Significant Fps drop

[SeanBeey]

Good morning all, I recently installed a Titan mosfet to my firehawk before this it was firing a consistent 340fps, after completing the build my fps has dropped to 240 I’m pretty sure im loosing pressure between the nozzle and hop unit. I’ve done the compression tests for the cylinder and piston and it’s holding really well, is there any way of testing the nozzle to hop seal ? 

Currently running stock gears m110 spring 

 

[Asomodai]

Cant help with regards to hop and nozzle pressure.  But even 340 fps is poor considering you have a M110 spring. You should be achieving 340 on a M95/M100

 

[SeanBeey]

Cant help with regards to hop and nozzle pressure.  But even 340 fps is poor considering you have a M110 spring. You should be achieving 340 on a M95/M100

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I don’t know why is has the m110 previous owner installed that, I might find once this issue with air seal is resolved I may have to drop the spring to a m100 

 

[Adolf Hamster]

Cant help with regards to hop and nozzle pressure.  But even 340 fps is poor considering you have a M110 spring. You should be achieving 340 on a M95/M100

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could be short stroked, would explain the drop.

look up the feeding tube see how the nozzle is interacting with the hop, one way to check is to lightly cover the end of the barrel with a finger and feel if there's air being blasted out from the feed tube.

that's if you changed the hop rubber while working on it, otherwise i'd be double checking the box itself, could be the nozzle isn't sealing against the cylinder head.

 

[SeanBeey]

could be short stroked, would explain the drop.

look up the feeding tube see how the nozzle is interacting with the hop, one way to check is to lightly cover the end of the barrel with a finger and feel if there's air being blasted out from the feed tube.

that's if you changed the hop rubber while working on it, otherwise i'd be double checking the box itself, could be the nozzle isn't sealing against the cylinder head.

Click to shrink...

Will try this after work thank you 

 

[SeanBeey]

Update, when I block the barrel end the air comes out of the fill tube? 

 

[Adolf Hamster]

Update, when I block the barrel end the air comes out of the fill tube? 

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make sure you're not blocking the barrel too heavily, does the nozzle look like it's making good contact with the hop lips when you look down the loading tube?

could be if you've changed hop rubber that the feed lips are too short giving a bad seal (i've also seen them get pulled open during installation particularly on tight hop units like madbull), or possible the whole unit is sitting too far forward (normally there's a plastic block, screw or spring somewhere who's job is to make sure the whole hop is pushed back against the gearbox properly)

other alternatives is the tappet plate/nozzle could be binding meaning it's not going fully forward, give it a push with your finger see if it runs smoothly.

 

[SeanBeey]

If I remove the hop chamber and barrel completely from the outer barrel and push it tight against the gearbox whilst blocking the barrel it makes a seal and no air comes from the fill tube, however when the gun is back together it appears to be hard against the gearbox but the air comes from the fill tube, I’m sure it’s gearbox related as this issue wasn’t there before I fitted the Titan and the hop unit/ rubber hasn’t been touched, is it possible for the gear timing to be out of sync with the nozzle ?