The 750 saga continues

Simon Yates said:
I do not believe that the pump body has been removed before today.
Click to expand...

I wouldn't be too sure about that.

Looking at the photo of the inside face of the oil pump housing, it appears that someone has put those divots in there by trying to force the shaft out before fluking the right position for it to pull out, then had a go at de-burring the damage around the shaft hole it with a countersink.

Putting that oil pump damage together with the incorrect gear timing, chisel marks on the crankshaft nut, spare parts left in the primary cover, and you'd have to assume that a previous owner was a gorilla. Come to think of it, it may not have been an owner. I've seen similar horrors performed by so-called motorcycle "mechanics" employed in bike shops.

I assume there are some raised bumps around those divots in the edge of the shaft hole. You can blame a bloke with a similar name to you, a Frenchman called Sim?on Poisson. He invented Poisson's ratio, which basically describes how a substance will squish out in directions perpendicular to the applied force. Where material has been displaced sideways by the pin being forced into the alloy housing, it will also displace outward from the face.

If it were mine I'd centre it on a lathe face-plate and give the inside face a very light skim around the shaft hole - not going away from the centre any further than necessary to remove raised burrs. But I'm guessing you don't have a lathe.

You'd need to be very careful with any hand-held de-burring tool not to score the area where the pumping happens. Using a piece of file blade or small emery stone risks damaging the inner circumference or part of the face that has to "seal" against the side of the pump rotor. If you slip with a scraper, you'll be shopping for a new pump.

If doing it by hand, rather than trying to file or scrape down any burrs that stick up from the inner face, I'd very gently peen them down with the flat end of a pin punch and small hammer. Then you'd only have to ream the hole back to its correct diameter. A much easier task.
 
Difficult to ream the bore, Cam.  There is a great big slot in the bore for the drive pin to pass through.

I've salvaged worse than Simons' pump.  A small flat scraper is ideal for removing Poissons bumps and a rattail file will clean up the bore sufficiently.  While axial clearance of the gears within the body must not exceed a certain limit, a few little dents around the bore edges won't matter much.  Scoring at the circumference surfaces are usually the bigger problem, reducing pump performance drastically.  The mating surface indeed looks like the pump has never been removed before, the butchery has ocurred with the pump body in situ.  The remains of gasket goo look like they are of the type the factory used, Simon probably found the fixing screws peened over as a locking measure.

A new pump body would be the best option, but these are getting scarce, and what you find, is often just as bad.

piet
 
Today, I passed a 12 mm reamer through the gear bore and removed a 'burr' which allows the shaft to now rotate freely.  The shaft itself is pretty straight so I just need to straighten up the gear a little (carefully). 
As Piet says, the circumference is ok and I cannot see any sign of a crack even with an illuminated magnifying glass.
Putting the shaft and both gears in the body it spins freely so I am hopeful that it will work well.
When this is done I shall reassembly allowing the shaft to 'position' the boby before finally tightening up with a spot of Loctite nutlock.
 
don't for get some Loctite 573 on the joint faces, wait 24 hours for it to set ,
then prime the pump by squirting clean oil from a pump type can down the oilway..............
oops forgot you don't have the barrels off
CLEM
 
Oil pump now rotates freely and the drive gear has been positioned as shown below (with the black line not the arrow in line with the crank gear arrow) and, guess what, the rebuilt ignition is now timed at TDC. :D.
Will check this weekend, fill the refurbished carbs for the first time and try to start it.
 

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I do not think that I can set the ignition timing properly without getting a complete new set of back plates and points.  The plates are distorted, there is evidence of some 'grinding' and the pivot pins are not vertical.
Because of the above the timing is very erratic.
The back plate, (presumably Bosch) is part marked Germany ZVUB1Z1Z.
Does anyone have a spare set, are they available or do I bite the bullet and go the electronic route?
 
It is nothing to do with biting bullets getting an electronic replacement. If you have a good functioning points setup you could just keep on using them, but when it comes to having to source all sorts of stuff to replace them with other points, the maths says to just take the easy way out and modernise it. Nobody will shoot you.
 
I think I've read on the forum before that points for Breganze 750s are getting hard to find. Andy Wagner's on-line catalogue shows their status as unavailable.

If your points are buggered beyond refurbishment, it seems your options may be limited to either adapting a points/backing plate assembly from some other bike, or going electronic. If it were my bike, I'd go for an electronic ignition without hesitation. It'll give you better starting, idling and more accurate control of spark advance. All of which will be kinder to the engine than a points ignition.

If you choose the electronic path, my suggestion would be an Ignitech because (in my opinion) they're the best value for money and the most flexible in their programming options. I dunno whether Red supplies an Ignitech kit with pickups for the 750s, but I presume he does because he's built a few engines. Send him a PM (forum ID redax5 http://www.laverdaforum.com/forum/index.php?action=profile;u=39).
 
Hi Simon - I've got a DMC (Witt) kit I just took of a bike I sold - don't know how much they are new - but whatever would sell at 60% of new cost - Regards - Phil
 
had a few inquiries about the DMC kit - not heard if Simon wants it - here's a shot of what's in it - I do have a pair of coils it was used with - but don't know if originals are Ok to use. was working when removed a few weeks ago - just prefer to use my own kit
- Regards - Phil


100_2245 by phil Toddd, on Flickr
 
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