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Old 20 February 2018, 10:48   #1
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Country: Sweden
Town: Stenungsund
Boat name: Thundercat
Make: Gemeni
Length: 4m +
Engine: 50hp yamaha
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Yamaha 2-Stroker 50Hp HMHO Tuning?

Hi

Getting fast for summer in Sweden!

My to do list:

1.135#Jets
2.Boysen Reeds
3.Exhaust mod?
4.Velocity Stacks
5.Cut rev-limiter
6.Weld Crankshaft?
7.Shaving Cylinderheads?
8.Mill Cylinderhead?
9.Remove Autolube.
10.Unsure of porting?
11 More tips??


I am tuning my Yamaha 2-stroker 50hp for my Thundercat.
I have red about sevrel tuning tips but still have a few questions?
How much can I cut off from the exhaustmanifold ? Is there a risk cutting off too much. As I have learned a 2-stroke engine must have some resistens? Maybe there is enough resistens inside motor ?

Why should I weld my Crankshaft if I cut off rev-limiter?

How much can I remove from the cylinderhead and how much shaving on cylinders?

Porting? only exhaust?

Grateful for all tips.
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Old 20 February 2018, 11:50   #2
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Welcome to the forum.

Roflhat is your man when it comes to tweaking the hell out your engine. If you haven't read this, grab a cuppa. My thundercat
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Old 20 February 2018, 12:11   #3
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Country: Sweden
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Thanks .
Will check this out a.s.p.

Cheers
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Old 21 February 2018, 15:52   #4
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Posted a reply on your other thread 
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Old 24 February 2018, 15:00   #5
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Country: Sweden
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Posts: 14
Thank you for your answer. Really helps alot.

I have now started working with my engine. Wondering if I should use my Reed Stops as in picture nr.2 or leave them out as in picture nr.1?
I have disassebled autolube and will run on premixed 1:50.I will probably make some kind of tray with a gasket for sealing, insted of leaving oilpump on motor.
I have looked at Hydro Techs homepage and was thinking of buying a High Perf Head Kit. But probably I can mill the original one instead? If I do mill the original one 1 mm do you think I also have to shave the cylinderheads?

Is this what I should put on for extra speed?

https://www.ebay.com/itm/Signature-S...JaXSLC&vxp=mtr



Cheers Fredrik
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