needin your help on porting/jetting

[QuadJunkies]

We are having some issues getting the Predator dialed in after having the Carb modded and the head ported.....Can someone tell me ,is it a good rule of thumb that when you have both thos e mods that you would jet up???
Originally, when it was just piped and runnign the vortex,it was jetted to a 175 and a 50 pilot,then when the motor came back rebuilt, they had put a 45 pilot and a 172 :huh well, it popped and ran like crap, done a plug readinh and it was white... So.... We jetted it to a 185 and put back in the 50 pilot, it seems to idle better ,BUT... it blubbers(hehe like my choice of wording:D :o ) and choks out a bit on bottm into mid, and clears up a bit on the top but feels weak on top.....Where do we go from here???:confused: were wondering maybe the needle??? We have ONE DAY to get this dialed in before Nationals !!! I cant remeber what the thing is that its called but we were told to disconnect the thing that controls if your throddle gets stuck wide open ???and put the jetting and pilot back to the 172 45 pilot ??? Were at a loss here........:(

[cals400ex]

i am not familiar with that bike but did the engine builder mess with the needle or needle clip?? i would assume 1 clip down from stock would be good.

what i would do to get you in the ball park is first get the bike to normal operating temp and the let the bike sit and idle for a minute. shut it off and check the plug. this will give you an idea of the pilot jet is rich or lean.

then start it back up and take it out and leave it at 1/2 throttle or so for a minute. quickly pull the clutch in and kill it. check the plug once again. the plug color will indicate rich or lean condition mainly dealing with the needle and clip position.

repeat the same process of with a full throttle run. make sure you keep it floored for several seconds to get a good reading. i usually like to keep it pinned until i know i am at top speed.


this is how i do it and i haven't had any problems yet. this at least gets me in the ball park.


i have read before that after a port job certain bikes did like to go down a size or 2 on the mainjet. i can't exactly tell you why, but that is just what i have heard. good luck

[QuadJunkies]

)I was hoping it would be YOU Cal that replied to this!!!:p We are vert familiar with how to do a plug reading god knnws we have done enough with 4 quads!!;) I did leave out one importnant thing last night ( I was tired I guess:o ) It also has a Modded Carb..... Maybe this is where its throwing is threw a loop...:confused: lol Also, We run c12 so plug isnt going to read quite the same . Even with the 185 and 50 the plug STILL isnt forming any color... Im goin to buy a new plug to day (a few actually) and I did tell Troy that it may not form some true color on a new plug right away .. Seems like we jet better to sound anyhow!!! I told Troy "its poppin and sputtering. its lean... and it was........Im not sure about the engine builder mssin with the needle or not, but this quad has never had an issue for us to jet so we were just a little baffled.......

[cals400ex]

what exactly was done to the carb? i don't think the port and polish should have changed too much itself from where you were before with jetting. now, with the carb being modded, i am not too sure. i guess it depends on what was done to it.


yeah, i am actually running aviation fuel in mine. the plug is a different color but it wasn't way different. the thing is, i like my plug to have a slight color change right on the bend of the tip of the plug. this color change might be hard to see and it may change from a tanish to a gray or something like that. it may be pretty faint too. also, sometimes the color change won't even be on both sides of the tip of the plug. sometimes i can only see on one side and the top of the tip, but not on the other side. i don't know if what i just said makes sense. it is somewhat hard to explain. anyways, hope you get her running good.

[QuadJunkies]

our plug readings are Orange.....:o I guess from the the link I went to says its OK for that color, I guess its just the fuel. Im not sure of all the ins and outs of the Carb mod,other than the person who does it on a ton of quads all the time and I guess its basically like making the Carb BIGGER......