When to shim??

[MaritimeManiac]

I've been looking into cracking the GB on my cm16 R8-l for the first time to see how everything looks on the inside but before I did I was hoping to get some answers.
This would be my first time shimming an airsoft GB, although I've rebuilt 4 stroke engines and such, so as long as I take my time I should be able to handle it.
Just curious when shimming should be done? How well shimmed do they come from the factory? From what I read the R8-L is the gun to buy as far as reliability and performance go for the combat machine line of guns and price range, so I shouldn't have to worry about doing too much to the innards too soon, but I've probably put almost 5000 bb's down it and I'd prefer to get preventative care done sooner then later so I'm not dropping everything on it at once when something breaks.

[ThunderCactus]

Always shim any new gun as soon as you have a chance.
They DON'T shim them from factory, they just throw shims in there and CALL it shimmed.
If you have a vernier it'll make shimming MUCH easier and MUCH faster.
Just don't let the gears rub together, don't let the sector gear squeeze the tappet plate against the mechbox shell, and check the bevel-pinion height and make sure the pinion fully engages the bevel.
Someone will tell you the bevel-pinion height is the most critical thing in the world, but it's not. As long as the pinion fully engages the bevel when the motor height is set, there's no need to split hairs. Any fine tuning of that adjustment can just be done with motor height afterwards.

[MaritimeManiac]

That's what I figured thanks thunder... I read they stepped up RD and the quality of parts put into G&G but didn't think they went as far as to make sure everything was properly shimmed. As for the vernier I have some precision measuring tools from doing valves and such on my dirtbikes and everything so I shouldn't have any issues there. Now that I know when to do it I'll keep a "how to" thread open when I do it and hopefully it's smooth sailing... Thanks for info!

[Spike]

Shimming bevel to pinion is the "proper" way to shim, though. If you're going to do it, you should do it right.

While you have the box open, you should also correct your angle of engagement. It can be done a number of ways, there's plenty of threads and videos on it.

[MaritimeManiac]

Originally Posted by Spike

Shimming bevel to pinion is the "proper" way to shim, though. If you're going to do it, you should do it right.

While you have the box open, you should also correct your angle of engagement. It can be done a number of ways, there's plenty of threads and videos on it.

Yeah I read up on making sure you start at bevel to pinion and go from there, some say start in the middle which just sounds rediculous to me from a mechanical stand point.

As far as AoE, ill read up on it more but i believe its something along the lines of adding sorbo pads or something of the like to the back of your cylinder head, making your piston sit father back and taking off some teeth? I'm likely slighty off with that explanation but again, ill look up on that too...thanks. I'm assuming the bushings don't come glued in place either so I might look into using a JB Weld or something to lock em in.

Anything else anyone can think of to take look at while I have it cracked open? I found some pretty detailed threads on Airsoft Society and here that seem pretty reliable so I'll just follow those as best as possible.

[Spike]

Bushings don't NEED to be fixed in place unless they're particularly loose. Like anything technical related, depending on who you ask, you'll get different opinions on that.

You're right on the AoE adjustment. You want the pickup tooth of the piston to mesh with the first tooth of the sector gear as much as possible. Sorbothane padding is the best way to do it, as it also helps reduce the shock of the piston assembly on the gearbox, but shimming the piston head with some light washers will also work.

G&G also tends to over grease their piston heads, so you might also want to clean and re-grease that.

[Styrak]

G&G's are pretty good out of the box, FYI.

[L473ncy]

Keep in mind that this sport is also plagued with 12 year olds who spout off crap or themselves believe in things like melded springs or other ridiculous crap like how some guns can break the laws of physics (AEG vs GBBR vs PTW vs Polar Star) or can't seem to grasp the concept of how mass, velocity, and energy interact with each other.

The only other thing I can add here is Airsoft Mechanics is a great site. Don't post there, just read and if you do need to post, have a well researched question. It's a goldmine of good information.

But like Styrak said, G&G's are good out of the box and ideally you shouldn't be messing with the internals unless you really know what you're doing, and you should figure out what the OEM baseline performance is before you mess around with things, but if you've dealt with fixing up MX bikes this should be a cakewalk.

[MaritimeManiac]

That's what I heard about the R8-l is that right outta the box there isn't much to do internally other than cleaning up parts a bit and doing the work stated above.

I think I should be good on getting the job done right if I take my time... None of my bikes have blown up yet because of a bad rebuild so hopefully that transitions over to Gearbox haha.

Appreciate all your input! I likely get a bit more feel for the gun and do some more research before I jump into things too quick.
Thanks again!

[lurkingknight]

Originally Posted by Spike

Bushings don't NEED to be fixed in place unless they're particularly loose. Like anything technical related, depending on who you ask, you'll get different opinions on that.

You're right on the AoE adjustment. You want the pickup tooth of the piston to mesh with the first tooth of the sector gear as much as possible. Sorbothane padding is the best way to do it, as it also helps reduce the shock of the piston assembly on the gearbox, but shimming the piston head with some light washers will also work.

G&G also tends to over grease their piston heads, so you might also want to clean and re-grease that.

Bushings can eventually grind the holes out over the course of the life of a gearbox, adding a couple drops of CA on the outside of the gearbox to help tack them in place will prevent it.

G&G v2s need sorbo, otherwise the front will crack off long before the bushings ream themselves loose.

[MaritimeManiac]

Alright... So what I have so far that I'm going to be doing when I do open up my GB (not in this order of course) is clean parts, hopefully get all gears shimmed properly, probably get the bushings glued in place just to give me the peace of mind and change the aoe.

Now I'll look into what the process is to adding the sorbos to the GB as well and it will be added to the list, with possibly a few other things if theres something else I find might be smart to do.

[lurkingknight]

sorbo pad IS the AoE adjustment.

people have shimmed between the piston body and the piston head but that adds weight to the piston assembly.

Take a 3/16 sorbo and remove the rubber pad off a good cylinder head and glue the sorbo in it's place. That's pretty standard fit for v2. some piston and pistonhead combos require more or less.

[ThunderCactus]

I guess everyone would jump at metal washers before looking at plastic washers eh?

[lurkingknight]

probably but the washers don't prevent the front of the gearbox from cracking off :P