Went to St Anthony dunes, which by the way are AMAZING! Go there if you can! 3 days in I was going up Devil's Dune and started losing power 3/4 of the way up. Turned back down the hill and the quad stalled, starter tried to turn a couple times and then just clicks. When I put the quad in gear I can't turn the wheels, so I'm assuming something didn't get oil and now the motor won't turn?! Any Ideas of what may have happened? Also, i'm thinking if this has to be torn apart and some major work needs to be done I might as well throw a big-bore in it? What's a good big bore kit that will keep my quad reliable and not require a lot of other changes?

well when you put the quad in gear you shouldnt be able to turn the wheel smuch if at all. the more motor work that is done the less reliable they become end of story there is no reliable big bore thats going to use stock motor parts and be reliable. when you install a big bore to get full potential your going to have to go all out or not at all. just up your compression while u have it down replace the crank and do the oil mod and valves.

put ur quad in first
then pull ur clutch in
have it on run and the key on
have the person on the quad in front of u start going slow
next is the most important
let the clutch out all the way really fast aka dropping the clutch
then if it wont start ur fuked cuz you are going to be spending money

Also what all is done too ur quad right now? maybe the reason y 3/4 is all it wanted to do. what gear were you in and where u holding it on the rev limiter? did it make any sounds before it stopped running?

dont just pull the quad in gear without the clutch in its not good on it

my .02 just tryn to help

Take the timing caps off the stator cover, take the spark plug out, and turn the crank counter-clockwise. if it doesnt want to turn, youve got yourself a seized rod bearing.

Just got home, we're 14 hours away. I'll probably try turning the crank tomorrow. We had another YFZ with us and you can easily turn the wheels by hand in 2nd gear. Pretty sure its the rod bearings or wrist pin or something ceized or broken. So big bores aren't going to be reliable? Even just like a 470? Aren't there kits available that replace the whole cylinder part of the motor as opposed to just a re-sleeve? Like the Ice Cubes? I've seen a lot of ads for those but they're a lot of $$ too...

CylinderWorks builds a +3mm big bore cylinder that is fairly cheap. They are on their second gen and so far we have not seen any issues with the new design. Its cheap too. Right around $100.

Check out our big bore kits here http://www.tqsatv.com/products.php?cat=62


The very last one on the first page is a great deal.

I'm less concerned with cheap, more concerned with reliability. I've heard that Falicon and M Madd? or something make good replacement cylinders? If I just did a WR crank and high compression piston like Wanna450 said, would I have to run race gas because of the high compression? Who makes the best High-compression piston? Weisco, CP, or just the GYTR?? You also mentioned doing the valves? Do what to the valves?

Get a JSR or NMotion 98 mil jug.. those are the only ones I have heard of that do not have epic failures all the time, but its gonna cost you a grand. I learned from experience when I blew my 14 hr motor, if your gonna upgrade anything DO NOT GO CHEAP BY ANY MEANS or you will regret it like I did.

By the way asking if a weisco or CP is better is going to open a can of worms. Do some research and decide on your own, either one is probably fine as long as you follow a STRICT maintenance schedule and change them out often. WR Crank uses a smaller wrist pin, which most people make you think that is going to be better for reliability, well think again, just use good parts, if your gonna do anything you are gonna have to do it ALL or your risking a break. Go falicon, for a crank, they have a good name, sure they have had failures in the past as well, but so has anyone, at least they dont have AS MANY..LOL> Do a long rod Falicon kit, less sidewall pressure. Just dont get your cylinder bored, or your going to regret it. Some people will tell you they had luck, but some, like myself, didnt. Weigh your own risks.

What about the Ice Cube kits? You said which ever piston I go with I should change them out often? Is that just with the high compression? I don't want to keep haveing to do this, so do I need to stick to stock and just do a WR or '06 crank??

I dont see a bb kit around a $100.00 Unless I cant see it?

I think that was a typo. He was saying that a CW 98mm jug is around $200

WTF!!! This is the first chance I've had ANY time to even look at my quad. So I pulled off the little crank access screw to try turning the crank by hand, and it turned!! so I screwed the cover back in and fired it up, it labored to turn for a second and then fired right up. I let it run and it idled for about 30 seconds then died. fired it up again at kept it at a little higher idle for about a minute then it died. I did this a few times and when its starting its like theres a spot in the stroke that it's having trouble turning, then it gets past that at fires right up; when it dies its like the motor comes to a dead stop right away. These motors are always a little clanky, so its hard to tell, but it sounds like it may be a little noisier than normal but nothing obnoxious. This thing died going up Devils dune at St Anthony, I went up and around it several times and it had no problem with the climb. It started losing power and running bad 3/4 of the way up the hill so I turned around to go back down. It died right as I started going down, tried to turn over for a second and then just clicked. We could not turn the wheels with 3 people with it in gear and towing it the wheels would just drag in the sand. Probably irrelevent, but I changed the Dyna-tech ignition to setting number 2 right before I went up the hill, thats not one I usually run, but I was playing around to see which setting would run the best out there. ANY IDEAS??!!

Glad to hear it won't be an imminent rebuild!

-Nick

u otta gas?

It sounds to me like a crank bearing is in the process of seizing up.

I'd agree.

I'd pull it down now and see whats going on before its too late. And by too late, i mean punching a hole in your bottom end and throwing the piston through some valves.

I agree this happened to me and i kept messing with it. Then it sounded like someone threw spoons in my engine. Pull it now buddy and put a new crank. Well since your putting a new crank might as well stroke it

Have you had a chance to dig into this problem any more? I would be very curious to know what the problem is because my sons 450r is doing exactly the same thing. We were at Dunefest and on the last day, he was riding down a trail from vendor row and it just died. There was no sign of any problem leading up to that point. When he tried to start it, it turned over really slow to start with and then just clicked like the battery was bad. We towed it back to camp and then took it out and compression started it and it ran fine for about 30 seconds with no abnormal noises and then it died again. When it does this, it seems to lock up the motor like there is something floating around getting caught in the gears because it is intermittent. One minute the motor seems to be locked and then it frees up. I have not had a chance to pull the plug out yet and spin the motor but I plan on doing that this afternoon.

If you have identified what is going on, please let me know so I at least know where to start. If anyone else has had a similar problem, I would like to hear what you found as well. I hope this is not going to be a chronic issue with this machine.

Thanks,

Brad

I was doing routine maintence on ours, and I noticed the clutch basket wiggled a little funny. I pulled the clutch basket off, and found that the cage that holds the balls in the bearing was falling apart. When I drained the oil, there were pieces of the bearing stuck to my magnetic drain plug.
This could cause the shaft to shift, and bind up the tranny.

Yeah, I'm pretty sure it's crank bearings too. I took the whole top end apart, there was a lot of tiny metal flakes in the oil but no sign of where they came from! The piston, cylinder and valves all look great. I'm just waiting till I get some more money together this winter to fix it. I have it torn all the way down now so I can powder coat the frame while its down, and I'm going to do a WR crank with a 12.5:1 and port/polish the head.

Pulled the motor apart and sure enough, the rod bearing is starting to seize up. It has several area's where it is stiff and wants to lock up when you rotate it on the crankshaft. What is the cause of this and is this a known issue? If so, is there a mod you can do to prevent it. You can see where the crankshaft started turning colors from getting hot. If ther is a known oiling issue, I would like to fix it while I have it apart.

Brad

its still to new of a bike to have any known issues, if this is a problem everyone starts seeing often, it will become a known problem, so far, you are the only person i have seen with an issue like this

I pulled the motor apart and found the rod bearing to be binding up and the lower portion of the crankcase by the oil pickup screen had a lot of metal shavings. I have not found where the metal came from since everything in the transmission looks great but my assumption is that the metal is fragments from the rod bearing.

I need to find a reputable shop in the seattle area to rebuild the crank. Does anyone have any suggestions?

Thanks,

Brad

Action Cycles in Tacoma. (253) 474-7770 ........... Tell him Todd sent you.

S&S in Puyallup

Here is a link to some pictures of what is left of the rod bearing from my sons 450r. The cage was destroyed.

Brad

YFZ450r repair pics

I had the same problem on my 06 yfz450...not sure why it happened. The push rod would turn like everything is fine, then after a couple of rotations it would start to bind then lock up completely. I also tore up my chain guide for the camshafts, which could be the culprit ...or an overheating issue I had, not sure. I am rebuilding it. I'll be following this thread.


-Matt

Here in Brazil we have 5 2010 YFZR EFI with that problem already. Yamaha crew just don't know what is causing this. The riding here is 95% dune. All the quads has no mods and the oil change and filter cleaning were made on Yamaha Service Center. I am searching the web to find out if there are any problem on the oiling design in the 09-10 as the other YFZ's with early years had.

westcoastatv what have you changed on your engine ? Have you done any thing on your oil bomb or case ? After the replacements, it did happened again ? Have you tested the oil pump before assembling back ?