Engine choices

[Cbreiter]

Hi, I am looking at getting a new engine for my kart. I am from Canada, so harbor freight isn't a good option. Princess Auto is my main source. I am looking at two in particular.
http://www.princessauto.com/pal/en/Engines/65-HP-196cc-OHV-Gas-Engine/8088379.p

and

http://www.princessauto.com/pal/en/Engines/7-HP-208cc-OHV-Gas-Engine/8445405.p

My main question is, beyond stock form is there any huge advantage to getting the larger one? I am looking to upgrade, with a bigger carb, high flow air cleaner, header, and rocker arms, valve springs. My main concern is, will the aftermarket parts for clones fit the 7 hp ones?

I want to add some gear ratio to my kart, it currently has a 72 tooth rear gear, which is a blast, but I would like to upgrade it to a live rear axle, and get a bit more speed, but still be able to roast the tires.

 

[itsid]

Well I think most parts should fit, others might not (piston perhaps, maybe con rod)

So after all, I wouldn't take the chance if you think about modifying it's internals
(conrod, piston or cam)

If you just want to remove the governor, and maybe add a bigger carb or something simple as that, the 7HP is most likely fully compatible to all available clone parts for that matter.

Maybe someone already tried that and can provide you with a more educated opinion

'sid

 

[Cbreiter]

Ok, I was just mainly wanting to do external things, with the exception of the valvesprings, rocker arms, possibly pushrods, and possibly a billet flywheel. I was just looking at the stock numbers for torque, and the 7hp is much higher than the 6.5hp. It's only 10 bucks more, so if all the other parts were the same, and interchangeable with the 6.5hp aftermarket parts, I thought, why not? Any more input from anyone is welcome on this! I'm running a 6.5 currently, but am looking to replace it with a fresh engine.

 

[itsid]

Don't let Chris hear/read that

In short terms:
Don't change the valve springs without changing to a billet conrod first!

I'm sure you recognize, that the conrod is on the list of parts that might NOT FIT.

'sid

 

[firemanjim]

You should still be able to get a billet con rod. They come in over sizes too. Most like the difference between those 2 engines is the rod length. (Longer stroke on the 208) With that being said, measure the length of the con rod (or look it up) and order the same length in a billet model. If you change the valve springs, changing the cin rod is a MUST....... for your safety foremost, and that of your engine block.

 

[itsid]

Well the con rod length is not what makes the longer stroke;
it's the crankshaft that moves the conrod (and therefor the piston)

And since the crankshaft is different already, it might aswell have a larger or smaller diameter where the conrod is mounted.
Also it has a different piston diameter, and since the piston itself is different it could be, that the piston pin is different and thus the eyelet of the conrod.

So you need to not only know the length of the conrod but also all internal diameters and other external measurements
...is the dipper shorter because of the additional stroke length?
and if, will a longer dipper hit the crankcase?

There's just too many variables here to just ignore them.

'sid

[EDIT]
Oh and another thing to consider...
according to the manual,
the 6.5HP engine is turning CCW (as all GX and clones)
the 7HP on the other hand is turning clockwise!

6.5 HP (page 3):
http://images.palcdn.com/hlr-system/Documents/80/808/8088/8088379_manual.pdf
7 HP (page 2):
http://images.palcdn.com/hlr-system/Documents/84/844/8445/8445405_manual.pdf

 

[landuse]

One factor you have to remember is the clutch that you are using. If you are going to use a TC (not sure what you have now), then a hopped up 7HP might turn into too much for a Comet 30 series to handle, and you would have to get a 40 series TC (which are PRICEY).

A cenrifugal clutch for a larger HP engine might also be more than what you are willing to pay (or the one you have now might not be up to the job)

 

[OzFab]

I would like to upgrade it to a live rear axle, and get a bit more speed, but still be able to roast the tires.

One or the other, you can't have both:
A high gear will give you a decent top speed but, acceleration will be lousy
A low gear will fry the tyres but, you won't be going very fast flat out...

Also keep in mind that, when you go from a single spinner to a live axle, you more than triple the rotating mass, which requires more torque to get it turning, to light it up will require even lower gearing...

Don't get me wrong, my live axle kart will "break loose" when I punch it but, it's hardly "roasting the tyres"...

 

[Cbreiter]

One factor you have to remember is the clutch that you are using. If you are going to use a TC (not sure what you have now), then a hopped up 7HP might turn into too much for a Comet 30 series to handle, and you would have to get a 40 series TC (which are PRICEY).

A cenrifugal clutch for a larger HP engine might also be more than what you are willing to pay (or the one you have now might not be up to the job)

I currently am using a centrifugal clutch, and it is rated to 13 HP, it's a hilliard extreme. I currently am running a 7:1 ratio (or close to it, 10 tooth clutch, and 72 tooth rear sprocket, on 6 inch tires). With just the single wheel I wouldn't doubt that you can lay 5 feet of rubber, but I want maybe a bit less, with more top speed. I was thinking to install a set of front brakes, so if I really want to roast 'em, I can, lol. I do have a 420cc (15 hp) that I had thought of putting in it originally, but the small blocks fit nice, and I won't have to cut a bigger hole in my fibreglass body on the kart. I just basicly want something that will go a tiny bit faster than now, and still have close to the same power. (more power would be awesome, but I don't want to put too much money into it at this point)

Here are some pictures of the kart.
http://i1284.photobucket.com/albums/a572/cbreiter/P9220141_zps72dfc21c.jpg
http://i1284.photobucket.com/albums/a572/cbreiter/P9220140_zps15b41fb7.jpg
http://i1284.photobucket.com/albums/a572/cbreiter/P9220142_zps938ad2a7.jpg

 

[machinist@large]

Please use the thumbnail format for pictures. If I had known that you had loaded bandwidth hogs in your latest post I wouldn't have klicked on it. And I know I'm not the only member on the forum with the same bandwidth issues.

EDIT; OK, when I posted the comment, they came up resized a little smaller, but I still have to ask you to use the thumbnails; they let those of us who don't have big city internet glance at them, and then decide if we want/ or need to load the larger image.

 

[paddlepop]

FWIW. I'd be wary of enclosing an air cooled engine in fibreglass bodywork. I know my Honda 7hp gets pretty warm after an hour or so and I'd want as much airflow past as posible. Granted, you may already have an air scoop and duct which may work better than an unenclosed mount. Just my thoughts.

 

[Scout]

There's just too many variables here to just ignore them.

'sid

[EDIT]
Oh and another thing to consider...
according to the manual,
the 6.5HP engine is turning CCW (as all GX and clones)
the 7HP on the other hand is turning clockwise!

Good catch on the engine rotation.

The manual with the HF Predator claims it to be a 7 hp, and displacement is 212. The difference between in displacement between the two engines linked could be in the crank, could be in the bore, could be in the head, like you said, too many variables.

Seeing as one is CCW and the other is CW, I think the choice is pretty clear. You could buy both and build a twin engine kart reminiscent of the old two stroke twins.

FWIW. I'd be wary of enclosing an air cooled engine in fibreglass bodywork. I know my Honda 7hp gets pretty warm after an hour or so and I'd want as much airflow past as posible. Granted, you may already have an air scoop and duct which may work better than an unenclosed mount. Just my thoughts.

I would't worry about enclosing a motor as long as there is ductwork to vent the hot air, the flywheel is a fan that blow air over the head and keeps it cool.

 

[Cbreiter]

I haven't had problems as of yet with airflow. The kart is open from the bottom, though I would like to add a pulse pump to it, so I could relocate the tank, and put a different air cleaner setup, and some sort of header, so I would be able to have a removable scoop that goes over the engine. I currently am running a 6.5 clone on it, and it hauls. I just want to refresh and slowly as time and funds allow, add some power, and a diff or a live axle. I'm pretty sure that the 2 engine idea would be cool, but I definitely would have to cut the body up then, which is something I'd like to stay away from.

 

[Cbreiter]

I'm assuming from the feedback so far, that I'd be best off to stick with the 6.5 clone, unless I was planning to stay with the stock configuration on the engine. On a side note, I did notice that they list the 7hp as CCW on the site, maybe the manual has a typo? I can check one when I go to buy an engine, as they have a few of each on display there.

 

[OzFab]

It depends how you look at it (LITERALLY): The flywheel on most engines rotates clockwise but, if you're looking at the PTO shaft, that means it turns CCW

 

[Cbreiter]

Yeah, I hear you on the rotation. The easiest way is just to check it before I buy a motor. Then I know for sure.

 

[OzFab]

Yep, all you need to do is slowly pull the starter & see what wat the PTO turns...

It's also possible to check with just a visual inspection; with no gearbox assembly attached to the engine, if the starter rope leads down into the housing, you can be sure the PTO will turn CCW as you look at it

 

[machinist@large]

Yep, all you need to do is slowly pull the starter & see what wat the PTO turns...

It's also possible to check with just a visual inspection; with no gearbox assembly attached to the engine, if the starter rope leads down into the housing, you can be sure the PTO will turn CCW as you look at it

Not quite; you need to look at what side of the crank the rope comes away from. If pulling the rope will spin the crank CW as viewed from the starter end, then you will have a standard engine (CCW PTO shaft rotation). If it spins the crank CCW (CW PTO rotation), then you have a reverse rotation engine....

 

[Scout]

Just pull the rope and see which way it turns.

 

[zbuck]

Just pull the rope and see which way it turns.

Amen. Scout, where are you located in Indiana?