Porting puch #3 1.5 cylinder

I have a puch maxi that I ported. I opened the intake 2mm on each side and lowered it by .5mm. I opened the exhaust port to 2mm on each side and raised it by .5mm. I noticed considerable low end increase and about 3mph top increase. I did nothing with the transfers. What do I do next? What are other peoples port changes for the 1.5hp open transfer cylinder. Any input?

Re: Porting puch #3 1.5 cylinder

email sent.

Re: Porting puch #3 1.5 cylinder


Re: Porting puch #3 1.5 cylinder

Why the hell won't anyone say anything here?????? Hasn't anyone ever ported a stock cylinder???? I ask a REAL question and all I hear is crickets!! WTF, I'd think someone would be glad to expound upon their triumphs. So what, I have to be ready to spend money on someone's product, or have a female name to get an answer??

I did the search function, alot, it's almost impossible to find info when everyone's thread titles are "Check this out" or "I have a problem." At least include a fucking keyword or two in your title dammit, this should be a forum rule; put basic info in the title so it can be searchable amongst 100,000 treads. This is why no one wants to use search, it doesn't find shit.


I'm building a moped to replace my car (a modified 98 Sentra, 0-60 in 5 seconds). I am doing this so that I can save money, 'cause I can't afford expensive shit and lots of gas, insurance, etc, but I still want my ped to at least somewhat kick ass, maybe even be a bit better than _some_ of these POS Chinese 50cc scooters. I don't want a scooter, I love mopeds, mopeds last, and are "me."

Re: Porting puch #3 1.5 cylinder

Seems like a nice mod.... do you got some pictures?

Re: Porting puch #3 1.5 cylinder

what do you want to hear? what do you do next? put a bigger carb on, get a pipe, get a kit. if you made a sentra go nil to 60 in 5 seconds shouldnt you have a little bit more common sense? chill out dude

Re: Porting puch #3 1.5 cylinder

Yeah, chill indeed. It hadn't even been a full day since your original post that you posted ranting and raving.

To answer your question, I switched to a cast-iron series stock puch cylinder before I attempted porting. You are probably quite safe raising your exhaust port further. Buy a few stock cylinders cheap, and experiment. If you have an extra cylinder you can fall back on, just keep raising the exhaust port and lowering the intake until performance begins to suffer, then you'll know exactly how far you can take it.

I haven't messed with transfers. On the aluminum series cylinders, the transfer ports are open, as opposed to the closed transfers of the 'hi-torque' cast iron series. The upside of the aluminum series cylinders is that they are able to build up to higher revs because of those transfers. You might try matching the profile of your transfers to the transfer cutouts in the engine case if they are larger. Either way, just match to whichever has bigger transfers. You might experiment with making larger transfers in the engine case, and then matching the cylinder transfers to that.

Re: Porting puch #3 1.5 cylinder

Sorry guys, I wrote that post right after getting a nasty email from my now ex girlfriend. I guess I was frustrated and kinda emotional. Yup Yup! Re-read my post today and was like "Yikes!!" Sorry...

Anyways, here's what's on the bike:

-Biturbo (portmatched)

-Very HC head, gasket remains and has to.

-15x41 gears

-homemade hi flo air filter

-b9 plug (perhaps too cold)

-The carb is a bing 18/14/108, this is a "square type" off a 96 puch korado. This carb actually outperforms my bored round bing 16, as it doesn't inherently leak and has more adjustments, better idle. Needle at second-down position, #60 jet. It does have to be adjusted from the other side of the bike though, as it is a "d" rather than an "s". Much better carb.

-3 shoe clutch tuned on a bench grinder connected to a variac power tap, opens moderatly high.

-regular 85 gas

-no air leaks I've found, this includes crank seals.

-I played with timing a bit.

-general plug inspection looks ok, but haven't done a "WOT only" chop.

Goes a little over 35 still. But does have the lo-end to haul my 200 lb ass. Runs great, but not at the 45 I am shooting for, in fact I rode a stock one that would do 40 (it had more gutless lo-end tho) If I go much taller on the gearing, she ain't happy, and neither are any cars behind me.

I will get pics here soon.

I must be missing an obvious problem, or a lot of little subtle problems.

Thank you artichoke for the info, I want one of those hi-torque cylinders, but am pretty broke right now (hell I really want a gila, a mikuni flatside, and a simo; but until I get the scrilla, that's California dreamin') I may try a slight more raise/lower on the ports, I wish I had a source for cheap decent used cylinders.

I have an old #1 cylinder, and I see little difference to the 3, so the 3's prolly not that much better.

Jets are different for this carb than the usual bings (they're fatter.) No Idea where to get them, and wondering if another super common jet, say from a suzuki or something, will thread in. Anyone know about the compatibility of jets?

Sorry again for the unchill... you guys are awesome, and thank you.

Re: Porting puch #3 1.5 cylinder


Re: Porting puch #3 1.5 cylinder

that actually sounds about right for your weight. i go 38.4 on an all stock 2 hp excpet for a proma gp. i weigh about 165 tho. try a b7 plug, or even b5. sound slike you need to upjet tho, i run a 68 and im lean. square bings might have a different rating system tho.

Re: Porting puch #3 1.5 cylinder

Sorry to tell you but us fat guys need more CC's to pull us around.

Your just going to kill the bottom end performance to get more MPH with 49cc's.... get yourself a 70 or 80 kit.

Re: Porting puch #3 1.5 cylinder

Bullshit. It's port map that matters most, not displacement. Though when you increase displacement, you do get a torque increase in the low RPMs that you just don't have with a lower displacement cylinder. 50cc's for LIFE!

Re: Porting puch #3 1.5 cylinder

without seeing pics im not sure if this helps but the cleaner your portjob is the better. i know you widened but is that shit perfect?

another thing to do is POLISH the exhaust port, you want that glass smooth if you can. you can also "roughen" the intake port. it helps the fuel atomize better in piston port engines.

i would be using a b6 not b9

Re: Porting puch #3 1.5 cylinder

So... your ported stock cyl is faster than a Polini or a Gila 80 or Metra 80? I call BS

Re: Porting puch #3 1.5 cylinder

I used a dremel with a small carbide bit to rough it in, then small files to _slowly_ finish it, I then chamfered the ports just like I found them. I left the intake "rough," and I used 2000 grit sandpaper to finish the exhaust port till it was nice and shiney. Intake and exhaust (and gaskets) are matched to cylinder, for smooth flow. It took 6 hours, and was like doing dentistry on a mouse, but from the info you guys have given me, I'm calling it a success. I got lucky as a first timer, very lucky. I may try going to 1mm up exhaust/1mm down intake, but I want a spare cylinder first, in case I make a lovely "modern art" ashtray out of this first one.

I'll get/try a range of plugs, though this one isn't carboning too bad...yet.

I should also look to see how well the transfers are matching up, if they're nice, I may just leave 'em alone, till I get a kit :-)

Re: Porting puch #3 1.5 cylinder

My ported stock cylinder is faster than polinis and metras that are tuned poorly, yes. What I was trying to say is that having a kit doesn't automatically make you faster. If the portmap of a stock cylinder lets it rev higher than a kit cylinder, the one that revs higher will win every time. My ported stock cylinder also runs reliably while other people on metra and gila 80s have broken down. And when your moped is broken, and mine is not, mine is definitely going faster than yours.

But yeah, my point was that the portmap of any cylinder determines how high you can rev it more than its displacement alone does.

Re: Porting puch #3 1.5 cylinder

To get us bigger guys (200lbs) going you need torque not RPM. Cubic inches make torque. All of the better 70 and 80 kits have decent port mapping and when tuned right make more power than a ported stock cyl.

I am glad you like your 50cc but he said he wanted acceleration and he weighs over 200... not a good candidate for a high RPM 50 cc ped.

Re: Porting puch #3 1.5 cylinder

Fair enough. I just feel like people neglect the the option of porting their stock cylinders too often. For accelerating a heavy dude, yes, a properly tuned, higher displacement kit will probably do the job best.

Re: Porting puch #3 1.5 cylinder

Ok, I'm going to get crazy and go 16x38, and see if I can tune in my clutch to do it up, I need more rpms though, and I'll need super springs, 'cause my clutch is almost maxed, I'm going to see if I can't dig up something at my local hardware store, Really strong springs, as strong or stronger than blues. My clutch is going to get hotter than a mutha, bike will scream, and hopefully go too. Might need a super clutch, or to modify this one.

Better trans fluid?? for high rpm landing?? What do I use? Oil? ATF?

Also, anyone know where to get a square 18/14 bing jet(s)? Or something that will screw in like some Japanese jet?

Also I saw this "tight" looking tuned exhaust for an x1/x2 minibike really cheap, if I welded a header onto it it would look fricking medieval. I wonder if it would work, or if I can calculate out the header length to work with this bike (yikes, sound waves, 'n shit). Might be a new miracle pipe. Are the x1/x2 minibikes 2-strokes or 4? (I know nothing about minibikes).

Re: Porting puch #3 1.5 cylinder

Here's the carb, note the fabbed flipjack chole lever thing, Piece of a brake cable and some rubber work in that stem to seal the thing, works great. See carb is backwords, but still works. Adj. screws are super reachable just behind coil from other side.


Re: Porting puch #3 1.5 cylinder

Here's the newest franken-filter, version 5.0, works better than it looks, I kinda squished it. Still has trouble with resonation of rubber, I think I'm just going to cut up old airbox.


Re: Porting puch #3 1.5 cylinder

Here's the bike. The black blocks in the jug fins are acoustic dampeners, bits of heater hose jammed in wet with carb cleaner, so they stick in there, and dry in. The seat is one of those off a free spirit, that were for sale recently, It is adapted with some custom brackets, it's strong as shit, and comfy. The better rear shocks make a big difference.


Re: Porting puch #3 1.5 cylinder

The seat bracket trix.


Re: Porting puch #3 1.5 cylinder

Id leave your gearing lower. 16x45 wont limit your top speed below 40 and it will increase your low end a lot. I have a maxi with a #22 cyl and a bullet pipe that is quick and gets to 40 geared at 16x45.

add some base gaskets

add some base gaskets run like 3 of em or 2 ones u make out of the thick gasket paper and port match if u havent already i didnt care to read what u have already done

Re: Porting puch #3 1.5 cylinder

Bump for jets?

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