FPS upgrades for HK53 (TM MC51 upper, CA ca33 lower)

[North West Outpost]

Re: FPS upgrades for HK53 (TM MC51 upper, CA ca33 lower)

So you don't think the piston not returning fully forward is too much of a problem?

Are you telling me that the pison isn't hitting the cylinder head?

If it is and it's starting it's next cycle thats what most guns do. The Bevel gear is held by the ARL. Only guns with fancy control systems do stop in the same place every time, even fast ones with AB dont stop dead at the piston forward position every time.

[matfan]

Re: FPS upgrades for HK53 (TM MC51 upper, CA ca33 lower)

So you don't think the piston not returning fully forward is too much of a problem?

Hey Pete,

The solution to your problem may not be any more than just the shims and timing. I have the TM G3 SAS (same internals as yours) and I just upgraded the internals with a hurricane m100 kit. Metal bushes are included in the kit so I swapped out the original tic-tac plastic ones, bought a shim set and set to work. At first I shimmed it a little too much (it was really cold when I did the work, heat expansion is my excuse!!!) and as a result, the motor heated up and a few times it would only partially pull back the piston. I fixed the shims and it worked a treat.

I suppose it is possible that your piston is returning fully but that you are observing it partially through the next cycle.

Getting a basic understanding of the principals involved usually helps with the diagnosis.

If the motor/battery is getting hot, it means that extra strain is present due to one of 3 things

Friction in the gears - incorrect shim job or the shafts on the gears are seizing on the bushes
Friction in the piston (not likely) – not likely, could be that pitting on the piston fouling on the port
Locked gearbox - timing / gear alignment is wrong

If the resting place of your piston isn't against the cylinder head it can only be 1 of 2 things
Friction between piston and cylinder (not bloody likely)
The bevel gear is grabbing the teeth on the piston at the end of the cycle - timing, timing and timing.

The whole 1 o'clock thing is basically a guideline. Take a look at the gearbox and imagine it turning. If the teeth of the bevel gear are close to the teeth on the piston at rest, you will have a faster response time but you also may engage again at the end of the cycle, Too far away and you may not complete a full cycle on a single trigger pull. I have found that using the teeth as a guide and not the raised thingy on the bevel makes it easier for me to think through the adjustments.

I would definitely be looking at your shims

As I mentioned before, I’ve just put a Hurricane M100 kit in mine and it’s gone from 280ish to 325ish. The kit comes with the following
Cylinder
Cylinder head
Ball bearing Piston head
M100 spring
Ball bearing spring guide
Metal bushings
New nozzle (with internal o-ring)

I know we can’t put links up so let me just say, I live in Camden and I walked down to the shop to buy my kit. It was (and still is) half price, although that wasn’t advertised on the website. Best £17 I ever spent.

Make sure you buy a shim kit as well, and take your time getting it right.

[PeteJC21]

Re: FPS upgrades for HK53 (TM MC51 upper, CA ca33 lower)

I didn't really see any plastic bushings in my gearbox, they were metal I think? I read somewhere that Classic Army guns usually come with metal, so I was just going to put a Systema M100 spring in there and leave the rest.

[matfan]

Re: FPS upgrades for HK53 (TM MC51 upper, CA ca33 lower)

I wouldn't advise doing that. That's like using a jackhammer to squeeze a square peg through a round hole. Fixing your issues will cost lest than the new motor you will have to buy if you use the m100 with sticky internals.

Metal bushes alone don't ensure smooth running... shim shim shim!!!

[PeteJC21]

Re: FPS upgrades for HK53 (TM MC51 upper, CA ca33 lower)

I wouldn't advise doing that. That's like using a jackhammer to squeeze a square peg through a round hole. Fixing your issues will cost lest than the new motor you will have to buy if you use the m100 with sticky internals.

Metal bushes alone don't ensure smooth running... shim shim shim!!!

Cool, I'll get a shim kit and do those along with the rest of the stuff.

[North West Outpost]

Re: FPS upgrades for HK53 (TM MC51 upper, CA ca33 lower)

If your bevel gear is anywhere near your piston when you pull the trigger you have bigger problems than the gearbox starting its next cycle.

Checking shimming is common sense and doesn't really need mentioning as far as I was thinking.

The SECTOR gear picks up the piston. PRE ENGAGEMENT is when the SECTOR gear rotates and picks the piston up befor it has hit the cylinder head. More usually on high speed setups. Never on single shot.

Like wise if the gear box is tight do you really think this will allow the sector gear to pick the piston up, rotate untill the piston slips of the release tooth. Then somehow the piston stops befor hitting the cylinder head...lol....And certainly wouldn't be firing at 270fps.

I give up.

Guys come on, use the new spring check your shimming and the other parts as you are taking the gear box apart, if all looks ok you should be fine.

[matfan]

Re: FPS upgrades for HK53 (TM MC51 upper, CA ca33 lower)

OK aside from the mixed up gear terms, I stand by what I said.
Shimming is common sense, to someone that doesn't need to ask, "is this a version 2 gearbox" (no offense Pete)

I've ignored the original post about it shooting at 270fps because it has been pulled down and reassembled a few times since then.

I'm not sure that anyone has suggested that it cycles then sticks. If you refer to the pic posted (with the yellow lines) you'll note that it is sticking very early on the compression cycle which to me seems like a timing issue resulting from incorrect reassembly.

If the gun does nothing but heat up the battery when the trigger is pulled it can hardly be described as anything other than a seized gearbox.

[Montesa77]

Re: FPS upgrades for HK53 (TM MC51 upper, CA ca33 lower)

I would just send it to a tech so they can deal with it. Could be so simple.

[North West Outpost]

Re: FPS upgrades for HK53 (TM MC51 upper, CA ca33 lower)

Tell you what I will do if that gear box was mine and I thought there were intermitent faults I would do the following.

I wouldn't be bothered if the overrun left the pison in the position shown as this happens when gear boxes don't have AB mosfets which of course not all gearboxes need them, in many cases fairly standard gear boxes will benefit from just a basic fet being installed.

As the gun has fired and not got stuck befor firing, would suggest the shimming is probably ok. But as the gear box has now been opened..Needs re shimming befor closing up.

I would take out and clean all moving parts, then clean the grease out of the shell, checking the trigger assembly particularly the contacts and clean them if you need to. Also check the rest of the wires for crush or nicks and replace if required.

Put the gears back in with one thin shim on each shaft, on the underside.

Try it with 3 on the sector gear, one on the spur gear and two on the bevel gear, all thin ones or variations giving the same dims. Put the gear box together with only the gears in it. Use at least two screws opposites to secure the box. Using either fingers or a small blade screwdriver wiggle the gear shafts one at a time and either remove or add shims untill there is a tiny movement. There must be a tiny ammount of play other wise you will have over shimmed.

Befor you open the gear box again turn it so the top is down wards and you are looking into the motor hole. Poke a thin screw driver through the opening and move the bevel gear making sure there is no resistance. If there is something is wrong with your shimming skills.

Open the gear box and make sure you know how many of each shim was on each shaft.

A light coat of Silicon grease on the piston runners, just a thin coating. A light coat of silicon gun oil on the inside of the cylinder and on the piston rubber O ring and the air nozzle Oring, not to much or you will be oiling your bb's and you don't want to do that.

After checking things are ok with the cylinder assembly put it back in or replace, fit the tappet plate arrond the trigger, make sure the springs are ok.

Turn the sector gear so the flat section (toothless) is towards the piston and put the piston in, making sure the the post that moves the tappet plate is at somewhere arround 13:00 or at least not trapped undeer the tappet plate and to the right. Do a dry run using your finger to drive the gears and make sure they cycle with the piston ok.

Take the gears out and give them a light coat of silicon grease put them back in with the ARL in place.

Take your new spring and the spring guide and give them both some silicon grease.

Using something to hold the spring guide in place follow Stalkers guide to put the gear box back together.

Thats it, then you don't need to worry about anything as you will have addressed it in the re assembly.

[North West Outpost]

Re: FPS upgrades for HK53 (TM MC51 upper, CA ca33 lower)

I would just send it to a tech so they can deal with it. Could be so simple.

With experience it is simple.

[PeteJC21]

Re: FPS upgrades for HK53 (TM MC51 upper, CA ca33 lower)

I would just send it to a tech so they can deal with it. Could be so simple.

I've always got this option yes, but really want to learn how to do this for myself if I can, its no fun otherwise!

Shimming is common sense, to someone that doesn't need to ask, "is this a version 2 gearbox" (no offense Pete).

None taken mate, you are quite right! I am very new to all of this and had no idea what I was doing at the start of the thread... I knew nothing of shimming, or bushings or any of it. I have learnt a lot thanks to all the advice I've recieved though, including that checking shims should be second nature. I still don't know what version gearbox I've got though!! :D (I'm assuming it is V2).

When I've got some money again (wife just blew my last pennies on Xmas shopping) I'm pretty much going to follow the advice left in the posts above. Where I've been fiddling a lot it has wiped a lot of the grease/lube off the parts, so stripping it all down and cleaning/re-greasing/re-shimming is a must.

I will be checking the bushes to make sure they're not cheapy ones along with the shims (a hobby shop in Asia sells systema ones for peanuts, as does Z1 I think) so will order new ones if they're not up to scratch. I'll test all the gears to make sure they move freely and seem secure, along with the piston and if I'm happy I'll go with the new spring. After everything I've read on here and what I've seen from the inside of the gearbox I think the problems I was having was down to gears not moving as they should. As I say it does seem to be firing ok now, but I think the problem will just re-occur until I sort the shimming out.

Thanks again for all the advice, I'll leave it there for now til I've got the money for the parts and work on it again early Jan.

[TB-Stalker]

Re: FPS upgrades for HK53 (TM MC51 upper, CA ca33 lower)

Sounds like a good plan, and yes you have a V2.