points, 2 condensers and 2 coils. they are all pretty much separate..

I posted a wiring diagram in this thread a while back which shows some of this.

http://www.motorcycleforum.com/showthread.php?t=97369

the coils points and condenser make up 1 "unit" on a common wire that is not shared with the other "unit".

I don't remember now if i checked both cylinders for this problem or not.

could a condenser just.... suddenly go bad? it ran fine earlier in the day, then last night it wouldn't start at all...

or would start for a second then backfire and die,

or when i revved the hell out of it it would go into convulsions and seizures and die...

i know this is an electrical problem, but i think there's a problem with the piston rings too, so i may fix that today. bike has 10k miles on it and was sitting for 36 years. not a bad idea to change them.
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Old 10-24-2009, 12:30 PM   #5
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Yeah, that diagram doesn't show the points and condensers, which are apparently inside the alternator, so I'll accept that they're separate. The other path for one coil to discharge through the other is through the orange wire from the battery, via the switch. If any of the connections between the coils and the battery is poor, the surge of current will cause the voltage on that wire to pop higher. All of the other devices, like lamps, on the coil side of the bad connection will see that surge, including the other coil. That surge through the other coil is apparently large enough to cause a small spark. You need to go through the orange circuit, looking for bad connections to repair, starting where the line splits between the two coils. The diagram implies that there are only two splices between the coil split and the switch; if true, that limits the points to test. The switch, of course, could have burnt contacts, so IF it can be opened, it's worth checking. Here's where an oscilloscope can help, if you have one.
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Old 10-24-2009, 12:44 PM   #6
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the switch was purchased NOS about a month ago, so i really hope it isn't burned out. ****ed thing cost me $130 plus shipping from Thailand. lol. can't be opened though. I don't have an oscilloscope, but do have a voltage tester, but i'm not sure that it doesn't have an oscilloscope feature on it.

and yeah, the orange wire is the only common wire. the harness itself is brand new also, i replaced it in September, and have gone over it a few times, but it's worth going over again given the current situation.

Maybe something came loose while riding it. it's probable. i may go ahead and replace the condensers too while i'm at it since i have two brand new ones sitting here.

and yeah, the points and condensers are on the stator. one set is yellow/black other is white/blue .

i'll check into this stuff and will update in a few hours.
thanks wintr
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Old 10-24-2009, 02:45 PM   #7
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i went through the entire harness and didn't find any bad connections. Given that their all new, there's no corrosion, and nothing grounding out that shouldn't be.

I replaced both condensers and still have the same problem, but the power to the coils is considerably higher now which is a plus.

the orange wire also goes to the right handlebar to the brake light switch in the lever, but, it works fine, and i don't think it would be that. i patched any worn through wires when i replaced the handlebars by cutting them, and re soldering them then shrink tubing them.


i'm at a loss.

Last edited by mitchberry; 10-24-2009 at 02:48 PM..
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Old 10-24-2009, 02:59 PM   #8
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It could be timing, it could be an oil seal, the pistons rings, it could be carb or intake related, or it could be your oil pump if you have one. The only way to tell is to look for other signs or to go through the problems one by one, I'm in the same boat as you right now and it sucks.

I would set the timing which is easy with the help of dial caliper or better yet an indicator with a spark plug adapter, you can get the first at habor freight for about $15.

I would clean the carbs and make sure they are synced up, and that the oil pump is work the same for both cylinders, and if this still doesn't fix it, I would inspect the rings and crank seals.

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Old 10-24-2009, 04:34 PM   #9
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ok, i have been able to push start it and get it to rev up, but it won't run at anything less than 1600 -1700 rpm.

it cuts out QUICK if it's lower than that. it doesn't seem like the extra spark is really hurting it at this point. and the condensers added a lot more kick to the plugs too.

but i still can't get it to run and idle, which, it did yesterday.
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Old 10-24-2009, 04:36 PM   #10
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You're still getting alternating strong and weak sparks? When they occur, are they exactly synced on both plugs, or is there a slight lag between sides?

Maybe your carb sucked some stray dirt into the idle circuits.
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