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Old 04 March 2018, 13:25   #11
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Also I used to make my own performance exhaust using hydrotecs photos as a reference (the website is unchanged since 2002 or earlier!)
They use stock Yamaha tuners cut down and then their own fabrication welded on. You can pretty accurately measure their dimensions from the photo and with a tuner in front of you and then make a replica if you are handy with an AC/DC tig. It used to take me 1/2 hr to make one.

When I worked at Yamaha dealer we used to use Yamabond if we had any on the go for the crankcases. If not then any sealant we had to hand - wellseal, hylomar etc as Yamaha machine the cases so accurately.
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Old 05 March 2018, 03:03   #12
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When measuring piston head clearance with solder, make sure it's lead as the new lead free doesn't squash as easily and will give a false reading, also use 1mm diameter solder and insert trough the plug hole above both sides of the piston above the gudgeon pins to prevent rocking. (just a tip guys) be careful not to insert it into transfere ports. I suggest setting to tdc then 15 degree back, to insert solder (also don't drop it inside use 1 length looped so you can feed it in easily).
I'm not sure about the std squish but I wouldn't run closer than 0.8mm.
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Old 05 March 2018, 11:38   #13
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Quote:
Originally Posted by phantom 19 View Post
Also I used to make my own performance exhaust using hydrotecs photos as a reference (the website is unchanged since 2002 or earlier!)
They use stock Yamaha tuners cut down and then their own fabrication welded on. You can pretty accurately measure their dimensions from the photo and with a tuner in front of you and then make a replica if you are handy with an AC/DC tig. It used to take me 1/2 hr to make one.

When I worked at Yamaha dealer we used to use Yamabond if we had any on the go for the crankcases. If not then any sealant we had to hand - wellseal, hylomar etc as Yamaha machine the cases so accurately.
Any photos of the exhausts you made? Did you do any work with the Yamaha 70hp's? I'm looking at making a new exhaust tuner for my CES. The one on isn't bad but theres a bit of a step from the flange to the tuner which can't be good for flow. Want to stick pretty close to stock for the class rules
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Old 05 March 2018, 16:56   #14
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It’s a long time since I last made one. I did have a nice polished alloy yam 90 one I bought from DB Marine years ago (they specialised in XR2s etc), that was a tubular cone type, you had to ditch the outer muffler, not sure who made it but it was very nice.

The ones I made were the standard tuner, cut off half way and then tig welded exactly how hydro tec do it. I may have some photos somewhere. I spent a long time flowing the exhaust through the mid block and midsection on the 90s, they have a few odd bits of casting which form restrictions.
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Old 06 March 2018, 06:57   #15
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I was thinking of designing one and either having it made using CNC or maybe casting the tuner section, although I suspect it will be easier and cheaper to spend time welding one together. Was going to have a new flange cut so I could test back to back and see the results

How much shorter roughly were the hydrotec ones to standard?
Here is the original one from my CES, I had it roughly replicated in stainless but I'm not 100% happy with it. Photo on the bottom is sort of what I'm thinking for a replacement

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Old 06 March 2018, 15:20   #16
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Milling heads.

Hi

Thank you.

Today I have made larger airintake on hood nr.1
Probably I will make my own exhaust in stainless with what you can see on picture nr.2.

About milling my heads. I have mesured them sevral times and as I can see they are exactly the same. Left one from my 50 hp Yamaha and the right one from a 40hp Yamaha. I was thinking of milling 1mm and I will also lathe out new squishbands. When Im finished the top of the head will look the same but depth of combustion chamber will be 1mm more shallow.

Am I on right track? Really dont know if this is right?Anyone knows how much hydrotech does mill on their heads?

1mm?
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Old 07 March 2018, 02:17   #17
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Loving your work!
What was your compression before? I would suspect the Hydrotec heads don't use massive compression as the kits are aimed at the US market with lower octane fuel
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Old 07 March 2018, 09:04   #18
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Compresion

I had more or less 120 PSI on all 3 118 124 119,

Have not yet milled my head. But probably I will take off 1mm. If anyone have done this on a yamaha 40 or 50 hp please tell me how much to start with.

Cheers
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Old 29 March 2018, 15:24   #19
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Porting & Exhaust

Porting and my own exhaustmod.Classic 2-stroke funnel to create underpressure that hopfully will drag out more exhaust fumes. Im looking for new 70hp Yamaha carburators to fit my 50hp Yamaha. Is there anyone who knows what carburators I should look for? Any special model or year of Yamaha Carburators?
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Old 29 March 2018, 15:30   #20
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Exhaustmod&Porting

New mods.
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