I was just trying to get the transfers to line up... but this time Ive gone too far... yeah Ill just use some caulk in those new holes... thats it..
thou hast made thy boat anchor
time to get fancy with the epoxy. dont use 5 minute or the twenty minute junk. clean the place with alcohol, mix up the epoxy, back the holes with tape first, let the epoxy cure 12 hours.
totally savable, but u have now lost all low end poo
I have? why is that?
small port increase flow velocity, you enlarged them greatly and then greatly reduced flow velocity. lgood ow-end power requires high-flow velocity at low rpms
you also lowered overall compression within the case by removing material.
So if he's adding a kit with large transfer ports, I thought you want to have the case ports match their size closely. If he wanted to maintain good low-end torque along with increasing high-end power/speed, how would he have done things differently, or are these mutually exclusive goals?
No need to worry about the primary compression ratio (the kind when the piston comes down) at least at mid to high range cause the pipe will suck a vacuum on the case anyway. Is that a K-star? If you don't like the low end performance you can always go back in and use a lot of regular JB weld sculpting a more original profile. It's good to 500F
Powerband mods are always mutually exclusive in two-strokes, it can be somewhat mitigated by the addition of a performance pipe. Some pipes are better for low end , some for mid, others for high. If he used a lowend pipe such as the stock or midrange pipe like the Proma circuit it would not match the specs of his portmatch and engine/throttle response would be out of sync.
When you portmatch or alter the angle of the ports inside the cylinder it throws everything off balance, you've got to get an appropriate pipe, an appropriately sized carb, and then upjet to some unknown value. Jetting is by far the most difficult job after a portmatch, especially if you're drilling the jets. I performed a case match and cylinder port job last summer on one of my Sachs engines and made similar mistakes. I matched the transfers (+3mm of material) and reangled them and added a Bullet pipe, neglecting to raise (or widen) my intake and exhaust windows and getting a larger carb. The result was oddly enough, terrific low throttle revs, which you never seen in a bullet pipe, has great takeoff. The midrange was absolutely GONE, and highend didn't feel like anything. Low 30s to low 40's took forever and it four-stroked (lean) at 40mph.
I've got this Morini MO1 engine I'm working on right now, it seems utterly hopeless. There's maybe 1mm worth of room to expand the transfers in a case-match and the crank is full of casting defects, plus the crank weighs almost nothing which I guess is great for low-end but I don't know about high-end. It's one of those money-pit projects. Me I got all excited about the Morini when it arrived...then I opened up the engine.
Its a 70cc tccd and homoet 6p.. the exhaust port raised about 1 mm the intake lowered the same. I'm waiting on the 6p still...
I wonder if i could get a machine shop to get that little rotor to fit my large shaft? Im trying to make a high rpm bike here and if I screwed it up well I paid for it with my own money, and I will have learned a lot. Anyways I have never worked so much in my life. I don't know how the rest of the world does it day in and day out. Wer it not for my burning desire for more moped stuff i would have quit my job already. Its not that cold outside...
what an amateur! stop destroying engines!
Dont be mean.
I'm just curious why it looks like you're taking your engine apart in the rain?
That bicycle was sitting outside and i wanted to see how much differance in size that little rotor was. It has been raining alot lately. I sure would like to lose the weight of the flywheel.
al is not lost anyhow. you can modify the transfers with epoxy putty or even liquid epoxy if you build a form inside the casing then shave away the unwanted material. i dont use a dremel much except to rough out stuff and then trust the finish work to rifflers n files. its slower but there is less chance of the dremel doing the dance of death if it grabs or eating away material that was a shadow and not a pencil mark OUCH
comando_brando only an amature butthead would post a negative comment rather than trying to help out a fellow mopedder after running int trouble.
I give you credit for posting pictures of this. There's so much talk about doing this on Moped Army but I rarely see pictures of what is considered "correct." This, although it didn't go exactly as planned, is a great learning thread for future reference. I'd like to see some pics of what people consider good jobs. If it doesn't work out, it's only an engine! A for effort!
so what exactly did he do wrong? I can see one of the case bolt holes is exposed a little. Is that it or did he dremel back to far or what?
That and the sealing surface for the base gasket has been made rather thin in some areas. I'd say a little work around that stud hole and see how it runs. Make sure to clean everything super good. Brake and contact cleaner works well.
Commando, don't be a jerk.
You can totally fix that with JB Weld.
I did much worse when I was learning, and you have to fuck it up to learn how to do it right. I must have destroyed 3 moby cylinders trying to find out how to port them. You just had the balls to show us your first one.
As far as "what he did wrong" it will still work like this, though the low end will be horrible. A more moderate porting job (not so huge and far down into the case) would work better all around.
thanks for the pics because i dont think i have ever seen a pic with the cylinder matched up to the case half where now i can picture how it all flows together
thanks for the informative pics
Guessing it's because he went so far back, but are you supposed to match and just round into the existing ports dremeling/filing only an inch into the case. How much is too much that will destroy the low-end?
I epoxied the little holes and am putting it back together now. Thanks for the nice comments! Ill post some more pics in a little bit. ~Austin
screw pics. post a video of how it runs
basically you don't want to drop them all the way into the case u will gain alot of upper midrange, loose a good amount of low end and gain some top end by taking all the way down like that.
its better to just match the point where the case meets the cylinder and smooth out that transition into the bottom end so the mix can flow better and is not spun into eddys buy an abrupt change from a small case to a large transfer.
pulling the transfer skirts higher towards the combustion chamber will also yeild similar results to bringing the cases down lower but they can still be controled some with piston timing (see a puch low torque cylinder and you will understand)
So the low end on this will not be as good as if the case was left stock? but if it was done just a little bit into the case the low end would be better than stock?
pics and vids, pics and vids
That makes a lot more sense. The high torque 2hp transfer ports are walled were as all others are left open.
Gave away my old cylinders or I'd post some pics.
Makes it easier to understand how velocity helps power the ped at low -end and surprised how in all of the previous porting forums nobody really specified the importance of not cutting too deep. Thanks Elliot
these are my old cylinder pics if you want to see them, the first three are the hi torque one and the second three are the hi speed ones.
Here is the cylinder that actually came off my bike. It was in good working order when I took it off yesterday. Did about thirty five with stock pipe and carb and stock 14:45 gearing if I let it wind up.
as you can see from the wimpy little ports that the hi torque cylinder had its performance left some to be desired. I have tested 4 different numbered cylinders and none compete with the (low torque?) open port version. I always take my dog with me who weighs 45 lbs. and usually pull a bicycle trailer behind my moped too (my dog can ride in a rectangular big milk crate). Any ways enough long winded crap. Here is the thing I want to tell you. I put my cylinder on and it looked like the ports lined up pretty well as I moved the piston up and down. See:
So then I tried to put my cool home made hi comp cyl head back on but it hit the piston. So I used that head off that bike motor in the other picture up there. It was a 75cc motor and worked perfect but made my motor look weird. Oh well. See:
But after i cranked down the head nuts to a maximum of 7 ft-lbs of torque (haha yeah right) I discovered that I need a 1 mm cylinder base gasket to make it dead perfect. but oh well another day right? Any way here is the old rectangular shaped manifold off the low torque cyl after I reamed it good with my trusty dremil to match the intake on the cyl. It is a 14mm manifold which is fine since I have a 14mm carby. see?
and a pic of the annoying thing assembled. Behold its splendor.
here is a little video of me starting it with the stock pipe because the estoril wont let me use the pedals. bummer. This little digital camera doesn't have sound for motion and I'm disapointed about that but hey its a loaner. It started right up the first crank by hand even. I swear on the Baghavad Gita. http://s265.photobucket.com/albums/ii211/dirtyrottenstinkingbiker/?action=view¤t=P7220054.flv
lol. nice ports. and the video is cool tooooooo.
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