Sled engines+silly people+warm weather=bad advice

[squat251]

Excellent.
...and vice versa. I've run lawnmowers at 15° F.

thank you. some of the people, no one brave enough to post here, are complete lunatics when it come to sled engines, not just here either, I've seen posts on other boards that made me leave right there and then, i don't know where people get the idea that these engines are soooo different that they just will not work for a go kart.

as for the differences of the two engines, a free air engine wouldn't be the best choice anyways, and as for the RPM range, that just means more air over the engine, and more coolness, makes up for everything also, lawn mower engines most certainly are made for air to go over them, thats why they have a fan, and cowling. now, they don't normally use air flow from movement, but thats still air flow.

 

[mike75925]

thicker castings would be like swapping a v6 for a v8 you will need a bigger radiator. the more heat retained, the warmer the fuel will be when entering the combustion chamber. could cause dieseling. if it doesn't shear the keys.

 

[Kaptain Krunch]

as for the differences of the two engines, a free air engine wouldn't be the best choice anyways, and as for the RPM range, that just means more air over the engine, and more coolness, makes up for everything also, lawn mower engines most certainly are made for air to go over them, thats why they have a fan, and cowling. now, they don't normally use air flow from movement, but thats still air flow.

I get what your saying, im not trying to argue. But the fan pushes air over the engine, whether its moving or not, a free air engine will get virtually no airflow at a stand still. Anyways, i get what your saying.

Mike, go ahead look at a sled engine, the castings on most arent noticeably larger than those of an industrial engine.

 

[squat251]

and i hate to correct you again, but sleds also have in the "small hood" a butt ton of vents on the front, so traveling 55-60mph down a trail is getting a lot of fresh air in there for that engine. i would also like to make the point, that at a standstill (and im not endorsing the use of a free air) the engine would be at idle, and have the clutch spinning, so lower rpm, and all the free air engines i have seen have the clutch set up to suck air in, not super effective on a sled, but if it was open on a kart, it should get somewhat adequate air flow. I'm not trying to argue, I just want every side pointed out, and breaking stuff like this down is a great resource for people who will read all this later.

 

[Kaptain Krunch]

and i hate to correct you again, but sleds also have in the "small hood" a butt ton of vents on the front, so traveling 55-60mph down a trail is getting a lot of fresh air in there for that engine.

I realize that, i was talking directly about the engine itself. The difference between a free air sled engine, and a mower engine, is that the mower engine will cool itself while not moving, whereas the sled engine needs to be on a moving vehicle to cool itself properly.

 

[squat251]

agreed, free air+not moving= hot motor.

 

[Kaptain Krunch]

Right, thats what i was trying to say the whole time, just didnt come out right haha. Your explanation is much better.

 

[squat251]

this should get stickied incase anyone has any question whether they should use a sled engine or not, I've seen way to many people post that its a bad idea, and the way i see it is, if your starting from scratch, use the biggest motor you can short of a car engine, your going to be able to build the cart to compensate, and if you have the motor, its not getting used, use it. you wont be disappointed...at all. of course this is assuming that you are building this for someone responsible enough to harness the power, and that you know what your doing, otherwise just wait till you can handle it.

 

[Kaptain Krunch]

You could just summarize the key points and then send it to a mod or something and see if they can sticky it as "sled engine FAQ's" or something.

I agree with you man, i see a lot of people putting hundreds of dollars into clones, and engines like that, when for that price of a clone, a billet flywheel and rod you could get a sled engine, and start to build a kart.

 

[squat251]

not to mention the top speed of say a 440 will destroy the most modded 6hp clone you can buy

 

[mike75925]

got any pics handy of sled engines? on air cooled here, (125/250 dirtbike) the sleeve with the cylinder minus fins = 1/2 to 3/4 on avg? engines with the forced induction of air for cooling are significantly thicker, but are way under powered in comparison. a 1966/76 rm250 produced 55horse. granted it's two stroke.

 

[squat251]

yeah, i do, just not online yet, the ones i do have are all the drive components. could easily google it.

got any pics handy of sled engines? on air cooled here, (125/250 dirtbike) the sleeve with the cylinder minus fins = 1/2 to 3/4 on avg? engines with the forced induction of air for cooling are significantly thicker, but are way under powered in comparison. a 1966/76 rm250 produced 55horse. granted it's two stroke.

not sure what your getting at here? that somehow sled engines are not as powerful or something?

 

[Kaptain Krunch]

got any pics handy of sled engines? on air cooled here, (125/250 dirtbike) the sleeve with the cylinder minus fins = 1/2 to 3/4 on avg? engines with the forced induction of air for cooling are significantly thicker, but are way under powered in comparison. a 1966/76 rm250 produced 55horse. granted it's two stroke.

I can get you pics of a dismantled 750 triple, its liquid tho.

 

[squat251]

yeah, sadly all the big ones are liquid, about 600 and up, they start to be liquid, wish they would make a nice fan 650, although im sure they do, they are just hard to find. liquids are beasts on sleds though, much much more powerful than a fan, just so impractical on a kart

 

[mike75925]

nah kap'n said the castings were about as thick as industrial engines

 

[Kaptain Krunch]

I dont have any free air sled engines on hand, but heres one i found on ebay, you can see the fins arent all that thick. Not sure if you wanted to just see the fins, or the thickness of the cylinder calls but this is what i found.

http://cgi.ebay.com/ebaymotors/John...nowmobileQ5fPartsQ5fAccessories#ht_500wt_1077

 

[mike75925]

looks similar to rd400 jugs/heads, but seem a bit thicker

 

[squat251]

perhaps I'll summarize this thread, and have jr dragster post it up, i definitely feel this will be a huge asset to all who are wondering if they should use a sled motor or not

 

[EagleTalons]

You'll have alot of summarizing to do because this to me is a mess of discussion.

 

[squat251]

and most of it is the good kind, intelligent arguments, and references, and a little ranting, its all good.
too bad you cant get any sled engines in montana...wait, dont they sled there? i mean... its like mountains and snow there right? in many places there you guys get snow sooner than most of the country dont you? why no sleds?