Jacobsen 321 set up for minibikes

[KB2ROCKET]

 

[KB2ROCKET]

Lots of work.
The idea here is to make a little 2cycle that is minibike friendly most of these engines are overlooked because of the challenges they have the biggest of them being making a mount for them .. the exhaust .. mounting a clutch in them and having it line up with the rear sprocket and rigging the throttle also many small 2cycles are used on snow throwers and outboards these engine do not have air filters .. I hope to overcome these obstacles ...
This engine was originally intended for use on a WWII army signal corps generator .. not your typical jacobsen reel mower

 

[KB2ROCKET]

thats enough for today

 

[1stlegendtx]

What is your exhaust plan? I always hated the exhaust on those things.

 

[KB2ROCKET]

Not thinking to much about the exhaust right now it turns out that this thing has an odd ball sized Pto biger than 5/8 smaller than 3/4 it appears to be 11/16 just my luck:doah: lol

 

[5horsebriggs]

Grind it down:shrug: or make a sleeve so it will accept 3/4

 

[1stlegendtx]

Is it the same as this?

 

[KB2ROCKET]

I have been taking the best of two engines to create this one the parts engine had a pulley on it so I pulled it off and guess what I found a split bronze bushing that allowed the pulley with the 3/4" bore to be used so I guess I will be using a 3/4" clutch lol

 

[KB2ROCKET]

Is it the same as this?

that guy must have machined down the crank that looks like A 5/8" CLUTCH just like the one I have

 

[KB2ROCKET]

What is your exhaust plan? I always hated the exhaust on those things.

The stock exhaust system is kind of odd but they are super durable I have never seen a worn out one yet

 

[rmm727]

Might be 16mm on the clutch. Check and see. Might be able to use a db clutch.

 

[KB2ROCKET]

When you convert 16mm to inches then to a fraction its 5/8"

 

[rmm727]

Maybe if you like rounding to the nearest whole number.

5/8" = 15.875mm
11/16" = 17.4625

Measure the crank with a caliper or a mic and see what you get. Maybe it is 11/16" but I wouldn't use a tape measure as the deciding factor.

 

[KB2ROCKET]

Maybe if you like rounding to the nearest whole number.

5/8" = 15.875mm
11/16" = 17.4625

Measure the crank with a caliper or a mic and see what you get. Maybe it is 11/16" but I wouldn't use a tape measure as the deciding factor.

thanks for the info and yes I agree tape measures are not the right tool for percission measuring

I have reduced the 5/8 clutch to its hub and I have decided to drill it out to a predetermined depth this will keep the clutch from traveling inbord because their is no step on the shaft stub then I can use a retaining bolt to hold it in place . after spending 3 days exploring this engine I have developed respect for its design it is very robust they really new how to make things in the 40s and 50s its a bit underpowered for minibike use but still very interesting to me at least

 

[KB2ROCKET]

well I got a clutch on there just need a center bolt and some set screws to help hold it in place

 

[KB2ROCKET]

I guess now would be a good time to start thinking about the exhaust a motor mount gas tank and throttle linkage

 

[bandit 40]

Very Nice KB :thumbsup:

 

[KB2ROCKET]

All the same and all very different but the one thing they all have in common is the crank stubs are all about 11/16 this is why they are very rarely seen on karts and mini's

 

[cumminsbayou]

All the same and all very different but the one thing they all have in common is the crank stubs are all about 11/16 this is why they are very rarely seen on karts and mini's

where are you getting this information from? they aren't seen one mini bikes and go karts a lot is because they are rare motors, and even more rarer down south because they mostly came on snow blowers. Another thing would be that with out a bigger carb on them the fastest you gonna be going is like 10mph. Mine had a carb with a bowl on it so this may could have been why.

 

[KB2ROCKET]

These were used on reel mowers edgers and the bright orange one was used on a army signal corps radio generator in WWII I have a few more parts engines I seem to be a magnet for them I like them because this is what my dad had on his mower when I was a kid in the 60's his was marked 2 1/4 hp and was most simular to the one on the left . The one in the center is locked up and is my next project