Magnet on rotor fixed miss

[650Dave]

After reading in another recent thread how the magnet in some replacement rotors can be sub-par, I thought about this possible solution to a problem that has plagued me for several months. Long story short: I bought a new rotor from a vendor to fix a charging problem on my 12,000-mile 1980 650. Well, the new rotor solved that problem fine. But shortly after installing the rotor, the engine developed a strange miss, but only when really warm.

Never suspecting that the new part was in any way related to the miss, I replaced the coil and plug wires, which were original. No change. Went through the carbs, three times. Nothing. Switched out the TCI box. Nada. New plugs. Ditto. Checked valve adjustment, spot on. Compression good.

The other day I read a thread about how someone put a small but powerful rare-earth magnet ($2.00 at Radio Shack) on top of the rotor's magnet, so I tried it. Bingo! This solved the issue. I have ridden the bike about 50 miles since then, and nary a hiccup.

As an aside: I wrote the vendor today letting them know that they may have a manufacturing defect in these rotors. I don't know what's going on exactly, but somehow heat affects the magnet's ability to signal effectively.

New guy here, btw, but was around the other site years ago, and have had bikes for a long time. I've had this one for 15 years.

Dave

 

[angus67]

i was wondering when yo would show up, dave. now we need shakernorm, and bob dammit, the information contained herein would tripple when coupled to 5twin knowledge.

 

[650Dave]

Well, those guys know a lot more than me! It's good to be among fellow enthusiasts, that's for sure.

 

[Frankenstein650]

Had the same problem with aftermarket rotor from egay. Ran fine without head light. Slight miss just above idle with HL on. Added a radio shack rare earth magnet to rotor pickup magnet and all is well. Thanks for the thread.

 

[xjwmx]

I don't know how strong the RS magnets are but there are magnets that are strong enough that they would charge the rotor magnet by being in contact with it for awhile. If I ever need a rotor, I'm going to make sure I get my old one back, rewound. I once had a rare alternator rewound at a local auto electric shop. I suspect they could rewind this thing too.

 

[Db1Rider]

Is there any way I can get a picture of this magnet? How do you install it and where at?

 

[EvenmoreXS]

http://www.radioshack.com/product/index.jsp?productId=2102642

They are small little guys, but very strong. They may have more than one size so check that out. Original rotor magnet is about the diameter of a pencil eraser.


On your rotor, if you turn it....counter clockwise,.....you will see a small circle imbeded into the rotor near the outside slip ring. This is the magnet that the pickup senses to tell the TCI box where the crank is and when the coil is to fire the spark plugs.

This is where the new magnet would go. Glue it well, but buy extra.


Someone correct me if Im wrong here.

 

[Db1Rider]

How easy is it to remove the old magnet? And thank you for your fast reply.

 

[EvenmoreXS]

Please chime in someone who knows for sure......but.....I dont think you remove the old magnet on the rotor. You just glue the new one over it. The rare earth magnets WILL surprise you with how small yet strong they are. I've also heard that you can "recharge" your rotor magnet by leaving a rare earth magnet on it for a period of time. Maybe if you werent riding for a few days you could let it sit there on the original magnet and see if it helps before your glue the new one on.

 

[Db1Rider]

The only issue I see is without removing the old one there isnt much clearance between the rotor and the pickup.

 

[Dennis]

you dont remove the old magnet
simply adhear the new one over the old and if needed shim the pickup

 

[Db1Rider]

Thank you. I managed to get it going there. Now my coil is bad. Ordering a new one on Mikes xs and new carb jets.