I have a 416EX that is extended via swingarm 4" and widened with DURABLUE I guess about 4" also. But what I'm getting at is in 1st, 2nd,& 3rd just fry the tires(18x11x8 Turf Tamer) on most surfaces except blacktop so I was thinking of stepping up to 20" Shredders on the rear but don't know if they will have a dramatic effect on lowend. The turf tamers seem to be a little over powered to me but I'm just getting into tne sport bike thing. I only ride for fun, nothing serious but I like to line up with my buddies every now and then.



I have a carb question also; WOT has stumble but fine everywhere else. had UNI FILTER but it got replaced by factory filter could this be the problem or maybe jetting issue [Keihin FCR39]

 

first question, does the quad still have stock gearing( counter shaft and rear sprocket size same as factory). there is a cheap alt. to buying new tires, unless you just want new tires. if you still have stock gearing buy a new counter shaft sprocket (sprocket on the engine) that is one tooth larger than what is on the quad now. this with compenstate for the 18" tires. stock gearing on the 400ex in for 20" tires on the rear. if going with one tooth larger does not help, go two teeth larger. just got this thought, are the turf tamers wore out? if so the will not hook up at all. you can pick up counter shaft spockets from $7 to $20 depending on brand. rocky mountain atv has some spockets for $7 that will work fine if you are not an aggressive rider.

 

Sounds like you bought this machine used, right??? The long swingarm and little rear tires both suggest that it has some weird mods for the track (maybe TT racing or something???).

Your problem isn't just tires, it is your way to long swingarm! That is the reason you are losing traction. Your weight is shifted so far forward that you no longer have enough weight over the rear wheels to get any bite. I can see maybe a +2" or something for sand drags, but +4" is really, really extreme???

The stock 400EX is a superb trail machine, but the previous owner messed it up for you. If you are just a casual trail rider, that long swingarm isn't at all appropriate! It is also making the bike longer, so you are losing a lot of turning agility, which is not good out on the trail. Find a stock swingarm and REPLACE THAT 4". None of the rest of us running stock swingarms, ever have any problem with traction whatsoever. And, lose those little Turf Tamers becasue they are to low (ground clearance) for out on the trail. Probably need to replace the front tires too.

And you also said "widenend with Durablue". Does that mean a Durablue axle, or wheel spacers??? If the bike is to wide, you will have problems wacking trees on a tight trail.

As for your carb problem, just throw on a UNI and see if the problem goes away. Stock filters are way more dense than a UNI, and you are probably running rich now.