I'm going to try playing around with the spring pressure on the driven (larger) pulley. I think if I can keep it from opening as soon as it does that I might be able to give it a bit more go out of the hole. Not sure if I'm thinking right there or not though.

Looking more at gearing, the belt drive system according to the manufacturer is 1:1 at high speed and 2.43:1 at low speed. Coming from the same jackshaft the driven pulley (larger) is on, I go into a 12 tooth sprocket which then goes back to a 24 tooth (2:1) on the rear jackshaft. From there I have the 18 tooth that goes down to the 60 tooth (3.33:1)
I'm wondering if I wouldn't be best off to go up in tooth count on the sprocket with the driven (larger) pulley thereby increasing the rpm at the rear jackshaft? It's actually the easiest of the bunch to change.
I can play with the engine and carb but the gearing is where I go off the rails. I'm thinking in terms of this thing hitting a wall out in a field and not building RPM. My goal is to be able to go faster where I'll be driving the most which is in the dirt. My problem is that I also don't know what the maximum RPM for the forward/reverse gearbox is. I'm thinking there has to be a reason they went 2:1 on from the driven back to the rear jackshaft.

Yes ^^ if you go back to my previous post, most likely the easiest way to address this is to add 4 more teeth on the axle / driven sprocket ( the last chain drive ) or go down 1 tooth on the smaller drive sprocket

I think I'll give it a shot. Not much to lose as the sprockets don't cost that much IF I can find one that bolts onto the gearbox the way this sprocket bolts on. If not, I'll have to look into changing the axle sprocket. My only concern with changing that sprocket is the clearance I have to the lower cover.

Here's a picture of the sprocket on the planetary


http://forums.pelicanparts.com/uploa...1508769199.jpg

My guess is those sprockets are 'off the shelf' from some supplier - you may have to get creative with 1 that's 'close' to your fitment.

I've had custom sprockets made for vintage motorcycles I've worked on where, as in your situation, were too tall for what I was wanted. They were surprisingly cheap. If you can't find a bolt on solution, Google 'custom sprockets'.

Know that the material of 'off the shelf' sprockets are hardened. So if you buy 1 ready to go and need to do some additional machining, it can be done be only by an experienced machinists.

Cab - Good luck. You know more about clutching than I gave you credit for. I understand what you say about alignment. It's different than a snowmobile.

BUT, I still say your belt looks too loose and that can cause your issue. Even with belt right, maybe clutches need service? UR on the right track about a spring in your secondary. If I can bore you with a quick story from 20 years ago:

I bought snowmobile from a widow....Seems like great shape, but from day one, it would always bog when taking off. Sometimes if taking off uphill, I'd have to lift the rear with one hand and crank the throttle with the other. Get the track really spinning, drop it an go.

Can't tell you how many times I was thru the carbs adjusting float level and jetting...After screwing around most of the winter: New belt and rebuild the clutch. Ran like new.....

Just an idea...

Bob,
I can't get over how loose that belt is either but I have shown it to the Kart place I bought it and they said that's "normal" for this type of system. The other thing is, with a tighter belt I actually had more slippage. I could hear the belt slipping when I was climbing a hill, that is now gone.

I have gone over this in my head to a point where I'm thinking I'm just going to add more power. I can change the gearing to accommodate the lower HP, lower torque engine OR after looking more into it, I can go with the Honda GX390 13 hp engine which to my surprise produces about 7 hp and 26.5 pounds of torque at 2500 rpm where my current produces about 5hp and 18.75 pounds of torque. On the top end at 3600 rpm the Honda produces about 12 hp and 22.5 pounds of torque where my current at 4000 produces 9 hp and about 16 pounds of torque. I know the HP gains aren't huge but the torque is a definite improvement and torque is where the work gets done. I think with the Honda engine I should be able to overcome the gearing a bit more and for $100 I figure if it doesn't work I can always get my money back or close to it if I sold the engine. There aren't many other options I have that I can say the same thing for.

I knew I should have jumped on that engine. It sold! :mad:

If you're going to do it...swing for the fences, 13hp is nothing.

Find a trashed Honda CRF450R dirt-bike, pre 2009 (with carburetor), Pull entire motor/trans out, configure a jack-shaft, shift lever with hand clutch...45hp w 6 speeds.

THEN you'll have a good time

When I used to race alcohol Karts on a buddy's oval backyard track, I geared the motor to run the RPM that I wanted at the end of the short straightaway. My Briggs Raptor 5HP with a few mods was actually more like 8-9 HP, and it seemed to run really sweet at 5200 RPM. For every 2 teeth I added (from a 58 tooth to a 60 tooth for example) on the axle, I gained 200 RPM. This worked because I was limited by the size of the track, and not trying to gain more top speed, just trying to get better lap times.

The ideal gearing is a 6 to 1 ratio which represents a 12 tooth sprocket, with a 72 tooth axle sprocket for starting out quickly while still having some top speed. I ran a 12 tooth sprocket and a 60 tooth axle sprocket to get less off the line power, and more high end response.

I never dealt with a third sprocket on a jackshaft, so my reccomendation is to experiment with gearing, or rear tire size (taller for more top speed). You can also add some PSI of air to the tire to get a larger circumference which will take the Kart a few inches farther for every rotation of the tires at the same motor RPM.

^^ If you add more air it does effectively increase circumference but that makes the overall gearing higher, making it 'taller' ^^

With that type of belt driven system shouldn't it be at 4200rpm at WOT no matter what speed in mph you are going? Unless it has weak springs letting the weights close up the gap too soon?

^^^^My guess is no ..........as peak torque always occurs below maximum HP/ RPM's. Also total gearing should be short enough that maximum speed is just past max RPM's / power.

So I found this online calculator and discovered that my final ratio is 6.67

Gear Ratio Calculator for Jackshaft Setup

I put 12 at the engine (driven pulley) then 24, 18,16 and hit calculate... BAM! 6.67 final ratio.

As for flipper's question, I'm thinking of it along the lines of driving my truck empty versus pulling a trailer. More weight and rolling friction means my truck has to downshift into 3 or 2 to keep the speed I want to travel. Now in the case of my truck, my HP is built in the higher RPM range as is torque. On my cart only one holds true. At 4000 RPM I'm generating 9 hp but I lost about 6 pounds of torque. This is what really has me interested in finding a Honda GX390 engine. The HP and torque at 3600 is still considerably better than my HP and torque at 4000 on the EX27. I'm thinking the Honda will have the power and torque to overcome the gearing or if nothing else it'll be able to get to its rated 3600 RPM with the current gearing.

Here's a link to the drive system operating https://youtu.be/0PS5_14SizU

I'm thinking more about the belt and some saying it's too loose. If the belt was too loose or too long in this case, I would think that barring the belt slipping I'd be able to build more RPM because the driven would never get pulled to full open and achieve the 1:1 ratio. I think if anything my driven is opening too soon keeping me out of my maximum torque range.

Just step up to a big boy toy..... :)


http://forums.pelicanparts.com/uploa...1508958338.jpg

But, with a continuously variable transmission like his that is driven by springs and weights the engine should be turning the same rpm at WOT regardless of road speed. That's how the snow mobile ones used to work. That is why I was wondering if the springs were weak it allows the weights to move prematurely or the torque cam spring in the secondary is weak allowing it to open up to quick as well.

Think of your electronically controlled CVT in a car when you put your foot down. It keep the engine at a specific rpm as you accelerate. This should be the same as it isn't a conventional centrifugal clutch that just engages or disengages. Unless I am looking at it wrong.

https://s.hswstatic.com/gif/snowmobile-12.gif

This is what gets me. The Kart can't overcome the added resistance/friction when driving off road. In the grass or a field, I get to maybe 3300 rpm and hit a wall where it won't go above that point. On the road I can build to about 4200 rpm.

The clutch engages at about 1600-1800 rpm which I think is right for the springs and weights in the clutch. I could up the driver springs so it engages at 2800 rpm but if I'm playing around down inside the woods, I don't think It will build enough speed to keep it above 2800 when I climb the hill on the way out. If the driven spring was weak it would put me into 1:1 ratio too quickly which is why I put a bit more spring tension on the driven to try to keep it in the higher torque range longer but that didn't seem to do much.
For fun I think I'm going to get a shorter belt and see if it makes a difference. Right now my belt is sized for a center to center distance of 8-5/8" which is what I have. I can buy a belt that is right for 8-3/16 center to center. It might be worth a try?

Those things are AWESOME... but I don't ride near enough to justify having one of those. For me this is just a toy to make getting tree stands setup. I just want to be able to get to the tree stands faster



http://forums.pelicanparts.com/uploa...1508965911.jpg

I keep seeing the older Honda 250cc Odyeseys for sale locally and would love to get one, but just don't have the area to tear up like I would need, to ride one properly.

I have seen a couple of those on CL as well. People seem to be asking what I consider crazy money for those things.

See what I mean? https://columbus.craigslist.org/snw/d/honda-odyssey-fl350/6341124329.html