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Monkey Z50A dating & frame number

Posted: Fri Sep 04, 2020 2:05 pm
by Finkey

Can any of you guys help me with the dating of my Z50A? I'm kind of confused with various references found on-line.

I have a Monkey Z50A K2 that has been imported to Finland in the early 70s and sold here as new. I bough it used in 1976 and the seller (the first owner) told back then that he'd bought only a year earlier and that it had been manufactured in 1975.

Now that I'm (reluctantly) planning to sell the bike away, I started browsing various sites to get some confirmation on its model & year of manufacture.

Its frame number is "Z50A-412506". This is a bit peculiar, since none of the references I found in the Internet tell anything about a serial number starting with number four. Furthermore, the years of manufacture of the K2 are told to have been 1970-1971. It has been stated that already in 1971 the serial# reached '399999', and that was the end of it. Obviously it can't have been, considering the stamp on mine.

Then, on the other hand, certain references tell that it was only as late as in 1973 when the Japanese and European Monkeys changed from Z50A to Z50J.

Thus, it seems obvious that the year of manufacture in this one is NOT 1975 as it was told to be when I was buying this. But that aside, can any of you guys elaborate this issue any further.

[BTW, some website mentioned that a date stamp (mm/yy) can be found "inside the swingarm" of a Z50A. That, of course, would be really hard to find :) but have you ever heard of such date stamps on any other surface of this model?]

With regards,

Re: Monkey Z50A dating & frame number

Posted: Fri Sep 04, 2020 7:27 pm
by wightegi
Send a message to steveST100 he knows a bit about the small bikes .


Re: Monkey Z50A dating & frame number

Posted: Fri Sep 04, 2020 9:28 pm
by steveST100
If its got a swinging arm it wont be a z50k2 as they were the last of the hardtails. If swinging arm maybe a Z50K3-6.
Some of the tanks had a date on the tab at the back,some of the time underneath it.
A photo of the bike may help.

steve g

Edit. Just had a look online and think it maybe a 73 Z50AK4 going off this site. ... -z50a.html

Re: Monkey Z50A dating & frame number

Posted: Mon Sep 07, 2020 7:49 am
by Finkey
Hi Steve,

Many thanks for your reply. Sorry for being unclear... being a non-native English speaker sometimes brings about these confusions. I meant that in my case it is hard to follow that odd piece of instruction by someone for finding a 'date stamp' inside the swingarm, because there isn't any swingarm to look at.

So, yes, this is a hardtail :)

I need to check that tank tab, thanks for the tip!

As for the site you linked, note that the K4 (and the K3 as well, for that matter) have a seven-digit frame numbers. Mine is a six-digit, as is the case with all frames from K0 to K2. Also, mine has no battery nor pedal brake (well... it has a pedal, but it's a DIY). So, everything suggests that this is a K2, except these various ledgers on various sites that do not know K2 frame numbers starting with number four (Z50A - 4xxxxx).

But hey, this can then be a true COLLECTORS ITEM --- It exists, but it has never been manufactured!! I wonder if I should increase the price :D

Here's the photo. The bike is in nearly original form; second rear view mirror added, DIY foot brake to replace the rear hand brake, DIY brass bushings in front telescopes, frame and tank repainted, rims painted over, tank cap replaced, the lower exhaust pipe cover is from model 1976, the rear exhaust pipe cover is DIY, rear light unit is missing (note that the rear light bracket is original even though it differs from the much more common form that is often seen on K2).

Re: Monkey Z50A dating & frame number

Posted: Mon Sep 07, 2020 12:20 pm
by wightegi
Does the engine number start with a 4 ?

Re: Monkey Z50A dating & frame number

Posted: Mon Sep 07, 2020 2:29 pm
by Finkey
Hi Wigthegi,

I do not know. The bike is at my parents' place and I live a few tens of kms away from them. I'm about to fetch in the coming days to fix the tail light etc.

I will check out the engine number as soon as I can.


Re: Monkey Z50A dating & frame number

Posted: Mon Oct 05, 2020 6:25 pm
by Finkey
Hi again,

Now I was finally able to take a look at the bike.... The engine number actually starts with '4' as was suspected by Wightegi above. The number is "Z50AE-463846".

Furthermore, there is a number on the tank tab, as was suggested by Steve. Being "741125" it very much looks like a date stamp (25th Nov 1974).

Then again, if we examine the website linked above (or for example the ... e-history/ , for that matter) the information is not at all consistent. This bike IS NOT fitted with rear shocks, battery or foot brake, but on the other hand IT IS fitted with the long rear fender and it has a six digit frame number and a six digit engine number.

In other words, there are mostly pre-1972 features as well as some post-1972 features. And the potential date stamp shows 1974 :D

Therefore, it just looks like the dating information on various websites is simply incomplete. This suggests that the export versions per year may have varied a lot.