40 series tc higher stall

[Dfish1247]

Hey folks, asking if any of you have used the higher stall springs and weights.

My son’s kart is a two seat yard kart. Has live axle, disc brake, 50t sprocket. Engine is a stock predator 420 with knockoff 40 series converter.

The thing runs awesome, but when floored from a stop, the engine lugs down some, then takes off. It’s not a carb issue, just the tc grabbing very low in rpms.

Anyway, I ordered the red springs, and medium rollers for the driver. Being the engine is stock as a rock, should I just install the springs and see how that does first? Or install both? Thanks in advance.

 

[Colemanman]

Have you adjusted the driven pulley spring yet to make it hold the low ratio longer? That might help with it lugging down a bit. Id try em both at once and see what happens. What stall are you putting in it?

 

[Dfish1247]

I haven’t. Only does this when you first give it gas. I’ve watched a few YouTube videos and they all do it, be it clutch or converter, however, it seems far less prevalent in the one video I found with the higher stall kit. All it is is the clutch/tc engaging, which lugs down the engine, then the engine revs into its intended operating range and all is fine.

The red springs and medium weights I ordered if used together net a 2600rpm stall. Red springs and heavy weights net a 2000rpm stall. I figured 2000rpm stall speed would be near ideal on a stock engine vs the 1400-1600rpm the converter stalls at out of the box. Way too close to idle speed.

 

[Colemanman]

Hmm thats weird that they the 40 series does it. I havent had thag problem before but then again im running a small block and a 30 series. My stall is 2200rpms. The 420 makes max torque at 2500 rpms if i remember right, so a 2500rpm would be your ideal rpm for the converter to hold the engine at. Same thing with clutches, you tune em to slip in at peak torque for peak power. Id say use the weights and springs and install em then your engagment is slightly above peak torque. Then if you still need more, try adjusting the driven to taste. Good luck figuring it out man!

 

[Dfish1247]

I had a 30 on the 8hp Briggs I found right after I bought the kart. It done this as well, just not as noticeable. The 40 series is working like it should, just engages too low. Doesn’t hurt anything, just annoying. This is on pavement, in grass just spins the tires.

The driven is still in the middle hole, I may try the other one if this doesn’t clean the issue up.

Here’s a couple pics, I’ve got other work to do besides this. Adding about 9” to the back so my son’s knees aren’t at his chest and my knees at my eyeballs, plus welding the correct motor mount vs that mess you’ll see there already.

 

[Colemanman]

Yea idk man ive never had that problem before and i got 3 bikes with a converter. Nice kart man. Looks like a solid foundation for a good project. The only thing i can think of thats similar to your problem is when i floor my coleman with a converter it revs up and slams in and kinda drops a few rpms but its not anywhere near lugging. Hope you figure it out man

 

[Dfish1247]

That is exactly what it does, floor it, converter engages and loads the engine, pulls down the rpms.

Thank you for the description, that is correct. Drive like normal, doesn’t happen.

Of course, this is my son’s kart, so I’d better not make it a hot rod just yet, he’s only eight.

 

[Colemanman]

Holy **** man thats a lot of motor for a 8 year old

 

[Colemanman]

Yea mine only does it when i completely matt it from a stop. Other than that driving normaly it doesnt. When it does slam in and slightly drop in rpms, it doesn't seem to hurt my performance. I remember when i was 410 back in 2011, my dad went to harbor freight to get a predator 212cc and they didn't have any in stock, so he bought me a 346cc 11.5 hp predator. Its long been discontinued and is now replaced by the 8hp 301cc predator. He stretched the kart 7 inches and moved the axle behind the motor and dropped the motor down 3 inches. It would go 59mph with a stage 1 kit, with governor and belt to chain jackshaft. Im currently reviving it.

 

[Colemanman]

Its cool your doing that with your son. It reminds me of when my dad put thag big ole honkin motor on the go-kart. It made me the cool kid in my small town. It would beat all the go karts and mini bikes i raced and would beat up on some quads and dirt bikes. I use to take it out just to find someone riding and flex my go kart on them. Those were good times.

 

[Dfish1247]

I’ll be worried when he graduates to cubic inches, cubic capacity ain’t as bad,lol.

I think this ones around 30mph or so, which is plenty. Now, when he is older, I doubt that’ll cut it, then comes the big buck internal parts.

He may have gotten the idea from my little stunt a couple years ago,however that involves 8 cylinders so not appropriate for here,lol.

 

[Colemanman]

Yea but still tho 420s are no joke. There mean motors. 30 is good for a kid his age. You could always gear it for more speed down the line.

 

[OPmini]

I have had the same issue with my predator 420 on my minibike and I have changed the springs before. It is a fairly simple operation you just put the clutch in a vise and I use a giant adjustable wrench (available at harbor freight for $20) to take the big nut on the top off. The springs come off easily and you just slide the new ones onto the retaining pins and voila! the hardest part tho is getting the lid and nut back on the clutch.

 

[Karts of Kaos]

Yea but still tho 420s are no joke. There mean motors. 30 is good for a kid his age. You could always gear it for more speed down the line.

wow only 30mph with a 420! I would think you would go a lot faster. whatever you are doing it probably is not putting any strain on your engine. also you could probably suffice with a 212 and go the same speed easily. I run a little 160 cc clone and I can do 30 I think. I hit 36 when I had a governor delete on a 212. and that could have gone faster with the right tuning. and by the way I have a ten tooth drive a 54 on the wheel.

 

[Colemanman]

Im not the dude with the 30mph go kart, i was just saying a 420 geared properly has the potential to get pretty insane speed wise. I got a 11.5hp 346cc predator go kart stretched and slammed down low with a clutch thatll hit 59mph, it pulls like a sun of ***** and has the governor still, with the throttle screw backed out. Im not even touching the potential of it yet and like i said its a 346cc, the 420 has even more potential more power. I have a brand new hemi 420 im gonna drop in it someday when i wanna go faster

 

[Karts of Kaos]

sorry, I quoted the wrong guy.

 

[Colemanman]

Your good man, mistakes happen

 

[Dfish1247]

If 13hp is too much for a yard kart, I’d hate to see what you think about 600hp in a 3300lb car,lol.

Anyway, still plugging away on the frame, hopefully have the motor installed today, and just maybe drive it.