Newbie needs help....please

[Lazrslong]

I was given a Yurf-Dog frame with a comet clutch and torque coverter. All are functional. I was also given a 5hp Briggs motor that is in nearly new condition. (pulled the head, the walls are pristine)

Here's my dilemma. The engine came from a tiller that the guy tore up the transmission within an hour of use. So, the engine's great but it only has a 1 1/4" stub shaft off the crank. (3/4" shaft) The comet clutch and torque converter set up requires a 2 1/4" stub.

My choice is to pass on the engine and buy a new one at Harbor Freight for $120 (little bigger motor, 6.5hp) and use the comet set-up or buy a Hillard Extreme and go direct.

The chain is a 40 pitch, the Hillard clutch is 12T and the axle sprocket is 45T. The axle sprocket will have to be changed soon. Im not worried about that right off as this is going to my 6 year old Grandson for his Bday. He's brand-new to all of this so I'm not to worried about the axle sprocket right this second. He'll likely tear a few things up in those first hours of driving anyway.

So, my question to the group is whether or not to utilize the free engine and replace the clutch or go with the new engine and utilize the comet clutch and T.C.

Any advice is appreciated. Im sure Ive left out pertinent information so ask away, I'll do my best to elaborate.

Thanks

Leo

 

[OzFab]

Welcome to the forum

Im sure Ive left out pertinent information

Rear tyre size

I'm thinking a Yerf Dog is a tad big for a 6 year old...

You can create an shaft extension for the B&S engine if you have access to a lathe or go ahead & take the easy route & just put a predator on there...

 

[Jzward1]

I would go with the predator motor and the TC, it will last longer and be better for the yerf dog set up. The centrifugal clutch might just get burned up if being used more off road

 

[landuse]

I would go with the predator motor and the TC, it will last longer and be better for the yerf dog set up. The centrifugal clutch might just get burned up if being used more off road

You are right, the centrifugal clutch probably would be burned up in offroad use (not in all cases though, just a general statement).

I would not use the sprocket combination of 12/45 though. That gives a 3.75:1 ratio which is too high, especially for offroad usage

 

[Lazrslong]

More info

Thanks for the replies folks. Okay, so at this early point it's looking like the new engine. This will likely be used almost exclusively in paved areas. Large parking lot available to us. The rear tires are 18 X 9.5 X 8. Im not worried about his size with regard to the control, steering wheel placement of his height. I took a lot of measurements and with the seat full forward he's tall enough and then some. Sprockets can be change easily enough. It's a 45 tooth at the axle. Suggestions there? Ill post some pictures as the assembly progresses and an inaugural ride video upon the event.

Thanks again.

Leo

 

[landuse]

Thanks for the replies folks. Okay, so at this early point it's looking like the new engine. This will likely be used almost exclusively in paved areas. Large parking lot available to us. The rear tires are 18 X 9.5 X 8. Im not worried about his size with regard to the control, steering wheel placement of his height. I took a lot of measurements and with the seat full forward he's tall enough and then some. Sprockets can be change easily enough. It's a 45 tooth at the axle. Suggestions there? Ill post some pictures as the assembly progresses and an inaugural ride video upon the event.

Thanks again.

Leo

I would change the 45T out for at least a 72T.

 

[Lazrslong]

Im a car guy (for real professional for 30 years), why? Serious question, are we looking for lowered speeds but easier on the engine? Thanks again, Leo

 

[Cart Man]

I run a 12T with a 72T on axle. Great torque and speed combination.

 

[landuse]

Im a car guy (for real professional for 30 years), why? Serious question, are we looking for lowered speeds but easier on the engine? Thanks again, Leo

with a gear ratio as low as 3.5:1, you will destroy your belt on your TC because it will never be able to fully engage. It will be slipping the whole time. A TC can handle lower gear ratios than a centrifugal clutch can, but there is a limit

As a car guy, you would also know that the tyre size matters in gearing. The larger the tyre is the equivalent of gearing higher. This means that you have to have a lower gear ratio in your driveline.

For karts, a general rule of thumb is a 6:1 gear ratio. This is not cast in stone, and is affected by many factors, but it is a guideline to work by

 

[Lazrslong]

Thanks

I understand the ratios. I didnt know what the ideal was. Thanks for telling me. The tires and sprockets are the originals so I wasnt sure if they should be changed to something more suitable for his age and the limitations of the engine and clutch system. I'll do the math and get a good combination that puts it closer to that.

Just an appearance thing, it would figure that the boy loves the color red. Ever try to cover yellow with red. LOL, Ill be painting a while.

Leo

 

[landuse]

I understand the ratios. I didnt know what the ideal was. Thanks for telling me. The tires and sprockets are the originals so I wasnt sure if they should be changed to something more suitable for his age and the limitations of the engine and clutch system. I'll do the math and get a good combination that puts it closer to that.

Just an appearance thing, it would figure that the boy loves the color red. Ever try to cover yellow with red. LOL, Ill be painting a while.

Leo

Maybe you can convince them to have a red AND yellow kart. Then you only have to do half the work

 

[Lazrslong]

Rear Tires and color

Another thought I'm having about this is the rear tires. The 13" jobbies in the back seem a little pointless as this will be used on pavement. As mentioned before, those are changing the final drive ratio. Any reason not to go to 6" in the rear as well? The kid he'll be "racing" when the time comes is a girl thats two weeks younger than he. Her parents and I have gotten her a kart that her uncle is gong over. It has 6" all around. I want to make both carts as evenly matched as I can. Thoughts on that?

Back to the color. I'm colorblind. Pretty badly but especially red and green. Of course he loves red. I'm going to go with it to placate his sensibilites but I'm think that I'll be wrapping most of the cage with pipe insulation and adhering it with duct tape. Anyone done a kart that way and anyone used red and iridescent blue?

 

[landuse]

When you say 6", do you mean tyre radius or diameter. Cos 6" is pretty small for a tyre

 

[Poboy kartman]

Another thought.... I'll be wrapping most of the cage with pipe insulation and adhering it with duct tape.

There are different grades of pipe insulation.....the economy variety being pretty much equal to "pool nooodles".... while the more expensive ones being very close to professional roll cage protection........

BTW....Every kid loves to put mom and pop in the red.....

 

[Lazrslong]

U.S. Has weird tire measuring numbers. The rim is 6". Picked up the predator engine today. Found a 20% off coupon online that they honored at the store. $96 + tax, out the door for $104. sweet. Remembering now that red really is hard to cover with. Painting the darned thing is going to take longer than the mechanical set-up. But I digress, the front tires are 175/70/6. Any reason not to down size the rear to those as well?

 

[Poboy kartman]

Rim width may be a consideration....you will also change your gear ratio....(most likely for the better in this case).....

As far as covering with red.....that's just one of the many reasons it pays to use the proper primers.....

 

[Lazrslong]

New snag. Or may be just ignorance. I need to know if it's the normal thing or I bought the wrong engine. I purchased the Predator engine. The PTO shaft ends about a half an inch from the outer end of the splined hub. That seems weird to me...is this normal or do I need to go find an engine with a loner PTO shaft?

Thanks for your help folks. Im lost without you.

 

[Lazrslong]

Follow up to this. Is it just a matter of getting a longer 5/16 X24 hardened bolt? That seems to me to be inviting disaster ie, vibrations, the bolt loosening (engine specs call for tightening it to 25 fp. I'm a automotive guy so a lot of what I think goes to closer tolerances and higher to torgue. ****, i dont know.

 

[firemanjim]

Tc's are run like that every day, all day.....
EDIT
Yes get longer bolt....

 

[Poboy kartman]

Sum of us donn reed thet guud....sew maybie a pickhure kood helps a leetle?

Ima thinking u may be oh kay....but........

Eye meen rally? Kin you cifer whutz haywire witha moterizeded vehickle over the telephony?

I'm just messing with you a bit....but pictures ALWAYS help!!!!

Welcome to the forum and please add a profile location.....(it gives me a head start if you're close to me.......and lets me know which way to run!")