Yamaha YZ80 2-Stroke Engine

[The_Ruppster_86]

Hi all,

About 3 weeks ago I acquired a '77 Yamaha YZ80 engine at work. I was contemplating the idea of using the engine on a vintage bike. See the thread Creia created:

http://www.oldminibikes.com/forum/general-minibike-talk/82777-yamaha-2-stroke-engine-mini-bike.html

We are going to do it... Below are some photos of the engine as I received it.

The plan is to rebuild/ modify the engine first then start looking for a suitable full-suspension frame. Thanks for looking! :thumbsup:

 

[truckfreek]

what kinda mini are you going to put it on? that would be cool on a mini baja

 

[jdogg]

I'd do it too!! :thumbsup::laugh:

 

[David wulf]

Put it on a bonansa MX , GR dave has one

 

[creia]

Put it on a bonansa MX , GR dave has one

$$$:scared:

 

[Neck]

Yeah! What bike will be receiving this jewel?

 

[toomanytoys]

That thing would be scary on a minibike. 18 HP at 10-11k RPM. Drops off pretty quick. Between 6k and 10k you aren't going to be able to hold on the power builds so quick.

 

[The_Ruppster_86]

what kinda mini are you going to put it on? that would be cool on a mini baja

Put it on a bonansa MX , GR dave has one

Yeah! What bike will be receiving this jewel?

We would like to use it on a full-suspension frame. Possibly a mini-cycle!:innocent:

 

[The_Ruppster_86]

That thing would be scary on a minibike. 18 HP at 10-11k RPM. Drops off pretty quick. Between 6k and 10k you aren't going to be able to hold on the power builds so quick.

Scary is what I'm going for.:thumbsup: The engine will not be all stock. I will post some of the mods done along the way. Thank you for the information.

 

[jdogg]

Go for it Jeff!! You only have to go as fast as you twist the throttle!! :thumbsup: And what I mean by that is if its too fast or too powerful for a mini its all up to you... you are the judge... you decide how far and how fast to twist that throttle!! I'd wear a full face motocross helmet and gear on this one though my friend!!

 

[David wulf]

That thing would be scary on a minibike. 18 HP at 10-11k RPM. Drops off pretty quick. Between 6k and 10k you aren't going to be able to hold on the power builds so quick.

Maybe a 2013 but not that 1977 model . JMHO

 

[paul_probus]

Make sure whatever you build from it has fat wheels! :devil2:

 

[toomanytoys]

Scary is what I'm going for.:thumbsup: The engine will not be all stock. I will post some of the mods done along the way. Thank you for the information.

I don't want you to think I was dissing your project. Just its gonna be scary fast. Wear a helmet!

 

[The_Ruppster_86]

I don't want you to think I was dissing your project. Just its gonna be scary fast. Wear a helmet!

I didn't take it that way at all. :thumbsup:

 

[The_Ruppster_86]

Go for it Jeff!! You only have to go as fast as you twist the throttle!! :thumbsup: And what I mean by that is if its too fast or too powerful for a mini its all up to you... you are the judge... you decide how far and how fast to twist that throttle!! I'd wear a full face motocross helmet and gear on this one though my friend!!

Thank you jdogg! I have a DOT helmet that I wear now but long pants, gloves, and pads might be needed on this project. :laugh:

 

[toomanytoys]

Maybe a 2013 but not that 1977 model . JMHO

Maybe so. But I bet that thing still builds power in a hurry in that RPM range. Maybe not 18HP, the power band is most likely going to be narrow and build up FAST.

I road some earlier YZs back when I was younger, and when those thing hit, they hit hard and fast. It was a major surprise when it came into power.

Most 2 strokers are like that either way.

I was never a good 2 stroke dirt bike rider.

 

[David wulf]

Toomanytoys yes they did hit hard and would be great on a minibike . I know they would smoke the XR75 we had back then . And with some port work i bet they could make 12 plus
:thumbsup:

 

[toomanytoys]

Toomanytoys yes they did hit hard and would be great on a minibike . I know they would smoke the XR75 we had back then . And with some port work i bet they could make 12 plus
:thumbsup:

:thumbsup: maybe give the super Powell a run for its money :Lol:

 

[David wulf]

:thumbsup: maybe give the super Powell a run for its money :Lol:

Maybe!!:shrug:

 

[The_Ruppster_86]

Yes, David Wulf you better lookout. The Yamaha is getting hungry for Powell lunch! :laugh:

Below are some more photos of engine disassembly. Enjoy.

Intake Manifold

Top End

Piston

Flywheel Magneto (Left side)

Clutch (Right side)