Yamaha Malta 3HP tuning for fun to presently 7.4 @ 5300

The progress on my 3Hp 70ccm 2stroke Yamaha Malta is as follows:

Attachment 422995

I am jusing a DIY hydraulic dyno with an electronic torque wrench on it. Data are "collected" by doing a video and typing them into a ecxel chart as many as i can. Then i kick out these who will not realy fit to the others. I think i get relatively reliable data doing this this way.

Sorry for the poor vid quality, but i had to handle my phone and the hydraulic valve wheel while stopping to breeze :p (Have to search for a nicer smelling 2stroke oil)

https://youtu.be/XAemR-L8sUc

I love it.

What mods have you made so far to the engine?

Rob

This one does have digital inner rotor ignition with a nice preignition curve fix programmed in the cdi, Glass Fiber Membran in stock housing, kart Membran carburettor tuned to slightely lean condition (A/F Ratio) with 16mm venturi only and 11:1 total compression ratio with .6mm squish band (approx. 40% of the bore)
Rest of "Block" and exhaust are stock!

next Target are 10HP @ less than 7,000 rpm (becomes much more difficult)
i will use another block with more rpm willing degrees of exhaust timing and surface space...

sorry for autocontrol typing on mobile pad combined with ginglish ;-)

Pictures of the dyno please, cool project!

Schnurle ?

Yes, with inlet into crank case.

That is an incredible amount of effective compression. What is your cranking compression reading? What type of fuel?

Can you provide bore/stroke/rod length please?

Pictures, we love pictures.

Rob

.6 , zero deck , gasket material?

Quote:

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Originally Posted by PPRINT

That is an incredible amount of effective compression. What is your cranking compression reading? What type of fuel?

Can you provide bore/stroke/rod length please?

Pictures, we love pictures.

Rob

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Hi Rob,

you are fully right. I did not use the correct word. it is 11:1 total! ( i will correct this in my above post)
(Bore 42mm stroke 46mm) : (combustion volume)

We can get up tp 102 OCT = approx 98 AON at gas stations. If i leave it at 11:1 i don't have to mix it with i.e. Toluol.

Timing checked with a degree wheel

Attachment 423038

The timing of a stock block is very low and one of the reasons why it dont like to go to higher rpm.
But the low data gives low rpm torque...
Intake 110°
Exhaust 150°

Attachment 423039

2 transfer channels only, but huge! Exhaust port gives a chance of positive influencing.

Attachment 423040

Ignition and carb changed

Attachment 423042

Tested on a hydraulic brake Dyno

Attachment 423041

enough pics? :)

gasket is aluminum
zero deck means what?

head machining of squish (angle):

Attachment 423045
Attachment 423044

Machining to head volume

Attachment 423046

Gauging of head squish angle

Attachment 423052

Attachment 423049

= 5.4°

But the next step i'll do is with another block. (slightely changed exhaust timing) using the above shown head. I will enlage the intake membran to max more surface (8 carbon blades) and cut another block in pices to see how much space i have to widen the exhaust channel before i brake into cooling channels.

Attachment 423055

from left to right: stock 3pcs steel reed, little more surface and 2 glass fiber reeds, huge surface and 8 carbon reeds

I'll see...

send this guy a 9.9 rude.......

Or a 78 8hp 164cc looper CHRYSLER with low water pickup lower unit, 53lbs, squash that 9.9!

Zero deck, piston height in bore in relation to deck at TDC.

Quote:

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Originally Posted by oldschoolltv

Pictures of the dyno please, cool project!

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Dyno pics are on YouTube link posted in " effects of shortening shaft length on 2 stroke " thread. Tried to copy and paste link for you, but I am, apparently, too computer illiterate to perform such function. Sorry.... I tried!