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Author Topic: 350 cc big bore conversion  (Read 3920 times)

Joss

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Re: 350 cc big bore conversion
« Reply #20 on: January 27, 2017, 11:07:01 AM »

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.

This makes perfect sense now.
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Dagra82

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Re: 350 cc big bore conversion
« Reply #21 on: January 27, 2017, 01:11:56 PM »

These are my tools and my sandpaper.



subir fotos
When I was polishing the cylinder head, I have realized that the cylinder head is cracked by the spark plug thread.
imagen jpg
So I lowered the head gasket
subir imagenes gratis
Now I have to save money to buy a second hand motorcycle butt, my wife kills me, uffff
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Dojy_biker

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Re: 350 cc big bore conversion
« Reply #22 on: January 28, 2017, 02:27:58 AM »

as a side note of interest:

i have, in the past, very successfully re-used the multi layer metal gaskets via this method:

Separate the layers, and pick one. (if the head and barrel are lapped flat you only need one)
Re-crimp a sealing bead around all the ports *
Degrease thoroughly
Spray a good even coating of Extreme high temperature exhaust paint (the kind that bonds when it cures) on the "new" gasket (there are many brands, some better then others, and gloss black is always better for some reason. Hicote is ok, but ive had great results from halfords own brand)
when dry, assemble engine with newly refurbished gasket.
be sure to torque down to spec.
on first run : run engine with no throttle, let it warm up and cure the gasket paint for time as recommended on paint can.
turn off and let it cool to warm enough you can still touch it.
Re-torque the head

* you can only do this once without metal fatigue becoming a problem, but you are only using one layer at a time so you have spares for the future.
heres my home made crimp tool:
« Last Edit: January 28, 2017, 02:31:56 AM by Dojy_biker »
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Hylife

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Re: 350 cc big bore conversion
« Reply #23 on: January 28, 2017, 09:12:44 AM »

Spray a good even coating of Extreme high temperature exhaust paint (the kind that bonds when it cures) on the "new" gasket (there are many brands, some better then others, and gloss black is always better for some reason. Hicote is ok, but ive had great results from halfords own brand)



Better to use Proper Silicone Sealant designed specifically for engine gaskets and you can reuse the sheet metal gaskets indefinitely. Only $10-15 a tube.
The entire crankcase is joined vertically using only silicone.

Pematex Ultra Grey exceeds the OEM specs of all metric bike brands and is oil resistant.


Spec sheet here: http://www.permatex.com.au/TDS/82194.pdf
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Dojy_biker

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Re: 350 cc big bore conversion
« Reply #24 on: January 29, 2017, 02:57:53 AM »

im a bit reluctant to use silicone on a head gasket. My method is basicly the same as the factory coating on the gasket.
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Hylife

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Re: 350 cc big bore conversion
« Reply #25 on: January 30, 2017, 05:44:21 AM »

The factory uses automotive silicone sealant on all mating surfaces. All auto factories do, even for cars etc.
Why be worried about the cylinder head? The entire crankcase halves are sealed ONLY with silicone sealant. There is no gasket used at all to join the crankcase.
Examine a new bike engine and you can see the very small amount of excess silicone that has squeezed out from the joints.

The sole purpose of a gasket is to fill in tiny imperfections in the mating surfaces for a perfect seal. That is why motorcycle head gaskets are usually made of some soft material like a copper/zinc (brass) alloy. Just smear a very very thin coating on both surfaces with your finger before positioning the gasket and tighten immediately. Don't worry about wiping away the tiny excess that may squeeze out, leave it there because you'll only make a mess. It peels off simple when dry.
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Joss

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Re: 350 cc big bore conversion
« Reply #26 on: January 30, 2017, 03:16:02 PM »

The factory uses automotive silicone sealant on all mating surfaces. All auto factories do, even for cars etc.
Why be worried about the cylinder head? The entire crankcase halves are sealed ONLY with silicone sealant. There is no gasket used at all to join the crankcase.
Examine a new bike engine and you can see the very small amount of excess silicone that has squeezed out from the joints.

The sole purpose of a gasket is to fill in tiny imperfections in the mating surfaces for a perfect seal. That is why motorcycle head gaskets are usually made of some soft material like a copper/zinc (brass) alloy. Just smear a very very thin coating on both surfaces with your finger before positioning the gasket and tighten immediately. Don't worry about wiping away the tiny excess that may squeeze out, leave it there because you'll only make a mess. It peels off simple when dry.

Agree completely. I've split 4's and 2's and its always been a smear of silicone on crankcase halves.
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Dagra82

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Re: 350 cc big bore conversion
« Reply #27 on: January 30, 2017, 05:13:50 PM »

Our hyosung only carries silicone when collecting the characters, the other takes gasket of factory.
I lowered the cylinder head gasket. The cylinder head gasket has three layers, I have removed a cap. Now the board is 1 millimiter less, so we do not lower the cylinder head
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Dagra82

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Re: 350 cc big bore conversion
« Reply #28 on: February 16, 2017, 02:10:06 PM »

I already have the cylinder heads finished and today they take the cylinders to rectify.

I have also polished the crankcase and I will change all the bearings for safety

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Re: 350 cc big bore conversion
« Reply #29 on: February 16, 2017, 05:27:17 PM »

I bought and used Loctite 3020 to re-use the head gaskets, after I saw some success with people using 3020 on cars, with the same shim-style gasket.

It comes in spray form, you apply a few coats, let it dry just until its tacky to the touch, the squish it all together and torque down. Ride for 50 miles then re-torque.
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