YD3203- I need help with- new tires? ackerman? shocks?

[Tonyzsi]

Hi All,
I have a few questions I was hoping I could get your feedback on. I have done a lot of reading through many posts in the past couple months, but I was hoping for direct feedback, especially since it seems many people have a YD 3203 or a similar kart and many others have a lot of good knowledge on this site!!!!!!

My Kart setup: stock suspension set as stiff as possible F&R, stock turf saver tires 15" front, 20" rear; Gears: 60 tooth axel & 9 tooth jack shaft (1 less than stock for more low end); Predator 212 engine with basic stage 1 upgrades: large intake w/ adapter, header and screw on exhaust & #35 jet; new belt & #40 chain. I can hit 27 mph on the road which the speed calc. says I should hit at 3,000 rpms. My governor is still in, but at even at 3,500 rpm I should hit 31. I would think w/ the upgrades and predator engine I should hit ~30. I guess it still needs more torque.

1) TIRES- I'm planning to get new tires: Kenda Scorpion K290 Knobby Tires in size 14.5 x 7-6 -front & 18 x 9.5-8 -rear. I’ll go back to a 10T JS gear to maintain my current gearing.
Does anyone know of any issues I might have or what I can expect in any difference in handling with these tires? I mainly drive around the neighborhood on the road, but I plan to go back in the woods now & then so I’m looking for a little more traction back there.
I went back in the woods a couple times and the kart did ok, although I did get stuck trying to get back up a hill. The TC/engine just bogged down and it couldn't push me up the hill. The tires didn't spin at all despite being in a little mud since we crossed a small stream at the very bottom. I'm ~220 lbs., but a friend's daughter who is ~100 lbs. was able to drive the kart up the hill. Before that I had cleaned & dry lubed the Driver TC and the TC was operating great. After that it no longer seems to accelerate nearly as fast. Maybe it's dirty and needs another cleaning, although it only has a 3-4 hours on it since the last cleaning which isn't much! The belt also seems a little looser than before. I tried to push the engine more forward to tighten the belt, but it is as far forward as possible. Is there another adjustment to help tighten the belt or maybe something I’m doing wrong to get the belt tight enough?

I’m also ordering a new green spring & new buttons for the driven TC. I haven’t touched that at all so perhaps it’s dirty and not operating fully to allow me to reach full speed/rpm’s.

2) Ackerman- I’ve read several posts on this, but I’m just not getting it. So if my tie-rod attachment is currently at point X and I need to move it in 1” to be on the Ackerman line (middle of rear axel to King Pin) then I will need to shorten my tie-rod by 1”. If I steer 20 degrees to the right and it moves my tie-rod 2” then won’t it still move my pitman arm by 2”? I don’t understand how moving the attachment point changes how much steering input is put in based on the same movement in the steering wheel.
I am hoping to improve the steering of my YD3203 as it scrubs the wheels horribly when you steer. If I’m drifting down my driveway and turn the wheels the kart actually stops due to the wheels scrubbing so much. I was going to try bolting a piece of metal to the current mounting points and drilling another hole about 1" in on the metal. I'm just not sure it would hold with just a bolt, but I don't have a welder. My neighbor might be able to help me as he has one, but I'm still not understanding how it'll do anything.

3) Shocks- Do you think the following hydraulic shocks would make a difference for my kart over the old manual adjustable ones? http://www.bmikarts.com/Hydraulic-Shock-Absorber-500-or-730-lbs-Load_p_3978.html Should I get the 500 lb or 730 lb shocks? I estimate my kart usually weights a total of ~600 lbs. (300 for kart + 300 for riders). Because the kart seems heavily weighted towards the rear I was thinking of maybe getting the 500 lb. for the front and the 730 lb. for the rear, but I’m really not sure if they’d be too stiff or not.

Thanks in advance for any replies! I appreciate as much detail as you guys can give me.
-Tony

 

[OzFab]

TYRES:
Even with a TC, 6.66:1 gearing on 20" tyres is a stretch; if you go down to 18's, stick with the current gearing...

You probably destroyed the belt trying to climb out of the ditch...

Here's the thing with "theoretical gearing": punching numbers into a speed calculator doesn't automatically mean that setup will work; 3:1 gearing & 20" tyres will give you a "theoretical" top speed of 70+mph but, you'll destroy something trying to move, you still need to consider reality; the fact that a 100lb driver could drive it fine when a 220lb driver couldn't make it move is a dead give away that the gearing is off...

ACKERMANN:
It's not about turning the wheels more, it's about turning the inside wheel more in relation to the outside wheel; with no ackermann, the outside wheel will guide the vehicle through a turn but, the inside wheel is not turned as much as the outside wheel & will fight against it, usually resulting in no steering at all; what ackermann does is turn the inside wheel farther than the outside wheel, assisting in the turning...

You are correct in saying

If I steer 20 degrees to the right and it moves my tie-rod 2” then won’t it still move my pitman arm by 2”?

...however, having ackermann is like having a head start in a race...

Lets say, for arguments sake, you move the tierod attachment point on the spindle; now, by turning the steering wheel 10°, the end of the tierod is now at its original starting point but, the wheel is turned 10° or, let's say, 1", by turning the steering wheel a further 10°, you also turn the front wheel a further 10° or 2"; the part you missed is what's happening to the inside wheel; due to the altered mounting point & the shorter throw of the tierod, by the time you turn the steering wheel 10°, the steering arm has moved 20° from it's original starting point, turn the steering wheel 20° & the original tierod anchor point is now 30° from it's original point...

Is that starting to make sense?

SHOCKS:
In simple terms, a shock rating is the amount of weight EACH SHOCK can take; now, let's do some math:

500lbs on each side of the front & 730lbs on each side of the rear; that's a total of 2460lbs... to support 600lbs? That's a bit excessive IMO, half that would be fine...

On the up side, yes, there's more weight in the rear than the front

 

[Tonyzsi]

Thanks Fabroman!

TYRES:
Even with a TC, 6.66:1 gearing on 20" tyres is a stretch; if you go down to 18's, stick with the current gearing...
the fact that a 100lb driver could drive it fine when a 220lb driver couldn't make it move is a dead give away that the gearing is off...

The stock kart comes stock with 6.0 gearing and a less powerful motor. I thought increasing the gear ratio up to 6.66 would provide better lower end, but still allow me to reach around 30 mph, but there doesn't seem to be enough power to get me there. If I add smaller 18" tires then I'm really going to gear it to a lower final ratio incl. the tires. That set up @ 3,600 rpm will only get me to 29 mph per the calculator. I was hoping for 30, but if it'll reach 29 I think that'll be good.
With the TC I was expecting better low performance while still reaching a decent top speed. I haven't been able to get either one! A friend has a ~2005 HammerHead 150 GTS with GY6 engine. Does that really have that much more power/TQ? That kart seems to have loads of power/torque in a bigger much heavier kart.

TYRES:You probably destroyed the belt trying to climb out of the ditch....

I hope I didn't destroy the belt as I didn't keep trying to get it out. I rocked it some and tried a few times, then gave up and got the lighter driver or 1 time a 4-wheeler to pull it out. I guess for $17 I'll find out and if it isn't the problem then I'll have a spare.

For ACKERMANN, I hear what you're saying and understand the concept, I just still can't visualize it or comprehend how it will move the inside & outside tires at different rates. I guess it's just my shortcoming. I'll just have to believe and try it and hope for the best.

For SHOCKS: I looked around on Ebay and many online parts sites and I'm not finding any shocks below 450 lbs. I'm wondering if they need to have the higher rates because if we have 250 lbs. of riders and you hit a big bump or go over a hill and jump a little then you're going to come down with much more force than just your weight.
HAVE ANY OTHER'S INSTALLED HYRAULIC SHOCKS ON THEIR Yerf Dog? If so please share your rates, how stiff they were and where you purchased them.
I may just buy 2 of the 500 lb. ones and try them out.
Thanks,
-Tony

 

[ezcome-ezgo]

My first attempt at this and my spelling is off, but... this should illustrate the path that wheels are wanting to take both with and without the optimal Ackermann Geometry.

 

[OzFab]

For ACKERMANN, I hear what you're saying and understand the concept, I just still can't visualize it or comprehend how it will move the inside & outside tires at different rates.

They don't turn at different rates, the turn at different points...

Ezcome-ezgo provided a good diagram to illustrate; think about a running track, if two runners start at the same point , one in the inside track & one in the outside track & run at exactly the same speed, the runner on the inside track will finish first; why? Because the inside track is shorter...

 

[Tonyzsi]

Thanks guys! I understand the concept of Ackermann and what's it's supposed to do. The part I'm having trouble with is that I'm going to move the tie-rod attachment point in 1" and then shorten the tie-rod by 1" so how will that change the angles of the wheels?

I made the following diagram and even though it's not precisely measured I think it helps me understand what will happen as I move the attachment points in and onto the Ackermann line.

In my diagram I can see that the blue lines are almost the same which is my current set up and why the wheels scrub so hard. The red lines are the new steering angles once I move the attachment points in and correct the Ackermann. I can see that while turning right the right wheel has more angle to it and should therefore follow a tighter turning radius.
Can anyone understand the diagram? Can you guys confirm that the concept of my drawing is accurate?
Thanks!

 

[ezcome-ezgo]

Looks good to me. Keep in mind that these points move in an arc around the king pins, not a straight line. But you've got the idea.

 

[Tonyzsi]

Thanks ezcome-ezgo! Good point about turning on an arc.

I purchased some thick 1 1/4" angle iron like this-14 guage+plated+steel+slotted+angle, that I'm planning to use to move the tie-rod mounting point on my kart. This isn't the lightweight stuff that you mount your garage door opener with, it is much thicker and doesn't seem to bend easy at all. I'm going to cut a piece ~2 1/2" long and bolt it to the original hole on the spindle arm and then bolt the tie-rod in ~1" so it's on the Ackermann line. I don't have a welder so I was going to use JB Weld to help glue to the angle iron to the spindle arm.
Do you guys think this will hold with the JB weld and a bolt? I can attach a better pic of what I mean if needed. My neighbor does have a welder so maybe one day I could ask him to weld the angle iron on in a few spots to give it extra strength in case the JB weld doesn't hold, but I think the metal is galvanized. Can that be welded?

I also had a question about the throttle on a Predator 212. I have my throttle cable adjusted as far as possible to give me maximum throttle. If I move it even another 1/16" then the idle rpms are too high and the kart take offs at idle. When going down the road at full throttle I can reach back and manually push on the throttle lever and get a little more throttle or rpms.
Am I forcing the engine past the governor a little or do you think I'm not getting enough travel out of the throttle cable to reach max throttle? I wish I could adjust the throttle up to 4,000, but I don't feel comfortable removing it. Maybe one day.

Thanks!
-T

 

[ezcome-ezgo]

I look at it this way: If the JB Weld fails at speed, how screwed would you be? This is your safety at risk here. You'd be better off with small holes and screws holding it together than any type of "glue", in my opinion.

Better post some pics of your throttle linkage as it exists. The wisdom of this forum will pour out.

 

[Sinbad001]

For your ackerman correction you said were not sure if your added piece of metal would hold with one bolt. Just use two.

http://www.diygokarts.com/vb/showthread.php?t=20078

 

[OzFab]

I purchased some thick 1 1/4" angle iron like this-14 guage+plated+steel+slotted+angle, that I'm planning to use to move the tie-rod mounting point on my kart. This isn't the lightweight stuff that you mount your garage door opener with, it is much thicker and doesn't seem to bend easy at all. I'm going to cut a piece ~2 1/2" long and bolt it to the original hole on the spindle arm and then bolt the tie-rod in ~1" so it's on the Ackermann line. I don't have a welder so I was going to use JB Weld to help glue to the angle iron to the spindle arm.
Do you guys think this will hold with the JB weld and a bolt?

Short answer, no...

I have the same concept on my kart, you either need to weld it OR add a third bolt to the equation...

My neighbor does have a welder so maybe one day I could ask him to weld the angle iron on in a few spots to give it extra strength in case the JB weld doesn't hold, but I think the metal is galvanized. Can that be welded?

If you remove the gal, it certainly can...

I also had a question about the throttle on a Predator 212. I have my throttle cable adjusted as far as possible to give me maximum throttle. If I move it even another 1/16" then the idle rpms are too high and the kart take offs at idle. When going down the road at full throttle I can reach back and manually push on the throttle lever and get a little more throttle or rpms.
Am I forcing the engine past the governor a little or do you think I'm not getting enough travel out of the throttle cable to reach max throttle?

More than likely; the only way to know for sure is to put the rear of the kart up on blocks/stands & observe what happens for yourself...