420cc farm kart

[scatteredsun]

Thought I'd finally put together a project post.

First off, I know nothing about karts and very very little about engines. I bought a frame off craigslist on a whim because I wanted to learn about it all.

Turns out I got a Tomberlin Crossfire 150r frame. No engine.

After a flurry of research and learning, I decided on a 420cc predator with a 40 series TC (had a lot fun learning all about TC.)

I realized early on that I'm going to have to chop off the engine cage on the swing arm unit. I pulled the swing arm off yesterday and it's going to go under the knife as soon as I have some free time.

The other hurdle I ran into was the factory axle. All the hubs were welded on. This wouldn't do as the sprocket hub was lined up for a tiny 150cc. I got a brand new, keyed, 1" axle and all the parts. They're set to arrive tomorrow.

I just got back from Harbor Freight with a 420cc predator. I found a super coupon that brought the cost down to 299.99. I happened to spot a Hemi model and snagged it.

I'll post a couple pics of the before and one of the engine assembly when it's all done.

I still need to find a welder (anyone in Seattle?) to weld the engine mount plate on.

After the engine and rear axle are all set, I need to bleed the brakes and bolt the seats on. After that, it's time for a test ride!

 

[firemanjim]

Take it to a muffler shop to get it welded if nothing else....

 

[scatteredsun]

There's a few machine shops around my area but that's a good idea if all else fails!

 

[TT540]

And air up that back right tire to see how long it hold air. Looks flat compared to the drivers side.

Looks like you found a good starting point.

 

[scatteredsun]

Good eye, it is indeed flat. I still need to get the old hub off that particular wheel. Two nuts are being stubborn. I'll make sure all the tires are full before the inaugural run.

 

[baloydi]

I liked the frame.

 

[scatteredsun]

Got my rear axle mostly done. Hub I got for the brake disk didn't fit and I need a couple more lock collars.

 

[scatteredsun]

Well poop.

Sprocket is too big. I'll have to have a shop move bearing flanges back to the end of the frame. I'm not sure what I'll do about the brakes now. Maybe flip the hanger around and mount it all backwards with a smaller disk?

 

[scatteredsun]

Just ordered my 40 series and an 8" brake disk with hub.

I still need to figure out what I'm going to do about that sprocket.

If I go to #35 chain, the 10T sprocket on the jackshaft will be too light and may break.
If I go to #35 and 72T:12T that only gains me .5" of clearance which may not do it depending on where the jackshaft sprocket sits

So that brings me to sticking with #41 chain and:

1. move the bearing flanges back. But that messes up my brakes
2. Move that swing arm support bar back an inch. I don't know where exactly my engine plate will go.
3. Put a notch in the support bar and maybe weld some bar stock to it to shore up it's strength? I dunno. Seems sketchy

 

[jawarren77]

Without knowing where the engine will mount, I would move the cross member to line up to where the shocks mount. That would give you good transverse support. Also, depending on where in Seattle you are, I have access to a welder but am no good at it.

 

[scatteredsun]

I'll know better once the torque converter shows up. I can mock up everything and figure out what can go where.

I went out and bought a HF flux core welder I just need to install a 20a outlet and then I can start playing. I'll probably still take the whole thing to a machine shop but I'll weld the heck out of my next kart!

 

[JaySweenor]

Big engine, small kart

I did this with an 18hp, hope it gives you some ideas...

 

[scatteredsun]

Got everything mocked up. Going to have a welder weld a bar parallel to the middle brace and two bars perpendicular along the engine mount plate so the plate will have support along its edges.

After that, I'll just cut a notch out of the middle support bar so the axle sprocket and chain will have room to clear.

 

[thatcrazydad]

You will have to update on the experience with the Duromax. I had looked at getting one, but they seem to have mixed reviews.

 

[scatteredsun]

Got the plate welded and painted. Engine is mounted, throttle connected (needs some adjustment, pulls too hard atm), chain is finally on and the right size, got the kill switch almost hooked up, just have to crimp on a bullet connector to plug in.

The chain was a huge pain the butt. It was either too long or two short. Finally found a connector link which gave it just the amount I needed. I was worried I would have to put risers under the engine. I don't have a lot of clearance between the engine and the cage above.

Next step is getting the ****ed sprockets aligned. I don't think GPS put the jackshaft sprocket and spacers in correctly. I can't get them aligned without the chain hitting the side of the driven pulley. I'll need to pull it off and go "spacer | sprocket | spacer" instead of "sprocket | spacer | spacer." This should give me more room on the edge for alignment.

After that, I just need to figure out how my brake caliper attaches to the mount (I should have taken pictures before I pulled it off!) and tighten everything up on the axle. Then it's time for a ride!!

 

[scatteredsun]

got everything mounted and aligned.
Kill switch is attached and working

Only three major pieces left.

1. Bolt the seats on. This should be fairly easy and straightforward, just haven't gotten around to it.

2. Fix rear tire. I thought maybe the rear right tire was just flat but it wouldn't hold air. Tried fix-a-flat and there is apparently a big hole or something because it flung FaF everywhere when I started it up to spin the wheels. My next step is to take the rubber off and check the inner tube. I got a new one. I may end up just getting two new 18" tires.

3. I can't figure out how to attach the rear brake caliper! It's driving me crazy. There's no mounting holes on it except for a short tube. May get a new rear brake caliper too.