Had a great weekend of balls to the walls riding. The show quad handles great, but it doesn't run very well anymore.

At the end of our Sunday morning ride, the engine ceased up within sight of Roadrunner. I've never had an engine cease on me but lets just say it like someone threw the back brakes on in 3rd gear.


So I got home yesterday and no matter how tired I was, I had to tear the quad down and find out what happened.

Turns out, the crank is toast, Its basically welded in the position you see in the pics. Looks like I will be splitting the case and doing a major engine overhaul as well.

I'm thinking semi-high compression piston (maybe 13.5-1), stroker crank, head porting, carb boring, and a set of cams.

We will see though, here's the pics of the tare down.

bummer it happened but like you said time to upgrade, good thing your a good mechanic, otherwise you would be looking at a grip of cash for the rebuild

That sucks!


It wasn't low on oil was it?

^^nope.. I checked it that morning...

Thats what i was thinking as well....

Damn Bugsy that just sucks.. Let us know if you find the cause..

So the piston in the sleeve was OK.. It was the crank that seized? Wonder what the bearings will look like..

If ya need some help, let me know..

Ouch, that does suck

And not a cone in sight

Just talked to the tech at motoworld and he was telling me that the 450's are notorious for the big end of the crank ceasing up. Although, this is the first I have herd about it.

At least you got back safely. Good luck on the repairs...summer project!

OUCH.

Crank Siezing is the worst.

But I'm betting your up to the task....get'er done.

Was the oil high enough viscosity for the temp? Between 110* temps and riding hard in the sand, you have to use the thickest oil recommended. I'm sure the engine got very hot.

yfzcentral posts alot about seizing cranks. thats glad you didnt get thrown off the bike. always check your oil before every ride. Nmotion big bore

That bites bro sorry to see that happen, but you know the old saying play big pay big, like you said time to go bigger,

Damn Dave

At least you were close to camp with plenty of help

a 490 kit is easy enough ...but since you are splitting the case anyhow you'll have it open to make some clearance... go BIG!!! ...send that pig up to a 520 or so

With the upcoming EPO, you picked a bad time to break the show bike.

he can have it fixed by this weekend

yeah if i had the parts...

but porting takes a couple weeks

DRAG!!!!!!!!!!

So it sounds like the Yamaha and Honda 450s are pretty much hand grenades, huh?

I wouldn't go with a big bore Dave. Maybe bump up the compression slightly, cams, and have very good headwork done to the cylinder head. Going much bigger than the engine was designed for is a problem waiting to happen.

Amen. if you love wrenching constantly just to keep the thing going - then go for it..
If you want it to run and run and run - Keep the internals within specs..

PFFFT!!



Don't listen to'm



DO go with a whole new jug though... one that has larger water jackets to accomodate the CCs ...it's a lil priceir than just boring out the one ya got... but you won't run the same risk of overheating

The 04-05 motors have been bad about seizing up. There is an oil mod you can do, but if I am not mistaken it is to help oil the wrist pin not the crank bearings. The 07's came with this oil mod from the factory. I have seen way too many 04-05's have crank bearing issues it isn't funny. I busted a piston on my 06 this race season and had Dee Manshack from Rage ATV build me a nice stock internal motor with custom grind cams that is very reliable and makes good power.

Bummer, but when a 4 stroke puts out almost as much power as a 2 stroke per size motor all you have done is shortened the fuse. Tis why I keep my 250r, anyhow keep us posted on the reason for failure....Was bummed when you got back to camp to pick up your van as a hauling vehicle....In my opinion lengthen the fuse don't shorten it.....Rather ride with you all weekend than see you sit in camp for part, some, all......................If you lived in Phx I would help you rebuild her.....

No BB here, Like furball said, I don't want to be wrenching constantly... I've had enough of wrenching on this quad. and this rebuild will put me at the edge of my technical know how when it comes to this stuff.

like i said, high comp piston, porting, carb bored, web +5 cams and maybe a stroker crank... I'm still researching.

^^^^ best advice your gonna get. that year was known for doin that! youll need to upgrade that bottom end first before you try and pump up the top.

^^ I'm also planning on doing the oil Mod while I have the case split and I have a feeling I may need to check my shift forks too...

Tell SndSmplr you want a refund on that POS he sold you!!!!

shouldve got a 2 stroke!

^^ at least I can stay on the bike I built lol

DOH!!!

So lets see if I got this right "The Show Bike was all Show and no go." And after 2 rides it went kaboom, Good thing more people didn't show up for the TEST RIDE huh.

Didn't you let Chummin ride it???

LOL yeah its def all show right now. Ya gotta figure I have 2 seasons of all out hard riding on the motor, so I figured it was about time for some work to be done. I just didn't expect to have to do it as soon

slam! damm it brutal in here!!!

OHhhhhhh.....



now it all becomes clear.

No chit!


You guys keep this up, they're gonna move this thread to PI.

hey i was getting tired and didnt want to quit. i went out the manly way.

well i hope everything turns out good with the rebuild. Try doing a full write up with the porting, compression, cam choice etc. dyno please! I know with the stock compression all these aftermarket cams dont do crap! you can polish the exhuast port yourself with a few hrs. and a dremal from homedepot. just smooth it out, dont take any material away.

I'm surprised it didn't get back to camp on bling alone.

man ain't that a to your show quad. I think he blew it up on purpose so he could put more power into it. being the show quad in all, the wife would have to let him fix it before anything else with the new house right

plus he wanted a fighting chance in the next epo. He thinks he has the advantage of all the new goodies he is going to smoke the competition. I came in 3rd with the stock internals and suspension. and the bling bling 20"s its the rider not the parts you add. but if it is the parts, my +2 LT suspension should help

Well, while all you guys were talking crap I got some more work done, heres the pistion, cylinder, wrist pin, and rod.

It looks like the wrist pin took a beating an was heating up also...

Well Dave, that is not the way to answer your own question. Sorry to hear about the loss man.

Any thoughts on this Diesel? I don't understand how it can "just fail"

Looks oil related. Once oil reaches extreme temps it rapidly loses it viscosity, Im talking within minutes! Loss of viscosity=loss of adequite lubrication. When that happened serious metal to metal friction started going down.......... hense the wrist pin gauling, burnt ring landings, and seized crankshaft. Im sure the 110+ degree temps in the dunes didnt help either.

You said earlier Motoworld did your last oil change. What did they use 10W-30 Yamalube? a 20W-50, preferabally synthetic, would have been ideal for the riding conditions in my opinion.

That's my diagnosis at least.

Hell, might not have been oil at all. Theyre all on a timer, the 450 grim reaper might have just caught up with your bike.

i think...and diesel can correct me if im wrong here...



you have the first year that they went with the True 450. (the previous yfz's were not actually 450's!) so when they pumped up the top end, it was too much for the old bottom end of that motor. in later years they upgraded the crank, and got away from this problem.

This is exactly what I was thinking as well. I would want to know exactly what they put in there, if they even changed it (unlikely that happened, but who knows) I think simply your oil broke down and everything locked.

Now for the YFZ450 history:

04 / 05 439cc with a short stroke and longer rod.

06 449cc with a longer stroke and shorter rod. Exact same Piston and cylinder as 04/05. Slight head modifications.

07 449cc EXACT same as 06. Now comes with piston wrist pin oiling system.

Issue with 06 crank: Longer stroke and shorter rod = more pressure on cylibder sidewalls and creates more heat.

Solutions:
WR450 crank. Makes the 04/05 a true 449cc keeps a shorter stroke and longer rod ofr less sidewall pressure.

Hot Rods is getting ready to release a 06/07 +3mm stroker crank for these bad boys. Set to be released sometime towards the end of July.

Dave and I were talking on the phone the other day about the necessity of the oil mod on the 06 and earlier quads. For the most part, I have seen many people have success with keeping up to date with oil changes and proper care. On the same token I have seen some fail. I personally beleive that when one goes higher compression, the oil mod is a must. on a stock 06+ YFZ I have seen it 50/50. I recommend it for peace of mind. Would the oil mod prevent what happened to Bugsy's bike, that is the ultimate question that I cannot answer yet. if the 07's continue to fail then the answer is probably no. And yes, I have seen some fail that had the oil mod done.

PDR

that sucks what happened to the bike, just time to make it faster and upgrade stuff is all

dam Diesel, you know your chit. Im always changing my oil. evey ride. it gets expensive but its only oil. probably just a tired motor or cooked oil. start ups are the worst for the engines. maybe with everyone testing it shutting off and repeatedly did a killin to it?

Looks to me like heat got the best of it.What type of oil and what viscosity?Did several people run it continually up something like olds.continuous hard runs in 110 weather may have pushed the cooling system.what type of coolant?Hows the water pump and radiator?

check out yfztech.com/forum they had a crap load of winners at the last 4scs in dumont.I never saw much on yfzcentral
as far as 2 smokes being more reliable I disagree.when you run out of gas you melt a piston.

Compression is not going to hurt it.with cams you want more compression.I say over 12.5:1 but thats if you don't mind buying race gas.

actually "mixxer" on trx450r.org does porting on just about everything and his turn around and price are pretty good and no one over there has a bad thing to say about his port work in fact they love it.He has a vender spot and has some very good knowledge to read up on.
I suppose yall want to know who the hell I am?
http://www.yfztech.com/forum/index.php?sho...hl=seized+crank
now that I look at the exhaust valves.what size main jet are you running and pipe air filter combo?

The Honda 450 that pulled him back did not have any problems.