McCulloch SP-81 Project (Experiment)

[stinkbait]

I have been collecting a few parts here and there to to start my new SP-81 project. I am going to take an ordinary 5-10A chainsaw and install a brand new, ported, SP-81 engine in it. I also plan on installing a huge walbro wb carb on it that I picked up a while back. I am going to have to do a lot of modifications to the intake to make it work. So far I have designed an adapter plate to mate the wb to the 5-10 carb box. I have also had a prototype of the adapter build on a 3D printer to see how well it fits. I also have the 5-10 tank/upper handle at the machine shop getting some things done to it. Here are a few pics that I have taken so far. I will get some pics of the brand new cylinder, crankcase, piston, and bearings up later. I plan on running a 16" roller-nose bar, that I already have, with .404 chain with an 8 tooth sprocket.

The carb

The Carb sitting in stock 5-10. Shown backwards from the way it will actually be installed. Will be rotated 180 degrees from what pic shows.

My carb adapter design

The prototype that I had made of my design

The grey stuff in one of the holes on the prototype is just some build material that wasn't completely removed. More to come soon.

 

[RandyMac]

Now we are talking, good stuff.

 

[stinkbait]

Now we are talking, good stuff.

I was wondering if there was someone that would be interested in this.

 

[RandyMac]

One of my projects is going to be an 82cc hotrod built to my own specs. It will be light, fast and loud.
Al Smith has some great ideas that I may borrow.

 

[jockeydeuce]

Very cool stuff!!!.....Builds like these are like building old skool custom bikes....I'll be following this one!

 

[mactodd]

Basically, a non-AV SP81....or, an 82cc 10-10. Either way, I like it! Helps when you can do SLA for RP!

 

[cat-face timber]

Very cool stuff!!!.....Builds like these are like building old skool custom bikes....I'll be following this one!

+1

 

[stinkbait]

Basically, a non-AV SP81....or, an 82cc 10-10. Either way, I like it! Helps when you can do SLA for RP!

Yes! Plus this one will be sporting a port job and a huge carb.

 

[leeha]

Nice thread, Nice build.
I will be following this one as well.
I'm curious if the 82cc motor can handle
the big carb.



Lee

 

[igpoe]

Even CAD people have CAD

 

[homelitejim]

subscribing, as I am putting a PM850 engine in a CP70L body.

 

[RandyMac]

What are your plans for the exhaust?

 

[paccity]

will be following,have a 80 and 81 to get some ideas for. something to play with other than the norm orange and white stuff.

 

[homelitejim]

will be following,have a 80 and 81 to get some ideas for. something to play with other than the norm orange and white stuff.

I love my SP81 and grab it in a pinch over my newer orange and white stuff of similar displacement, and not that it is much faster, just more Bad A$$ed.

 

[stinkbait]

Nice thread, Nice build.
I will be following this one as well.
I'm curious if the 82cc motor can handle
the big carb.



Lee

I hope it can handle the carb. I'm thinking that it will probably do fine at WOT, but have trouble idling. I really have no idea if it will work. I know that the Homelite 650 uses the WB carb and its only 18cc bigger than the SP-81. I'm hoping that the porting will help. The only thing that I don't like is that there is no choke.

What are your plans for the exhaust?

I am planning on using the stock 81 muffler. I am going to open it up bigger where it bolts up to the block and make my own custom cover.

 

[little possum]

Hooray Stinkbait!

 

[Brian13]

Subscribing!!! This looks like it will be an interesting build.

 

[stinkbait]

Here is another pic. The only things in this pic that are not new is the crankshaft and the coil, everything else is NOS.

 

[hoss]

:beauty3:Great idea!opcorn:!!!

 

[little possum]

Mitch, did you happen to see Scarrs thread on "reworking" the ports on the 394. Maybe something to consider to get rid of the McCulloch groove for compression release?