iam trying to find out who makes the 426 &416 kit for the ex,out of the three which would be better i mostly trail ride ,i like to hill climb & play race once in awhile.iam looking for more power then just a k&n filter & pipe.would just a port &polish with a quicksilve carb be enough or do you think i should go with a big bore kit.iam looking for mostly low &mid power ,thanks an advance

 

by just going with the 416 or 426 big bore kit you aren't going to notice much of a difference. The 416 kit is only a 5% increase in displacement, so don't expect even 5% increase in power. What helps is running a higher compression piston than stock. At least a 10:1 or a 11:1 but with high octane. Also, there is really no need to purchase these kits off a company, you can order the piston and rings and that from someone like JE and then just have your local machine shop bore the cylinder to fit the new piston. Or you could save some money and just do a higher compression piston in your stock bore.

 

I have install alot of the kits that you are asking about and as previously saaid to really gain hp you need to go with a high compression piston. Along with the pist you should go with an alround cam to help the motor breath. While you have the motor torn down you should have the head flow ported. All of these mods will work well together and give you the power that you are looking for. You don't need to buy the big bore kit from any one just buy the piston kit and have a local shop do the machine work. The 416 in a .080 bore in the stock sleeve and the 426 is a .120 bore in the stock sleeve. that is the max that can be bored out of that sleeve.

 

how do you know if its a high compression piston.so it would be the same size piston,whats different about them(stock)& high compression.also i have a question about igniton advance what is it ?what does it do.i seen one on curtis sparks,web site are they hard to change.would a 14tooth sprocket help too?thanks

 

A high compression piston has a higher crown on it than the stock piston so when it is at top dead center the volume on the combustion camber is smaller which causes the air/fuel mixture to be compressed more. As far as ignition advance that is controlled buy the cdi box on the 400ex. The cdi box is easy to change. Advancing the time of a motor will give it more bottom end power but can also cost you top end power if it is advanced to much it is a trade off. Changing the sprocket to a 14 tooth sprocket will give the 400 a little more top speed but you will loose alittle of the lowend torque do to the higher gear ratio. Let me know if you have any other questions and I will try to help.

 

I agree with every thing said except for, stock counter sprocket is a 15 tooth so going down to a 14 will give better bottom end, losing top end. I noticed a big difference going to a 14 counter sprocket. I did not notice the 16 as much as the 14.

 

Big bore = cheap horsepower. If you want more power at a cheaper price, go with a high compression piston, port it, get a exhaust, a carb, and I'd go with a cam and heavier springs as well. You'll notice a differenct in performance.

 

cdracing,,you were right with everything except the 14 front sprocket. Stock the 400 has a 15 so going to a 14 will lose top speed but make acceleration a bit faster and you will be going through the gears quicker.

 

The 400ex does have a 15 tooth sprocket. My mistake so going with the 14 tooth will give you more bottom end and quicker acceleration with some loss in top end speed. The price in front sprockets (cheap)you might get a couple different ones so that you can play with the gear ratio depending on the type of riding you will be doing, smaller sprocket for tighter riding areas and a bigger one for more wide open areas.

 

yeah,,esepically if your doing some riding on country roads or long fields with quads faster than 400s like raptors,,they wont know what hit them when you pull past them with different gearing that will let you reach much higher top speed. But of course this setup wouldn't work well for most tracks, trails, etc.