JUST GOT MY YFZ TODAY BABY!! now i got questions..

[beastlyone]

alrite, now would you guys reccomend buying and rebuilding the topend immediately? i know yamaha reccomends rebuilding the topend every 50 hours, and im clueless as to how many hours are on the bike. Also it has a HMF slip on it, i want the entire system because i know it produces the most hp with the entire system. Would it be worth it to buy a new exhaust like an N-Motion, or would buying a new header for it be just as good? and if it would be just cheaper and as good to buy a header, can i only use the HMF header? And any performance suggestions would be great guys, thanks

[jshtex]

Our 04 is on its third piston and second cylinder. I didn't "have" to change them that quickly but I also didn't want a failure in the top end $$$.

The gaskets are not that expensive and if your doing the work yourself I would say tear it down and at least look at it. If you have a piston or pin failure it will cost you a lot of money to fix that.

As for the HMF, we have a sport slip on and I am 99% sure you have to use their header, but truthfully I don't think your going to see a very big gain in using it over the stock headpipe / HMF mid pipe setup your running now.

If your planning on racing it (other than Drag Racing) it is probably fast enough the way it sits. I would spend my money on the suspension.

[beastlyone]

would you reccomend new gaskets if i went for a new topend? And as far as rebuilding the topend, all it really needs is the piston, rings, and pins right? And finally as far as the 11:1 and 12:1 pistons, would you you be able to run 93 octane with the 12:1 ? And is going with the high compression piston like 11:1 worth it?

[jshtex]

You definatly want new upper and lower head gaskets. The only other gasket that you have to remove to tear down the top end is the big rubber one under the cam cover and it should be fine, just be carefull pulling it off cause I bet it is expensive.

The 04 / 05 yfz's come stock with 12.5 to 1 compression, and yes they will run fine on super unleaded.

There is a chance you might need a new cylinder. Just get a service manual and check it (you can usually find service manuals on the internet). Look for problems on the front side (exhaust port) of the cylinder wall.

[beastlyone]

do you have any websites where i could find a new cylinder? i tried doing searches and all that came up were the big bore kits, and thats outta my price range by far right now

[GPracer2500]

04/05s are 11.9:1 stock

[jshtex]

Originally posted by GPracer2500
04/05s are 11.9:1 stock

Doh... Your right, maybe I was thinking of the GYTR Piston?

I get my cylinders at the local yamaha dealer but I get a good price....

There are several sourses online for oem parts.

[Toadz400]

If the YFZ runs fine and doesn't smoke at all I wouldn't worry about rebuilding it unless you are absolutely that worried about something going wrong. It would be a good idea as you don't have a clue as to how many hours are on the engine. Are you just going to do a top end rebuild or are you going to do the crank too? If you do the crank make sure to have the oil mod done while you're in there. As for new gaskets, you always want to get new gaskets when you take it apart. I would recommend running the 12.5:1 compression piston as you are still able to run on premium (93-94).

As for the HMF, I would just stick with the slip-on and spend your money elsewhere like your rebuild or suspension. If you plan on racing you want to have suspension way before you even think about performance mods.

[pnut420]

I love my nmotion pipe, but I got a 9 inch can on mine and I would go with the 12 inch if I did it again. The pipes are really loud but I like the way it sounds and performs.

If you don't ride the piss out of you yfz all the time, then I wouldn't worry about a rebuild until it started smoking some also. Its once you get it bored out and aftermarket pistons that I'd start replacing it more often like 50 hours. Just keep up on the oil changes, these motors do seem to like frequent oil changes. I went a year straight on my 400ex riding every other day and it was fine, but thats a whole different deal. :D

[SRH]

Originally posted by pnut420
I love my nmotion pipe, but I got a 9 inch can on mine and I would go with the 12 inch if I did it again. The pipes are really loud but I like the way it sounds and performs.

If you don't ride the piss out of you yfz all the time, then I wouldn't worry about a rebuild until it started smoking some also. Its once you get it bored out and aftermarket pistons that I'd start replacing it more often like 50 hours. Just keep up on the oil changes, these motors do seem to like frequent oil changes. I went a year straight on my 400ex riding every other day and it was fine, but thats a whole different deal. :D

once its smoking its too late

[beastlyone]

Alright that sounds good then, i think just to be safe when i get the money ill take out my motor and drive it over to my local shop to have the cylinder bored out .020 over with a new piston, rings, etc.. and a port and polish job. Does anyone know what this "Oil Mod" is? And does anyone know roughly how much a crank rebuild would go for?

[jshtex]

The "oil mod" basically squirts oil on the bottom of the piston and the pin during operation. The case is machined for it from the factory but in the 04 - 06 quads the holes are not there to supply the oil. The 07 bike comes with it stock.

As for the bore job, personally I like the reliability of the stock bore. But hey we race XC so reliability is the key. Our bike with some bolt on's and the cam mod is plenty fast.

[pnut420]

Originally posted by SRH
once its smoking its too late

Once the rings go bad on a stock piston it not too late. Its not like its crank bearings going out.

[jshtex]

Originally posted by pnut420
Once the rings go bad on a stock piston it not too late. Its not like its crank bearings going out.

I have seen a few pistons (or pins) let go and do real damage to the motor.

Personally I'm not waiting for smoke..... It's way cheaper to tear it down a little too soon than too late.

[pnut420]

Originally posted by jshtex
I have seen a few pistons (or pins) let go and do real damage to the motor.

Personally I'm not waiting for smoke..... It's way cheaper to tear it down a little too soon than too late.

Yeah Im with you. I thought he picked up an 06 at first, then saw in the sig it was an 04. Might as well do a top end and cam.

[beastlyone]

yeah thats what im trying before any real serious riding, i found a kit with an aftermarket crankshaft and a 12.5:1 piston i was thinking about getting for about 439.99, then a gasket kit for like 40 from motosport.com for just the topend, and other then that i think i would be set on my engine, just maybe a port and polish in the future:D

[motomanmike]

The yfz is a very finicky engine it seems. Things just have to be right or bad things happen. As for boring, you actually from what i understand have to sleeve the cylinder because they are nikasil coated which just can't be bored out, it can be replated or sleeved. However Nikasil is very durable. I have seen engines where the pistons blew to peices and the cylinder still not have scratches in it. I'm sure its a good extra precaution to replace the cylinder but personally i did not on my last rebuild. If you are looking for some serious midrange power which is very usable i'd go with the WR crank and piston. It will get you the displacement (true 450) and compression ratio (around 12:1)you want however i would recommend using premium fuel. (when i say premium i mean not at the gas station i mean at least 100 octane). If you do use the WR GET THE OIL MODIFICATION DONE TO YOUR CASES. All they do is drill a couple holes and an o ring galley to shoot oil under the piston onto the wrist pin it costs about 50 bucks. Most engine builders won't send one back to you without doing this modification. These engines and many other 450s not just yamahas are notorious for breaking or seizing wristpins because of the heat and stress on that vital area. The WR crank uses a slightly smaller wristpin however this crank set up has been recommended over the 06 crank. 06 cranks regardless of what people say are having the same trouble as the 04 with the lower rod bearing blowing out. As for your quad before you go all crazy and rebuild it, do a leakdown test and see where if any blowby occurs. If the proper maintenance was performed and the quad wasn't ridden on the road at high rpms all the time its more than likely good for awhile just change the oil all the time. Don't question "should i change my oil" just do it. ALL THE TIME. The guys i ride with say their golden rule is to change your oil so much that you keep it clean enough that other people would take it out of your engine and put it in theirs. Its much cheaper than buying cranks and cases and pistons etc. etc. etc. I would be much more concerned with the valves and clearances than anything else at this point in time. Check the valves and do the leakdown test with factory tolerances and make a decision from there. JSHTEX is right however, with the power these motors make stock, i wouldn't go crazy. I just tried this setup because my motor trashed the heads and i decided to just replace the crank and piston while i had it out on the bench. I'm much happier with this setup for motocross than stock. Oh and as for worrying about money and spending too much. You shouldn't think about what money you spend. Its quite an addiction once you get started putting parts on. FEED IT

[beastlyone]

Originally posted by motomanmike
Its quite an addiction once you get started putting parts on. FEED IT

haha i like this guy, exactly where i come from, just wrong leaving things stock

[FoxRacing81]

Wait wait wait wait....do not tell me I just spent over 7,500 on an 06 quad...brand effin new...and now it is going to need rebuilt every 50-60 hours?

[jshtex]

Originally posted by FoxRacing81
Wait wait wait wait....do not tell me I just spent over 7,500 on an 06 quad...brand effin new...and now it is going to need rebuilt every 50-60 hours?

We went from a 426ex to the yfz too... It's definatly not the same animal. You bought a high output factory racing bike and it is going to need more maintenance. Thats true for all the 450s not just the yfz.

I have heard of folks who claim 100+ hours without a top end, I just wouldn't push it that far myself. Especially not for the way we use ours (XC Racing).

Really you should be able to do the top end and adjust the valves for $200 or so, if you do the work, so it's not a huge deal.

It's all part of racing. Ain't it great.

[FoxRacing81]

:( I spent almsot 8 grand to race the bike without any worries....if I wanted something I was going to rebuild, I woulda went with a used something...

I don't have the money to be effin rebuilding every couple months...this blows...so much for not having to worry about anything....

[beastlyone]

how hard is it to replace a piston in a top end? the place i would take it to is talking about honing it and all that and sayin 5-700 bucks! noooo f***in way. If i just wanted to go with a high compression piston, rings and all that with new gaskets, how hard would that be? any sites showing processes on how to do it?

[motomanmike]

Dude, quit freaking out. DO YOU HAVE ANY IDEA HOW MUCH RIDING 50 TO 60 HOURS IS????? ITS BRAND NEW DUDE. My quad finally popped this year, its 06 my bike is an 04, now that it popped i find out the previous owner swamped it under water, ran the bejesus out of it on the road and seldomly changed the oil. Thats two years of hell on a quad. What type of racing or riding are you doing first off? Also just to help you feel a little more secure, points leader in B class district 7 is on a STOCK yfz. Its ran strong all season. My recommendation would be buy a "time bomb" its a little device that records hours the engine has spent running, very small very simple, cost about 40 bucks and is well worth it. It sounds like this would make your maintenance schedule structured because it will TELL YOU THE HOURS, no guessing. I would change the oil every three to five hours, and check the valves every 8 to 10 hours after your break in period and first service with valve adjustment. Clean your air filter after a day of riding in dusty places. Make sure you oil the filter with real bought in a can filter oil and run a fuel filter. They are like three bucks and good insurance QUIT WORRYING AND RIDE THE THING THATS WHAT YOU BOUGHT IT FOR!!!! ITS BUILT TO RUN NOT BABY!!!

LET ER EAT!!!!!!


Hey beastly if you read this, how are your clutches holding up?? I replaced with EBC heavy duty it seems to be ok but i'm wondering about longevity. I ride pretty hard. Do those dirt diggers hold up in the XC races? I've heard alot of guys running the VERY EXPENSIVE nine plate system but i don't know if its all worth it?

[beastlyone]

Originally posted by motomanmike


Hey beastly if you read this, how are your clutches holding up?? I replaced with EBC heavy duty it seems to be ok but i'm wondering about longevity. I ride pretty hard. Do those dirt diggers hold up in the XC races? I've heard alot of guys running the VERY EXPENSIVE nine plate system but i don't know if its all worth it?

Yeahh i mean ive only had the thing about a week but with the riding ive done on it its verrry niice, a huge step up from my 400ex clutch (stock). But put it this way, my friend had a 2002 banshee with alottta work done to it, he destroyed both jugs, pistons, cranks, rod through the block, the whole deal.. the only thing that really survived was the clutch casing and the clutch. Plus he rode that thing HARDDD like slipping the clutch and riding the clutch alottt, dragging, and it was still fine when he took it apart after his engine blew.

[motomanmike]

yeah thats pretty impressive, banshees are pretty hard on clutches too, anything with huge amounts of power and a hard hit.

[beastlyone]

yeah basically you got it man, sad part is i think hes takin it out nd put it in this 404 stroker banshee he picked up haha, so that shows it right there

[motomanmike]

We just can't ever seem to be happy with what we have can we LOL. I know i can't. It all ties back to that addiction thing i think.

heres my peice o work no show, all go

[Prey]

i just bought an 05 yfz friday.

i have seen motoman mention lower rod bearing, what i am wondering are these questions

1, what known issues are there with the YFZ (I am guessing lower rod bearing is 1 of them) there was mention of modifying with oil holes, what is the issue/symptoms

2, this bike is for my wife who is fairly new rider and it wont be ridden hard in the near future, with that said (and i saw mention of adjusting valves) how often should the valves be adjusted and what are the clearances.

and lastly, is the 06/07 cylinder a bolt on to the 04/05 or did yamaha change the stroke to get more CC's?

thanks in advance for any information you guys can share

[motomanmike]

.010 on intake valves and .015 on the exhaust side is what the book recommends, i like to get it as close to that as possible WITHOUT GOING TIGHTER. Loose valves are much better than tight ones but not too loose. There is a nice grid in the factory service manual that shows the conversions with clearences and what shims to use to make things easier. ALWAYS USE A TORQUE WRECH WHEN TIGHTENING CAM CAPS. ALWAYS. I TIGHTEN THEM TO 7 to 7.5 ft pounds. Anymore and you could risk problems. Other than that i'd run engine ice in it if she's a newbie putting around, these bikes run kinda warm at slow speeds. As far as the 06 head it will work. They got the displacement out of the piston stroke and piston from what i understand. I wouldn't buy an 06 head though, very expensive, just get the 05 ported by TC and it will be even better than the 06 stock head. Also with the oil mod it helps with wrist pin failure. It costs about 50 bucks but you have to send the case that the clutch cover attatches too, the one the oil filter sits in. If that quad wasn't abused or raced you probably got another year or year and a half before you might need a rebuild however it is hard to check cranks when they are in the case though.

[yfz stealer]

I was just reading the post on top and everyone says that riding on the street is very bad why????????? just wondering because i do it every weekend or so should i be worry:eek2:

[tye101]

heres mine

[tye101]

one more

[yfz stealer]

Originally posted by tye101
one more
what kinded of shocks are those