1981 YZ465 Won’t Run, Need Help

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10/1/2018 7:27 PM

I haven’t started my 465 in a long time and have been trying to get it going. I have never had any issues with it and it has always ran perfect.
I got it to fire up and it ran bad, back fire, loaded wouldn’t run very long. Prior to trying to start it I did the obvious, fresh gas, cleaned carb, cleaned air filter, checked spark. No good. Changed plug, no good. Disconnected the kill switch, no difference. Tried swapping the coil with my 250, not quit the same but same result.
When we did get it running, it took a lot of effort to get there.
Anyone got any ideas?
Thanks
I added a photo just because I like pictures!
Photo
I am resting after kicking the shit out of it!

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10/1/2018 8:12 PM

Try changing the spark plug boot. Mine was rusted. I cut 1/4" or so back until I got shiny wire. Clean the frame where everything electric mounts. These old ignitions can be a little cranky. I have a full spare setup in cabinet for my 465 and there are lots of ignition parts floating around on Ebay.

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The older I get, the faster I was.

10/2/2018 7:17 AM

Don’t forget to pull the ignition off the crank & check the grounds for corrosion too!

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10/2/2018 7:35 AM

Spark plug cap corroded or woodruff key sheared may be

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10/2/2018 5:09 PM

smx94 wrote:

Spark plug cap corroded or woodruff key sheared may be

that happened to a 465 and 490 I owned key crumbled was out of time

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10/2/2018 6:20 PM

Try the obvious cleaning out of the exhaust pipes. When the spooge hardens up from sitting your air flow is limited. Had this happen on a few bikes. Exhaust is crucial on a 2 stroke.

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10/2/2018 7:58 PM

Thanks for the tips. Some good stuff here. Don't have time to check it until the weekend. I will let you know what i find.
Thanks

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10/3/2018 4:48 AM
Edited Date/Time: 10/3/2018 4:48 AM

Your petcock may have a slow leak while turned off... I bought a 465 this summer that would start but wouldn't rev. I tried everything and then pulled motor and cylinder, crankcase was full to the bottom of the piston with fuel.... Cannot believe it even started and ran !!!

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Your Birthday is dated off the Life, Death & Resurrection of Jesus... Just saying :-)

10/3/2018 12:17 PM

Remove and clean the pilot jet as the small holes in it are most likely clogged.

Paw Paw

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10/3/2018 5:07 PM

smx94 wrote:

Spark plug cap corroded or woodruff key sheared may be

Can't believe I didn't remember the woodruff key. I have shared mine just from backfiring. I keep a couple in my toolbox a nd just found one in my truck.

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The older I get, the faster I was.

10/4/2018 8:53 PM

Paw Paw 271 wrote:

Remove and clean the pilot jet as the small holes in it are most likely clogged.

Paw Paw

I did the carb 3 times. pretty sure that is not the problem. I believe it is in the ignition system, somewhere. I am going to check the plug wire better and the woodruff key.

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10/5/2018 11:12 AM

Sounds like what happened to mine. It always started (sometimes 5 kicks, sometimes 25 kicks, but always started). One day it would not start and following some advice from some friends I removed the spark plug, turned it upside down and a ton of fuel came out of the crankcase. Flipped her back over, put in the plug and bingo she fired right up.

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When in doubt gas it! It may not cure the problem but it will end the suspense!

10/5/2018 12:41 PM

Two strokes are pretty simple engines. They need fuel, air, compression and spark to run. I approach a non running engine by going after the easy stuff first.

Pull the plug and look for spark - no spark and you should start trouble shooting the electrical system.

No spark diagnostics
First try replacing the plug, they do go bad or get fouled. If that didn't do it try disconnecting the kill switch, most kill switches work by grounding the coil circuit so if they short out they won't allow spark to occur. The next test requires a volt meter that has the capacity to determine resistance of wires/coils. A manual is handy as it will have specific values for the various coils but I find that if you don't have spark it will be clear to see if the coil is bad. Using the volt meter on the Ohm setting you should get a value for each coil when you measure it against ground. If you get 0 then you have a bad coil as it should have a value. If you get a 1 then you have a shorted coil. If the coils check out then there is a good chance that the CDI is dead, there is no real check for these so it's a replace it and cross your fingers test that you were right.

Spark but no fire.

I first check by pouring a small cap full of gas in the cylinder and kick it over. If it starts or tries to start you may have a fuel issue. If it doesn't start you have two options. Option one is check for spark at the right time as that is important. Pull the ignition cover and see if the stator is loose/moved or pull the flywheel and check for a broken key. If none of these are it check the compression, most two strokes need at least 100psi of compression to run, anything below that it won't light. 120 psi or more is ideal. If compression and timing are good and it still won't start with fuel in the cylinder then I'd swap out a CDI as it could be too weak or lost time (the older hitachi MX/DT/YZ ignitions use to fail with weak spark).

If non of those finds the issue then your SOL... LOL

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10/5/2018 5:51 PM

Pull the kill button and try it

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10/5/2018 6:27 PM

Also scotch brite the coil where it faces the inside of rotor and the inside of rotor too. rust there will lower the spark

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10/5/2018 9:49 PM

I checked the spark on the plug. it did have spark but it seemed to be intermittent and weak. That is why I think it is ignition related.
I also checked the fuel. pulled the fuel line, turned the pet chock on and fuel came out. Shut it off and no fuel.
I also disconnected the kill button. The bike ran, but the same, extremely shitty.
Tomorrow I will give it a go, with all these suggestions. I am hopeful one of these will get my bike running.
Bets on what it may be?

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10/6/2018 3:50 AM

Poor connection at the spark plug cap or rusty coils/ flywheel magnets.

My TS 185 motor would miss fire off the start for a minute or two until it got fully warmed up at a few harescramble races until I sanded the coils and flywheel. Nearly pulls hole shots now if the straight is short enough. Lol

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10/6/2018 2:01 PM

If you said woodruff key!? You are correct! Photo
Just picked 1 up from the hardware store, not metro though. Going to try and make it fit. Keep you all posted on the out come.

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10/6/2018 2:30 PM
Edited Date/Time: 10/6/2018 2:32 PM

You do realize that the key is basically for locating the flywheel in the correct orientation on the crank. It does nothing to hold things together.
The tapered end of the crank and the taper of the flywheel are where the interfacing of the two, when flywheel is properly torqued, combine to form a tight ,press like fit. That is why you need a puller, and hear an audible "pop" when the flywheel is pulled off of the taper.

Several ignition systems are / have been non keyed units. When pulled up on the taper, the key is pointless.

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10/6/2018 3:52 PM

Well this one has never been apart, at least not by me. When I removed the cover the nut and fly wheel where lose and key sheared. Once I installed a new key and torqued it back in place, it fired right up.
The bike hadn’t been risen in years and ran perfect when parked.

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10/6/2018 4:26 PM

Dang glag the bike has "risen" !

Those bikes are a hoot to ride fast as long as you don't plan on stoppig anytime soon. laughing

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10/6/2018 5:13 PM

I want to thank the Vital MX Old School team for all the tips, it really helped me in getting my bike running again. I tried to post a video of the bike running but I was not successful. Anyhow, thanks again!

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10/6/2018 7:57 PM

thats great you got it going from the great suggestions here.

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10/6/2018 11:14 PM

wfoskir wrote:

I want to thank the Vital MX Old School team for all the tips, it really helped me in getting my bike running again. I tried ...more

You lucked out. I had mine flood so bad I had to remove the pipe and pour gas out of it. I did everything I could to start it and with it out of time it just kept sucking gas into the bottom end. Think I'll try to start mine tomorrow.

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The older I get, the faster I was.

10/6/2018 11:17 PM

project racer wrote:

You do realize that the key is basically for locating the flywheel in the correct orientation on the crank. It does nothing to ...more

Apparently the the key is not worthless. The shaft and flywheel would need to be an interference fit for the key to be pointless. The manufacturers put them in for a reason.

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The older I get, the faster I was.

10/7/2018 3:37 AM

project racer wrote:

You do realize that the key is basically for locating the flywheel in the correct orientation on the crank. It does nothing to ...more

captmoto wrote:

Apparently the the key is not worthless. The shaft and flywheel would need to be an interference fit for the key to be ...more

Don't ever buy a PVL ignition. You'll spend hours looking for the key.

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10/7/2018 8:37 AM

project racer wrote:

Don't ever buy a PVL ignition. You'll spend hours looking for the key.

I don't need to. The PVL is purpose built to work without a woodruff key. The YZ ignition is not. Apples and oranges.

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The older I get, the faster I was.

10/7/2018 9:03 AM

captmoto wrote:

Apparently the the key is not worthless. The shaft and flywheel would need to be an interference fit for the key to be ...more

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.

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.

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10/7/2018 11:08 AM
Edited Date/Time: 10/7/2018 11:11 AM

OK. Point is , if the flywheel was torqued, and properly seated on the taper, it would have never rocked enough to break the key. The key is not a crutch for a loose flywheel that is not up on the tapers. Your crank end and flywheel tapered surfaces have probably been nibbled on by a loose flywheel rattling back and forth on them for who knows how long, until the crutch (key) finally said enough.

A keyed crank does not know or care if the key is actually installed, provided the flywheel is torqued and up on the tapers. Main reason for being keyed is flywheel to crank orientation.

Just a simple way to get things close ,timing wise.

And for what it's worth ,once the key broke, the flywheel slipped ,and ignition timing was lost. No way it was going to "keep on running" when it slips time.

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10/7/2018 11:16 AM

I've jacked around with a few ignitions. This was the 1987 YZ80T system I ran on my 79 YZ250 Champion short tracker. Photo
Photo

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