Working on a KWA M4A1.

baker_Jeff · December 1st, 2010, 18:54

It needed a new cylinder head. Replaced that. Piston oring wasn't sealing, so I replaced that. Put everything back together, test fired, and the tappet plate broke. Well crap.

Took it apart and replaced the tappet. Double checked everything, good seal on the piston and all that. Put it all back together and test fired... shooting 150fps.

The thing is... if I turn the gun upside down... FPS will jump to 390. I'm using Green Devil BBs and a midcap.

I've never seen this before. Any suggestions?

spartan117 · December 1st, 2010, 19:30

Quote:

Originally Posted by baker_Jeff

It needed a new cylinder head. Replaced that. Piston oring wasn't sealing, so I replaced that. Put everything back together, test fired, and the tappet plate broke. Well crap.

Took it apart and replaced the tappet. Double checked everything, good seal on the piston and all that. Put it all back together and test fired... shooting 150fps.

The thing is... if I turn the gun upside down... FPS will jump to 390. I'm using Green Devil BBs and a midcap.

I've never seen this before. Any suggestions?

have you check the hop up?

baker_Jeff · December 1st, 2010, 21:13

Tried with hopup all the way on, all the way off, and in between. No difference

Canadian Psycho · December 1st, 2010, 22:08

Try checking the lower hop-up feeding tube. Often that will get mis-aligned and cause the FPS to drop like that.

baker_Jeff · December 1st, 2010, 22:10

Quote:

Originally Posted by Canadian Psycho

Try checking the lower hop-up feeding tube. Often that will get mis-aligned and cause the FPS to drop like that.

Oooh good tip, will check tomorrow and report back. Thanks fellas.

baker_Jeff · December 2nd, 2010, 13:14

It appears to be okay, and is nice and tight. Wtf

Any other suggestions?

skavnjer · December 2nd, 2010, 13:39

I would suggest trying a different mag. but whatever the issue is, it has to be something that is damaged/loose. maybe something with the nozzle, it could be something to do with the hopup assembly (right side up something getting in the way, upside down it moves out of the way kinda thing...) check the hopup chamber for obstructions.

Amos · December 2nd, 2010, 13:39

Did you use the proper V2 cylinder head?

baker_Jeff · December 2nd, 2010, 13:47

Yeah, OEM replacement.

BuyAirsoft.ca · December 2nd, 2010, 14:46

Try swapping out the feed tube with a different one, I had a gun where that fixed it not to long ago, no idea why it went screwy, but its worth a shot.

Also, check the nozzle to make sure its moving its full travel.

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December 1st, 2010, 18:54	#1
baker_Jeff Trader rating Join Date: May 2008 Location: Edmonton, AB	Working on a KWA M4A1. It needed a new cylinder head. Replaced that. Piston oring wasn't sealing, so I replaced that. Put everything back together, test fired, and the tappet plate broke. Well crap. Took it apart and replaced the tappet. Double checked everything, good seal on the piston and all that. Put it all back together and test fired... shooting 150fps. The thing is... if I turn the gun upside down... FPS will jump to 390. I'm using Green Devil BBs and a midcap. I've never seen this before. Any suggestions? __________________ Founder of Capital Airsoft in Edmonton Out of the Game 04/22/16

December 1st, 2010, 21:13	#3
baker_Jeff Trader rating Join Date: May 2008 Location: Edmonton, AB	Tried with hopup all the way on, all the way off, and in between. No difference __________________ Founder of Capital Airsoft in Edmonton Out of the Game 04/22/16

December 1st, 2010, 22:08	#4
Canadian Psycho Personal Mule.....PM for rates! Trader rating Join Date: Oct 2004 Location: Alberta	Try checking the lower hop-up feeding tube. Often that will get mis-aligned and cause the FPS to drop like that. __________________ "Those who have long enjoyed such privileges as we enjoy, forget in time that men have died to win them" Franklin D. Roosevelt

December 2nd, 2010, 13:14	#6
baker_Jeff Trader rating Join Date: May 2008 Location: Edmonton, AB	It appears to be okay, and is nice and tight. Wtf Any other suggestions? __________________ Founder of Capital Airsoft in Edmonton Out of the Game 04/22/16

December 2nd, 2010, 13:39	#7
skavnjer Trader rating Join Date: Jun 2009 Location: London, Ont	I would suggest trying a different mag. but whatever the issue is, it has to be something that is damaged/loose. maybe something with the nozzle, it could be something to do with the hopup assembly (right side up something getting in the way, upside down it moves out of the way kinda thing...) check the hopup chamber for obstructions.

December 2nd, 2010, 13:39	#8
Amos Trader rating Join Date: Aug 2006 Location: Japan	Did you use the proper V2 cylinder head? __________________ Custom Builds: FA3674U Krinkov G3SD6

December 2nd, 2010, 13:47	#9
baker_Jeff Trader rating Join Date: May 2008 Location: Edmonton, AB	Yeah, OEM replacement. __________________ Founder of Capital Airsoft in Edmonton Out of the Game 04/22/16

December 2nd, 2010, 14:46	#10
BuyAirsoft.ca Trader rating Join Date: Oct 2010 Location: Central Alberta	Try swapping out the feed tube with a different one, I had a gun where that fixed it not to long ago, no idea why it went screwy, but its worth a shot. Also, check the nozzle to make sure its moving its full travel. __________________

Working on a KWA M4A1.

Doctor's Corner