PW80 no start

[jamesbeaty]

I had this in the Yamaha 2-stroke section but realized it should be here:

Hey Everyone,

I am new to the forum and am just getting back into bikes, but this time I am trying to get the kids interested. My wife and I have TW200s and the kids have a pw50 and jr50. I recently found a pw80, in good shape, at a decent price $350 so I picked it up. It ran OK, 1) held idle (at first with choke and once it warms up holds idle without), 2) and responded OK to throttle for the first month that I owned it (Keep in minds I only ran it 2 or 3 times for 5 min or so) Then about 1 month ago she began to die after idling even after she was warm. The only way she would run was with the choke fully on and then would die while idling or after running it around for 2 min or so. I have never really have had her running for more than 5 - 7 min. She ran like this for 3 - 4 times over a 2 week period so I decided that she maybe running lean and the carb needed cleaning. So here is my thought process:

Possibly fuel issue

• I cleaned the carb twice and it did not make a difference. ( I mean a good cleaning in a heated ultrasonic bath!!!) - thanks to Kenny for cleaning it the second time.
  
• Even tried starting fluid and she will not start
  

Maybe no sparky

• I then changed the plug and this did not make a difference ( i might have messed up the CDI because I kicked started it about 10 - 15 times after changing the plug but I forgot to put the plug cap back on the plug)
  
• During one session of trying to fix it, when grounding the plug on the head there was no spark, but every time since I have been able to get spark when grounding the plug on the head and kicking the bike over
  
• I checked the impedance measurements for the coil and it check out OK
  
• Even borrowed a buddies CDI and coil off of a BW80 and still did not make a difference
  
• ***If I am seeing spark does that mean it is adequate to start the bike (even with starter fluid)
  

Compression

• I do not have a compression tester but I did the old "finger over the hole" test and it seemed fine
  

So this is where I am at:

I purchased a knock off carb from zoom zoom parts but have not installed it yet

I have the coil and CDI from a BW80 (I know they are a little different but I would think it would at least start the bike)

My concerns are even if the carb is bad it should have started with the starter fluid (sprayed into the cylinder through spark plug hole, and into the carb intake). This leads me to beleive that it has no spark but I can clearly see it sparking (although is does not appear to be a big spark - but what do I know) when I kick it over and ground the plug to the head. Finally it could be compression but I doubt it.

I would appreaciate any thoughts or suggestions any one would have.

Thanks,

[SuperChief]

When you are cleaning the carb, did you blow out the pilot circuit with compressed air? Sounds like your pilot circuit is not properly functioning. The spark issue would be unrelated if the bike is running with choke off or on.

[Smacaroni]

The BW and PW CDIs are pretty much the same.

Get a compression tester. You are covering a hole that is 113 sq. mm or 0.175 square inches, at 80PSI, that's 14 lbs of force, at 60 PSI, that's 10.5lbs of force. Can you say you know the difference between holding a 10lb weight with one finger and a 15 lb weight with one finger? I honestly can't say I'd know the difference. BTW 80PSI is fairly normal. Poor compression would certainly keep your bike from running, even when you spray ether in the cylinder. BTW, don't do that. I've blown the threads out of a head and that's a heck of a lot of work to fix.

Buy the $40 or so compression tester, the one with the extra adapters the $25 one doesn't have. Somewhere along the line, you'll need them and you can't buy them separately. Post your compression specs.

Edited March 7, 2012 by Smacaroni

[jamesbeaty]

When you are cleaning the carb, did you blow out the pilot circuit with compressed air? Sounds like your pilot circuit is not properly functioning. The spark issue would be unrelated if the bike is running with choke off or on.

Thanks for the response. I did blow air through the pilot circuit, but it would not hurt to do it again. But that is no longer my first concern, because the bike will not start at all now. I cannot get it to idle. I know there are three things I need to get going: spark, fuel, and compression. I am pretty sure I have compression, and I can use starting fluid to make sure I have fuel. Does this mean that it is a spark issue. Could the spark I am seeing not be "strong enough".

Thanks again for the response. The other options once I can get it to start is to just throw on the new carb.

[jamesbeaty]

The BW and PW CDIs are pretty much the same.

Get a compression tester. You are covering a hole that is 113 sq. mm or 0.175 square inches, at 80PSI, that's 14 lbs of force, at 60 PSI, that's 10.5lbs of force. Can you say you know the difference between holding a 10lb weight with one finger and a 15 lb weight with one finger? I honestly can't say I'd know the difference. BTW 80PSI is fairly normal. Poor compression would certainly keep your bike from running, even when you spray ether in the cylinder. BTW, don't do that. I've blown the threads out of a head and that's a heck of a lot of work to fix.

Buy the $40 or so compression tester, the one with the extra adapters the $25 one doesn't have. Somewhere along the line, you'll need them and you can't buy them separately. Post your compression specs.

Will do. I definitely would not know the difference between 14 and 10.5lbs. Shoot, I probably wouldn't know the difference between 15lbs and 5 lbs. I was going to buy the harbor freight tester. (is that a really bad idea.) But I will check compression in the next couple of days and post the results. Thanks!!

[Smacaroni]

I've never used the HF tester, but the one I picked up from Advance Auto Parts works well. If you were closer, I'd offer you a deep discount on a slightly used second one I have because I thought I blew the first one out.

And no, that's not typical for a PW80 or any two-stroke from the factory to my knowledge.

Edited March 7, 2012 by Smacaroni

[SuperChief]

Thanks for the response. I did blow air through the pilot circuit, but it would not hurt to do it again. But that is no longer my first concern, because the bike will not start at all now. I cannot get it to idle. I know there are three things I need to get going: spark, fuel, and compression. I am pretty sure I have compression, and I can use starting fluid to make sure I have fuel. Does this mean that it is a spark issue. Could the spark I am seeing not be "strong enough".

Thanks again for the response. The other options once I can get it to start is to just throw on the new carb.

No but your stator could be the problem. You could see spark on slow rotation, but when the bike is running it could be malfunctioning causing a loss of spark. I would definately get a pressure check done. Nothing wrong with harbor frieght. There is another PW80 post down on this forum with a great carb breakdown. Never hurts to verify you have all the o'rings.

[highflyernick]

PW80s have a cheap plastic guard in between the stator/works as a chain guide guard. Mine happens to have snapped a chain and went right through that, so now all the dirt and whatnot goes right into the stator/ignition and whatnot. Needless to say, doesn't have a very good spark at the moment, needs to be cleaned/guard fixed. Maybe you have gotten some dirt/water in the same area I did. Just a thought.

[jamesbeaty]

PW80s have a cheap plastic guard in between the stator/works as a chain guide guard. Mine happens to have snapped a chain and went right through that, so now all the dirt and whatnot goes right into the stator/ignition and whatnot. Needless to say, doesn't have a very good spark at the moment, needs to be cleaned/guard fixed. Maybe you have gotten some dirt/water in the same area I did. Just a thought.

I will definitely check it out- thanks for the suggestion

[jamesbeaty]

The BW and PW CDIs are pretty much the same.

Get a compression tester. You are covering a hole that is 113 sq. mm or 0.175 square inches, at 80PSI, that's 14 lbs of force, at 60 PSI, that's 10.5lbs of force. Can you say you know the difference between holding a 10lb weight with one finger and a 15 lb weight with one finger? I honestly can't say I'd know the difference. BTW 80PSI is fairly normal. Poor compression would certainly keep your bike from running, even when you spray ether in the cylinder. BTW, don't do that. I've blown the threads out of a head and that's a heck of a lot of work to fix.

Buy the $40 or so compression tester, the one with the extra adapters the $25 one doesn't have. Somewhere along the line, you'll need them and you can't buy them separately. Post your compression specs.

OK - so I went to AutoZone and "borrowed" ( put down a $40 deposit that I will get back) a compression tester. I got 0 compression on the pw80 so I decided to test it on the pw50 and got 0 compression there as well. Hmmm something seems fishy. So I went to Sears and bought the same compression tester and it read ~ 125 psi on the pw80 so I think the compression is good.

So - on to spark??? or on to fuel. Doesn't the lack of starting with starter fluid mean fuel is not the primary issue.

Do I check stator, coil, plug wire, plug cap in that order.

Is there any way to tell if my spark is strong enough?

Edited March 9, 2012 by jamesbeaty

[SuperChief]

I would be leaning towards the stator not properly functioning. You would see spark at slower revolutions ie hand cranking while holding a spark plug to ground. You need to read that out. Start there, then move to your CDI once your stator is verified good or bad. I have no knowledge on these PW's. I'm a KTM Dad so my knowledge is only limited to what I would check on my KTM. Sorry I can't be of more help. Smacaroni is the PW expert here...

[jamesbeaty]

Looks like it is on to the stator

HighFlyerNick - I will check out tat plastic guard that you mentioned too!!!

[highflyernick]

Looks like it is on to the stator

HighFlyerNick - I will check out tat plastic guard that you mentioned too!!!

Yea, you know how the stator guard, doubles as a front sprocket/chain cover. Just sometimes, like in my case, the chain had broke once and put a hole through the plastic, so anything that flung off the chain forwards, went right through onto the flywheel/stator etc. Doesn't help with spark!

[Smacaroni]

OK - so I went to AutoZone and "borrowed" ( put down a $40 deposit that I will get back) a compression tester. I got 0 compression on the pw80 so I decided to test it on the pw50 and got 0 compression there as well. Hmmm something seems fishy. So I went to Sears and bought the same compression tester and it read ~ 125 psi on the pw80 so I think the compression is good.

So - on to spark??? or on to fuel. Doesn't the lack of starting with starter fluid mean fuel is not the primary issue.

Do I check stator, coil, plug wire, plug cap in that order.

Is there any way to tell if my spark is strong enough?

125 is actually really good for a PW, other members have new top ends and only found 80PSI.

Sure, the easy way to test the spark is to take a younger sibling if you're a minor, or a neighbor you aren't fond of, ask them to hold the, spark plug connected to the plug wire, and with the other hand, hold on to the motor or anything that is metal on the bike. Kick it, if he jumps, the spark is ok. If you can see the blue spark in the plug, it's good.

In all seriousness, there are tools, but I concur with everyone else, check the stator. Get a manual from Yamaha of Australia http://www.yamahaownershandbook.com.au/?r=0 and look for resistance specs on the stator. I don't know them off the top of my head and there's a chance Yamaha won't tell you.

Pull the cover, look for broken wires. Clean all the contacts including grounds under the tank. Last an easy test would be to buy one from eBay. They shouldn't be too expensive.

[jamesbeaty]

OK - so I ordered a flywheel puller and flywheel holder (from ebay and Amazon respectively) and they should arrive mid next week.

I will check the resistance on the stator and the wires from the stator to the coil / CDI and will post the results. Thanks for all of the advice.

-James

[jamesbeaty]

I checked the resistance on the ignition coil (it was slight high maybe .4 ohms and the spec is from .26 - .36). My voltmeter may also be cheap and not able to get good reading at low values.

The secondary coil was 4KOhm and the spec is from 3.5 - 4.7 KOhm.

The CDI magneto (I assume this is the stator) was about 200Ohms and the spec is from 193 - 235 Ohms.

I wonder if the stator works intermittently.

I have two possible next steps. Pull the stator (CDI magneto) and swap in the one from my buddies BW80 or put in the new knock off carb.

Any suggestions?

[Smacaroni]

If you're sure it's electrical in nature, swap parts from the BW to the PW till you get it to run. IIRC you tried ether and if it won't start on ether there's only two causes, electrical or compression. Also, the system is simple enough, there's the switch on the handle bars, the CDI and coil under the tank and the stator, which is the most difficult to get to since you need a flywheel puller. Should take about an hour to test and another half an hour to put everything back the way it should be.

I'm not real keen on knock-off components, especially as a diagnostic tool, so the carb would be the last thing I'd try.

Edited March 20, 2012 by Smacaroni

[jamesbeaty]

Sorry for the long delay between post but I am back with new info.

Pulled the flywheel and everything looked great. I purchased a puller from ebay and used a Harbor Freight oil filter wrench to prevent the flywheel from turning (http://www.harborfre...ench-36845.html).

I tested the impedances on the coils and stator again (everything check out within spec) and then tried to start it. It caught for a second and then died. Next I tried to start it at WOT and it started and idled very rough. It will start and idle very rough (most of the time it will die after 20 seconds or so) as long as I have the throttle wide open.

Keep in mind even though I have the throttle wide open it is barely idling.

Any thoughts?

Edited April 8, 2012 by jamesbeaty

[Smacaroni]

Clean the carb again, completely remove the carb (be sure to unplug the oil injection pipe), disassemble, soak in carb cleaner, blow out the passages, replace any O-rings, reassemble and reinstall. Again, don't forget to plug the oil injection back in when you're done.

This is to ensure we're not dealing with a carb problem.

What did the compression test read?

The other thing you can do is keep swapping BW parts in, in fact, swapping in the BW carb if you're able is probably a worthwhile test.

[jamesbeaty]

I like the idea of swapping in the BW80 carb. The compression test read 120 PSI.

Hopefully I can get this thing running in the next couple of weeks because the weather is starting to turn up here.