best results with 177 polini

[FurlanPx]

hi, I'm new here, I'm from Italy so I don't understand german, but I think most of you can speak english. I saw (many pics) and I read some techniks(I undesrtood a little) you're very good in motor tuning, so I want to know your best results with a 177polini. In this winter I'm working a motor like this:

177 polini (little tunned)

original crankshaft (no money for a full circle :grins: )

reed valve of rgv 250 6 petals with an hand made manifold

28phbh(I will try also a 30phbh or a 28/30 tmx)

hand made exhaust

23/65 with 4th z36

200 clutch with dr springs(I don't think will need a reinforced clutch with ring)

bye

Marco from Udine,Friuli, Italy

[karoo]

I think that the reedvalve you're planning to fit is way too big to be used with a carb of 28-30mm diameter. I'd consider the reed valve of the rgv 250 if you're planning to use a 34mm carb. For 28-30mm, the reed valve of the RD350YPVS or TZR125 should be just right. It's also easier to construct a carb flange with no sudden changes in area which helps throttle response for the smaller reed valve. The smaller reed valve won't be any restriction for a carb of 28-30mm.

Is the hand made exhaust you mention custom made or off the shelf like PM Evo etc.?

Regarding the gear box, you should check to have the new type of gearbox fitted since '86 (the one with the flat cruciform) installed. It withstands the stress in tuned enginges much better than the old type when it comes to jumping gears. Resulting from that, you also have longer intervals between changes of the cruciform. The 36 4th gear is also fine, though a good Polini engine would also pull the longer 35 4th gear with the 23/65.

The original crankshaft should be fine! When fitting reed valves it is often desirable to mill down the crankshaft even further to let the gasses flow easier. A full-circle crank only has benefits where the reed-valve is positioned directly under the cylinder base (and the original inlet is closed completely), so that the incoming gasses don't interfere with the crankshaft!

A clutch ring is only necessery in high revving engines, so it depends on your port timings and the exhaust pipe. If your powerband ends at 7500 you probably won't need it. Some people also say that fitting a very light flywheel can cause clutch damage if it isn't reinforced. What port timings are you planning to use? Do you rather want a racing or a touring engine?

For touring I'm quite happy with port timings of 120° at the transfers and 178° at the (mildly broadened) exhaust port. With these timings you won't get the most power out of the engine, but it has good torque at the bottom and a strong midrange (with an old PM 24). But to achieve these timings you'd have to add a spacer under the cylinder base to raise the cylinder and you'd also have to shorten it at the head sealing surface (by the same amount that you raised it).

Greetings to Italy!

Bearbeitet 20. Dezember 2004 von karoo

[FurlanPx]

I see, so I will search a rd350 reed valve, and the rgv valve will fit a future px 200 engine but, the rgv reed isn't like the aprilia rs reed? I think they are very similar, or not?

I forget to say that I want to use a hp flywheel, I tried it and I found very good acceleration, but I cannot test in speed but I think that I will lose some of it...

If I ride with a passanger the hp it's bad...but for the moment I have no woman so it is not a problem :grins:

The exhaust is hand made by me, I calculate it with "exhaust calculator 2", the duration of inlet port is 120° and 170° exhaust port ( original duration of my polini(this is the second version, the first version was 115°, 175°))

I want a good torque so I use to original port timing.

The cruciform is the first type, no lusso type, I have one new in garage and I used it, I know that the lusso cruciform is better, I think that I will fit my engine with a lusso version.

For the crankshaft if I will fit a full circle because my idea is to work the engine like this(pic) so the full circle doesn't distrupt the flow.(green line)

If I use a orignal crankshaft I will join the boost port with the reed pack with a "pipe" to make the reeds feel the depression of the boost, mmm it's difficult to explain, in this way I will have a longer duration of thw reed open(red line). And if I want I can close the holes and reduce the duration. (but this is a project :wasntme: )

My engine isn't for race, is for a street racer, so half between touring and racing.

bye

Marco from Udine,Friuli,Italy

[FurlanPx]

uhm,,, the pics,,, can I post pics from my hd?

[PMS]

Greetings from Ludwigsburg/Stuttgart!!

If my 3 in one-motor works,I will send you a message.

3 in one: one motor (PX 125er)

3 cyl.:166 Malossi ...177Polini..211Malossi(if they works.. )

reed valve: MRB with RD 350

Carb.:30TMX

crankshaft: 125 Mazzuchelli

clutch:200 PX old with polini 23/64

hand made exaust

we will see...

Tom

[FurlanPx]

this is a pic from px200 engine cases, but it'is the work I want to do

Bearbeitet 23. Dezember 2004 von FurlanPx

[karoo]

This pic shows my Polini as it's being shortened on a mill. I only took material off on the inside of the sealing surface to have the head self-center it afterwards. If you look at the head from the bottom, you see that its sealing surface sticks out quite a bit and is round (with exception of the ears where the cylinder studs go). I then removed these ears, milled the cylinder to have 0,6mm more diameter than the outer diameter of the head and had a perfect fit (that's because of thermal expansion. The head will expand more than the cylinder, so you have to have some clearance there)

Which RS-reed valve do you have in mind? The one from the RS125 is not same as the one fitted in the RS250. The RS250 engine is bought from Suzuki, it's exactly the same like the RGV250 engine, except the signs on the cylinder (and probably on the casings, too) read "Aprilia" instead of "Suzuki".

I don't know Exhaust Calculator 2, but I'll try to have a look at it. I build expansion chambers myself, but until now I have only done some for a tuned 200 engine. I already had the PM, so there was no need to build it on my own... But someday I'll have a try for my small Polini, that's for sure!

The difference in gearboxes isn't the cruciform alone, the main drive shaft of the Lusso has some little slots in it, into which the cruciform is pressed when driving, so it can't jump out that easily. The gear wheels are also slightly different (thicker section where the cruciform engages, different contour on the fourth gear on the tire side). So swapping the cruciform alone wouldn't be helpful in any way.

[FurlanPx]

ok, interesting the work on the cyilinder!

and what do you think about my project? the one of the pic?

[FurlanPx]

sorry but I don't understand german

uhm, karoo and what are your best results with a polini 177 engine? in speed acceleration torque...and how is your engine worked?

[gertax]

this has recently been posted in our lately introduced Largeframe Performance Topic

Ok, hier mal das Diagramm von meinem Cousin:

177 Polini

Worbel Langhub Schali

HP4

Eigenbau Membranblock mit Malossi 4-Klappen Membrane

Indischer PX-Block

200er M-Speed Puff

34er Delorto Flachschieber Gaser

<{POST_SNAPBACK}>

there are several more dyno graphs kicking around here, you might want to dig them up using the search function

Bearbeitet 20. Dezember 2004 von Gerhard

[Arschbrand]

Don´t worry Furlan. This guy is famous for his short circuited mind

Bearbeitet 21. Dezember 2004 von Arschbrand

[Arschbrand]

Well Furlan, in the pic wich you have posted it seems that the crankcase is allready widened to have the boost port steady open. What is the pipe for?

[Mike]

graffman's posting rights were disabled for the next 10 days.

[karoo]

Until now I haven't been on the dyno with my engine. So I can only tell you, that the power delivery is as smooth as I want it to be on a engine intended for touring. Maximum horsepower has never been my goal. It doesn't rev past 7300rpm, but it reaches this speed regardless of if I'm driving up or down a hill in fourth gear.

This is a pic I took of my intake when it was nearly finished (you also see that some material has been taken off the crankshaft, but I don't have a picture of the crank alone):

The reed casing is designed to take a Malossi reed. The reed will even slip a little bit into the engine casing and sit just several millimeters above the crankshaft! The Malossi reed isn't bad, but for a 30mm carb I'd go for RD or TZR, they look much more promising. I have to admit that the reed casing looks somehow twisted and crude, but it gets the job done and flows well. This thing was at first only intended to check if it was possible to fit a Malossi reed under a SI24 carb (which by the way seems to work out) and has been machined in minimum time without having taken the exact dimensions of the engine and the reed cage. I've first run the engine with a Mikuni TMX32, although I really hate this carb. But it was registered in the papers of the chassis I first run the engine in. Later on I now plan to use a carb of 28mm diameter. I think it's gonna be a PHBH28, they're the cheapest

As to your drawing: It's a little difficult to interpret. If I understand you right, you're talkink about two ways of fitting the reed valve:

The first way is to mount it in front of the crankshaft, so that the new intake will sit entirely in front of the crankshaft. That way the intake would correspond to the horizontal part of the green line you've drawn. This is a very good way which should, in theory, yield the best results! But until now there hasn't been any real comparison of similar engines with only differing intakes, so it's difficult to tell if the theoretical advantage really works out. In addition to that you'd have to weld the casing and remachine the sealing surfaces. This is not only costly, but also bears the risk that the casings might warp after welding.

The second way is to mount the reed in a more traditional way (somehow like mine or the intake manifolds designed by MRB, Malossi, MMW, Planet Scooter et al). But apart from enlargening the original intake you plan to fit a pipe from the reed casing directly to the boost port? I don't see any real advantage through this tube. A properly enlarged intake will always connect the reed to the crankcase. If you the add a machined crankshaft you have a pretty good cross sectional area whenever your engine is able to intake. The pipe would shorten the way of the suction pulses rather marginally and had to be of reasonable diameter to be able to flow some extra mixture. Also you'd have to find a place to fit it so that the gasses escaping out of the reed can be drawn in through this tube... plus you'd have two new joints to seal, but this shouldn't be a real problem there.

You can even take the second concept a step further and fit the reed in a way, so that its flow is aimed directly between the crank webs. This can be done without welding, here you can find some pictures of the very good work from an austrian tuner (Stroh). But there's plenty other ways to do it. If you remove one engine bolt you could move the intake a bit towards the cylinder which helps the flow bypassing the crank. This can be done with epoxy if you trust it in a street engine (I do). Welding will only be necessary (or desirable) if you want to place the reed completely in front of the crankshaft.

Bearbeitet 21. Dezember 2004 von karoo

[FurlanPx]

Good work your engine reed case!

My engine will reach the performances of yours, a touring engine with a good torque and top end speed, but not too exagerate. 7300 rev and a torque 4th gear goes well for my goal!

Yes my draw was made too fast....

however you understand the second type, the red draw, but it was only an idea. The function of this pipe is to short the distance between the boost port and the reed pack, so, when the piston is in BDC and it does'nt pulse the reed anymore, this direct join between reed and boost allow the inertial depression of the exhaust, throug the boost port to open the reed valve earlier and so I will have a loger inlet duration. But maybe this is the same effect that I reach using a thicker petal....so I don't know if it is useful, this is the couse that I ask in this forum

instead you don't understand the first(green) way.

I understand what you understand, and it is a very good way to tune the engine but it is not for a touring engine for sure! there's so much work, it costs too much and like you said, there's the risk that casings might warp after welding.

With the green line I draw the original profile of case, the one in the pic is worked in that place, alluminium was take away to straight the street for the mixture flow more direct to the cyllinder. And in this way maybe I can mount a full circle, because the mixture has got enough space to flow good....but I think is not necessary a full circle because working on the thikness and the material of the read I can reach the same results using a original crankshaft.

you said

"You can even take the second concept a step further and fit the reed in a way, so that its flow is aimed directly between the crank webs."

yes, good tip!

and...what kind of epoxy do you use? do you know devcon f? I need a good epoxy that I can use in another engine, to repair a original rotary valve!

bye

Marco from Udine,Friuli,Italy

[FurlanPx]

and I want to use a head like this (made by my friend with a cnc machine)

eheheheh :grins:

Bearbeitet 23. Dezember 2004 von FurlanPx

[FurlanPx]

up :wasntme:

[karoo]

7300rpm sound faster than it is - that's around 120-125km/h on a 3.50-10 rear tire, depending on the exact type of tire. But not bad either, especially when the engine still has a good pull in fourth gear.

I completely misunderstood the meaning of the green line as you first posted it. After I reread it it was quite clear... That's a good way for gaining some extra cross sectional area if you need it. But I don't think it's enough to still have the same flow in combination with a (unmodified) full circle crank. Even if you add really much material (be it welded aluminium, epoxy or a bolted on fitting aluminium piece plus epoxy or whatever), you'd end up with a channel to the crankcase that barely has the necessary cross sectional area, but has a sharp turn at its entry. If you want to reduce crankcase volume, a modified full circle crank or HPC crank should be better in my opinion.

To form the channel from the reed to the cylinder base you'd have to add at least as much volume like the volume you'd reduce crankcase volume by fitting a fully round clutch side crank web. The channel in itself could be somehow better in terms of flow when compared with the same cross sectional area (you should have more with a modified crank!), but its entry would be inferior.

As for your pipe: it's difficult to predict exactly how it could help. At 8000rpm and 60°C of gas temperature the pressure pulse should travel ~7-8mm per degree of crankshaft rotation. 3° of gain should only make a minor difference... But that's not the point here as I think. I'm rather concerned about the entry to the pipe. The gasses would have to take a sharp turn to flow into that pipe which would result in increased flow resistance. Hmm... but I think it shouldn't hurt things, anyway. Provided you don't add 100ccm of volume to your crank case, of course

Devcon F: I have never worked with Devcon products, but they seem to have a good name. A quick google search showed, that quite some tuners have used it with success in their two-stroke engines, so I think it should be okay. I personally like to use Loctite AL1, which has now been replaced by Loctite A1. But afaik it's only available in big packages (500g minimum).

[FurlanPx]

ouch!

you misundertood again! my draw was very very bad so! :plemplem:

mmm, the green line rapresent the ORIGINAL profile of carter, i cut off the material that was in the green line to allow the flow to be more straight than before! I hope you understand now :grins:

Yes, I thought over the pipe.....so I think it's useless because of the very high speed of the pulse of depression...I will havo no measurable performance gain.

Now I want to buy a worb5 lippenwelle long stroke, for a tourist-performance engine a longstroke it's ok, more torque and power end even if at low rev, it's good. And 190cc it's better than 177cc, and it's profile is the best with reed valve, so I can only slight modify the inlet port for a 4 petal reed valve(malossi manifold or home made manifold) and it doesn't need to weld or epoxy the engine, so I will have a more reliable engine.

What do you think?

Merry christmas from Italy, GSF!!

[FurlanPx]

[FurlanPx]

[graffman]

[FurlanPx]

karooooooo

[karoo]

Sorry for the delay, I was snowboarding in Austria so I couldn't post earlier

In part of my last post I was talking exactly about what you just said about the green line. My whole point was, that the cross sectional area wouldn't be enough if you combine it with an unmodified full circle crank. In every other case, it's fine. In my engine I have removed lesser material because I think that I already had enough cross sectional area through modifying my crankshaft. But you'll see how much material you will have to remove when grinding.

If you want to save some money you could buy a normal long stroke crank and do the modification yourself. All you need is an angle grinder and duct tape (plus teflon tape if you can get it, it looks like duct tape except that it doesn't stick. That way you can stuff it between the crank webs and the conrod) to seal off the bearing. And a load of brake cleaner.

But I don't have any personal experience with a longer stroke on the Polini. Be careful about your port timings or you could lose some punch at the bottom (though you should then have some real gain at higher engine speeds)... But many people are running their Polini with a longer stroke and are happy with it.

A good home made manifold should be better than the Malossi reed valve manifold in every way. If you have access to the right machines I would definitely go for it! The problem with the Malossi part is that its flow is aimed very much to the clutch so that there is a high risk of breaking through when enlarging the intake. Other parts like those from MBD, MMW or S&S don't have that problem. But they're more expensive... you pay for the extra quality. Plus the RD reeds are supposed to live longer than those from Malossi. If I were to design a new engine for me I'd go for a big RD reed in a selfmade manifold. Or a TZR reed. Depends on what's easier to obtain.

But anyway - sounds like a nice engine that you're planning