hey guys, im reading up on the 440 bore kit for the 400ex from weisco. they let you choose two different compressions. the 12.5:1 or the 11:1. i was wondering what you guys thought would b better. thanks

 

The Wiesco kits used to be known for not giving you actual comp ratio. I am not sure if this is still true. I woudl ask the question. i do believe that it had something to do with a XR400 motor having a diff. deck height (maybe it was head gasket), and many of these kits were made originally for the XR.
In ACTUAL compression ratios, I would not advise going over 11.1 on a stock con. rod.

 

is this all i would need for the 440 bore...440 or do i need other things... im buying a 400ex that already has a 416 bore in it.. ported,polished, web cam. but i think id upgrade it to a 440.. is this all i would need?

 

http://cgi.ebay.com/ebaymotors/ws/eB...spagename=WDVW

 

Heads up on the 11:1 piston from Wiseco. If you set it up with stock gaskets for the 400EX you are going to end up with around 9.4:1 compression. I just went through this on my 440 build this winter. I ended up going with no base gasket and a .027" head gasket from cometic. I still only ended up with 10.6:1. Although I am happy with the results, I would advise you to look into buying a Ross or JE piston.

I too believe that.

Nothing against Wiseco, just a heads up for ya. I wouldn't go over 11:1 on pumped gas, stock rod and stock engine studs.

 

polarsport500-From what i have seen and experienced the 416 build can perform as well as the 440 so you may want to put your money into some other performance parts and go with the 416 that is already there.As far as compression ratios go i also have heard that the wiseco pistons are not quite as high as advertised.My wife has a 440 ex with a 11:1 wiseco and a friend has the identical motor by the same builder except that he has 12.5:1 and the performance is so close that it is hard to say what is better.My wifes does seem to do better at the shorter races and the 12.5:1 does better at the longer races so that is something to consider.We have ran the wifes 440 plenty hard for two years now and it has all been dune riding which we do about 35 to 40 weekends of the year so as far as reliability is concerned we have had good success with the wiseco.I see that you are considering a yfz and although that is a very fast quad your 416 can be set up and tuned to run right with the yfz even the ones that have the cam mod and are piped.Remember that the 11:1 can run on pump gas but the 12.5:1will require at the least a 50/50 mix of pump and high octane "race fuel" and that can be expensive these days.

 

thanks for the info... u say the 416 can be setup to run with the yfz? im buying this 416ex from some one in a few days.. he says its ported, cammed, polished, and its got that 416kit in it. iv seen a video between a 416ex and a yfz and it lookd like the yfz won pretty good.. check it out it on yfz central.com. but what should i expect outta this 416ex. and how cna i make it run with a yfz. thanks

 

yeah, you will need more than a regular 416. the compression ratio, the cam, the pipe, carb porting, larger valves, proper jetting will all make a difference. you can do a few things differently for drag racing than you would probably want to do on a mx bike. for example, you might want to go larger on the valves for drag racing but for mxing it may not be needed.

 

i wouldnt worry about con. rods as putting a hole in the piston and blowing head gaskets. this would happen be4 the rod failed. however if u use high octane race gas then it would be no problem. i know its expensive but ask urself if it only takes about 3 gallons to fill ur quad than its only gonna cost 6 bux to fill the tank with race gas. if the people at wiseco dont say the bottom end needs to be stronger than itr probly doesnt need to be. just decide if u wanna have to buy race gas or octane booster. but also think that if u use race gas it can sit in a tank longer before it goes bad. hope this helped.

 

i would say 12.5:1 or maybe even a 13:1, u want high compresion for performance, just have to run slightly higher octance gas, thats all