1981 YZ465 Won’t Run, Need Help

barnett468
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barnett468 10/7/2018 6:59pm
10/7/2018 6:59pm
project racer wrote:
Don't ever buy a PVL ignition. You'll spend hours looking for the key.
captmoto wrote:
I don't need to. The PVL is purpose built to work without a woodruff key. The YZ ignition is not. Apples and oranges.
wfoskir wrote:
Totally agree with you Captmoto, if the key was pointless it would not have been designed to be there. I am sure Yamaha spent a lot...
Totally agree with you Captmoto, if the key was pointless it would not have been designed to be there. I am sure Yamaha spent a lot of money on engineering it for a reason. Also, if it was pointless my bike would have continued to run when it sheared, not the case.
Anyway, I am extremely happy it was that simple fix and the bike runs great.
The angle of the taper on the crank is around 1/2 degree different than the angle of the taper on the flywheel. When the flywheel nut is tightened, the taper on the flywheel is forced to conform with the taper on the crank, and this causes the flywheel to clamp on to the crank, and this clamping force is maintained by the torque from the nut on the flywheel. This is exactly why you need a flywheel puller and a bfh to remove the flywheel. The only time a key "should" shear is when the tapers are worn or the nut comes loose.




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project racer 10/8/2018 3:43pm
10/8/2018 3:43pm Edited Date/Time 10/8/2018 3:48pm
barnett468 wrote:
The angle of the taper on the crank is around 1/2 degree different than the angle of the taper on the flywheel. When the flywheel nut...
The angle of the taper on the crank is around 1/2 degree different than the angle of the taper on the flywheel. When the flywheel nut is tightened, the taper on the flywheel is forced to conform with the taper on the crank, and this causes the flywheel to clamp on to the crank, and this clamping force is maintained by the torque from the nut on the flywheel. This is exactly why you need a flywheel puller and a bfh to remove the flywheel. The only time a key "should" shear is when the tapers are worn or the nut comes loose.




Thank you. Many do not own, or know how to use a dial indicator. One of the main reasons for keyed ignition flywheels. The keyed location gets the flywheel in "range" to allow for precise timing by moving the stator plate to the correct BTDC setting using the dial indicator.

If not for the keyed locator, many bikes would never run again once the flywheel was removed , as the only way to restore the correct flywheel location on the crank would be by use of dial indicator.

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project racer 10/8/2018 4:00pm
10/8/2018 4:00pm
Recall my older brother had the flywheel off his Shell MX250B Yamaha one time. Slid the flywheel back on, and the key "walked" out of the groove during the re-installation process. It allowed the flywheel to slip ever so slightly, and the bike ran just as the 465 described here.

Would never clean out, always fat on the carburetion during first practice session. I had the tools in hand as he came off the track, but he was being such a cock face about it, that I just quietly set the tools down, and walked off, taking a seat in the stands, and watched the rest of the nights races. AHRMA National, Ocala ,1999.

The 250 got shoved in the trailer. Have not ever put my hands on that bike since.
1
riv187
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riv187 10/9/2018 7:27pm
10/9/2018 7:27pm
I'm not surprised on the sherred key on a 465. It has a external flywheel,lots of inertia,,,and open bikes without decompression releases are known for kicking back violantly. Probably kicked back while trying to start..the shock of the flywheel sherred it and caused the problem.

The Shop

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wfoskir
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wfoskir 10/9/2018 9:29pm
10/9/2018 9:29pm
riv187 wrote:
I'm not surprised on the sherred key on a 465. It has a external flywheel,lots of inertia,,,and open bikes without decompression releases are known for kicking...
I'm not surprised on the sherred key on a 465. It has a external flywheel,lots of inertia,,,and open bikes without decompression releases are known for kicking back violantly. Probably kicked back while trying to start..the shock of the flywheel sherred it and caused the problem.
That makes sense to me and likely what happened.
wfoskir
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wfoskir 11/18/2018 8:25pm
11/18/2018 8:25pm
Round 2. The bike is doing the same thing again. Won't run, back fire... Checked the fly wheel and pretty sure that is not it. I can't get if off the shaft to see if the key has sheered or partially. So I am guessing that is not it. However, I can't remove the fly wheel to dig deeper in the issue. Ruined one flywheel puller trying to remove it (the puller i have didn't leave many threads from fly wheel to push bolt). Just got the new one, tried again, but that sucker will not budge.
This sucks. the bike was running fine. I took it to the track a few weeks back, fired it up, it was warming up, i was too excited and tried to take off before the clutch was ready. That was it. would not fire back up
Murph
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Murph 11/19/2018 8:18am
11/19/2018 8:18am
The best way to get a stuck rotor off is to put the puller on it, tighten it and heat up the rotor with a heat gun, then get a reasonably heavy hammer and give the end of the puller a good whack. Always worked for me.
450exc115
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450exc115 11/19/2018 8:39am
11/19/2018 8:39am
Sounds like you sheared the key again. This time it moved enough to bind up the taper. How did you torque the nut and replace the spring washer if you didn't do it last time. Also check your timing as too little advance will cause you to shear keys.
wfoskir
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wfoskir 11/19/2018 12:00pm
11/19/2018 12:00pm
Ok, I did have the puller on it and gave it a whack. I did not use heat though. I will do it again using heat and see how that goes. I put a bit of WD40 on it, so it will be marinating.
I was thinking the key may be partially sheared. But just by looking in there it looks ok. If I get the fly wheel off, I am sure I will find the problem. I will check the timing as well when I get in there.
Thanks for the tips.
Mario
450exc115
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450exc115 11/19/2018 12:31pm
11/19/2018 12:31pm
Just so you know WD-40 is not a penetrate oil. It's a water displacer (WD). You want to use a penetrate oil like PB blaster or something similar. In your case since this was off recently it won't help as I doubt any rust or scale has built up to hold the flywheel on. You can use an air impact to help separate if you have one handy. Otherwise leave the puller on torqued down and walk away from it for a few days.
project racer 11/19/2018 1:30pm
11/19/2018 1:30pm
How long of wrench are you using on the puller bolt ? A short bar or wrench won't do, especially if the flywheel is moving as you try to crank down on the puller bolt. Get a 1/2" air gun, and give it a few bumps, while holding the flywheel still. A strap wrench around the flywheel will help hold it.
wfoskir
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wfoskir 11/23/2018 2:37pm
11/23/2018 2:37pm
Flywheel is off. The key is perfectly fine, everything looks clean and fine. Nothing below/beyond the flywheel looks as if it has never been touched. The screws holding the ignition look brand new and there are no marks on the ignition plate that show any adjustment. Not sure where to look for the next problem?
project racer 11/23/2018 4:07pm
11/23/2018 4:07pm
Have you checked the full exhaust system for critter nests ? Is the air filter in good shape ?
Brian_Bowles
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Brian_Bowles 11/23/2018 4:57pm
11/23/2018 4:57pm
Did you clean the pathways in the carb that lead to the jets?
450exc115
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450exc115 11/23/2018 5:20pm
11/23/2018 5:20pm
Measure the resistance on the coils against the manual.
wfoskir
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wfoskir 11/23/2018 9:39pm
11/23/2018 9:39pm
project racer wrote:
Have you checked the full exhaust system for critter nests ? Is the air filter in good shape ?
Yes and yes.
wfoskir
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wfoskir 11/23/2018 9:40pm
11/23/2018 9:40pm
Brian_Bowles wrote:
Did you clean the pathways in the carb that lead to the jets?
Yes.
wfoskir
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wfoskir 11/23/2018 9:48pm
11/23/2018 9:48pm
450exc115 wrote:
Measure the resistance on the coils against the manual.
This i haven't done. I will be checking this tomorrow.
Thanks

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wfoskir
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wfoskir 11/24/2018 3:55pm
11/24/2018 3:55pm
The primary on the coil tested at 1.2 ohms and the secondary tested at 5.8K. I also did the kill switch and it was 1.3 when I pushed it. But as I held it, it went to zero. These all seem to be with in the specs of what the manual says. I am not sure about the kill switch though. When I tested the secondary (spark plug cap) I did not get a reading at first, but after a few try's I did get the reading. Not sure if it was me or the coil.
I also removed the spark plug, put the plug cap back on and kicked the bike over. There was spark but it seemed to be intermittent and or a bit weak.
I am not sure what to check next but I am thinking of replacing the coil because it is suspicious.
450exc115
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450exc115 11/24/2018 5:01pm
11/24/2018 5:01pm
You need to check the stator coils also. One generates the spark voltage and the other triggers the CDI to fire.
Hasletjoe
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Hasletjoe 11/24/2018 5:08pm
11/24/2018 5:08pm
wfoskir wrote:
Flywheel is off. The key is perfectly fine, everything looks clean and fine. Nothing below/beyond the flywheel looks as if it has never been touched. The...
Flywheel is off. The key is perfectly fine, everything looks clean and fine. Nothing below/beyond the flywheel looks as if it has never been touched. The screws holding the ignition look brand new and there are no marks on the ignition plate that show any adjustment. Not sure where to look for the next problem?
Just curious if you have adjusted this timing. Looking at the location of the screws, this looks very advanced (assuming the rotation is counter clockwise as we look at it).
wfoskir
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wfoskir 11/24/2018 5:26pm
11/24/2018 5:26pm
wfoskir wrote:
Flywheel is off. The key is perfectly fine, everything looks clean and fine. Nothing below/beyond the flywheel looks as if it has never been touched. The...
Flywheel is off. The key is perfectly fine, everything looks clean and fine. Nothing below/beyond the flywheel looks as if it has never been touched. The screws holding the ignition look brand new and there are no marks on the ignition plate that show any adjustment. Not sure where to look for the next problem?
Hasletjoe wrote:
Just curious if you have adjusted this timing. Looking at the location of the screws, this looks very advanced (assuming the rotation is counter clockwise as...
Just curious if you have adjusted this timing. Looking at the location of the screws, this looks very advanced (assuming the rotation is counter clockwise as we look at it).
If the bike ran fine prior to just recently acting up, I haven't touched the timing, it doesn't appear to have moved(no marks from what the screws are), the screws where very tight, could it really be the timing? Even if it is advanced?
I believe the rotation is counter clockwise. But I honestly do not know if the timing is advanced or not. Never even looked at prior to starting this repair.
barnett468
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barnett468 11/24/2018 5:43pm
11/24/2018 5:43pm
wfoskir wrote:
Flywheel is off. The key is perfectly fine, everything looks clean and fine. Nothing below/beyond the flywheel looks as if it has never been touched. The...
Flywheel is off. The key is perfectly fine, everything looks clean and fine. Nothing below/beyond the flywheel looks as if it has never been touched. The screws holding the ignition look brand new and there are no marks on the ignition plate that show any adjustment. Not sure where to look for the next problem?
Hasletjoe wrote:
Just curious if you have adjusted this timing. Looking at the location of the screws, this looks very advanced (assuming the rotation is counter clockwise as...
Just curious if you have adjusted this timing. Looking at the location of the screws, this looks very advanced (assuming the rotation is counter clockwise as we look at it).
That is the fully retarded position.
project racer 11/25/2018 12:59am
11/25/2018 12:59am Edited Date/Time 11/25/2018 1:25am
When the 465 came out in 1980, it was a very hard to start bike. The ignition did not make good low speed voltage. Really had to give it a boot to get the engine turning over fast enough to generate adequate spark.

It was ,kick, kick, kick, KaPOW… Kick some more. It got a little better for 81, but still could be a bit difficult to start.

A dial indicator will tell you real quick if timing is set within spec. Initial timing advance is just that. The CDI box controls the rest of the ignition advance.

Does the bike have fiber reeds in it ?
NoMuff2Tuff
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NoMuff2Tuff 11/25/2018 4:16am
11/25/2018 4:16am
Even if the stator ohms out OK it still can be bad and the bike not fire or run bad, seen this happen a few times. Stators can do some weird things and have you scratching your head because it tested OK
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Hasletjoe
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Hasletjoe 11/25/2018 11:38am
11/25/2018 11:38am
@Barnett468 is correct, this is the fully retarded position.

I would think if you have not touched the timing and the bike quit starting, it should not be timing. Just for grins, leave a plug in the cylinder and take a second plug and check for spark. A crude way to check low speed spark as Project Racer referred to....
plowboy
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plowboy 11/25/2018 11:51am
11/25/2018 11:51am
When you have things back together...pull the plug, stick it in the cap. Ground the plug on the head. Have someone kick it over like crazy. You should see a big fat BLUE spark. If the spark is orange/yellow or only intermittently blue...buy a new stator or have it rewound with new enamel coated copper wire. I ain't joking.
wfoskir
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wfoskir 11/29/2018 12:38pm
11/29/2018 12:38pm
I received the new coil I purchased, installed it, 3 kicks and it fired right up. It ran great!
But a new problem came up, the clutch will not disengage. I have not had a chance to dig into it yet but I am happy to get past the ignition/starting issue.
I am thinking the coil was my problem the whole time. It would work intermittent, cause the bike to back fire, fly wheel came loose, fix fly wheel, bike runs (by luck), run the bike a second time, clutch doesn't work (thought it was just a cold clutch), now bike will not start, new coil, bike runs, but clutch is not cold, it just doesn't work.
I still think I am winning this fight.
Thanks for the help and tips.
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newmann
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newmann 11/29/2018 1:09pm
11/29/2018 1:09pm
Clutch plates are stuck?

Don't use Barnett Kevlar plates if you replace them. They will wear out your inner hub and pressure plate in short order. Very abrasive material it seems. Killed my 74 CR250 and 81 YZ250 before I went back with OEM plates and fibers. Tranny oil was always filthy after a ride day with Barnett's.
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wfoskir
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wfoskir 11/29/2018 3:15pm
11/29/2018 3:15pm
newmann wrote:
Clutch plates are stuck? Don't use Barnett Kevlar plates if you replace them. They will wear out your inner hub and pressure plate in short order...
Clutch plates are stuck?

Don't use Barnett Kevlar plates if you replace them. They will wear out your inner hub and pressure plate in short order. Very abrasive material it seems. Killed my 74 CR250 and 81 YZ250 before I went back with OEM plates and fibers. Tranny oil was always filthy after a ride day with Barnett's.
Thanks for the tip on the clutch parts.

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