KS P90 - Shredded Piston - Where to start?

[Mr Brainz]

So I think I shredded my piston on my Cybergun / KS P90.

I wanted to have a crack at fixing it myself. Not sure what I need.

What I would love is:

• Recommendations for a piston (don't know what one I need)
• Recommendations for a new spring (gun is hot - 390fps)
• Anywhere there's a guide that may help me

Hope someone can help.

Thanks,

B

[Clone1B]

Re: KS P90 - Shredded Piston - Where to start?

M90 spring, any piston which matches your current one's tooth count and with some metal teeth on the end.

[badger906]

Re: KS P90 - Shredded Piston - Where to start?

youtube would be your best bet for a guide. Just type in "version 6 gearbox"

I recently picked up an SRC 15 tooth piston on ebay for £12, has half metal and half plastic teeth. I was impressed by the piston for the money, as normally i go madbull or systema ect and pay £££.

When it comes to springs im a guarder fan, a m90 spring will give you roughly 300fps, and an m100 will again give you roughly 328fps. other factors obviously play a factor.

Luckily for you version 6 gearboxes are by far the easiest to work on! just make sure when you take it apart, you have the air nozzle pointing to the right (as that will mean when you sperate the gear box, the bottom is the half left on the table)

Also note the orientation of the oblong shaped bushings, as they can go one of two ways

[airsoftman227]

Re: KS P90 - Shredded Piston - Where to start?

i like prommy pistons personally.... and id fit an m90 spring.

have a crack by all means, but if you dont feel completely happy doing it, id get it done by a techie.... itll be cheap. i mean, i only charge 15 for a complete rebuild and reshim!

[Benjii]

Personally, I always go for the same piston. SHS half steel toothed piston. As far as spring guide go's, I would go for a SYSTEMA bearing spring guide, run like a beast. And for springs, I go for madbull/element.

Hope it helps!

Ben.


Sent from my iPad using Tapatalk HD

[Mr Brainz]

Thank you all for your replies.

I found an American video with a guy changing the piston on an Echo-1 P90. He had exactly the same problem with a bad BB getting jammed and it shredded his piston. His gun is making an identical sound to mine. I was using a fresh tub of King Arms 0.28s. Was on the 0.28s to try and keep the FPS down. Looks like I'm going to have to write off those 10,000 I bought.

When my mate tried some in his TM M4 they were jamming on Semi every now and again. That should have been my first hint they were shifty.

I've had the back off and pulled the gearbox out. I'll have to watch some version 6 gearbox vids before going for it. So thanks for that tip.

Is it wise to double check the number of teeth on the piston as originally suggested, or is there a specific name for the one I need?

Thanks for your help again.

B

Sent from my GT-I9300 using Tapatalk 2

[badger906]

Re: KS P90 - Shredded Piston - Where to start?

just like to recomment on my post, i meant SHS piston not SRC my bad :P

[Mr Brainz]

Cool. I've re-read everything posted and after looking around on shop sites the stuff makes more sense.

I'm still close to cutting my losses and buying a brand new TM one.

Still. Gonna have a crack later this week as I'm pretty skint right now.

I'll let you know how it goes!

Thanks again for the help.

[jagillham]

Re: KS P90 - Shredded Piston - Where to start?

Using heavier BB's to get below 350fps is CHEATING and DANGEROUS! A good way to get banned from the local sites! FPS only measures speed, but is used to work out power. Takes more power to throw something heavier at same speed! (Rather I threw a tennis or cricker ball at you at say 40mph?!)

To correct the above post, Guarder springs are rated in SP, not M. Secondly, the SP90 is approx 330fps, the SP100 being approx 360fps.

[Mr Brainz]

Hey I know mate. I got stitched up by a gentleman on here saying the gun chronoed at 330.

My site threatens to chrono every time but never does. So I risked it. I'm fairly new to this so I'm still learning. I didn't "cheat" intentionally.

The shop that chronoed the gun for me suggested the heavier BBs as a way to get around it. I was trying to keep to the rules. Obviously the shop just wanted to sell me more expensive BBs. You could say karma caught up with me.

It's probably the last time I ever buy a second hand gun or buy a cheap Chinese brand.

[jagillham]

Re: KS P90 - Shredded Piston - Where to start?

Ditch the shop, not 2nd hand goods! You can pick up own chrono for under £30, or change a spring for £10 + some of your time.

It's all great saying "Oooops" after the event, but shaking the guilt of taking out somebodies tooth (or even eye?) takes a little longer. I doubt you'd want people firing your direction with kit they "assumed" was OK. Often it is the same people who "assume" the weapon is clear before blinding some poor sod in the safe zone!

Running at 350fps .28's will be fine (should carry nicely infact) and will be equally good in a GBB pistol - so all is not lost!

Lesson for today, take advise from places like here from several people, rather than a shop who wants your cash.

[badger906]

Re: KS P90 - Shredded Piston - Where to start?

i dont know what reputable shop would give the advice of using heavier bb's to lower the fps for a chrono such places should be shut down!!

My local site (urban assault) chrono every gun before the day starts, which helps cut down on hot guns, but, it doesnt stop people using heavier bb's and lying about the weight.

Ive been on the receiving end of a very hot gun before, it was one day at RAF waterbeach in cambridge (a temporary site).
And i was walking along the side of a tree line with another chap. Then before we knew it BB's were flying through the tress and bushes at such power it was like having stones thrown at us. The tress and bushes did nothing to slow down the power.
We were both left bloody and bruised. Luckily it was dealt with after a few complaints.
I never found out exactly what the gun was shooting at, but i heard one or two people a few weeks later saying it was over 450fps.

[Genesius]

Re: KS P90 - Shredded Piston - Where to start?

theres no point in ditching the gun for a £12 fix. buy a piston and an sp90/m90 spring or cut some coils off of your excisting spring. you really need to know how to change things like your piston yourself so you can do it on site if you need to. It will save you lots of money in the long run. by all means carry on using the .28's after your gun is shooting below 350fps on .20's. they will fly slower but travel further and be more accurate.

[Mr Brainz]

That last batch of 0.28s is what jammed in the gun! I don't trust this batch. I'm back to 0.25s if I fix this.

[Fluxeor]

Re: KS P90 - Shredded Piston - Where to start?

Before ditching the BB's, take the time to clean your inner barrel, especially if it's a 2nd hand gun. It could very well be filthy and lined with detrius that could be causing the jamming. Once you've cleaned it out and replaced the piston/spring, fire off a mag or 2 in Semi-Auto to see if it still jams (obviously, stop the moment you think there's a jam and get out the cleaning rod again to remove the offending BB). Often reputable brand bb's arn't actually the fault unless you have a tightbore barrel with quite tight tolerances (unless they're crappy yellow 0.12g plinker BB's or you've been sold repackaged rubbish).