Crossfire 150R 670 swap build

[Lakemanroy]

sorry for the long post.
Ok, I started this build about a month ago. I can’t believe how much work it actually was.lol I cut the swing arm, and extended it 4” or 4.5” I don’t remember.
welded 1x2 framing everywhere. Layed a 3/16“ plate on top and welded it in. Engine plate welded on top of it. laid 1x2 flat ways as engine risers to give more clearance for the CVT. Flipped the axle over swapped the rotor to the center, and sprocket to the outside. Made a bracket for the caliper. Had a sprocket made to fit the hub. Cut the rear bumper, and added like 4” so the exhaust would go underneath it. Added some framing to it for strength. cut the roll cage in the rear, so I could raise the rack up for engine/air cleaner clearance. welded new supports to the front of the rack, and bolted in like factory, but added a small weld so it wouldn’t rattle. i connected the back of the rack and drilled holes to match the existing holes. I raised the fuel tank and moved it tord the rack so it would fit. Changed the little shut off valve and went with 5/16” Tygon fuel line. I’m 6’2” and long legs, instead of stretching the front of the cart I cut the side rail where it was welded, and cut the tube part of the way back by the seat. I pushed that rail out like 3”, and used a piece from the rear rack and welded it back together.

The gy6 ran excellent, just too small for a heavy go kart. I did the air cleaner, PWK carb, exhaust. It ran great. 34.5mph which is good for a heavy crossfire R. I live in southern Ky and it we have big hills, and the 150 didn’t have enough torque. great little motor tho.

Now to the 670 predator part. Removed the limiter, low oil sensor, built a header, air cleaner, before I touched the go kart. 780 CVT from go powersports, which I will never deal with them again. I flipped the driver around so the belt is pushed the same direction to cut down on belt slip. Drilled the jets out which I have done for years racing boats, cars, quads, and whatever I could race.lol I popped out the Welch plugs so I could adjust the richness of the carb with the screws. I Went with 12/60 on gearing, with a 22” tire. Added the oil catch can, for the oil sloshing and being sucked up in the carb Causing smoke when I ever you do a donut. I loved the gearing had plenty of power, and still great top end. 3800-3900 was 50 mph. Well i smoked the belt after 3-4 hours. I changed to 10/60, which I really don’t care for. 4000 is 45mph, but hard to take off in the grass without spinning. I swapped to a double cogged belt G-Force. you proly know what that cost. The belt is like .34 shorter, but it seems to be working so far, but time will tell. I talked to the rep at comet, and was advised by them. Also lightened the weights in the driver so it would engage at higher rpms so it would kinda jump out at the belt and grab it instead slow and easy to cut down on slip per comet. That is where the belt would slip on the driver in the lower part. first attempt raised it to about 1800 to 1850. Second attempt I’m at 1950 to 2000. Seems happier there. I have a cam, springs, and the short pushrods for it, but haven’t installed them Yet. I’m sure I will get a real carb for this thing, or dual carbs. The factory carb runs a lot better than I thought it would after some mods, and adjusting. Anyway that is my go kart build to date. i proly have about 100 hours in this thing to date. I named “A.I“ for “Absolutely Irresponsible“.

Thanks,
Roy

 

[ezcome-ezgo]

Well done Roy, looks awesome. Assume you are in SE KY?

 

[Lakemanroy]

Thanks. South central by lake Cumberland.

 

[Lakemanroy]

Looks like I posted this in the wrong place. Feel free to move it. Sorry

 

[Denny]

Your fine. Just what is so irresponsible about it?

 

[Lakemanroy]

Your fine. Just what is so irresponsible about it?

I have twin boys that are 23. I don’t need either of them getting hurt. Gearing it down to 6.1 in the gravel which we have a lot of here, it is a little wild.

 

[panchothedog]

I like the name, and what you have built, A lot. Nice work. At 23 your Sons are grown men. My oldest Grandson turned 22 today. He hasn't quit asking me to make the karts go faster for almost 7 years. They'll be fine. Has to feel pretty good when you put your foot in it. That's a lot of displacement for a go kart.

 

[Lakemanroy]

I like the name, and what you have built, A lot. Nice work. At 23 your Sons are grown men. My oldest Grandson turned 22 today. He hasn't quit asking me to make the karts go faster for almost 7 years. They'll be fine. Has to feel pretty good when you put your foot in it. That's a lot of displacement for a go kart.

Thanks.

 

[ezcome-ezgo]

Lake Cumberland is the hand of God. Or TVA I can't remember. Anyway, pretty country up there.

 

[Lakemanroy]

Lake Cumberland is the hand of God. Or TVA I can't remember. Anyway, pretty country up there.

Yeah it is beautiful here. I’m here for the lake.

 

[Functional Artist]

Howdy & welcome

I got relatives from the Corbin Ky area
...& have been to the Cumberland Falls State Park many, many times
...& even saw a Rainbow in the Dark, there when I was a kid

Interesting kart
...but, we need more pics (state law)

 

[Edwin Spangler]

even saw a Rainbow in the Dark,

Thanks, now Dio will live in my head for the next week!

 

[Lakemanroy]

Howdy & welcome

I got relatives from the Corbin Ky area
...& have been to the Cumberland Falls State Park many, many times
...& even saw a Rainbow in the Dark, there when I was a kid

Interesting kart
...but, we need more pics (state law)

Yes the famous Moonbow.

 

[Lakemanroy]

Ok a little update. I’m getting use to the 6.1 gears. Spun the tires in the gravel for over a 100’. lol. I broke the new belt in enough I guess. I special ordered a jack shaft that came in and installed it. Everything seems to be good, so I hit the main road. It hit a wall I figure the valves were floating. It is a touch lean on the top end, and a little lazy up there. My little recall tach only said 3690. I know it was higher than that. Anyway hit a new high mph. 55.1mph. 6.1 gear ratio, 22” tires, 780 CVT. For the math to work out it had to be close to 5000, or the tires are growing from centrifugal force. I also weighed since have a scale for high performance boats. I’m an Allison boat guy. Weighed 635 with oil, battery, and about a gallon of fuel. Add me that is 835. So far a 21mph top end increase over the 150.

 

[panchothedog]

Maybe you should try that 11 tooth sprocket. Sounds like you have PLENTY of low end at 6 to 1. Should lower your rpm enough to cruise on down to the boat ramp without beating the snot out of it. FWIW, on all of the smaller predator engines, once you start hopping them up ( stiffer valve springs, big lift and duration cams, carb, compression ) really starting to spin them, it is considered safe ( for longevity ) to replace the stock rod and flywheel. They are manufactured to run consistently at 3600 rpm. Failures are not unheard of in the
5800 to 7000 range with stock internals.

 

[Lakemanroy]

Maybe you should try that 11 tooth sprocket. Sounds like you have PLENTY of low end at 6 to 1. Should lower your rpm enough to cruise on down to the boat ramp without beating the snot out of it. FWIW, on all of the smaller predator engines, once you start hopping them up ( stiffer valve springs, big lift and duration cams, carb, compression ) really starting to spin them, it is considered safe ( for longevity ) to replace the stock rod and flywheel. They are manufactured to run consistently at 3600 rpm. Failures are not unheard of in the
5800 to 7000 range with stock internals.

Yeah, I did all the research on these before I bought one. watched a ton of videos. I figure a billet rod, and aluminum flywheel will be in my future. I’m sure a carb too.
not sure if the dual carbs, or one carb set up. I have a big bore Banshee “390” i built 15 years ago. I preferred the dual carbs over the single, but that is a different animal. It still has the single carb on it. I may still have the dual carbs somewhere for that.