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Author Topic: 350 cc big bore conversion  (Read 3919 times)

albertinhouston

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Re: 350 cc big bore conversion
« Reply #10 on: January 17, 2017, 09:42:07 PM »

I was asking about the 306 upgrade
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Mansour_Zianour

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Re: 350 cc big bore conversion
« Reply #11 on: January 17, 2017, 10:44:15 PM »

I was asking about the 306 upgrade
I was able to find a pair of off brand 63.5 pistons with 15 mm pin. After cc'ing the head and measuring the compression ratio, I had to machine the top of the piston to adjust the compression height for a safe compression ratio. The original sleeves had to be removed for a bigger sleeve. The cylinders wear machined to fit the new sleeves.  The ID of the new sleeves wear machined to fit the new pistons. As far fuel delivery, I had to reposition the TP sensor and I also used a 50K Ohms potentiometer in series with IAT sensor(very important) which it is mounted on the left handle bar for easy adjustment. It advances  the ignition timing and fools the ECU to think the air is colder than what it really is(richens the mix). The potentiometer has to be adjusted every time I ride with respect to the air temperature that day. It might sound complicated but it works very well and it is very easy to feel the best setting. This is a good mod if any one has a free flow air filter like K&N and a must with a free flow exhaust , even on the stock displacement. It is like rejecting carbs(good old days) when you modify the intake and exhaust. I don't have a wideband sensor on the bike but I do feel the injectors lean out at very high RPM's. I don't run the bike at red line for long periods anyway. Like I said before, I changed the rear sprocket to a smaller size due to more power available and higher top speed. I have the Arrow full exhaust system which sounds like a mid size Pantah(Ducati) engine.
« Last Edit: January 17, 2017, 10:53:22 PM by Mansour_Zianour »
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Dagra82

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Re: 350 cc big bore conversion
« Reply #12 on: January 20, 2017, 12:54:36 PM »

Hi , im spanish ,Piston of diameter 61 as maximum, of more diameter they remain very fine the shirts of the cylinder.






subir foto
I bought 58.5mm pistons for safety.
The compression distance is larger and to solve the cylinder head gasket is removed a blade and left with 2 blades in the head gasket.
When I have photos I will put them.
Now I am saving money to be able to rectify the cylinders and buy rodaminetos better to support the new pistons.
While I wait I am polishing the butts.
The exhaust mirror and the same intake but the beam with sandpaper 80 to mix well air and the gosolin before the entrance of the valves.











Today I will start with the other butt.




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Joss

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Re: 350 cc big bore conversion
« Reply #13 on: January 22, 2017, 08:22:08 PM »

80 grit is some mighty rough stuff for valves and cylinders, are you sure you mean 80 grit (the sandpaper in the back of one of the photos does look like 80 grit :-\)? Are you then using some stages of finer grit afterwards to polish?

Personally I'd of just stuck them in the ultrasonic cleaner but if your wanting to shave metal off then I can see why youve used sandpaper.
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Dojy_biker

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Re: 350 cc big bore conversion
« Reply #14 on: January 23, 2017, 05:46:04 AM »

obviously not 80 grit. most likely typo for 800
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umop-ǝpisdn

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Re: 350 cc big bore conversion
« Reply #15 on: January 23, 2017, 11:07:01 AM »

The thing in the background looks like scotchbrite to me.
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Joss

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Re: 350 cc big bore conversion
« Reply #16 on: January 23, 2017, 12:01:49 PM »

obviously not 80 grit. most likely typo for 800

Is this obvious enough for you?

The thing in the background looks like scotchbrite to me.

Top right and above the valve, that's 80 grit.



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Mansour_Zianour

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Re: 350 cc big bore conversion
« Reply #17 on: January 25, 2017, 11:04:35 PM »

Hi , im spanish ,Piston of diameter 61 as maximum, of more diameter they remain very fine the shirts of the cylinder.


Dagra82,
You have barely increased the displacement and from what I see, your piston's compression height is like 2mm lower than the stock which is going to lower your compression ratio to less than what it was stock. You have done lots of work on porting and polishing the heads and it seams like you are not going to gain much with such small increase in CC and lowered compression. I suggest you do some calculation and at least make sure your are not going to have lower compression than 10.5. I hate to see all this effort going to waist with no improvement in power.





subir foto
I bought 58.5mm pistons for safety.
The compression distance is larger and to solve the cylinder head gasket is removed a blade and left with 2 blades in the head gasket.
When I have photos I will put them.
Now I am saving money to be able to rectify the cylinders and buy rodaminetos better to support the new pistons.
While I wait I am polishing the butts.
The exhaust mirror and the same intake but the beam with sandpaper 80 to mix well air and the gosolin before the entrance of the valves.











Today I will start with the other butt.
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albertinhouston

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Re: 350 cc big bore conversion
« Reply #18 on: January 25, 2017, 11:27:24 PM »

Where are you located?
I might be able to supply you with some doner parts IF after you help me with a kit. At a discounted price of course. lol
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Dagra82

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Re: 350 cc big bore conversion
« Reply #19 on: January 26, 2017, 04:59:34 PM »

The valves, and polished exhaust to mirror, for the exit of the gases. The intake (after the carburetor nozzle) is polished to a mirror and then sanded with 80 grit.Because if you leave the admission polished mirror, does not mix the air well with gasoline, that is why it is brained not to make the crystal effect
I will try tonight to put more photos and explain better.
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