Sorry for the long post but this is my first post on the forums however I have searched for hours with no luck on the subject, so forgive me if I missed something or do something wrong. Ik its alot of detailed info but hopefully to eliminate any confusion and limit the questions that you may have about it and what happened, so I just purchased this quad from a buddy who knows a fair amount about them and it is a 400ex with a 426 big bore kit, not sure what brand or piston, compression of the piston either, but its supposed to have kibblewhite valves in it, stage two hotcam, a hot rods crank, the carb is jetted again not sure of the exact jetting used, Duncan full fat boy 4 exhaust, the head is port and polished, and a few other things that currently slip my mind, I have rode other 400exs and 450Rs and this bike is fast compared to the others, so there is definitely a few of those things done to it however I do not know if all of it are true or not, keep in mind Ive only had this 4 wheeler a couple days, and have not had a chance to tear it down and look for myself, so I took it out to ride it for the first time just a short ride down the road and back to get an idea of exactly how fast it is and to get the feel for it, it is a fresh motor but has been broke in by him and rode by several people with no issue I had let it idle a few mins, its alittle difficult to start if its cold and the very first start of the day but once its started and shut off it turns over alittle slow kinda like a weak battery but fires up after 1 or 2 revolutions every time, I assume due to compression because if I fully depress the throttle it frees up and spins much quicker, as I was going down the road somewhere on the top end of fifth gear Im guessing between 60 to 65 mph, I had it at wot but the bike was still increasing in speed and rpm and had not reached the rev limiter, this is important because I do not think the valves floated because I had not hit the rev limiter and had only been at WOT for a few seconds, when it just died like the flick of the ignition switch, or kill switch and Im positive I had not accidentally bumped the kill switch in either direction, no hesitation I.e. spitting and sputtering of any kind before it died just hauling butt and bang she was dead, do not be confused there was no actual bang or noise of any kind it just died, so Im almost positive that was electrical maybe the stator going bad or loose connection on the cdi im not sure but my question is once it died naturally the back tires locked up and it immediately slid to the left so the tires could not spin freely I thought it had seized up but it didnt because I grabbed the clutch and it straightened out I downshifted and dropped the clutch to try and bump start it with no luck but the tires did spin and the engine had compression I could hear it in the exhaust so I knew it wasnt seized, instead of trying again and potentially hurting the motor i came to a stop put it in nuetral and hit the start button, fired up instantly like new money still felt good and strong no hesitations or vibrations however I noticed that the stator cover gasket was pushed out from between the stator cover and the case, Im assuming from excessive crankcase pressure? It looked like exhaust or could have been oil mist coming from between the two every time I gave it throttle for the first two or three revs, then it quit, I limpted it home just in case it wouldnt start again and I dont want to be stranded in the road, My question is has anyone ever seen or experienced this for themselves and if so what did you find to be the cause and the fix for it, any information is appreciated because I am new to 400exs however I am a heavy equipment mechanic by trade and that is my profession so I do have a good understanding of most of the engine and how it functions but its not diesel and its definately a different breed of animal from a CAT D8N dozer, I should have most of the tools needed to perform any diagnostics test on the engine and trans and know most of what you are talking about, thanks guys
2004 400ex blew the stator cover gasket out at WOT
1 - 9 of 9 Posts
Joined
·
4,390 Posts
Welcome to the forums. I have never seen a stator cover gasket blow as it shouldnt be under any pressure. Usually they will just leak a very small amount of oil if they dont seal up all the way. I would suggest posting a picture of it if you can. As i would like to put my eyes on this. First thing i would think of for shutting off at wide open throttle would be a fuel delivery issue. Maybe a restriction in the filter in the tank petcock or an inline filter if it has one installed. Could also be an electrical issue related to the amount of vibration caused at wide open throttle near the rev limiter. I would investigate fuel first though. It could even be the carb has junk in it that got kicked up at that instant. Hard to say. But the gasket blowing shouldnt have anything to do with it IMO.
@SlammedRanger I will definately keep that in mind, the only reason I felt like it was more of an electrical issue is because it never once hesitated or sputtered, made any kind of noise and in my personal experience usually if something were plugged like a inline strainer wouldn’t it start to show signs of running lean for instance backfiring on deceleration or hesitation of any kind during acceleration instead of an immediate stall? I mean that’s just my way of thinking and I’m here asking guys like you for any advice because you have much more experience than myself on these machines so I will definately check on it to make sure that’s not actually the case and I’ve tried to include a picture for you let me know if there is anything wrong with it and I will try to get you a better one, I can tell you that before I left on that short test ride that the gasket was not sticking out like that before I left because I looked the engine over closely for leaks or anything like that and it was not that way, it may not have happened during the stall that is just what happened and I noticed the exhaust or mist coming from around the bottom and noticed it then, I wasn’t sure if there would be crankcase pressure behind that cover or not but I couldn’t imagine any other reason it would come out other than improper installation
Attachments
Joined
·
4,390 Posts
Picture is good. To me i would bet when they installed the gasket they missed the hole in it and ripped the edge alittle. But i would also think if the bolts were torqued properly it wouldnt allow the gasket to move anyway. Those bolts can be very easy to over torque and strip them out. I would be careful of that. But there should be a crank case breather coming out of the top rear of the engine and going into the side of the intake tube. If someone capped that off for some reason the pressure could then build in the case and blow out all kinds of random gaskets i would make sure thats clear aswell. As for the bog or cutting out before stalling. I have actually had lack of fuel act just like that before. It wouldnt be really noticable at wide open throttle but at lower speeds you would feel a bog or cut out before it died most likely. I also know coils and cdi's can die at high vibration times. I would also be checking the spark plug which will require a 17mm low clearance socket. You may have to order one as even the highest end set of tools probably wont have this. MotionPro makes one and thats what i have. These spark plugs are well known for coming loose.(Most of the time because they didnt use the proper socket to tighten it).
Ok so I just got home and have had a chance to look it over, the cdi box was hanging by the connectors, I guess it bounced off of the little hanger it’s supposed to be on and I noticed there was a black wire with a white stripe going to it and it has a section of the insulation missing from it right at the back of the connector, also this motor according to everything that I’ve been told was done to it, I’m just gonna take a wild guess but should probably run no less than 93 with octane booster and that’s probably pushing the bare minimum as far as fuel goes and I know my buddy would be the kind of guy to just throw 87 pump gas in it to let me ride it and sell it, I’ve noticed a pinging every now and then when it gets warm but never had it stall like that do you think it’s possible that with the high compression and low octane fuel at high rpm it detonated or pre ignited before top dead center and tried to rotate the crank backwards and seeing as there is only one piston it stalled instantly? Just a theory because it’s def not any kind of high octane fuel in it atm it doesn’t smell or look like it, also I just found out that they did not install new piston rings and I’m at a loss as to why he would install all those performance parts and a new jug but use used rings... that concerns me now, it looks like I’m going to need one of those sockets that you mentioned because I def want to do a compression test now, it has fair compression and runs decent so I doubt he accidentally put a ring in upside down or anything like that but we will see, Do you happen to know what psi is acceptable on a 426 I found the stock pressures but nothing on a 426 that I’m sure is going to be higher
Joined
·
4,390 Posts
I would say on a fresh topend north of 150 would be a good number. If i remember correctly my 416 had 155 or 160 when i did a compression test on it last. But it was a few years ago i did that so my memory could be wrong. I would think if your over the stock compression number which is like 128 i think you will be good enough. More than likely you are 11:1 or 12:1 as those are the common numbers for this engine. I would run premium at the minimum. 50/50 race fuel would be ideal. Did you check the crank case breather?
I did the breather was not capped off and everything was connected, I blew through it with compressed air and nothing came out amazingly it doesnt look like there is hardly any oil residue in it at all however it is leaking around the stator cover. It did not leak much overnight but I fired it up to warm it up so I could check the oil level in it and it started leaking within 5 mins of idleing and it also looks like its wet around one of the exhaust ports on the head which usually indicates your rings are going bad doesnt it?
Joined
·
4,390 Posts
Oil dripping off the header collector can be a few possibilities. Valve cover gasket leaking above it and running down to bottom. Valve seals(usually you will get blue smoke on start up),rings(you will get blue smoke after riding for alittle bit that will get worse and worse). Or if they removed the valve cover recently that is the lowest point of the head and it will drip oil if you dont jack the front end up first.
1 - 9 of 9 Posts
