new project...

[RanmaSal]

First off, I'm new. If this has been discussed before I could not find it while searching... and I looked till my eyes watered I read so much. You all seem to have WAY more knowlege then I so here we go. First I'll tell all the specs I have then I'll ask the question.

2 seater cart with front suspension
7HP OHV Briggs
Hillard Extreme Duty #40/41 3/4" bore 10 tooth clutch (new)
60 tooth on live axle
17" tall 10" wide knobbies rear tires.

I weigh 250 lbs and while testing this cart it does not want to grab at all unless it's flat with no steering applied. After it's up to speed (past 5MPH) it's no longer an issue. Only from a stop. Tire pressure is 10PSI front and rear as the tire says is the MAX PSI. What's the deal? I've tested the engine and it's spinning up no problems, oil is fresh on the inside, gas is new, spark plug and air cleaner are new. I've checked for alignment of the clutch and axle and they are dead on with a plum line and the chain itself isn't binding. the cart rolls like nothing else. very very smooth. The cart did do better with my brother on it who's about 175, but both him and I agree the cart should do better. I've oil the brass bushing on the clutch and I've sanded out the inside which did help some, but not as much as I would hope. The first time I rode it the clutch did get very very very hot and smoked like a freight, but I've tested all friction surfaces and it did not crack and the springs all test the same tention when I took those off. I thought it was the paint on the outside bubbling off... I know I could stand to loose the weight myself, but sheesh... kinda harsh way to find this out.

Basically I would like to know if the current situation is because of a "cheap clutch" or am I going to have to cut off the rear tires (someone lovingly welded the rear rims onto the axle before I got it) or am I missing something? 6:1 gear ratio with a 7HP engine should be more then enough. I've ridden my fare share of carts so this seems like a clutch issue, but as I am more of a rider then an engineer I thought I'd air towards the side of experience and ask someone more worldly then I. I was seriously thinking about getting a different clutch...

 

[TOO FAST]

2 seater with suspension, plus 250 lb driver. I think your just pushing the envelope with that combination. I had a 13 hp honda on a heavy kart and I'm over 200lbs - very sluggish like you said (the kart I mean). With only 7 hp you definitely need a
torque converter style clutch - this raises your start off ratio hugely (Brendenov shhh) while keeping your top end the same
It solved my problem completely. Your wouldn't even think it was the same kart - woke right up!

 

[RanmaSal]

2 seater with suspension, plus 250 lb driver. I think your just pushing the envelope with that combination. I had a 13 hp honda on a heavy kart and I'm over 200lbs - very sluggish like you said (the kart I mean). With only 7 hp you definitely need a
torque converter style clutch - this raises your start off ratio hugely (Brendenov shhh) while keeping your top end the same
It solved my problem completely. Your wouldn't even think it was the same kart - woke right up!

Thanks for the advice man... unfortunatly I don't have torque converter monies (just like everyone else) so I think I'm going to cheap on this and build a 2-1 jackshaft to increase the final drive ratio to 12-1 instead of 6-1. I know I'll lower the top speed in half as well, but the cart ULTIMATLY is for my nieces and nephews and my son, not me. I do have another set of wheels I COULD put on there that are only 10 inches like the fronts but that is such a PITA. I have another cart that my brother and I are building using a Rotax 440 and primary and secondary clutches we got off ebay a couple years ago for less then 100 bucks. Engine runs, but we can't test the clutches yet, but even new they are not THAT bad when shared between 2 brothers, right? I am totally going to post pics in progress on this cart as we build it. Right now it's planned on being a 1 seater. Have an older frame as a guide and basis, but are going to add rack and pinion we have laying around off of a Festiva as well as all of the hydrolics for the brakes, rotors... full roll cage, 5 point racing harness... all everything we've gotten over the years for LESS then 200 bucks total! Have welder and no common sence. Will build... but that's another thread.


What do all of you think about either getting smaller tires on the back OR using a jack shaft to increase the final drive?

 

[anderkart]

Hey RanmaSal, welcome to DIY.
Your post was the perfect description of a kart that needs a Torque converter. It'll get ya rolling!

 

[TOO FAST]

To know your speeds go the the home page of this site and go down to speed calculator - easy way to determine your speed with
different ratios etc. Right now your kart is set up for 30 mph

If you have 2 ratios you multiply them to get the final

 

[anderkart]

Whoops, shorter rear tires would help a bunch too.

 

[RanmaSal]

Hey RanmaSal, welcome to DIY.
Your post was the perfect description of a kart that needs a Torque converter. It'll get ya rolling!

Got one laying around you'd be willing to let go for really cheap? I'd be more then willing to put one on if I had the money for it. I've learned from this post that I'll either have to put the smaller tires on it, install a jack shaft on it, or loose weight... but as this cart won't be for me per say, but for kids who are in the 100-130lb range riding alone.

You guys are awesome and have much respect. I'd buy you a beer if you lived near me

 

[RanmaSal]

To know your speeds go the the home page of this site and go down to speed calculator - easy way to determine your speed with
different ratios etc. Right now your kart is set up for 30 mph

If you have 2 ratios you multiply them to get the final

Yup. I remembered to check everywhere for everything when I got on this site so I didn't seem like a total noob. I know gear ratio's very well from being an automotive tech, however I know NOTHING about centerfugal clutches, which is why I asked. If getting a better clutch, like a Comet, is not going to help my current config then I'll just change the final drive ratio!.

2/1 jackshaft on a 6/1 ratio makes a 12-1 final drive! or smaller tires... MAYBE I'll find a more powerful motor somewhere for cheap!!!

 

[TOO FAST]

I guess we don't know what you know or don't know so I always
try to make understandable for a newcomer to the hobby, Hope
your not offended me trying to explain gear ratios to you. lol

I think ups could deliver the beer

 

[RanmaSal]

I guess we don't know what you know or don't know so I always
try to make understandable for a newcomer to the hobby, Hope
your not offended me trying to explain gear ratios to you. lol

I think ups could deliver the beer

You never have to worry about me being offended, and sometimes I can come across like a prick if I know something *gasp* I know I know... and I seem like such a nice guy!

So this is what I'm going to do to fix the issue. Found a guy with an older 8HP Briggs to trade my newer 7HP OHV Briggs. That upgrades me to a 1" shaft and my brother has a Comet Clutch 10 tooth #40/41 from another project he's going to give me and I'm down grading to 14" dia. rear tires. I'll only have 3 inches of ground clearence for the bottom of the 60 tooth #40 live axle sprocket, but apperently I need smaller rear tires and a better clutch/motor combo. It really frustrates me to no end that to buy a clutch that would work perfect for my application it would cost a crap ton of money. I was seriously thinking about adding a low/high range, shifter level and linkage, friction clutch and pedal... cause I have 90% of all of that from different other projects (yes, I have ALOT of projects LOL), but then it wouldn't be a cart for my niece anymore. I really want to keep it simple so she can have a ball with it. Once I get the rear rims off of the axle from where some idiot WELDED them on I'll get the others on there, get the new (to me) motor on with the comet clutch I'll post back to let you know how it worked out. Thanks again for all of your feedback. UPS would ship the beer, but you'd end up with 2 broken bottles and a tattered 6 pack holder.

 

[TOO FAST]

Good luck with the rims, and you could always run a jackshaft and
with the extra power of the other engine it would work fine. Your
nieces etc would probably have more fun being able to spin around and such than have a high top speed. Safer to, especially
it they are novices.

 

[RanmaSal]

Good luck with the rims, and you could always run a jackshaft and
with the extra power of the other engine it would work fine. Your
nieces etc would probably have more fun being able to spin around and such than have a high top speed. Safer to, especially
it they are novices.

So I made the trade! This 8HP motor is so dang clean... it's scary! I also got the Comet clutch #40/41 10 tooth from my brother. Construction of the 2 clutches are completely different. I'm having a very very very hard time getting the 8" rims off of the axle since they are all inclusive and the rim itself mounts to the axle and doesn't use a "hub"... I'll get it, but the 1 side took an hour with tons of PB Blaster and an air hammer. YIKES! I really hope this works.

So the new config is going to be this:

8HP Briggs engine
Comet Clutch #40/41 10 tooth clutch
60T #40 axle on a 1" live axle shaft
145-70/6 knobby "Balloon" tires

If you don't think it'll work I'll go on EBay and buy a cheap "under motor mount" style jackshaft kit and run the larger knobby tires. 10-14-10-60 on the motor mounted jackshaft kits I've seen on there... I know I have a 20 tooth I would replace the 14 with... I believe the total gear ratio with the 14 is 8.4:1 or I could trade it out to the 20 tooth and have straight up 12:1 ratio. I don't wanna do it, but if I gotta... 3 inch smaller overall tire diameter with a more powerful and torquier engine and MUCH better clutch... I'm tempted to put on the other rim for a "test" run once I've mounted the engine (which I'm going to do on my lunch break) and figured out the throttle cable for it to see if I REALLY need to keep beating on that other rim to get it off..... to many decisions...

 

[mike75925]

if it's for the kids, it should've been fine as is. daddy just wanted to play hunh?

 

[RanmaSal]

if it's for the kids, it should've been fine as is. daddy just wanted to play hunh?

my niece is 160lbs and just about a foot shorter then me... and she's only 13. Add the weight of one of her sisters riding with her and you have 220-230lbs (depending on which sister) on the cart. it's alittle less then me so I want to make sure the cart can handle me on it with no problems so they don't have any problems.......... and daddy might wanna get out there once and awhile to

 

[RanmaSal]

Update

I finally got the 1 rim off the axle (took 2 hours with a carbide bit, air drill, air hammer, sweat, and TONS of compressed air). I changed the rear tires/rims to a split rim that bolts to a hub for easier removal. I have about 1 1/2 inch clearance below the rear sprocket. I had to cut off the engine mount plate and reweld it to a new location since the Comet Clutch only goes onto the engine output shaft 1 way, welded in a new floor pan, redid the throttle linkage, and adjusted the sprocket. When I go on my lunch break today I'll hook up the chain, air up the front tires, install a kill switch, and temp mount a seat. I'll let you all know the results! I really hope that it goes as planned!!!

 

[RanmaSal]

I finally got the 1 rim off the axle (took 2 hours with a carbide bit, air drill, air hammer, sweat, and TONS of compressed air). I changed the rear tires/rims to a split rim that bolts to a hub for easier removal. I have about 1 1/2 inch clearance below the rear sprocket. I had to cut off the engine mount plate and reweld it to a new location since the Comet Clutch only goes onto the engine output shaft 1 way, welded in a new floor pan, redid the throttle linkage, and adjusted the sprocket. When I go on my lunch break today I'll hook up the chain, air up the front tires, install a kill switch, and temp mount a seat. I'll let you all know the results! I really hope that it goes as planned!!!

We have a winner! Well we will once I get new rubber on the front end. tires popped on the first turn, but it didn't have the same problems as it did before. Note to self... when you goto the store tonight for tires make sure to get a kill switch. that was f-ing special.

 

[TOO FAST]

We're all waiting for the pics

 

[RanmaSal]

We're all waiting for the pics

I'll read up on how to post them in a few once I go out there to take some! Got the motor mounted ALOT better on the kart and fixed a snaffoo with the brakes and one of the wheels.

Seems the set screw I was using for the brakes (drum brake with no keyway... I know it's the wrong darn brake for the axle, but it's what came on the frame and it's what I got) broke off, so I put in a longer setscrew that I was able to CRANK down on. Now the cart stops. Had another issue where I forgot to put the axlenut back on (hey, it was like 1am and I was tired) after doing something and was riding it through the front yard and the rear tire passed me!!! Almost done with work, so I'll go snap some photo's and let ya see it. She's ugly as sin, but HOLY COW she runs fast now!