Upgraded MP5 Speed Problems

[webtek23]

I just upgraded my TM MP5 with a M100 spring and metal bushings. I think that my gun may also be missing some shims, as I could only find like 5 inside the mechbox. I lubed all the gears with white lithium grease and then reassembled. The gun also has a 9.6V 2400Mah battery. When I fire the gun it has a very low ROF. I was under the impression (from looking at what other people said about their equivalent guns) that this setup would give me some great power (around 350fps) and still maintain a high ROF. Could something be wrong? I already ordered new shims so that I can eliminate that problem. Could there be another reason? The gun has a EG700 motor which I have heard are more for high torque, low rpm applications. Could that be the reason? Would an EG1000 make that much of a difference? I did get the gun used, so let me know of anything else you could think of that could be affecting ROF

[Greylocks]

Check the mechbox assembly again. Maybe something is binding.
Check if the battery is fully charged.
The ROF should be a bit slower than with stock parts, but not that slow.
The more power you try to get, the slower the ROF will be unless you start getting into a lot of expensive upgrades.
Pick what you prefer; power or ROF.

My opinion; the point of this game is to touch someone with a BB, not blow it through them. So simply adjust your gun properly instead of tossing in parts.
350fps is very safe, so my bet is on you not being familiar with upgrading.

Find someone local to you who knows more, and go see them.

[webtek23]

The battery is fully charged and I have already done quite abit of upgrading, however this gun was used and I think there may be some underlying problems I have not seen. The gear timing and everything was setup properly, and I just thought that this setup especially with a 9.6V battery would have a higher ROF. Any other suggestions on what to look for? If I cannot fix this myself, then yes I will take it to be looked at.

[Mantelope]

Sounds like you messed up the shims and made it too tight somewhere. Take it to someone with experience shimming.

[mcguyver]

Look at the amount of grease used and where it is applied. Lithium is a very sticky grease with good surface tension. It will coat your gears and mostly stay there forever. However, if you used too much, especially on the back side of the spur and bevel gears, it can add so much resistance to the turning of those gears as to make one think that the mechbox is over-shimmed. This could be your problem.

As far as shims go, any guides that tell you how to shim and which ones go where should be used for toilet paper and nothing else. The number of shims, where they go and what size to use depends on the mechbox, bushing and gear combimations. There is no right answer to exactly how many get used, and I've done some boxes with less than six and some with almost 20 shims.

The EG700 has to be the best Marui motor out there. It can turn a 190% PDI spring in my SPR/a at 15 rnds/sec shooting 450+ fps with a 9.6v 2100mah battery. So I don't think that is a problem for your gun.

And as stated before by myself and others, there is ABSOLUTELY NO SUCH THING AS GEAR TIMING. It has to be the biggest myth in airsoft.

[webtek23]

Ok, well as for the issue of gear timing, could anyone give a link to a good site that would talk about the basics of how to install and calibrate new shims. Also, there are several screws missing from the gearbox. Where could I get new ones? Can I order them? Should I check home depot?

[CDN_Stalker]

Gear "timing" is a myth, it's only the relationship between where the anti-reversal latch is set in relation to the sector gear position. Enough proof out there based upon experience to prove it. Timing, nah. Setting the two up properly, yes. Some claim that you can set it anyway you want, it'll auto-set itself. In which case if the piston jams full back and won't cycle, no amount of trigger pulling will auto-set that.

I think that most likely the battery isn't able to put out enough juice to supply th motor under load. My MP5 when I ran on 8.4V 600mAh mini-batteries, had a great rate of fire and would last for 1100-1200 rounds. When I put in my 150% spring, the rate of fire dropped about half, and my batteries only lasted about 400 shots. Jumping my battery up to an 8.4V 3300mAh battery made the rate go up a fair bit, but still under what stock gave me. Tried a 9.6V 3300mAh battery, rate went up to almost stock levels. I'll add in that unless the mechbox was properly shimmed (as in trained eye & feel), then it could be done up too tight and causing all kinds of problems.

[webtek23]

Ok sorry I should have used the term "gear timing" in my last post. That wasnt really what I was asking. I wanted a site that gave advice on how to shim the gears in the mechbox (the only one I am looking at now is a install guide on Arnies Airsoft for a Super High Speed Full Tune Up Kit). So a link there would be appreciated as well as my earlier question about where I can get new mechbox screws

[CDN_Stalker]

Might be a good idea to let be known roughly the rate of fire you have now. Like "it takes you 10 seconds to empty a 50rd mag" kinda slow slow, or it takes 4-5 seconds where the stock set up took 3 seconds to empty? Upgrading with a heavier spring will give you a lower rate of fire than stock as it is. You might try your gun with a higher mAh battery as well to see the improvement (there will be one) in the rate of fire and see if it's satifactory to you.

[mcguyver]

Start your shimming with the spur gear first. Pick a shim for the bottom and set your sector gear in next with the shim to align it properly with the spur gear. Do the same for the bevel gear. Then put shims on the tops of all three gears and assemble the mechbox (use the screws) without the cylinder parts or spring. You should have good rolling of the gear train with virtually no lateral gear play. If it's not the case , keep adjusting your shims until you get it. Real simple and no "tutorial" can help you with that.

All you need is your eyes and a small screwdriver to try to move the gears laterally.

As for setting up the ant-reversal latch with the sector gear position, some will argue for and against it. I think its a waste of time personally, as I've seen between 1 and 5 anti-reversal stops on various makes of bevel gear. Couple this with the rate of gear reduction, and what you get is miniscule sector gear movement between stop points. It's not enough to make any difference for anything, including "trigger lag".

I've never seen a piston lock back, except when is was twisted in the piston guides.

[webtek23]

Ok roger that on the shimming. I will try that later. I still wanna get these missing mechbox screws though. Where can I order them, or where can I go buy them (Home Depot, Lowes, etc)?

[mcguyver]

They are metric threads on some and a "sheet metal" type thread on others. Depending on which ones you're missing, it's worth a try. Just make sure that your new screws are countersunk precisely where they need to be and no larger than the originals in other places. Or you may have a tough time reassembling your mechbox into the gun body.

[Cerwin]

Dude this is a fairly detailed tutorial of a mechbox

http://www.airsoftplayers.com/mechbox/tutorial.asp

hope it helps

[webtek23]

Yeah I have read that many times lol. Any more info on those screws? I could really use a link to them on home depot or something...

[CDN_Stalker]

Zero chance you will find those screws in a hardware store. Best bet would be to try a hobby shop or something. Seeing as how a lot of RC cars and such are made in Japan, I'd say if you bought in examples of the screws they will have something in stock or in the back.