ver.2 question

[Rogue46]

so upgrading was very good on my m4 (j&G) used t.m and modify guts,but now it is louder than before.and i wondered if turn the piston cylinder where the air slot is to one side horizontally, right now its lined up on the underside,lined with the piston teeth will that make a difference??i wasnt certain if it would make a diff. where it was.help tip please.thanx

[yuhaoyang]

Keep the porting to the outside of the mechbox.
Adjust your motor height, or check your gear shimming.
Also, do you mean JG or G&G?
what parts did you replace?

[Kos-Mos]

Porting position is completely irrelevent. It will work regardless of where it is.

As for the noise, you probably shimmed the gears wrong. Each time you change the gears or bushings, you have to redo the shim job from the start.

Motor height can also be the reason, but I think it is more the shimming that is the problem.

[rogue 46]

t.m shims modity gearset.modify bearing piston guide.stock t,m spring.using a 8.4 1100mah.so ok i might turn the cylinder so the slot is to one side. it may be "gasping" for air intake alittle.

[rogue 46]

yeah ..when i was apart, i set the gears in only and gave it the spin.nice and smooth,i shimed the sector gear with two shims and one one the tranny.that maybe why?

[yuhaoyang]

actually that isn't the intake, the cylinder port is to expel excess air, turning it to the side will stop it blowing the grease off your gears.

Anyways, if all 3 gears turn smoothly, then check your motor height, and check how well your sector gear teeth mashes with the piston teeth.

[CDN_Stalker]

Originally Posted by rogue 46

yeah ..when i was apart, i set the gears in only and gave it the spin.nice and smooth,i shimed the sector gear with two shims and one one the tranny.that maybe why?

Each gear MUST be shimmed one at a time (start with the middle one), put the mechbox shells back together and put some screws it (two will do), then give each gear a spin to see if they move freely, then check for too much side to side shifting. Once you get the spur (middle gear) shimmed right, move to the sector gear (the one that pulls the piston back), and while keeping the middle gear in place, shim it on the left side so it clears the spur gear teeth (no rubbing), then put the shells back together with screws, spin test and side to side, when good move to the bevel gear (obviously the last one). Generally no shim is placed on the bottom axle of it so it helps mesh with the motor, but do the same shim and test with all the gears in place. All gears should spin freely for a couple turns together, and once that's done you reassemble the mechbox and install. Might take you up to an hour to do a perfect shim job, but it's worth it.

[yuhaoyang]

Just as a theory, I still think that the bevel gear should be shimmed like all other gears, if it were to mesh with the motor because the pinion gear is pushing it up, I think that it would create an uneven distribution of force on the gear axle, and if the bushing or gear quality is poor (there is a gear wobble, even if unnoticeable), it would cause gear tilt, and mess up the teeth meshing with the spur gear as well... And I run 2 bearings with the bevel, which are more susceptible to damage, so just as personal preference I would recommend just regular shimming on the bevel, and then accordingly adjusting the motor height.

You won't really come off any worse?

Then again, I'm just a perfectionist.

[Azathoth]

Originally Posted by yuhaoyang

actually that isn't the intake, the cylinder port is to expel excess air, turning it to the side will stop it blowing the grease off your gears.

No, The point of the port is to reduce air volume in the cylinder see the sticky by madmax in regards to matching cylinder volume to barrel volume.

You are somewhat correct. during the back stroke of the piston (during compression) lubricant and grease can be dragged by the piston, the amount of gunk is likely minimal.

[Kos-Mos]

Originally Posted by yuhaoyang

Just as a theory, I still think that the bevel gear should be shimmed like all other gears, if it were to mesh with the motor because the pinion gear is pushing it up, I think that it would create an uneven distribution of force on the gear axle, and if the bushing or gear quality is poor (there is a gear wobble, even if unnoticeable), it would cause gear tilt, and mess up the teeth meshing with the spur gear as well... And I run 2 bearings with the bevel, which are more susceptible to damage, so just as personal preference I would recommend just regular shimming on the bevel, and then accordingly adjusting the motor height.

You won't really come off any worse?

Then again, I'm just a perfectionist.

Too much to one side will cause problems. But centered is most of the time wrong. It need to protrude in the motor hole just past the beveled teeth. Any more will cause the motor to be too outside and too little of the gear surface will engage. Too inside and the motor will hit the notches to that interact with the ARL.

[CDN_Stalker]

Originally Posted by yuhaoyang

Just as a theory, I still think that the bevel gear should be shimmed like all other gears, if it were to mesh with the motor because the pinion gear is pushing it up, I think that it would create an uneven distribution of force on the gear axle, and if the bushing or gear quality is poor (there is a gear wobble, even if unnoticeable), it would cause gear tilt, and mess up the teeth meshing with the spur gear as well... And I run 2 bearings with the bevel, which are more susceptible to damage, so just as personal preference I would recommend just regular shimming on the bevel, and then accordingly adjusting the motor height.

You won't really come off any worse?

Then again, I'm just a perfectionist.

If you shim the bevel gear away from the motor gear, it'll cause the motor gear to not mesh properly and cause it to slip off. I only mentioned it because of experience, not because of any theory. One thing you should know about me, I mostly speak from things I've seen, that is my opinion based upon experience and from having to fix and upgrade many dozens of guns over the past few years. I'm not just picturing things in my head, I'm actually saying what happens in most cases because I had to unfuck many guns. Under the bevel it's either a very thin shim, of no shim at all. There is no guide for this, it's all based upon the parts at hand, the gear type, bushing type, mechbox type, etc. Everything has to be custom setup based upon what the system is. No guide will give you everything you need simply due to the fact every manufacturer has different tolerances.

[yuhaoyang]

Originally Posted by CDN_Stalker

If you shim the bevel gear away from the motor gear, it'll cause the motor gear to not mesh properly and cause it to slip off. I only mentioned it because of experience, not because of any theory. One thing you should know about me, I mostly speak from things I've seen, that is my opinion based upon experience and from having to fix and upgrade many dozens of guns over the past few years. I'm not just picturing things in my head, I'm actually saying what happens in most cases because I had to unfuck many guns. Under the bevel it's either a very thin shim, of no shim at all. There is no guide for this, it's all based upon the parts at hand, the gear type, bushing type, mechbox type, etc. Everything has to be custom setup based upon what the system is. No guide will give you everything you need simply due to the fact every manufacturer has different tolerances.

Ack I misunderstood your original post. I thought you were referring to what crunch had said before about leaving the bevel gear free to wobble up and down, because the pinion gear pushes up his bevel gear.

But yeah, again, my misunderstanding, and yes, to the OP, the lower down the bevel is the better, under the condition that it doesn't rub against anything.

[CDN_Stalker]

Yup. And the space between the gears is important too.

Regarding the port, it's not to get rid of excess air, it's to match the cylinder volume with the barrel volume. MadMax had a good article on this a few years ago, the difference between ported and non-ported is basically 'hard start and soft start', in a short barrel you need to have 100% power right at the start, so the port is there to do that, the piston is moving at full speed and by the time the head meets the end of the port, full power is applied once sealed. In a non-ported gun, because of the longer barrel length (and greater internal air volume), the soft start is allowable because the BB will still be in the barrel by the time the piston reaches full power stroke.

And, for the heck of it, I tried a full cylinder in my 350fps MP5 at one point, I lost 30fps.

[Con Murder]

YA just finished swapping out a A&K m4 gearbox internals and it was a non ported cylinder. The gun was at a ball crushing 280 fps with .2 and this guy had been playing all year like that!!! Shame is he killed me more than anyone else this year!!

[coach]

Originally Posted by Con Murder

YA just finished swapping out a A&K m4 gearbox internals and it was a non ported cylinder. The gun was at a ball crushing 280 fps with .2 and this guy had been playing all year like that!!! Shame is he killed me more than anyone else this year!!

those are stock marui numbers. I know there are a few guys that have been running marui's bone stock for years. never needed to upgrade as they are happy with the consistent 280fps.