What is the approximate top speed of the A/C 400, after several hundred miles? Will the performance be much different then when new.--Thanks--Mike

 

roughly 50 mph give or take a few. pretty much all the arctic cats from the 250(older styles. not sure about the newer ones) up to the 500 run about 50mph. the smaller bore sizes just take longer to get there. i believe the 650's and 700 run at about 60 mph. someone will correct me if im wrong. Its been know that when the 400 gets about 4-600 miles on it the motor starts to get up and go a bit more. feels more powerful.

 

Mine really woke up after about 600 miles. It's still no rocket though, but good enough for me. My top speed with 27" Bearclaws is an indicated (by speedo) 53 mph. Definetely wakes up after a few hundred miles.

 

About 50mph for a 400, my 650 ran 65mph stock, 63 with the new springs.

 

Around 50mph most of the time, on occasion 52mph

 

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

Mine really woke up after about 600 miles. It's still no rocket though, but good enough for me. My top speed with 27" Bearclaws is an indicated (by speedo) 53 mph. Definetely wakes up after a few hundred miles.</end quote></div>


I'd say yours really woke up. 27 inch tires have 6% more circumference over a 25 inch. Which means your speedo would indicate 6% less than you are actually going. So if your speedo says 53 then you are actually going 56 mph.

Let's swap engines. On a good day mine can only do 52 mph with 25 inch tires turning up the old RPM's.

 

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

What is the approximate top speed of the A/C 400, after several hundred miles? Will the performance be much different then when new.--Thanks--Mike</end quote></div>

Yes they wake up quite a bit - however, I don't think that I would be doing a great deal of top end runs with a new engine. If you do a top end run then make sure you don't hold it there for any length of time and then bring it right back down and let it cool off so the rings can contract again. The pitfall is that your rings won't seat properly and you will loose compression and eventually and prematurely start to consume oil.

You will be shaving a lot of steel with expanded rings and that will be mixed in with your oil... Imperative to change oil frequently with a new engine until fully broken in.

From an ecconomic point of view it is better to use 'dino oil' during break in because of the cost from frequent oil changes. Your engine will break in perfectly fine with synthetic but will cost you a lot more money. I would change oil and filter at 100, 250, 500 miles at least.

Oh and never hold a new engine at a constant speed for any length of time, keep changing the speed up and down. And stop the engine often for a cooling period, maybe every 10 to 15 miles, at least for the first 100 miles.

 

<div class="FTQUOTE"><begin quote>Originally posted by: buckaroo50

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



Mine really woke up after about 600 miles. It's still no rocket though, but good enough for me. My top speed with 27" Bearclaws is an indicated (by speedo) 53 mph. Definetely wakes up after a few hundred miles.</end quote></div>





I'd say yours really woke up. 27 inch tires have 6% more circumference over a 25 inch. Which means your speedo would indicate 6% less than you are actually going. So if your speedo says 53 then you are actually going 56 mph.



Let's swap engines. On a good day mine can only do 52 mph with 25 inch tires turning up the old RPM's.</end quote></div>

Yeah, make no mistake, she's screaming at that speed, but I have yet to hit the rev limiter. I won't find it either, it sounds like it's over-revving by that point and I'm not going to push it. My manual is quite a bit faster than the wifes '04 400 auto. I've hit the limiter on that at about 49-50, and I'm running 25" Goodyear radials on that one. Didn't buy them for top speed though, and they'll go anywhere I point them.[img]i/expressions/face-icon-small-happy.gif[/img]

 

I hear you there, mine works hard to get the last 150-200 rpm's. on a top end run. Sounds like yours is really good up there, could be because of the manual tranny. I know the engine without a rev-limiter would be capable of 9000-10000 rpm with the right camshaft.
I was thinking if the gearing was set to only get 55mph at say 9500rpm. Man what a midrange punch that little engine would have. It would almost sound like a chainsaw though.

 

I live at or close to sea-level and when I run the railroad bed I can consistently get 52mph. I go 11 miles north and run at 500 feet above sea-level and there is no way I can hit 52. If I take it up into the hills 1500 to 2000 feet above sealevel, I can't even get 50 mph out of it. It is amazing what loosing only a few percent of hp or 1 or 2 hp can do, especially on a relatively small engine like the 400. I would almost bet that at 5000 feet above sea-level the 400 would be hard pressed to hit 45 mph, without rejetting the carb and changing the sparkplug, it would be running so rich you'd think the choke was still on. lol..