Old MTB servicing query parts

[monkeyspanner]

Hello people

I bought an MTB second hand some years ago , it must be about circa 2010, it was in reasonable to good condition but the last owner never really serviced it . So i set to and cleaned it up and fitted some new parts cleaned and re-greased , the usual stuff. It is a KONA Fire mountain with the 7005 ali frame and quick release wheels . Shimano gears and rock shox dart one forks.
After that i used it for a short while it then sat for some years until now when i delved deeper into it to get it on the road again and something i never noticed before has got me thinking . The front axle appears to be too short for the fork drop outs as only 3-4 mm is engaged into the inside of each drop out. surely the threaded ends should engage the full thickness of the dropout which is 8mm ?.
The front hub is a Quando high performance. The two wheel rims are different as well , which makes me wonder why ?
The front is a 26" x - plorer by Weinmann in disc braking format , the rear rim is a ZAC Rigida 79 26inch.
So why would someone put two different rims on a bike and what were the original rims in the sales catalogue of that circa 2010 ?.
The rear hub is FH M475 which i have rebuilt .
The inner tube schrader valve is too short for the x-plorer front rim so can i buy tubes with longer schrader valves ?.

Any help appreciated please

[531colin]

Sounds like one wheel has been replaced.
No idea about Schrader valve length!

[PT1029]

Don't worry about the front axle. The amount of axle sticking out is normal, and designed for standard (steel/non suspension) fork dropouts.
Suspension forks normally have quite a fat dropout thickness.
Non matching wheels is a cosmetic thing. The important thing is they are the same diameter (not always the case on used bikes!!).
Some makes of tubes come with longer schraeder valves than others, so you might have to look at a few different makes to find a longer valve (take the old tube with you to compare?)..

[Brucey]

probably the rear wheel has been replaced; statistically speaking, rear wheel failure is ~x4 more likely. The last bike I had with ZAC 19 rims got changed to presta valves because I used epoxy resin to bond Al inserts into the rims. If a valve seems too short, it may just be badly fitted, so check this first.

[monkeyspanner]

the schrader valve is 33mm on the x plorer rim and can just about get the nozzle onto it for inflation , its quite a tall rim.
I dont know why the rims are differrent and i,m not sure what the previous owner did to the bike ?. But when i initially took it apart years ago it was filthy, the grease was as thick as hard butter, i had never owned an MTB before .