Torque converter not reaching full ratio

[Njaiu1]

I have a 2 seater i'd guess around 200lbs without people. ~500 with
13hp honda GX390
30 series tc
10t drive sprocket in tc and 54t axle
tires are 19x9.5-8.

The problem I'm having is the belt on the tc pulleys only go about 1/4 of the way. It doesn't get even close to the top ratio. So i can only go like 5-10mph max.
However if i lift the rear tires off the ground it will (after a little while) reach the top tc ratio.
I'm not sure if the initial engagment rpm is too low thus not giving it a long enough rpm range, if my gearing ratio is off, or if the motor just isn't powerful enough. Which i hope not as the motor I replaced was only a 150cc and it had a 32t driven gear. I'm not sure what the drive gear was as it was inside the transmission.

https://www.bulletlines.com/1-torque-converter-p/55.htm

Any help would be greatly appreciated as i'm really stuck and don't know what to do next.

 

[Njaiu1]

Update: I've been working on the go kart today. While looking at it I realized there was a screw that limited how wide open it would let the throttle go (the motor was off of a power washer so it makes sense that it would be limited so much). I removed this screw and boom my kart flys now.....maybe a little too fast. I can already tell I'm going to be going through belts like crazy. I'm going to have to invest in the 40 series tc.

 

[anickode]

5.4:1 is also a pretty tall gear ratio for 19" tires.

 

[itsid]

Good to see you have found the culprit!

Yeah anickode I agreed.. until I punched in some numbers in my beloved (and overly cautious) calculator and it didn't throw a warning message (well not below 650lbs or such)
So it should indeed work with the torque of a gx390

I'd still say it's on the edge though, especially considering the poor series 30 isn't made to take such abuse..

but until a matching series 40 is mounted I guess the belt wear will be managable

'sid

 

[landuse]

Update: I've been working on the go kart today. While looking at it I realized there was a screw that limited how wide open it would let the throttle go (the motor was off of a power washer so it makes sense that it would be limited so much). I removed this screw and boom my kart flys now.....maybe a little too fast. I can already tell I'm going to be going through belts like crazy. I'm going to have to invest in the 40 series tc.

Glad to hear that you got it sorted out!

 

[67StingrayJ]

Njaiu1,
Do you have any photos of your build? I'm interested in the engine swap and TC mostly. I have the same cart as you and I'm just not getting enough power out of the things. It bogs down really bad in the sand and engine never seems to hit is max RPM.

 

[Njaiu1]

Ill upload a few. Anything specifically you're looking for?

 

[Njaiu1]

Here are a few more

 

[Njaiu1]

Njaiu1,
Do you have any photos of your build? I'm interested in the engine swap and TC mostly. I have the same cart as you and I'm just not getting enough power out of the things. It bogs down really bad in the sand and engine never seems to hit is max RPM.

As you can probably tell there is a lot of custom work that I did. The hardest was probably the axle. I would advise buying a new axle since the original one has everything welded on. There was a lot of grinding welding and regrinding to make my setup work. Also was a lot of welding on the engine mount plate. Think you could post some pictures of your kart?

 

[67StingrayJ]

hey, great post. I'm doing something similar to my kart now. I cut the top cage off the rear assembly and put in a 420 predator. I just waiting on the mount plate to come in the mail. Please post pictures of what you did to the rear axle. I have been thinking about grinding off the rear hub for the gear but had reservations.

---------- Post added at 08:54 AM ---------- Previous post was at 08:43 AM ----------

If anyone had a good lead on seats that will fit this thing let me know. The wife already said to me she is moving it up on the priority list.

Also, Njaiu, do you plan on adding reverse to your buggy? I designed a FNR gearbox last night and today I'm pricing helical gears. depending on the cost I may end up buying a Polaris FNR or just forgetting it all together. Seats (and seat belts) first...

 

[67StingrayJ]

ok, update. I too ground out the weld out of the rear axle and hub to re-position the gear. I ground a little bit to far trying to get rid of that weld but it will be ok I'm sure. The 420 predator is mounted and connected. The 40 series CVT seems to be quite strong. I haven't driven it yet, still modifying the seat. I'll post pics tonight.

 

[JTSpeedDemon]

A common theme with Predator 420 swaps seems to be the space problems.