From what I've read, my friend's bike must be about 1989......We need a manual to put it back together...The number on the frame is F6123876. Please help! We are missing out on too much looking @ it on my workbench

There aren't usually manuals for bikes the way you can get Haynes Manuals for cars, but they're usually far more generic than cars, so you can usually manage with stuff like the Park Tools tutorials. Sheldon Brown's website also has a lot of information.

Just how far have you taken it to bits?

Are we talking Diamond Back BMW or Diamondback MTB? Vintage BMX can offer some help but you will not find a repair manual specific to one model and year of bike. As suggested above, go to the Park Website and you can search by area on the bike for repair help. https://www.parktool.com/blog/repair-help

Besides my opinion that there are no Diamondbacks worthy of being classified as vintage as opposed to just plain old, there's nothing exotic or special about your bike, so any general tutorials or basic bicycle repair books will cover what you need to know to get this working right.

As a rule, tutorials aren't usually comprehensive, so you have to divide the job into categories, such as align wheel, service hub bearing, service BB, etc. and work your way through the bike part by part.

Oh dear.

I sense an exciting journey of discovery in the offing...

Even the tutorials online at the best sites (parktools.com/blog, sheldonbrown.com are two of the best) do not necessarily cover all situations. Park's site in particular focuses on "lab" conditions - parts are clean, lubricated, not bent or corroded, compatible with each other, etc. Your friend's bike of course does not have such luxuries, and if it's disassembled there may be missing parts, the cost of which can quickly add up. As you seem to be starting from scratch and I have no knowledge of your mechanical aptitude all I can say is that you have to balance time, energy and money in order to decide how to proceed.

If you want to get the bike on the road quickly and safely then I would take it to a shop to at least obtain an evaluation of what is needed short and longer term. Perhaps get what is needed for safety done by them and then learn to do the rest gradually - if you are willing to invest both time and energy. It takes both time and effort to seek out, understand, and then apply the proper repair procedures when you have never worked on a bike before.

It's a BMX. There's not a whole lot going on there.

Learn how to set the preload on a bearing, and sort out a brake, and that's pretty much all you need...

Although if you have trouble figuring out how to reassemble the bike, I'd suggest getting assistance from someone who has a bit of experience with bikes.

If you take a bunch of pics, we can probably get you there.

Where did the OP say it was a BMX? Diamondback made (make?) MTBS too, I've got one from sometime in the '80s.

What about the Axis /Axis TT (high end steel and Titanium versions) and Vertex WCF series (early carbon fiber), granted now they are just a Accell brand, but back in the mid 90's they made some very good MTB's, which fall in to the retro category, as for vintage, they are still 20-30 years too young for that

i think a lugged mountain bike with bull moose bars from 1982 would count as vintage





PS, OP, pretty sure that serial # indicates 1986 manufacturing year

Wow, had NFI DB were doing MTBs that early. Any half-decent MTB pre-86 or so is a collector's item, innit?

Oops, thought he did for some reason.

The serial number F6 would allude to a 1986 bike, so quite possible BMX as pre- mountain bike

F6123876. is Fairly bike serial number company Taiwan, 6 is 1986 and 12 is 12th month, so December. Almost certainly a Diamond Back BMX.

I expect after 9 years, the OP has either figured it out or given up.