Proma Bad Snake Af05

[Lucass2T]

Hi

On what kinda setup range would this pipe work best?
I bought one brand new some time ago to put it on my 86' vision.

Specs:
(variated) af05
47mm/65cc Polini cast iron bbk
12mm Gurtner (peugeot speedfight 2) carb
Malossi CF reeds
Rubber airbox intake boot drilled
Top racing 16/32 primary gears.
90/90 rear tire
Milled out combustion chamber for a proper squishband, though the squish is still stock thus the CR is lower than stock. It's going under the mill, goal: 0,8ish squish.






It ran like crap.
First it needed a 20 sizes downjet. That tells me the engine isnt needing as much fuel and thus not producing as much power as it did before. Then ran it with airbox rubber removed, with drilled rubber, without airbox. And ofcourse tried different jets in between.
The motor showed wayyy slower take off, lower top end and no real noticable powerband. I thought, maybe its the super long gears with the tall tire and lack of other real engine mods that prevents it from reaching the powerband. Ran it with the rear wheel raised, no real audible powerband and not really revving out really high...at least not much higher than with the stock pipe.

Whats up with this pipe? Does it need to rev beyond 10k to make any power? Doesnt seem like it when looking at the terribly long and straight non tapered header...
Do i need to port the polini, bump up transfer duration? Does it need more compression? More ignition timing?

[motormike]

You don't say how many cc's the Polini bbk has,
but I assume you have increased it beyond 50.
What is the rating of this pipe?

[Lucass2T]

You don't say how many cc's the Polini bbk has,
but I assume you have increased it beyond 50.
What is the rating of this pipe?

True, but im not aware of any other cast iron polini bbk besides the 47mm/65cc? I know theres a 47mm aluminium one tho.
And Im not sure what the pipe's rating is, probably for a bbk. And even if its not rated for a bbk but for a bone stock 50cc jug....it still had to show signs of a powerband 'somewhere' in the rev range since the header is thinker and there is somthing that resembles a chamber.

[Meatball]

12mm carb for 65cc may be your issue. Should be in the 17mm-19mm area.

[bonesv]

"I thought, maybe its the super long gears with the tall tire and lack of other real engine mods that prevents it from reaching the powerband."
You haven't mentioned anything about the belt drive and pulleys, clutch springs, or roller weights. These items must also be considered to achieve the proper "power band".
A stock belt drive and bbk/"better" pipe/carb will not bring happiness. Is this belt a honda belt for this model scooter? Lower the roller weight a little, and you could try installing higher rpm "stall" springs in small increments to find the sweet spot! Hope this helps!

[Lucass2T]

"I thought, maybe its the super long gears with the tall tire and lack of other real engine mods that prevents it from reaching the powerband."
You haven't mentioned anything about the belt drive and pulleys, clutch springs, or roller weights. These items must also be considered to achieve the proper "power band".
A stock belt drive and bbk/"better" pipe/carb will not bring happiness. Is this belt a honda belt for this model scooter? Lower the roller weight a little, and you could try installing higher rpm "stall" springs in small increments to find the sweet spot! Hope this helps!

All stock, new belt, new rollers. 8/9 gram'ish.
Variator and cooling fin are in great shape. But these parts arent part of the problem. They have nothing to do with the engine acting sluggish and lazy. I did raise the rear wheel to listen to the powerband characteristic...but couldn't really hear it kick in.
I did try lighter rollers tho, from 1 gram, 2 gram up to 3 gram lighter. No effect.

@meatball
Disagree. The polini leaflet recomends, and i quote; Stock pipe + stock carb. And other than that, a 12mm works excellent on this cylinder. That thing has tiny tiny tiny little ports. Havent measured trans and ex timings but I bet they're in the stocker range.

[Meatball]

The polini leaflet recomends, and i quote; Stock pipe + stock carb. And other than that, a 12mm works excellent on this cylinder.

Aaaaaand what pipe are you using????

Good luck

[Lucass2T]

Stock pipe atm.

[Wheelman-111]

Greetings:

I ran the 16/32 primaries on Flash1 and Flash1 - with a LeoVince Pipe and a 24mm carb. Regardless of modifications, I believe that the 7.83 overall drive ratio is challenging for a 65cc SE05 engine to get underway. You can compensate to some degree with extremely light variator weights, but take-off will never be brisk. If you get a tail-wind, near-100KPH top speed is possible.

[benji]

That pipe looks like it needs to go high in rpm to make any power. Try up jetting and running on the stand until it gets to 9-10k maybe. If you down jet you'll limit upper rpm power. Also, maybe a free-er flowing carb would help, but it should still provide enough air and fuel for it to rev up.

[Lucass2T]

Greetings:

I ran the 16/32 primaries on Flash1 and Flash1 - with a LeoVince Pipe and a 24mm carb. Regardless of modifications, I believe that the 7.83 overall drive ratio is challenging for a 65cc SE05 engine to get underway. You can compensate to some degree with extremely light variator weights, but take-off will never be brisk. If you get a tail-wind, near-100KPH top speed is possible.

Yea probably.
I don't really believe the transmission nor that 12mm are the problem. It's either the pipe which has a terrible design (like lots of other cheap pipes, too long header and chamber shape completely off) or the cylinder isnt suited for that pipe. Look, Polini says this particular cylinder is suited (which means, timed) for a stock pipe and carb. And looking at those tiny ports, it's capable of flowing next to nothing.

So putting a 24mm on this engine is just plain rediculous, im not even gonna consider that an option. A 24mm is for engines producing 15hp and up, this one isnt even in the area of 5hp. Already tried lighter rollers, it just won't show me any kind of powerband. Heavy or light, it pulls just the same.

@benji, tried jets from 60 up to 120...

I shall rephrase my question:
In what rev range does this pipe feel comfortable?

For example, a Yasuni C16 feels comfortable in the 10-12k area.

Meatball already hinted on a potential problem a few posts ago. Cylinder = suited for stock pipe, but I try to make proma pipe work on cylinder that is suited for stock pipe. So what should i do? Do i need to bother measuring the ports and maybe raise them? Or is that pipe no good and you can port and grind whatever you want, it will never run good?

[motormike]

We are a willing group, but to my knowledge, nobody here has ever seen the pipe in question.
Solid characteristics of said pipe are unknown to the board.

[Wheelman-111]

Greetings:

As Mike said, I've never seen anyone post about a Proma pipe here either.
I didn't mean to suggest that a 24 was in any way Ideal for your Polini 65, but a CV24 was what I experimented with. Yes, with a snail/butterfly throttle and vacuum-operated secondary slide and all, probably the only reason the carb could work at all.
However, recalling that 14mm is the stock carb size (?) perhaps the 12 is a limiting factor? At one point I had an Arreche 17.5 that worked pretty well. Maybe a happy medium out there?

[Lucass2T]

Greetings:

I've never seen anyone post about a Proma pipe here either.

http://www.hondaspree.net/phpBB3/viewto ... 16&t=12213

Been inhaling too much two stroke fumes Wheelman? You commented multiple times on this build

Ah well anyway, im gonna bump up the compression an maybe put a thick base gasket under the jug. Then try again with this pipe. Who knows what will happen.

[benji]

I think you may be right about the bore not timed right for the pipe. Airsal used to make an aluminum bore for that af05 motor, I don't know if it's any higher revving tho. The real big elephant in the room is the motor/case itself- these little vertical Honda motors just ain't meant to rev up to 10k like a Minarelli or piaggio motor can. If the pipe is meant for 10k+, and you didn't do some Carter porting, it may be a lost cause.