ST2-NG Pre-build "Think Tank"

[Master Hack]

Use a bigger wire then.

 

[pgemin]

I built an ST3 several years ago - it contains very similar plans to the ST2 NG. I asked myself many of the exact same questions you are asking.

I too miss minibuggy.net. I was a champion lurker with no posts in14 years.

In short, here are a couple of my solutions:

Brakes: I use one rear brake and added two front brakes. I had a professional welder secure the brackets for the front brake calipers. I matched the rotor bolt pattern to the wheel lug pattern. Make sure your wheel wells are big enough to handle the rotor and caliper.

Electrical: My first engine was a 1994 Polaris 650 3-cylinder converted from fuel injection to carbs and there was basically no electrical except a kill switch, spark plug wires, and a CDI. I blew that engine 14 months ago. My new engine is a 2007 Polaris 700 (I bought the whole functioning snowmobile for $2800 in February). I just got the engine fully installed and running in the buggy 2 months ago. For the electrical on the new engine, I painstakingly cut and extended the harness to the necessary locations (this was easy for me as it was similar to a job I had for several years).

Live axle: I use Porsche 924 CV axles - they are cheaper than 930's and give me 13 inches of travel. The extra width on the rear is compensated by the very wide front end (I think the plans got the total front width wrong).

Jackshaft setup: I have a dual-jackshaft setup: CVT driven pulley and 12 tooth sprocket on the first jackshaft, second jackshaft has ~28 tooth sprocket and 12 tooth sprocket, to final 46 tooth sprocket on the live axle. I don't recommend using smaller than 12 tooth sprockets on 1 inch jackshafts. The final sprocket and brake are welded to a collar that mounts on a 1-1/4 inch keyed shaft.

I have many other lessons-learned, but this should help with several of your questions.

 

[Kartorbust]

I built an ST3 several years ago - it contains very similar plans to the ST2 NG. I asked myself many of the exact same questions you are asking.

I too miss minibuggy.net. I was a champion lurker with no posts in14 years.

In short, here are a couple of my solutions:

Brakes: I use one rear brake and added two front brakes. I had a professional welder secure the brackets for the front brake calipers. I matched the rotor bolt pattern to the wheel lug pattern. Make sure your wheel wells are big enough to handle the rotor and caliper.

Electrical: My first engine was a 1994 Polaris 650 3-cylinder converted from fuel injection to carbs and there was basically no electrical except a kill switch, spark plug wires, and a CDI. I blew that engine 14 months ago. My new engine is a 2007 Polaris 700 (I bought the whole functioning snowmobile for $2800 in February). I just got the engine fully installed and running in the buggy 2 months ago. For the electrical on the new engine, I painstakingly cut and extended the harness to the necessary locations (this was easy for me as it was similar to a job I had for several years).

Live axle: I use Porsche 924 CV axles - they are cheaper than 930's and give me 13 inches of travel. The extra width on the rear is compensated by the very wide front end (I think the plans got the total front width wrong).

Jackshaft setup: I have a dual-jackshaft setup: CVT driven pulley and 12 tooth sprocket on the first jackshaft, second jackshaft has ~28 tooth sprocket and 12 tooth sprocket, to final 46 tooth sprocket on the live axle. I don't recommend using smaller than 12 tooth sprockets on 1 inch jackshafts. The final sprocket and brake are welded to a collar that mounts on a 1-1/4 inch keyed shaft.

I have many other lessons-learned, but this should help with several of your questions.

What stubs were you using for the axles and did you run discs for the hubs or did you have custom hubs made to run the single disc brake?

 

[pgemin]

What stubs were you using for the axles and did you run discs for the hubs or did you have custom hubs made to run the single disc brake?

I'll try and explain in plain English, but since this is your thread, I'll limit pictures.

Outboard Rear:
Rear stubs and hubs were from a Honda Accord (I think). I cut the stubs off like the plans said using a Lathe and put in a 1-1/4 inch dia counterbore on the back side. I welded a 1-1/4" dia section of ~5 inch long key stock to the back of the stub on the outboard side and welded the other end of the key stock to a homemade flange that mates to the CV axle. The key stock insertion was necessary to ensure the CVs would not rub on the A-Arms and to fit with the bearing uprights. The hubs were modified from 4 on 4 inch bolt pattern to 5 on 4-1/2 inch to match the plans (changing the bolt pattern was a waste of time, IMO).

Inboard Rear:
The sprocket is welded to the collar. I made a custom flange that is welded to the collar and bolted a Honda Civic brake rotor to that.

Additional important notes: I had to lengthen the rear A-Arms and mount them outboard of the bearing uprights to clear the CVs.

 

[Kartorbust]

So bad news, the plan files were saved on my MicroSD card in my phone and my phone no longer can read the card. So they may no longer exist. I need to find a microSD to full SD adapter and see if I can retrieve the files on my computer. Did not really forsee this as a potential problem.

Been waiting for it to warm up more for the weekends so I can try to rebuild the Spirit engine. I'm kind of confident I can get that to work. Once it's running, I'll pull it out of the sled, sell the sled carcass or scrap it to free up garage space, then if I can get the plans retrieved, I may start building. If not, option B is get KJ Raycing VF-1 plans and build one of those with this engine.

 

[Kartorbust]

Did some inspecting on the engine for a few minutes today. Looks like if this thing runs, I think I found a spot for a starter.

 

[Kartorbust]

In other news, I was smart enough 4 years ago to email the plans to myself. My phone is being dumb and will not download them, so I forwarded them to my brother who will have redundant copies as well as a hard copy as well.