416 built to 426

[drm416]

I'm thinking about making my 416 a 426 is it the same bore with different comp ratio or everything different

[knelson]

1mm larger piston

[cals400ex]

406, 416, 426, 440, etc......all these numbers are is the size of your motor in cubic centimeters. thats the easiest way to put it. these numbers have nothing to do with the compression ratio. that has to do with the dome on your piston and the combustion chamber on your head.

[drm416]

Would it be best to go 1mm larger bore for the 426 or go ahead and put new sleeve and make it a 440? Because something is not right with the 416 my son stock 400ex will spank it and thats not going to work. The only problem is i have heard that the 440s don't hold together as well like blowing head gaskets. So any input you guy can tell me would be great Thanks

[underpowered]

it is all up to you. any motor can be reliable as long as it is put together well and broke in correctly. my 426 has been together for 3 years now with only a few headgasket problems. i tor it down a month or so ago to rebuild it and when i checked the bore, it only had about 1/2 degree of taper to it. it was in no way in need of a rebuild so i stuck a new piston in it and let it go. A Properly (emphasis on properly) built 440 will be reliable. I would say go ahead and re-sleeve it witha big bore sleeve and do a 426, that way you can are already sleeved for a 440 when that time comes. or you can just bore it out to a 426 on the stock sleeve (mine is) and then resleeve when you need to later down the road.

[drm416]

So will the 426 run with a stock 400z?

[underpowered]

a 400 witha pipe should run with a stock z400. a 426 should blow it away. my 426 will run with stock 450's.

[cals400ex]

is the stock 400ex all stock? in other words when you say stock do you mean no mods at all or is there no internal engine mods?


give me the build profile of the 416. what brand and compression piston? what gaskets? what pipe? what jetting with what carb? what cam?


another tip: make sure the throttle cable is adjusted properly. where the throttle cable goes into the housing on the handlebars you will see a screw adjustment. you will have to pull a rubber boot away to see the adjustment first. make sure there is only like 1/4 to 1/3 of an inch of slack in the throttle lever. if there is too much your carb will not be opening up fully. this will drastically decrease power. on the other hand, if there is no slack it will feel like the throttle is sticking open. so this obviously isn't good either.

[drm416]

The stock 400ex has a supertrapp slip on on it and that is it no other mods.


The 416 was built when i purchased it so i don't really know nothing about what it has except for factory carb with 138dyno main anything bigger seem to run to rich by looking at the plug. I guess i need to just tare it down and start from scratch that way i know what i got.

[cals400ex]

yeah, i am wondering if it actually has a 416 in it. :(

if it was me i would not get a 426 or a 440. we have builts 406's, 416, 426, and a 440. its not that the 440 runs bad or anything. we just can get the 416 to run just as good. plus the 426 is a tight fit for the stock sleeve. in our 426 we always put in a larger sleeve just like the 440 requires. i would get a service manual first. then take it apart. a 10.8:1 416, with a hotcam and a full exhaust will be a nice runner. that would probably be a good time to drop the dynojet kit since you probably don't have all the jets. i would get a stock needle (if the dynojet one is in place) and then using keihin mainjets from now on. like i said, make sure that throttle cable is adjusted right. that can make a killer difference if there is too much slack in it. other things that can hurt you when dragging: bad wheel/axle bearings, unbalanced/bent wheels or axle or brake rotors, brakes dragging, rider weight, gearing, tire sizes and weights, and rider ability/knowing the quad.

also, a 416 by itself won't give a huge gain. however, a 416 piston will complement a cam and a good full exhaust really really well. the stock cam in crap. it is not aggressive at all. it almost needs to be more aggressive with a all stock bike. so make sure you upgrade cams. the full exhaust system will also help a ton when dragging. just some things to consider.

[drm416]

Thanks for your advice I'll tare it down and check it out when i get the time and money it does still run decent for now. Just had a new baby so it all about her for now.

[bwamos]

Originally posted by drm416
The stock 400ex has a supertrapp slip on on it and that is it no other mods.


The 416 was built when i purchased it so i don't really know nothing about what it has except for factory carb with 138dyno main anything bigger seem to run to rich by looking at the plug. I guess i need to just tare it down and start from scratch that way i know what i got.

Something is wrong. I'd think you should be much larger than that on your main if it's on a 416. A stock 400ex runs a 148 main, no? (I'm running a 160 main w/ a 400ex carb on my 330ex).

I'll wager your cam chain timing is off a tooth or two. It feels like your towing another quad behind it, doesn't it.

[drm416]

It did until i put the 138 dyno jet in it felt like it wouldn't rev all the way. I'm going to tare it down and rebuild it that way i know what i got.
Thanks
Darrell