Topic: Points Question on a 74 CB550

[jimbo]

When I put my bike up for the season, it had developed a healthy tap.  I went out and started it up and did some poking around.  For some reason I opened my points cover and noticed that one of my points was not moving.  Before I get my hopes up, could 2 dead cylinders cause a knock like that.  My mind says it could because the the two cylinders that were firing would have to pull the two back down instead of combustion doing the job but...  it could just be wishfull thinking.

Anyone have any thoughts on it?

[MetalHead550]

Two dead cylinders would def. make some noise, especially via backlash in the gearbox.  It would pretty much sound like the motor was about to come apart due to, as you said, having to drag those other two cylinders through their combustion cycle.  The point not breaking contact would cause either 1 and 4 not to fire or 2 and 3 not to fire.  Wonder if its just frozen, way out of adjustment or the spring is worn out on that point?  Been awhile since Ive been in there.

[TwoTired]

Actual sounds are more descriptive than the written word.  Tap Tap Tap could be a raven at your chamber door. 
It is however, less likely that two problems occur simutaneously.  The points should be a pretty easy fix.  Why not give that a try and listen for your dreaded noise?  It's not hard to believe that an engine can make nasty sounds when only half the cylinders are functioning correctly.

The primary chain has no tensioner, for example.  It will snap around loudly with only two of four firing pulses.

Cheers,

[crazypj]

doesnt 550 break through main oil galley if chain gets too worn
PJ

[TwoTired]

Jeez,
I guess I have to pass the "Captain Bringdown Award" to PJ.

 

[jimbo]

Well, tomorrow is supposed to be a warm day here so, I am planning on slapping in a set of points that I have from my parts bike.  Any cheats for setting the gap?  My feeler gauges are in my toolbox out of town so I am going to try to guestimate it.  I'll post the results tomorrow.

[TwoTired]

One of those folding matchbook covers is about .013 inch.  Fairly close to the .016 setting recomendation.  Should run until you get closer to a real feeler gauge/tools.

Be aware that points can develop a surface oxide that prevents current flow.  They can appear to be making physical contact, but not make electrical contact.  Emery cloth is nice to correct this.  But, away from proper tools, the non-painted side of a match book cover with some vigorous sawing motion can wear through that unless the points are badly pitted.

Good luck!

[crazypj]

If you have a wife or girlfriend the emery boards they do their nails with works pretty good and does both sides of the points in one go.
PJ

[csendker]

I don't believe that it's good to use sandpaper, as I just did last night.  I think the silicon grit gets in there and screws things up.  I dressed them up a bit last night, and this morning 2/3 not firing.  Some quick work with a way-to-big steel file and I'm running again.  I've heard of a 'points file' but cannot find such a beast with a quick search.  Is there such a thing?  Isn't an emery board like hard sandpaper?  Would an actual nail file work better? Or am I just nuts?

[dusterdude]

there is such a thing as a points file,but unless you can find an old school auto parts store i doubt you`ll find one.

[jimbo]

Well, I was able to just regap the points that were on the bike.  Contacts looked good.  All I can say is wow!!!!  That thing runs like a scared dog.  I guess all this time I was just running on two cylinders.  Sadly enough, it actually ran fairly well all things considered.  Getting the other two cylinders firing completely eliminated a flat spot in the acceleration curve that had been plauging it.  I actually almost popped the front tire off the ground when I was under heavy acceleration due to me not being used to the power.  The knock is not as defined so I am going to do some general maintenance (Sync Carbs, Adjust CamChain and Valves) and see how it does.  If I can just make it through this season, I'm going to do a complete off frame restoration next winter.

Thanks for the advice!!!

[TwoTired]

I don't believe that it's good to use sandpaper, as I just did last night.  I think the silicon grit gets in there and screws things up.  I dressed them up a bit last night, and this morning 2/3 not firing.  Some quick work with a way-to-big steel file and I'm running again.  I've heard of a 'points file' but cannot find such a beast with a quick search.  Is there such a thing?  Isn't an emery board like hard sandpaper?  Would an actual nail file work better? Or am I just nuts?

 I can't speak for all nail files or abrasive boards, but the ones I commonly see have sand grit glued to both sides.  Silca grit will indeed embed into the points metal, reducing their contact surface area and increase heating effects, or point burning.  Using such a device on points would be a desparation action in an emergency situation.

The emery cloth I use has a jewlers rouge coating on one side only.  The back side of the cloth works well to clean and burnish the contact surface after using the abrasive side.  This will take care of any surace oxidation.  Also, this is usually my last step for reconditioning when the points are pitted, after using my points file, purchased long ago in an automotive supply store.

Here is a contact burnishing tool for $1.65.
http://www.halted.com/commerce/catalog/product.jsp?product_id=14383&czuid=1143680414734

For knocking down the bad pits and peaks use a needle file first, followed by the above burnishing tool.
http://www.brownells.com/aspx/NS/store/ProductDetail.aspx?p=6767&title=DIAMOND+NEEDLE+FILES

Cheers,

[crazypj]

 I thought it was an emergency situationwhile waiting for new points to arrive. Nice links, diamond needle files. you can get emerald or diamond nail 'files' as well at Wallgreens but they are a lot more expensive.
PJ

I

 I can't speak for all nail files or abrasive boards, but the ones I commonly see have sand grit glued to both sides.  Silca grit will indeed embed into the points metal, reducing their contact surface area and increase heating effects, or point burning.  Using such a device on points would be a desparation action in an emergency situation.

The emery cloth I use has a jewlers rouge coating on one side only.  The back side of the cloth works well to clean and burnish the contact surface after using the abrasive side.  This will take care of any surace oxidation.  Also, this is usually my last step for reconditioning when the points are pitted, after using my points file, purchased long ago in an automotive supply store.

Here is a contact burnishing tool for $1.65.
http://www.halted.com/commerce/catalog/product.jsp?product_id=14383&czuid=1143680414734

For knocking down the bad pits and peaks use a needle file first, followed by the above burnishing tool.
http://www.brownells.com/aspx/NS/store/ProductDetail.aspx?p=6767&title=DIAMOND+NEEDLE+FILES

Cheers,