Treats piston port VS MK reed kit, A Review

Got a cheap little maxi to play with and started experimenting with some kits.

Setup:

Puch maxi

e50

STOCK transfer ports. I kept these stock so these can be compared as a bolt-on-and-go kind of kit.

Rito crank

New Bearings/seals

3 shoe clutch, kickstart springs

18x45 Gearing

2.5" sava MC51 tires (tire size affects gearing)

Estoril pipe, derestricted, shortened 2"

Stock points, 17* btdc

Magellan GPS

First kit I threw on it was the treats 1.5 70cc kit with the stock 14mm bing and 14mm round intake. It didn't really like to idle, possibly due to the round intake on the square intake port of the kit... not quite sure. BUT it ran well, was easy to tune (72 jet in the 14 bing), and was super easy to install. That setup hit 47 on a flat road, GPS'd both directions. Took a while to get up to that speed though. Here's a picture of the bike with that setup:

And a plug reading with the 72 jet and no air leaks:

Next setup I've been wanting to try was the reed kit that 1977mopeds.com sells as the "Lil Gila" . It looked like a cool kit, having a bridged exhaust port and nearly gila size reed block and not having to bore the cases like you do with a gila. BUT I didn't like the price or the fact that it didn't come with gaskets.

Did some digging and found this thread where a guy states that the kit is made by MK (not to be confused with MetraKit) and is a copy of the awesome Athena/AJH 70cc big reed kit so I found some on ebay for $150 shipped with gaskets and a bigass intake .

I had a mikuni TM24 flatslide laying around that I figured would work great on it, so I picked it up and did some research while I was waiting the 13 days to get to my house. I found this thread and this thread that had good info on it.

So then I finally got my kit.

First impressions:

PRO:

Nice casting

good looking nikisil

LARGE transfers with easy increase to metra large port transfer size. Barely seals on a e50 without welding.

Nice piston, drops through the cylinder easily.

Comes with gaskets and nice rubber coated 2 petal reed block (SS reeds, not CF.)

Sweet bridged exhaust

Huge nearly gila/mb5 size reed block

Nearly 360* intake duration

pre-chamfered ports

Ring gaps located near top of piston, not near exhaust port

CON:

Round exhaust port, could use some reshaping for a larger port to utilize the bridged exhaust.

Goofy fin pattern won't match a puch head

Intake duration could be raised to 360*

Long wrist pin clips. See notes later on.

I was itching to port the bridged exhaust port something like this , but I wanted to run it stock first, then port and retry.

SO I took some pictures of the kit and did a test fit. Seems like this has the same ring-in-the-exhaust problem as the 1977 kit. Here's some pictures. Transfers don't open all the way by 3.4mm.

You can see in this picture where I marked the ring gap locations:

Here's a port map:

With a single thin base gasket:

Exhaust: 25mm = 175*

Transfers: 35mm = 114.3*

Blowdown: 30*

With a 3.4mm spacer/base gasket combo:

Exhaust: 21.6mm = 193*

Transfers: 31.6mm = 135*

Blowdown: 29*

If you went somewhere between the two, with about a 2mm base gasket:

Exhaust: 23mm = 186*

Transfers: 33mm = 128*

Blowdown: 29*

I bolted it on with the thin base gasket, hope the ring still cools. 186* or 193* exhaust timing is pushing it for a one speed.

Reed block needed some cleaning. Picture with reeds:

Without reeds:

After filing the upper, lower, and inner sides. Couldn't do the outsides without compromising the sealing surface area.

Wrist pin clips were too long for my liking and I didn't want to lose a clip from the extra mass, so I clipped them a bit shorter. Here's a comparison:

Here's pictures of the hose I bought from Kragen (with part #) to mount the carb and everything installed:

Here's a video of it running. Had to drop down to a 10 idle jet to get it idling right.

Went for a test ride with the GPS. Hit 48 but got there effin quick! Clutch engages at 25 and it RIPS from 30-48. I'm sure this kit could pull 18x36 easily and could benefit from a ported exhaust port.

Re: Treats piston port VS MK reed kit, A Review

Overpriced Parts /

Same gearing^^ as 1.5 kit? 18x45?

Re: Treats piston port VS MK reed kit, A Review

Yep. Kept the same gearing for both. I don't think the treats kit could pull steeper gearing, but this definitely wants to.

Re: Treats piston port VS MK reed kit, A Review

id try 16x36 before 18x36... id like to see a riding vid with the lower gearing though!

Re: Treats piston port VS MK reed kit, A Review

If anyone wants to offer me a cheap 36t, let me know! I've got 13-20t front sprockets to play with. :)

I've got a gopro that I can do riding videos with. I'll compare both gearing runs with videos once I find a sprocket.

Re: Treats piston port VS MK reed kit, A Review

Overpriced Parts /

Ya 17-18x40 is plenty of gear.

18x45 = 16x40 so you were running 16x40 So you will hit well over 50mph with just a little more gear

Re: Treats piston port VS MK reed kit, A Review

18x40 is about the same as 16x36, so I'll grab a 36t and play with front sprockets.

Re: Treats piston port VS MK reed kit, A Review

i saw that kit, looks nice but the exhaust is just asking for porting.

looks to me like an AJH athena but the exhaust is wacky. It would be interesting to see what reeds fit in there.

Re: Treats piston port VS MK reed kit, A Review

we side to side compared, it's a Athena copy for sure, transfers are almost exact bridged the same too i think.

exhaust is ported dumb, i think the 45mm alukit piston is better (lower crown height)

Riggsby chime in.

Re: Treats piston port VS MK reed kit, A Review

Yea, I'm going to mess with:

1. gearing

2. porting the exhaust to the moon

3. see what a base spacer and milled head produces

If the spacer produces good results, I'll keep it, if not I can go back to the previous setup.

After that, I'll take the cylinder to the CNC and mill a passage for the top transfer, kind of like a polini but only one to match the boost port at the top of the cylinder.

Here's what I'm thinking about doing to the exhaust. The crosshatched area is what I'll be taking away:

Re: Treats piston port VS MK reed kit, A Review

fuck a spacer, just extra dicking around, you can get the same results by just porting, then you aren't screwing with your deck height and getting the bottoms of your ports up off the piston crown at bdc.

thats exactly what i'd be doing with the exhaust, maybe even crowning it a bit, i cant remember the timing off the top of my head but i know my fast airsal tomos is 22mm from the top of the exhaust to the deck, so you could probably round it up into there a bit.

dont forget to drill some holes in the piston to lube that bridge, guessing whoever is knocking these off in bumfuckistan isn't doing thermal analysis on that bridge to see if it wants to puke into the cylinder. maybe a bigger radius on the top of the bridge too, if you get into messing with that, that big flat port top looks like it wants to eat rings.

Re: Treats piston port VS MK reed kit, A Review

Agreed, that's why I put the big radii in, I'm afraid of rings getting caught. The only way to get a better radius between the bridge and the top of the exhaust port is to raise the exhaust port, which is fairly easily but I don't have to tooling to raise the transfers. That's why I was planning on a spacer.

A spacer also gets the piston out of the transfer ports at BDC.

I've been thinking about the oiling holes, so those are on my to-do list. Maybe even flatten that side of the piston the tiniest bit. I've seen that done on some pistons with bridged exhausts.

Re: Treats piston port VS MK reed kit, A Review

thats good thinking, i mean that if you put the spacer in there, your transfers will be hanging over the piston, you can get eddy currents and weird burn patterns from having that overhang, unless the piston is already hanging in the transfers in which case, yeah...

Re: Treats piston port VS MK reed kit, A Review

Yeah, right now the piston is hanging in the exhaust and transfer ports by about 3.4mm. :/

Re: Treats piston port VS MK reed kit, A Review

Im not smart on this stuff but that porting looks like alot of those high hp scooter cylinder portmaps...

Re: Treats piston port VS MK reed kit, A Review

I was going for something similar to this:

Re: Treats piston port VS MK reed kit, A Review

I just noticed the above kit has an angle to the top of the exhaust port. Made mine angled and reduced the overall width to match their exhaust port width. I don't want to break a ring and destroy the kit and piston...

Re: Treats piston port VS MK reed kit, A Review

If you use a treats reed piston the deck height issue gets corrected, but still the insane timing issue still persists. And you'll still need to countersink a head to set proper squish.

The Athena piston I got has a higher deck height, but the cylinder also has extra meat on the bottom of it where it meets the engine case. This evens out the deck issue. I'm not sure about the squish on it, I'll report back tomorrow with more info, either here or in the original 77 reed kit thread.

I think this cylinder with that port map would be good maybe only as a race cylinder, but you'd run it spaced and timed at 193°. I feel like the ring doesn't have to reseat itself at bdc with the unported exhaust and lower exhaust timing, but ported huge it'll need to reseat to cool so it doesn't bulge into the port. If its timed at 193° it'll need a super tuned clutch, hpi or other mini rotor ignition, a huge expansion chamber, maybe side and rear bleed to help low end. Revving high will require holes drilled in the piston to cool the bridge, ringland porting, maybe some bbf tech, proper squishing/compression, a reed spacer with a 4 or maybe even 8 petal top block. It would probably fucking scream though. And at 125 for a cylinder and piston from 77 its not bad once you have everything else.

Re: Treats piston port VS MK reed kit, A Review

You know, I actually had a thread bookmarked about piston replacement on the real athena where they compared the height and I totally forgot the treats reed kit piston is 3mm shorter from the wrist pin to the crown!

Here's the thread in case anyone was wondering:

https://www.mopedarmy.com/forums/read.php?7,2721604,2721957

I actually have one of those pistons NIB that I can try out once I mill a head to countersink it. Thanks Riggsby! <3

Re: Treats piston port VS MK reed kit, A Review

woah, 3.4 mm?!?! thats terrible, even those moby parmakits that come all crazy from the factory aren't even that bad.

could you trim a little off the piston too?

the other thing i've done when its just a little off, especially on stock cylinders, is recess the face of the piston where the ports are, to match up with the port bottom. 3 and a half mm's is crazy though. you should probably cut the cylinder down on top if its that bad, or just find the right piston.

Re: Treats piston port VS MK reed kit, A Review

Even with the right piston in there the exhaust timing will still be 193°. Also I think the treats reed piston has the ring gaps on the exhaust port side of things, which might become an issue once you port it out so crazily.

This cylinder is basically a sprinter cylinder I feel. With all the fixings done to it, I bet it would have no problem pulling to 11k and spinning 12k with 18x40 gearing.

Re: Treats piston port VS MK reed kit, A Review

Adam Riggsby Wrote:

-------------------------------------------------------

> Even with the right piston in there the exhaust

> timing will still be 193°. Also I think the

> treats reed piston has the ring gaps on the

> exhaust port side of things, which might become an

> issue once you port it out so crazily.

>

> This cylinder is basically a sprinter cylinder I

> feel. With all the fixings done to it, I bet it

> would have no problem pulling to 11k and spinning

> 12k with 18x40 gearing.

Damn, forgot about the ring gaps on that. I could relocate the pins or just go back to the spacer theory...

Even 18x45 spinning 11k would put me at 60 (theoretically)

Graham Motzing Wrote:

-------------------------------------------------------

> woah, 3.4 mm?!?! thats terrible, even those moby

> parmakits that come all crazy from the factory

> aren't even that bad.

>

> could you trim a little off the piston too?

Yeah, it sucks. Basically ALL the ports need to be 3.5mm shorter on the bottom. Then the port timing wouldn't be affected and it would flow better. Here's a picture of the piston at BDC looking through the exhaust port (you would see the same thing IF you could look through the transfers):

(edited)

Re: Treats piston port VS MK reed kit, A Review

If I ever run this it will be with a spacer and an o-ringed countersunk head. These kits have the potential to be monsters, especially ported the way your planning. With an exhaust port that big it would probably match up nice with the treats pipe or one of the mlm gila pipes.

Re: Treats piston port VS MK reed kit, A Review

Hmmmm. I've got a friend with a treats pipe I could borrow for a day to compare to the shortened estoril. Ugh, why can't finals be over already?!?

Re: Treats piston port VS MK reed kit, A Review

46mm of exhaust port width should be able to take up the huge treats pipe chamber. Is that map to scale? Like could I print it out and tape it in my cylinder and use it as a guide? Making the exhaust side of the piston flat with oiling holes is a good idea.

Lower gearing should help out with the clutch side of things as well. I'm excited to see what you get from this kit.

Re: Treats piston port VS MK reed kit, A Review

No, it was just a screenshot. I can do it as a 1:1 another day. BUT let me try the porting first. I don't want anyone having a doorstop just because of an idea/drawing that I had.

Re: Treats piston port VS MK reed kit, A Review

This kit is gonna sit around anyways waiting for a race engine so no real rush. I do appreciate it though. Are you gonna case match when you do the porting? How are you gonna have the 3rd transfer cut?

Re: Treats piston port VS MK reed kit, A Review

Yep, going to case match when I have the air dremel out to do the porting.

The 3rd transfer I'll do on a Haas CNC at my school. The upper part of that booster port is about 18mm wide, so I'll create a transfer just above the cylinder skirt 18mm wide and about 6mm tall/deep.

Re: Treats piston port VS MK reed kit, A Review

This cylinder would probably be great on a za or a tomos.

Re: Treats piston port VS MK reed kit, A Review

I had a gila za. Now I'm learning to play with e50s. ;-)

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