750 Oil Breather

Bazz · Mar 7, 2006

While the motor on my 73 750 is stripped I was thinking of relocating the breather tower as per the 850 set up. I would be interested to learn of others experience with this conversion-ie is it worthwhile. I had pnly run the motor for a short while after acquiring the bike so don't know whether there was any problem with excessive oil return.

Cheers

Bazz

ILLF8ED · Mar 7, 2006

850 breather

Hi Bazz,

I did the modification to my '72 750 which has the same type crankcase. There was no noticable difference for me. I'd wait to do this after doing the more important upgrades such as the swing arm modification, sleeving the Amal carbs or Mikuni conversion and an electronic ignition. Your '73 750 should already have superblend main bearings on the crankshaft supplied from new.

sparkplug · Mar 7, 2006

Hi:
Which modification is to be made to the swingarm?
Sorry, I know it's not the thread but...

fastback · Mar 7, 2006

Sparkplug,

There should be info in previous threads, take a look at the info and the version of the mod I did. I liked this because it didn't require welding after I had painted the frame. Take a look at the pics of my set-up of Heinz Kegler's Swing arm spindle lock rings http://www.nortonfastback.com/html/mods.html

Cheers,
Philip

sparkplug · Mar 8, 2006

WOW :shock: Looks great!

Thanks, Fastback!

ILLF8ED · Mar 8, 2006

swingarm mod

Sparkplug,

You didn't ask the purpose of the modification. The tube in the engine mount that the spindle goes through gets worn out of round which causes movement of the spindle with a fulcrum at the single bolt in the center. This causes some poor handling characteristics. The modification is to eliminate this movement by adding two additional fixing points for the spindle. This is definitely a worthwhile modification. There are several variations. The one from Heinz looks like a fairly easy one. Others involve two extra bolts through the engine cradle tube securing the spindle at each side of the original bolt.

sparkplug · Mar 8, 2006

I imagined it had to do with the worness of the swingarm, but now it's all clear. How do you check this movement of the spindle? I've held the wheel and pushed from side to side looking for looseness, but seems to be right...

ILLF8ED · Mar 8, 2006

swing arm mod

Put the bike on the center stand. Hold the rear tire, moving the swingarm slowly side to side while viewing the area of the swingarm bushes. Look for movement there. Be careful as there is also movement at the center stand attachment. There should not be any movement in the rear isolastic engine mount. Side to side isn't allowed, only up and down - back and forth - verticle plane. Once the swingarm side to side movement is eliminated, you will notice the handling improvement.