"Cylinder Matching" and a couple questions about ports about this 45.5mm Malossi MBK kit

Dudes,

I have this 70cc Malossi AV10 kit, which I bought with a little advice from you all. I'm pairing it with some Polini AV10 cases. The interesting part is, the transfers on the case are larger than the cylinder. As seen here;

My question is, can I extend the "ramp" lower in order to match the case, and if so, should i take deeper or widen at the top at all. I'm hesitant to grind away in the same manner I would for case matching.

My other question is about the top transfer, and the weird non-window inside the cylinder shown here (long and verticle);

I have no idea why it's there, it's directly below the little V that's similar to those you sharpen on gila kits for flow. Maybe that's common.

Anyway, just wondering what sort of prep I should do here.

Thanks!

Re: "Cylinder Matching" and a couple questions about ports about this 45.5mm Malossi MBK kit

Those ports look good as far as chamfering, but it's always good to do a quick once over and make sure there's no sharp edges.

As for the top transfer, there's probably a hole in the piston for that.

If you want the most out of the kit, you could match the transfers. That takes some skill because you have to direct airflow in a way that it directs air over the piston crown and also forces exhaust air out of the exhaust port. In short, study up on some transfer dynamics. I don't think leaving the transfers on your cylinder alone will truly kill your performance. Take baby steps and see what works.

Re: "Cylinder Matching" and a couple questions about ports about this 45.5mm Malossi MBK kit

Malossi bores are so clean!! I just picked up an LC 45.5 for my 103..very clean ports...allthough I have one casting slag dot in the corner i need to remove, and it's sure in a spot.

Anyway...yeah...my 47mm eurocylindro kit for my moby has the windowed piston and the extra booster...I think it's to add port area to the booster to help lengthen the blowdown duration. That sound right?

I like to have matched or slightly smaller transfers on the case than the bore, I fear the loss of correct flows as well as compression could become a factor. Interested to hear the results...either way it goes.

Let me know if ya want to go with a kit with larger transfers...I'll take that malossi off your hands if ya want.

Holla!! (edited)

Re: "Cylinder Matching" and a couple questions about ports about this 45.5mm Malossi MBK kit

Rob @t ATTN! Burrito /

ive always matched the ports to the case and kit, whichever needs modified. the g2 kits always need it for some reason

am i the only one that thinks that chamfering is sloppy? i'd touch it up.

Re: "Cylinder Matching" and a couple questions about ports about this 45.5mm Malossi MBK kit

@ rob...now that ya say something...the chamfering is a little wonky on that moby bore...my LC 103 malossi is super clean...sans slag dot.

If they are smooth tho..it'd be fine IMO, but a little clean up and matchy match never hurt anything.

Re: "Cylinder Matching" and a couple questions about ports about this 45.5mm Malossi MBK kit

Yeah, I didnt even notice how wobbly it was until I took the picture.

To what Tommy said -

When you're talking about directing flow, that's what I was concerned about. Too much or too little velocity as a result. It doesn't seem like ramping the transfers to the case on the top would hurt in that regard -- as long as I dont change the overall angle of the flow to the port. Does that logic seem reasonable? Basically, I'd rather not have that wall there.

Re: "Cylinder Matching" and a couple questions about ports about this 45.5mm Malossi MBK kit

It's a little all over the place, but chamfering is to prevent the ring from snagging, and to transition. The malossi cylinders I've always gotten have decent chamfering like this. The first couple I touched up, the the rest of them I left alone. So long as there aren't any knife-edges and sharp 90 degree port windows, you'll be alright.

Re: "Cylinder Matching" and a couple questions about ports about this 45.5mm Malossi MBK kit

With respect, I know what you mean by chamfering, I was referring to the flow of air from the case, to where it enters the cylinder, the wall that is created by the smaller transfer port on the cylinder. Evening out that.

That's the case shaped base gasket that I have on the to show the discrepancy between the cylinder and case transfer ports. I really should have mentioned that! (edited)

Re: "Cylinder Matching" and a couple questions about ports about this 45.5mm Malossi MBK kit

sorry, I was directing the chamfering stuff to those other guys...

Yeah, you can reshape the slopes on your transfers, but I'm not 100% sure because there's no picture of how the engine cases look with the flow from the intake. The key to transfer reshaping is "less is more." You're not opening things all crazy like, just smoothing out any discrepancies. I would probably only go in about 4-5mm deep and just smooth the slope to the engine case transfers. You would know better because you know how the air is flowing from the intake through the reeds and into the case. It's pretty intuitive, air likes to flow straight. Just line everything up and figure out how to make sharp edges and hard turns into the most gradual turns as possible.

Re: "Cylinder Matching" and a couple questions about ports about this 45.5mm Malossi MBK kit

For the sake of some thoroughgoing Moby talk, I've added some pics of that too. You don't have to go through the whole analysis if you don't want to, but here's what they look like -- for posterity if nothing else.

(edited)

Re: "Cylinder Matching" and a couple questions about ports about this 45.5mm Malossi MBK kit

I guess I'd trace out that gasket on the bore...then follow the existing angle of the transfer to the line. I wouldn't cut into the transfer if possible, just EXTEND those angles to match the case and not have a wall there. Nice and smooth. Should be fast as hell!!! keep it up!

Re: "Cylinder Matching" and a couple questions about ports about this 45.5mm Malossi MBK kit

You should take the shelfs off where there is a transition from the carters to the lead ins of the transfers (think that is what you ask in the first post with the gasket on the cylinder base). Anything less the 90 degrees is goodly and anything that does not leave a pocket is also a good thing. The shelfs make eddys in the flow and the pockets can make a accumulation of fuel separated out from the air. The fuel separation is bothersome because it can make a lean charge, also once the bubble of fuel is too large it will separate and go to the combustion chamber. A bubble of fuel will not burn but will make a cold spot and create divots in the piston crown or the head.

Also put the piston into the cylinder with the crown level with the exhause port floor so you can check if the piston skirt cut out is not shrouding the transfer entry. Also check the alignment of the cut out on the skirt with the cut out on the cylinder and make them match.

Reed valved engines are not so sensitive like a piston port so you can remove the material without having to be anal about primary compression ratio.

Put a slight angle on the bottom of the piston skirt so the periphery does not work like an oil scraper and rob the cylinder walls of oil. Also slightly open up the top of the oil journal on the carter halfs so the mains can get lots of goodly oil.

The chamfer on the ports looks a little harsh, but if you dress the piston and get it damp with oil and run it up and down the cylinder and not feel the ports when the rings pass, then you are good.

Re: "Cylinder Matching" and a couple questions about ports about this 45.5mm Malossi MBK kit

That transfer you see between the two ports coming up from the case has a matching hole on the piston that flows air through it from the bottom of the piston. If you want you can cut that area out and have it go down to the case transfers there so all three come up from the case.

And quit calling the cases carters.

Re: "Cylinder Matching" and a couple questions about ports about this 45.5mm Malossi MBK kit

jesse thats what they are called on a french bike CARTERS

Re: "Cylinder Matching" and a couple questions about ports about this 45.5mm Malossi MBK kit

No, they are called cases. That's the French word for an engine case. By that train I should refer to every part by the French word, or the German word for Sachs cases and Italian for vespa cases. The only reason you call them carters is because Christophe did, admit it.

Re: "Cylinder Matching" and a couple questions about ports about this 45.5mm Malossi MBK kit

I refer to them as both...I picked up the term from euro 2t modding sites i think. Cases, carters...potato po-ta-to

Let's see that bore all matched up!!! (edited)

Re: "Cylinder Matching" and a couple questions about ports about this 45.5mm Malossi MBK kit

^ I'm gonna start prepping it this week I hope, I gotta get me a jewelry file, or the like too! Best polish my exhaust port while Im at it.

Re: "Cylinder Matching" and a couple questions about ports about this 45.5mm Malossi MBK kit

If you follow the french sites then potato means something about how well your engine runs at a certain rpm. Then they have a picture of a literal potato with rpm ranges next to it as their sig. I'm not going to start talking about potatoes though.

Re: "Cylinder Matching" and a couple questions about ports about this 45.5mm Malossi MBK kit

^LOL. HOLLA!!!

Re: "Cylinder Matching" and a couple questions about ports about this 45.5mm Malossi MBK kit

That's what I did. You can bring the polini ENGINE CASES out to match the malossi ports on the outside edges a little bit as well.

Re: "Cylinder Matching" and a couple questions about ports about this 45.5mm Malossi MBK kit

I'm glad you posted! I was just headed over to post a pic as well. I like how you sharped the top transfer.

Yeah, the Malossi ports are wider on the bottom of the side transfers, and the top port. Case is longer, as shown in yours (see market on mine cylinder). Just for the record.

The sleeve sticks out into the crank area (dunno what else to call it) on the intake side. Look in the picture on the left. I wonder if it's anything to consider reshaping --

Re: "Cylinder Matching" and a couple questions about ports about this 45.5mm Malossi MBK kit

Looks like the intake side is obstructing flow and putting a place to collect a bubble of fuel just up towards the stud bump.

Re: "Cylinder Matching" and a couple questions about ports about this 45.5mm Malossi MBK kit

Trim that skirt bro! That cast corner looks UGG.

Re: "Cylinder Matching" and a couple questions about ports about this 45.5mm Malossi MBK kit

Shit's gnar right? It is advisable to cut that? If so, I'll just make sure I add a nice chamfer to the new edge and return it to the same condition of the former one.

I'm paranoid, but the skirt comes down REALLY close to the case as well.

Re: "Cylinder Matching" and a couple questions about ports about this 45.5mm Malossi MBK kit

I'm talking about the cylinder skirt that gets in the way from the intake to the transfer (if that's what you're talking about). There's also a huge corner cast in the cases right above that side transfer.

All you're doing there is profiling it for air flow. Shape the skirt and the case so that air moves straight to that transfer. You may need to trim your piston skirt as well so that air flows in at bottom dead center. Just don't take off a lot of material. It looks like there are a lot of case bolts in that area?

Re: "Cylinder Matching" and a couple questions about ports about this 45.5mm Malossi MBK kit

You can do quite a bit of flowing with those cases from the intake side out. Trimming the piston skirt, cylinder sleeve, case edges. Depends on how wild you want to get. One of the things that people do with fast scooter builds is to build plates to angle the reed valve closer in the direction of the ports. I haven't even bothered to do that one myself but I've seen it on some motors on euro forums. Get wild with it.

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