Torque converter /general karting question

[kailand09]

Hey guys, just joined. I've read up a few posts and am trying to figure a few things out.

I am looking into purchasing a roller from craigslist and it says it comes with a TC. Without looking at it yet, I'm not sure which model but I'm assuming its a comet 20 or 30.

The motor I plan to use is a generac GN-220 7.8hp ~215cc engine.

Here is the ad: http://milwaukee.craigslist.org/for/3359165411.html

So I'm assuming the comet will work just fine with that motor, correct? Just make sure to gear it right? Will 7.8hp be a bit sluggish for something of that size (assuming when only carrying one person?).

Do you think that is a good deal? I know I should probably check if the TC springs are still good, what else is an easy way to notice of the TC is still ok? I don't know that I want to sit there and take it apart.

Thanks for the help.

 

[Doc Sprocket]

Welcome to the forum. A couple of quick observations-

*That looks a lot heavier than it has to be, for it's size. Personally, I would either go with a much larger engine, or more likely, give that one a miss and keep shopping.

*It appears to have the backplate and driven unit from a Comet TAV2 or clone. I do NOT see the drive unit there (or belt)! Beware, if he does not present the rest of the unit, you're into some bucks.

*If the CVT units aren't rusted into two big hockey pucks, they are pretty much guaranteed salvageable.

 

[kailand09]

Thanks for the quick response! Wasn't expecting anything until at least after class!

*You say it looks heavy (not trying to question at all here!) but what makes it seem that way so that I can know in the future what to look at? I'm mostly interested in a 2-seater so we have the opportunity if 2 want to go for a ride. Is my motor generally a bit small for that?

*Great observation, I hadn't noticed that! The drive unit is the one connected to the actual motor shaft right, correct? $350 would definitely be too much for that if he doesn't have the drive unit.

*Good info too, thanks! I had thought it was about that, and watched a few videos on how to fix em up a bit and how important cleaning/maintaining them can be. Read on here a few things to check for with them.

EDIT:
I also would like to note that I'm willing to change karts up a bit and do some changing, I really was only looking on CL for a frame to base off of. Would it be worth it to cut off the cage and change it/flooring on there if that is part of the weight issue? A friend of mine is a master welder who said he would help a bit, but thought it best/most cost effective to find something similar to what I listed.

Thoughts are appreciated!

 

[Doc Sprocket]

Sorry- You'll have to forgive me, I'm doing about 6 things simultaneously... Umm- Haow do I describe a "look"? It just looks like overkill. I'm generally guilty of overengineering, and that even looks too dang beefy to me. Big steel, and lots of it. Also- just noticed lawn tractor spindles, steering, and front axle. Junk.

Look for a "stickied" post in our engine/clutch section on maintaining your torque convertor. A ton of good info in there, written by a guy that does it professionally.

My personal opinion? I'd avoid this one...

 

[kailand09]

Awesome advice. Thanks!

Please don't worry about replying right away for me! No need to apologize

My friend who works as a welder expressed issue making our own frame as he says there are certain types/ways to weld a frame and different types of metals to use in certain spots. Would it be too difficult to take a single types of steel and make a frame with little experience but checked by someone with welding experience?

We wanted to make our own originally, but went with his advice. Also, cost wise, I fear that may be more expensive to just make our own as opposed to a CL score?

Thanks for your opinion, as a mod here I definitely will follow your advice!

 

[Doc Sprocket]

If you have a competent welder at your disposal, you should not have too much trouble building a decent enough frame from commonly available mild steel tubing. Your friend would be right about what he said IF you were building a race car or something similarly freaky. For basic go kart purposes, just drop on by your favourite steel supplier, and have at it. No need for special alloys or Chromoly or anything.

That said, for your first project, it may well still end up cheaper/easier to score a used frame from somewhere, and modify it to suit your purposes (or simply fix it up and bomb a new engine on it.

Should you choose to build your own frame, I highly suggest purchasing a set of pre-engineered plans, and following them, it will take a lot of the guesswork out of things, and even tell you exactly what materials you'll need. A half-decent welder/fabricator should have no problem following a decent set of plans. It's your call really.

 

[kailand09]

Exactly what I needed to hear - I went ahead and actually found that this site has a huge part done about plans here http://www.diygokarts.com/kart-plans/frame-2-seat.html.

I think I may just opt to make my own frame then, to ensure it is lightweight. I may just veer away from TC then, and go with a regular clutch to save $$ unless I find a used one.

Thanks again!

 

[Doc Sprocket]

Glad I could help. One further thought- If you're going to have two people in the kart (potentially) and running off-road with maybe some hills and stuff, I do suggest a CVT (torque converter). Big-time performance improver! Yes, it will run you a few bucks, but well worth it.

 

[OzFab]

Do you think that is a good deal?

Short answer; NO!

$350 for a chunky, (likely) heavy, home made frame with a dodgy front end, inadequate brakes & no engine? As for the cvt; you're gonna need something in the realm of 9hp to move that beast, rendering a 30 series cvt useless.

You can get a lot better for a lot less; keep looking...

http://milwaukee.craigslist.org/bar/3306676800.html

http://milwaukee.craigslist.org/spo/3357154191.html

http://milwaukee.craigslist.org/for/3360535150.html

 

[kailand09]

Awesome, thanks for the input. I suppose I will make sure to drop the extra cash for that.

Thanks for those other links! I have seen those, and am looking for something a bit different, but really appreciate it. I'm really glad I posted here hah!

I'll definitely make sure to do a build thread when we figure it out, probably will happen sometime in the winter

EDIT:

Do you think it would be worth it to design in a suspension if we only off-road sometimes, or skip over that as it may make things more complicated?

 

[OzFab]

That comes down to personal preference. Some would say "better to have it & not need it than need it & not have it".

Suspension can be complicated & confusing if you don't know what you're doing; figuring out correct mounting points,spring loads, etc... not to mention expensive. I'm not talking hundreds of dollars but it will up the overall price & build time.

If you plan to do most of your driving on pavement & grass, keep it simple, at least for your first build.

 

[kailand09]

I will heed to that advice, thanks man. Very informative ya'll are here.

 

[kailand09]

Had another question, and decided all the info is in here so why make a new post?

Anyway, I have decided to make my own frame based on the 2-seat design on the front page. Since I will be using that 7.8hp engine I listed above, I want to get all I can out of that engine.

The question is, then, would it be worth it to grab a different exhaust such as these :
http://www.bmikarts.com/shop/?shop=1&cat=169

Will it be too hard to fit one onto an engine it wasn't made for? Is the mounting for the exhaust fairly universal on engines? I plan to upgrade the air filter, and maybe get new springs and upgrade the flywheel (as listed here http://www.affordablegokarts.com/performance_basics.php).

I also plan to give the engine a good once-over as it has been sitting (albeit empty) for a bit. Do these all end up giving the engine a decent bit of better performance on an engine like I have? I would assume they do- but this is my learning project and I don't have direct experience working with engines. While my engineering background says it makes sense to give better performance, I am unsure how tangible that is before I spend the $$.

EDIT: I know that some of these upgrades get costly, and then you might as well buy a new engine, so I'm trying to stay under that threshold! lol.

 

[kailand09]

Another few questions.

I tried a search for fengin got nothing. Has anyone used the fengin torque converter (seems imitation of comet ones)? Would you say to steer away from these imitation like TC's?

Also, is it best to buy the axles and steering components, or is it easy enough to just build them?

Does anyone recommend any particular breaks for a moderate sized kart with two people? I was thinking of just a mechanical 6" disk break?

 

[OzFab]

The question is, then, would it be worth it to grab a different exhaust such as these :
http://www.bmikarts.com/shop/?shop=1&cat=169

Will it be too hard to fit one onto an engine it wasn't made for? Is the mounting for the exhaust fairly universal on engines?

Universal for clones, yes but, from engine to engine, there can & usually is slight differences. You need to find something specific to your engine or, alternatively, make your own

I plan to upgrade the air filter, and maybe get new springs and upgrade the flywheel (as listed here http://www.affordablegokarts.com/performance_basics.php).

The problem with that list of upgrades is it's all over the place. For examle, you don't install stronger valve springs before upgrading the conrod & flywheel, unless you want to be picking up bits of your engine from the side of the road.

Once you remove the factory governor, the valve springs act like a natural governor, allowing the engine to rev to aruond 5000rpm before valve bounce occurs

I also plan to give the engine a good once-over as it has been sitting (albeit empty) for a bit. Do these all end up giving the engine a decent bit of better performance on an engine like I have? I would assume they do- but this is my learning project and I don't have direct experience working with engines. While my engineering background says it makes sense to give better performance, I am unsure how tangible that is before I spend the $$.

All upgrades/modifications change performance, it's a matter of trial & error to get the desired effect.

True, you could end up spending a lot more on mods than you paid for the engine in the first place so, choose wisely.

Having said that, I would be looking for a more reputable CVT. Starting off @ 7.8hp, it won't take much before a 30 series cvt is rendered useless.

A good, inexpensive source of hydraulic brakes is a used rear setup from a motorcycle; you can usually pick up a whole setup for around $50