Has anyone ever seen there speedometer go over 62? Mine gets there and stays. i was wondering if there is a limiter or is 62 as fast as it will go. I checked it with my gps and it says 61.8. Will a exhaust and k&n filter along with a jet kit get me anymore top speed? Do I have to re jet if i remove my spark arrestor? Thanks

 

I also have a vinson 5-speed and have noticed, on various forums, this question of top speed asked a lot. The response is always the same-62 MPH. I imagine the responses have come from riders of stock as well as modified vinsons. It seems the answer is always somewhere near 62.

 

Yeah I have been doing some reading and you are right 62 is about it. Thanks for the response

 

Breaks every speedlimit in the US except for the Interstates.. LOL....

 

<div class="FTQUOTE"><begin quote>Originally posted by: packer

Has anyone ever seen there speedometer go over 62? Mine gets there and stays. i was wondering if there is a limiter or is 62 as fast as it will go. I checked it with my gps and it says 61.8. Will a exhaust and k&n filter along with a jet kit get me anymore top speed? Do I have to re jet if i remove my spark arrestor? Thanks</end quote></div>

More than likely you will have to rejet. Less restrictive exhaust and air flow will lean you mixture. It will also advance your timing. Most ATV's can not adjust the timing (short of changing the cam sprockets, or cam itself), so you may have to compensate with changing the gap on your sparkplug which also changes your timing a tad. Once that is done then you may have to change heat ranges on your plug to get the correct burn.

As far as top speed, the potential is there, however more than likely you have a rev-limiter that will only allow the engine to turn up so far. With the added boost in HP then a gear change would get you more top speed at the same RPM. You can change your gearing with a ring and pinion swap out or change the tire size.

In some cases (not all), simply changing the exhaust and air filter will do little for you and in some cases will lower the performance and gas mileage unless other factors are also changed to get the potential out of the mod. In most cases the performance goes up a tad because of the lean condition produced (lean and mean as they say), however, too lean can lead to a melt-down (burnt valves, burnt hole in piston, welded rings etc). One second running screaming fast then next second major enginge damage - with no warning - bam!!! too late.

 

My philosophy is - unless you are racing for money (and need the extra little edge) then what is the point.

If you were able to get a 5% boost then if you have 40 hp will 42 really make a noticible difference to justify the money spent. And how often will the extra 2hp be utilized and really needed.

If you can go 62mph and somehow got around the rev-limiter to yield 65mph from the 5% boost. How often is that going to be a benefit for you.

And heaven forbid - if you have a melt down - big bucks.

It probably is cheaper and better just to buy an ATV with a bigger motor. Because by the time you get done doing the correct mod's and doing them properly to gain the potential. You may end up spending the same amount or more total.

From the factory most ATV's are set to run rich (less chance of a melt-down and less warranty issues to deal with). A proberly tuned stock engine can perk the performance up to a noticible level. Simply rejetting at a cost of about $2.00 per jet can give good boost and efficent performance. The correct way to rejet is to jet for max efficency and hp then to go one jet larger (rich). Just as in life - being a little on the rich side offers a cushion.

My personal experience I went from 150 to 147 to 145 to 142, to 140 on the main jets until I hit the optimum peak, then put the 142 back in. It really perked my pull and mid-range, and pulls strong with no flat spots throughout the rpm's. With the stock 150's it flat spotted from mid-range on up using WOT- it pulled but it worked hard to get up there. On a short sprint of a particular distance I could only best about 40mph, that same srint now yields me 47mph. My machine still only tops out at 52mph on a good day with 50mph being the norm (restricted top end from the rev-limiter).

On a top end run using WOT (Wide Open Throttle) if you notice that if you back the throttle off a tad (1/16) that your engine smooths out and seems to pull a little better and doesn't seem to be working as hard then the chances are you are rich and a smaller jet can help.

 

It is my opinion that one of the best ways to get more hp is with the dial-a-jet induction system from Thunder Products, want a different jet then just move a dial. Because it is an induction system and inducting air you can also get a remote float bowl and hook an auxilary fuel supply to it (quart bottle). Then instead of introducing more air it will introduce the auxilary fuel (my preference is alcohol). Alcohol burns cooler and on the surface thus lowering your combustion chamber by 100 degrees or more, ionizing (breaking down big drops of gas to a fine mist) your fuel mixture at the same time and allowing better dispersion and more efficent burning of your fuel.
Being an induction system it will only supply what your engine is calling for. Your engine can only supply a certain amount of air or fuel, Depending how you set up dial-a-jet if your engine calls for more air then the dial-a-jet supplies it. If you set it up for a fuel boost then if your engine says I need more fuel, then here comes the alcohol from the dial-a-jet induction.
The dial-a-jet runs about $80 or so, the induction remote fuel bowl runs about $150, total $225. The best part is you will always be jetted properly and always have the correct mix and it is a variable system giving only what your engine is calling for to gain maximum effency.
This is definetly on my Christmas list.
If this is interesting to you then check it out at <a target=_blank class=ftalternatingbarlinklarge href="http://www.thunderproducts.com/dial_a_jet.htm
">http://www.thunderproducts.com/dial_a_jet.htm
</a>
The remote float bowl is at the bottom of the page or this link
http://www.thunderproducts.com/dial_a_jet_remoteFB.htm

 

Most of what buckaroo says is very true, With the exception of changing intake and exhaust changing timing. That is BULL. The valves operate off the cam, The cam operates off the crank. You could take the carb and the exhaust completely off and the valve timing would know no difference.

 

It is half a doezen of one and 6 of another. If an engine is firing at 4 degrees, it will always fire at 4 degrees, however with less restriction it may now need to fire at 6 degrees to match the closing of the valves and the peak of the compression (or when it is supposed to fire). So either you can look at it from the stand point that it has not changed but needs to be changed or is has changed because it is suppose to fire when the valves are closed and the compression is at peak or just before peak.

What I said was because the ingniton timing was off because of less restrictive exhaust and since there are no timing adjustments on most ATV's that maybe you also will need to change the cam or sprockest (meaning to have a cam that would assure that the valves are closed when the spark gets there) more or less a 'torguer cam' with less duration on the lift.

If not then, if you take a car to the drag strip and unbolt the exhaust from the headers, why do you need to make ignition timing changes and carb changes..

So how does one word this - the timing is now late and needs to be changed or the timing has not changed but is out of sync with the closing of the valves?

Any way you want to state it, the timing is no longer in sync with the closing of the valves. And why are the valves ahead of the spark - it is because there is less to restrict or slow them down. This is commonly refered to as backpressure. On the intake side the valves are ahead because the engine has less sucking to do to get the volume of air into the engine.

Is it BULL or not bull? Anyway you want to look at it, The timing will be off.....

 

<div class="FTQUOTE"><begin quote>Originally posted by: OhHell

Most of what buckaroo says is very true, With the exception of changing intake and exhaust changing timing. That is BULL. The valves operate off the cam, The cam operates off the crank. You could take the carb and the exhaust completely off and the valve timing would know no difference.</end quote></div>

If you took the exhaust completely off then why would the engine run like crap. The valves don't know the difference and nothing has changed... It is called back-lash,,, and that being the case then we would not need to have any valve-lash (gap) to compensate for the timing.

And why do we need a precise gap with the sparkplug. It is going to fire at the same time every stroke. How can changing the gap change the timing or does it really change, or does it only change the duration, maybe it delays it because it takes longer to jump? The cam and valves don't know any difference. If we had a different cam that closed the valves sooner maybe we would not have to change the gap on the sparkplug or change the timing.

Tell me why if you take a 34mm carb off and put a 36mm carb on it will run like crap and visa versa. Could that possibly have something to do with the engine sucking air and free flow, valves closing and timing of the spark...

Whether a change, physically changes something or not, it still puts it out of sync and needs to be readjusted And if it didn't change why would it have to be readjusted?

But heck don't listen to me it is all BS, and I don't have a clue about engine threory. See what it says below - I'm just a Dummy...