ESE's works engine tuner

[adegnes]

...worse case scenario I will do it by hand with sand-paper..

One big advantage of doing it by hand with sand paper or small files - it's slow, very hard to screw up.

[adegnes]

Playing with the belt tensioner.
Whats better? Both pictures are with the variator in "low gear"



vs



Yeah, pipe is ugly I know...

[senso]

The first one seems to provide a smaller footprint, less pulley to put your feet into, but I don't think the skate bearings will be up the task, maybe using a belt tensioner from a car might be a better option, from some small 1.1 to 1.5l engine will be compact and have everything included(bearing, rolling surface, eccentric adjuster, spring/hydraulic tensioner) in a ready to mount piece with 2 or 3 bolts, the best part is that you get all that for 30-40€.

[adegnes]

Belt tensioner from a car is a good idea, thanks!

[TZ350]

I was mistaken, the maximum I can go is 22mm from top of cylinder to top edge of the exhaust port, with the stock 91mm con-rod and 41.4mm its just shy off 186º, the transfer all sit at 32.5mm from top, about 124º timing for A and B, being the C a bit lower with around 117-118º.That gives 31º of blow-down, but with limited area.

I still don't like a lot of the idea of raising the cylinder and machining the top, because I just gain timing in all the ports, so the blow-down remains the same and 1mm will leave the cylinder with almost 130º in the transfers.

The degrees of blowdown may remain the same but if you are widening the exhaust port, the blowdown STA increases, its the STA (Specific Time Area) that is important.

The timing of the exhaust port becomes important because of the all important pipe resonance reinforcement you get around 190-194 duration of the pressure waves in the pipe.

[breezy]

Playing with the belt tensioner.
Whats better? Both pictures are with the variator in "low gear"



vs



Yeah, pipe is ugly I know...

hello, just an obserevation, shouldnt the front pulley be turned the other way so that the rollers push against the sheave to grab the belt, or am i seeing it wrong. yeah seeing it wrong.. rollers still push sheave

[adegnes]

hello, just an obserevation, shouldnt the front pulley be turned the other way so that the rollers push against the sheave to grab the belt, or am i seeing it wrong.

It does exactly that, the outer moving sheave is pushed towards the inner stationary sheave by the rollers. It's just mounted inside out compared to most scooters.

[breezy]

yeah sorry just edited post... does anyone know the dimention from the center of the front variator shaft( crankshaft) and the clucth wheel shaft on a piaggio zip 50cc 2t.

[wobbly]

From the 50cc pics its easy to see that you can get into the waterjacket and firstly bead blast then secondly metal spray the cast iron above the EX.
This works very well, we have been metal spraying the cast iron bore cylinder tops on KT100 Yamahas for years, then spraying the alloy fins as well to
get the rule book legal overall cylinder length dimension after machining the base to drop the port timings.
And its the effective port area you need to use ie is that 600mm2 times the down angle cosine ?

[lodgernz]

[QUOTE=adegnes;1130828775]Playing with the belt tensioner.
Whats better? Both pictures are with the variator in "low gear"

I don't know about variators, but if they were toothed or fixed pulleys, the first option would be the one, since it provides the belt with more wrap-around on each pulley

[adegnes]

[QUOTE=lodgernz;1130828838]

Playing with the belt tensioner.
Whats better? Both pictures are with the variator in "low gear"

I don't know about variators, but if they were toothed or fixed pulleys, the first option would be the one, since it provides the belt with more wrap-around on each pulley

That makes sense.

[Drew]

[QUOTE=adegnes;1130828842]

That makes sense.

To a point. But the extra 'drag' is less than desireable, one would think.

I'd get a shorter belt, and let it tension with the pulleys like it's meant to.

[adegnes]

[QUOTE=Drew;1130828853]

To a point. But the extra 'drag' is less than desireable, one would think.

I'd get a shorter belt, and let it tension with the pulleys like it's meant to.

The drag thing makes sense to.
It's single variated, originally the whole engine was the tensioner - spring loaded and swinging back when the variation was happening, the rear pulley is just that; a pulley, no moving sheaves.

[jasonu]

hello, just an obserevation, shouldnt the front pulley be turned the other way so that the rollers push against the sheave to grab the belt, or am i seeing it wrong. yeah seeing it wrong.. rollers still push sheave

I would have thought no tensioner was appropriate as the moveable sheave increases and decreases the amount of belt needed as it moves in and out. That is how it works on my Polaris Sportsman 700 twin quad anyway.

https://www.google.com/search?q=pola...ms%3B480%3B360

[lodgernz]

Senso, now that you have cut your CRM50 cylinder, is it possible to measure the thickness of the sides of the exhaust port near the cylinder wall?
I am wondering how wide we can go at the top of the port before breaking through