Is there a cheap solution for my defect rectifier

My batterry on my Z1300 1979 won,t charge at all but the voltage from the rectifier looks oke it delivers 13,5 volt at 900rpm and 14,6 at 2000rpm. and 14,6 volt at 4000rpm.
I just found a internetshop in Holland MLM -PARTS -BV that has a solution for me they have a Electro Sport Rectifier for 99,5 euro
Is there a cheaper solution for my defect rectifier ,can i use a used rectifier from an other bike from a motorbike junkyard?

If you're measuring that voltage you reported at the battery terminals then it's not the regulator. Batteries will breakdown and get to the point where they have to be replaced so don't discount a problem with the battery.
The negative plates in the battery cells are made up of a grid material which has a spongy lead material applied to that grid. Over time those flakes of spongy lead will break off and they are supposed to fall into a reservoir at the bottom of the battery. Sometimes, if a piece of that material is too big, it will get trapped between a positive plate and a negative plate and will short out the battery. This is one reason why gell cells were invented. The only problem with gell cells is that they don't produce electricity or recharge as quickly as wet cells do and for this reason, different charging rates need to be incorporated into the charging circuit. Don't use gell cells in a standard KZ1300 charging circuit. The output voltage is too high for the gell cell and the charging circuit will over work itself trying to charge the battery This will burn up the stator.
1 test you can do to find a dead cell -
First, pull off the battery caps and take a voltage meter and dip the voltage meter probes into 2 adjacent cells. Don't put them in so far as to touch the plates, just far enough to wet the tips with the electrodes from the volt meter. You should read 1.5 volts approximately. Do this between the next 2 adjacent cells. So you're going to test between cells 1&2, 2&3, 3&4, 4&5, 5&6. If you get a 0 volts on one of the tests, you now know that you have a dead cell and the battery needs replacing. Any charge that the battery would have taken on will be discharged by the shorted cell so the battery is junk.

Thanks for your replay but I can asure you that the battery is fine it is a brand New one and not a dry cell.
I Just tested the 6 diodes and found one did not work.
I tested between the 3 yelow and the White /red trace and the black wire.
Is it safe to buy the cheap rectifier from Electro Sport made in Amerika?
Does anybody has experiance with this Electro Sport divice?

And any internal fault like that is very likely to affect the batteries' terminal voltage, as an accumulation of the cell values, so you can measure that.

Or also stick it on an intelligent charger / tender which would flag many voltage or charge-retention problems.

I wouldn't even consider an OEM style V/R anymore, since installing this one about a year ago. Simplified wiring - no need to "remove the plug and solder the 3 yellow Stator-leads" as is recommended for the OEM style.
The three Stator leads now go directly to the V/R via a very robust plug and a second plug (from the V/R directly to the + and - of the battery.
Shindengen MOSFET R/R model # "FH020AA" Do some research and make certain you're not buying a knock-off piece of China copy-crap !

I'm with Scotch on this one. Having just replaced both the stator and R/R from Fortnine- which is the made in China stuff. Both suppliers I have used - Fortnine and Ricks supply the same parts from the same manufacturer- Electro-Sport. However- I sent my larger B2 stator to Ricks to get it rewound. Next time round , it will be the Shindengen Mosfet.

The Chinese stuff is good for 3 or 4 years in my experience.
So the reality is - there are no cheap options . Each part is about $140 or so and to be replaced every few years.