MP7 Problem, Gear Timing
 

I got my MP7 when they first came out, and I bought it new. Since day one though, it's had some troubles. When firing on full-auto, the BBs would usually just drop out of the barrel and fly about ten feet. Semi-auto was better but it would often have the same problem. Not all the time though, which is strange. Now, when it does this, the gun sounds like it's dry firing. This makes me think that the nozzle is retracted when the piston moves forward to push the air out of the cylinder.

So, I took the gun apart, and upon inspection of the gearbox I have found that the gear timing apears to be off from the factory, since the nozzle was about half way back at 'zero'.

After opening the mechbox, I also found that the damping foam on the cylinder head was partially torn, and there was a chunk that was about to break free. I removed all the damping foam, since the asymetric nature of the torn foam would probably affect accuracy. That's a minor detail though. The main issue here is ger timing.

So: Has anyone here had similar issues? How did you fix it? Any thoughts or theories?

So, how did you fix the "timing problem"?

It only did that to me when the battery was weak.

In my experience, there is no such thing as "gear timing". The gears reset to "zero" after the completing one cycle.

I dont know how many times people have to say it, but, THERE IS NO SUCH THING AS GEAR TIMING. If you have any mechanical sense whatsoever, this should be very evident the first time you take a mech box apart. Your problems are coming from somewhere else.

LOL

Anyhow yeah I had the same problem with mine. till I lubed up the mags and fires great now

No such thing as gear timing? Maybe I'm not explaining this right... Sorry if my terminology is off here.

I'll put it together again with the loading nozzle/tappet plate all the way forward, i.e. the sector gear is not actuating the tappet plate at all.

OK, re-assembled the mechbox today, did a test run, and for some reason the piston got completely chewed. The entire first tooth is cracked off. No idea why, although I have heard of other people chewing up MP7 pistons.

This is really getting frustrating...

Just to add another .2 cents - when i first got mine, I had issues with BB's just plopping out or firing wildly. Same as Blastyman mentions, I tried a little silicone spray in the loading rod before filling it with BB's, which in turn lubed up the mag, its been 100% ever since. Hope it helps! (after you get a new piston...)

[bump]More input anybody?[/bump]

Sorry for the thread jack but you've gotta love it when people regurgitate what others have said yet don't offer any solution other than, "the problems are coming from something else". Sorry for the rant.

Nic,

Did you ever get this fixed? I seem to have the same issue.

EDIT*** Hummm, I cleaned out the berrel and lubed it up some more. Seem to be working better now.

Man this gun is worse than a woman.

All aep's suffer from the same problem.

When ever the, not feeding / bb's dopping / no distance or power thing comes up...

Just fill a mag with bb's, put a few drops of light weight silicone oil on the top bb in the mag.

Presto, problem solved.

As for the chewed piston.... that sux. Sorry.

your piston problem is quite obvious...

you removed the foam on the face of the piston head.... so your piston was always too far foward when the sector gear catch the first tooth, so it is slipping every cycle..

get a new piston head

yeah, you should be able to push the piston all the way foward in the cylidner till it stops(including cylidner head), then you should check to see if the sector gear grabs the first tooth.

Yeah if your ripping stuff off teh piston head, things are gonna hit the fan man:(

GO GO THREAD NECROING!

I haven't checked this thread in over a year (oops), but the piston spacing thing makes a lot of sense. I have also heard that these guns came from the factory with improper head spacing, resulting in chewed pistons. I'll probably buy an aftermarket piston/head combo, and try that, since I'm kinda getting into airsoft again.

For shits & giggles, doubt it's been mentioned before, but new guns are shipped with the hop up completely off. I only post this because I read "BBs roll out the barrel", classic example of zero hop up.

As far as 'gear timing', when mechbox is open, set the sector gear (the one that pull the piston back) with it's teeth away from the piston. All you need to do. None of this 'one O'clock' stuff, just make sure the teeth are away from the piston and you are good to go.

Stalker, did you ever try to assemble a mechbox with the sector gear engaged with the piston? Just curious to see how long it took to find all the parts on the floor, hehehe!!!

Nope, can't say that I have. :D Am sure someone out there did though.

(Had to say an oops last night, saw the thread and responses, posted my reply, saw it was an OLD thread. Say oops?)

Old thread, but still relevant and helpful to me. The hop up was adjusted, and all components, including the magazine, were well lubed.