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in this thread, I want to discuss how 4-cycle atv engines work- what the different types are... how they are set up and which you prefer. To start off, are the cams on ALL atv 4-strokes powered by a cam chain? I know that on say a lawn mower or logsplitter engine, the cam is turned by the tappet, pushrods, and valve rockers. Which is better and why? Chain-driven cams or pushrod-driven cams? Are the pushrods just an old version and everything is transforming to chains or the other way around...or not at all? Just looking for some explanation, history, and downsides/upsides...
I've always been a craftsman tool guy because I worked for sears auto for about 10 years. I was in Lowes the other day and they have pretty much everything craftsman now, for some time. They'll even warranty old tools I'm told, like sears did. So I'm happy about that.
Below is a quote from a response to similar question from yesterday:
"Easiest thing to check is trash in the main jet. if it idles fine, then the idle circuit and low speed jet is clear. if it bogs off idle that's when it's transitioning to the main jet."
I will go ahead and open up the carb and check the main jet, but please respond to this post as if the main jet is squeaky clean.
Below is my post:
Only starts and runs on Full chock.
Does not matter what position I have my "mixture" screw. Tried it at zero, 1 turn, 2 turn, up to five turns. Spent a few hours confirming that the position of the mixture screw does not resolve issue.
Runs great at idle and if I slowly engage throttle, it will rev up as expected. But, quick rev up or when I am trying to drive it, it spits and sputters and looses power.
I also use a propane bottle and did not find any obvious leaks, and the vacuum port is hooked to fuel peacock and I also made sure to simply block the port with my finger to see if that would resolve the issue.
New Carb (after market), New Coil, Fresh Gas. No leaks at manifold boot, hot battery. Good gas flow. Runs too good to be a valve issue, or cylinder, great compression.
I can move the choke out a tiny bit, and it will still run, but will still bog down when I try to power it up.
I also have a 250 trail boss Polaris that I require to run at full choke, but it has power at all throttle potions.
I suspect it is running rich as the choke is on, but will not run with it off.
Any details would be appreciated.
By Dwight Williams
Ok, so I bought this scream of a deal the other day - a 94 King Quad 300 for $40.00. It's been sitting outside with no carburetor on it for about a year. Its rusty, missing some parts, wiring is all cut up and spliced etc. No seat, no racks but the plastic is all there minus the headlight housing. Anyway, who can pass up a $40.00 quad right? I get it home and looked at the sight glass for oil level, it's about 1/2 oil and 1/2 water. I drain it, refill it and turn the motor by hand (recoil starter is missing) and it turns over just fine. I worked on the wiring for about an hour and got it to turn over with the electric starter and got enough of it sorted out to get a spark. Did a quick compression test, 70 lbs. Wet test bumped it up to 90. Ok, so rings and cylinder washed out with water for a year, not too surprised. I thought 'what the hell' and sprayed some starting fluid in it and it ran for about 2 seconds - enough to show it's got life. Since then the compression has gotten worse, I can't get enough pressure to activate the carb diaphragm, therefore no fuel pump either. The compression is now around 60.
Anyway, my question is....is it worth it to try to get this thing going? I tore the top end down today and the cam and one of the rockers is pretty worn. I figured a top end job would be about $100 or so, depending on the condition of the cylinder but I'll probably have to put a cam and rockers in it as well. Doing some research on ebay I figure I'll have to spend about $500-$700 to make the whole machine right again. Much less just to make it run and use as-is but I won't really like it until it's right. I don't mind doing the work, I actually enjoy it but I'm concerned about what all that water did to the rest of the internals, I can't really test it all out until I can make it run.
I know it's a basket case but I'm not into it much at all, even if I do the top end and find something else wrong I'm still not out much. I'm leaning toward ordering the top end parts and going from there unless you can convince me otherwise - any way to check the rest of the internals without tearing it down? I plan on flushing the oil cooler before I do another oil change, I've drained it twice now and it gets milky almost immediately just turning the starter - I suspect the oil cooler is polluted badly.
I'll get some pictures today if anyone want to see them.
I saw this article on Motosport and thought it was pretty good. Anyone add anything?
You might think hopping on-board an ATV and going for a spin is just as easy as taking your regular 4-wheel car for a ride around the block. After all, both have four wheels. How hard could it be?
In many respects, you're right. Some adventure riders choose quads over their two-wheeled counterparts of the dirt because there's less chance of crashing and it's easier to learn. ATVs also offer more manageability for younger riders to get acquainted with outdoor riding than a dirt bike.
However, beginner riders on ATVs tend to make the same mistakes that result in crashes, roll overs and injury that could be avoided with some instruction and know-how. If you're looking at a fun family outing by renting ATVs or want to get into the sport take advantage of the following points and avoid the same mistakes so many other first time ATV riders make that end their day early or before they barely get started.
1. Nerf Bars
Get Nerf bars. These are not soft cushy add-ons that are cousins to the football you use during backyard football games. In many respects, Nerf bars are gigantic foot pegs. Don't bother with traditional foot pegs because you'll constantly slip off and because of the "I feel safe factor" that comes with riding a quad you'll also have a tendency to let your feet drag when riding. That's a recipe for getting one or both of your feet caught in the back tire resulting in serious injury. Nerf bars allow you to stabilize your feet and get maximum control over the ATV
Rest your feet easy on Nerf bars
2. Rolling Over
Believe it or not, it's fairly easy to roll an ATV over. And you don't want to be on the bottom of that sandwich.
The most common way of ending underneath a quad is looping out. That's done by hitting the gas and having little to no experience with the power of an ATV. The front spikes up like an out of control stallion, throws you onto your back like a bucking bronco and then pins you like a UFC Champ.
The second way is when you're having a bit too much fun sliding around in mud or other slick conditions, the tires finally do what they're designed to do and grip the ground but the rest of the bike, with you on it, keeps going.
Finally, those who think they've found their bearings take aim for a steep slope and try to conquer it only to end up upside down or in their attempt to arch alongside said steep hill, tumble over the side.
3. False Sense of Security
This goes somewhat hand-in-hand with the roll over capability that many riders fail to appreciate therefore they also neglect wearing proper protective equipment. Don't think wearing jeans, t-shirt and sneakers is adequate protection when riding a 4-wheeled machine powered by a gas engine that doesn't have seatbelts. You need a helmet, goggles, gloves and riding boots at a minimum. Once you start ripping it on the track or trails add a chest protector, neck brace, knee brace, etc.
4. Throttle Control
Everybody wants to skip the kiddie stage and get right into hair-raising speed when it comes to riding ATVs. OK, most everybody. But for those who do so many put on the cloak of invincibility and think a quad is merely a mini car that finally enables them to release all sorts of pent up childhood inhibitions.
So they jab their thumb into the throttle with the expectation of a controlled roller coaster ride. Instead, they loop out and end up underneath the quad or manage to stay seated only to careen off course and introduce their 4x4 to a large tree. ATVs normally have a thumb throttle and most have an automatic clutch so the clutch is one less thing to worry about. So go slow and figure out how much "thumb" is too much and get used to the speed and power an ATV delivers before really going for a ride. Oh, one more thing, learn to take your thumb off the throttle!
It's not to hard to loop out on an ATV
5. Loading the ATV
Never, ever ride an ATV up a ramp into the back of a pick-up. If you want to know why just go to YouTube. If you want to know how to load an ATV check out this fine piece of quality information on How to Load a Motorcycle, Dirt Bike or ATV into a Truck.
The bottom line to riding an ATV the first time is treat it like you would anything that comes with a modicum of danger. Careless behavior endangers you and others but with common sense and a willingness to learn you'll enjoy of lifetime of riding quads.
For additional information on riding and/or maintaining ATVs see:
10 Quick Safety Tips for ATV Trail Riding Tips for New ATV Owners Choosing the Best ATV for Beginners 10 Things That Alter Your ATV Performance Written By: AndrewT
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