YZ285 for motocross use

I currently ride a YZ250. For the mx tracks I ride on, tight corners with fairly short straights, I feel I need a bit more torque from the motor to make up for my lack of momentum through the corners.

I have read all the threads regarding the YZ285, most seem related to off-road/trail riding. I would be interested in comments on the motor from anyone use a 285 on the mx track.

Does the motor gain bottom and a smooth roll on or does the bike become a mid-range bike with a big hit?

Jetting also seems to be problematic?

Is the increase in performance worth the investment?

The alternative is a TM300MX, but the I love the handling of the YZ.

As an alternative to the 285 if you don't decide to do it, don't know how much you've played with jetting/gearing/pipes.

My bike really woke up with leaner jetting. Enough so that it feels good with a 48T rear now.

Lots of people like the bottom-mid pull with the "FMF Gnarly", leaner jetting and a 51 or 52T rear.

Just a possible alternative for tight tracks.

It depends on how you have the cylinder modified.. You'll gain a little umph off the bottom just cause the bigger piston.. Then from there, you can install different power bands or port it to suit your taste.. :thumbsup:

I LOVE my WR285 for everything from moto to swimming.. :thumbsup: Very versatile set up with simple gearing changes..

As was said though, you can do a LOT with jetting, gearing and pipes without spending the 600.00 or so cash that it takes to build up the 285.. :thumbsup:

Im sending my motor to eric gorr. I have read post by bikerdude and he has convinced me this is the way to get at those four strokes. I currently have a yz 250f and and a 250 2 stroke. I love how light and numble the 2 stroke is, but I am looking for more torque, I will let you know how it works out for me.

Thanks for the comments.

As for the gearing/jetting/pipe set-up, I have experimented with different set-ups and have found the best set-up top be a 51 rear tooth sprocket with a DEP pipe (my opinion this moved exchanged mid-range power for more bottom and top). As for jetting, I feel I have got it as good as I am going to get it.

The is very good in the present set-up, but I would like a little more roll-on power coming out of corner, hopefully without sacrificing the present top-end.

Does the extra 35cc make a noticable gain for the money?

lhcyz250racer, I would like to hear your comments once you have your bike up and running.

One thing I do not want to do is go back to 4 strokes. I have been down that route and the heavy feeling and maintenance are not something I appreciate.

Yea buddy I have put the 51 sprocket on as well and have played around with the jetting. I am excited to try the 285 kit, sounds like the ticket, and like most fun bike to own. Don't get me wrong I love 4 strokes but nothing compares to a good running 2 stroke. My main concern is jetting but it should be cake with a few plug chops. I am debating to get the head milled for race gas or not.

I could not agree with you more, the 285 sounds like it will provide that needed bit of torque to make the 2 stroke the perfect mx bike, at least for myself anyway.

I am no 4 stroke hater myself, they do have their good points, but I feel the 2 stroke is good fun.

My experience with running high compression motors are; they provide a good boost in power, but one needs to leave enough lee-way in the octane rating of the fuel to account for climatic changes, otherwise the bike becomes extremely sensitive as far as the jetting is concerned.

When do you expect to have the kit up and running? Be interested to hear your on track experience with the 285.

Ive never dynoed my bike but rode it back to back with my ol 265.. The 265 was flat out jumpy off the bottom but fell flat early, which I attribute to porting.. My 285 has the same jumpy feel off the bottom but will sing to the moon!! I would say I picked up 3-4 horse from mid to top.. Enough that I ride tight tech trails with a 14/48 gearing and no need for clutch.. Chug, chug, BRAAAP!! Wheelie wheelie, WHOA! :thumbsup: LOL

LHC, you will love this kit and yes.. Worth the money.. I also have some jetting you may be able to use.. When you get it done, shoot me a message Ill give my set ups :thumbsup:

How much of the powervalve remains with the 285 after it is machined to accomodate the increased cylinder bore diameter?

Is the 285 piston a Wiseco off the shelf part for a different machine, or special proprietary design?

How much of the powervalve remains with the 285 after it is machined to accomodate the increased cylinder bore diameter?

Is the 285 piston a Wiseco off the shelf part for a different machine, or special proprietary design?

That is the down fall of this kit.. Piston only available from MaxPower.. Eric Gorr can supply the 265 and 275 pistons, but not the 285.. MP only... Which reminds me, I need to call and order another.. Its almost time :thumbsup:

When you see the cylinder, you will be scared to put it together.. Look at your stock cylinder, you'll see you have approx 3 mm between the cylinder wall and the water jackets.. Now, keep in mind, we go from a 69.4 mm piston (stock, I think) to a 73.44 MP piston.. Thats two mm per side, when you are working with 3 or so to begin with.. Thin Thin Thin, but I assure you guys, I abuse my motor and it has given me no problems.. It probably has 50 hours on it, with no ring or gasket replacement..

I know I know, shame on ME Bikedude :thumbsup:

How about the powervalve? How much remains? How is the shape of the powervalve changed by all that machining? What is the resulting effect on the power?

You are saying that you have to purchase the piston directly thru MaxPower? Do they have a patent on this particular design that requires purchasing directly thru them? How much are they popping people for it? Can a different Wiseco be substituted that will invariably be cheaper? How much heavier than stock is the 285 piston?

Yes, it is a Max Power patent.. They have two available.. One is 190 plus shipping, just a standard Weisco dual ring piston.. (Weisco builds it for them) Then the one I splurged for is 240 and has some kind of special Apticote coating for better wear.. Im not sure of any weight difference between those two, but would assume similar to stock, plus a few grams... So far as the PV is concerned, it is just machined back at the same angle as stock, just enough to clear the pison in its closed position..

hey bikey dude, where's the bikey 285 video you promised us... :D:worthy:

patience is a virtue, yes! but there is just too much excitement to see yah playin with that "whoopie machine" you got there!!!

ain't gibbons 285 sounding so sweet and mean :)

http://www.gibbons-audio.com/wr285-roost.wmv

Braaaaap!! Going moto trackin tonight.. Maybe, just maybe, you'll get lucky in the next few days!!!

hey bikey dude, where's the bikey 285 video you promised us... :worthy::ride:

patience is a virtue, yes! but there is just too much excitement to see yah playin with that "whoopie machine" you got there!!!

ain't gibbons 285 sounding so sweet and mean :D

http://www.gibbons-audio.com/wr285-roost.wmv

Thanks Kiko! This one's for you... some low-end torque wheelies! No wind noise this time, so you can turn it up, and she does sound pretty sweet in the low-end me thinks. :)

Just try to ignore the 4-joke you'll hear in the background when I'm coming back down the hill... :banghead:

http://www.gibbons-audio.com/wr285_wheelies.wmv

That is the down fall of this kit.. Piston only available from MaxPower.. Eric Gorr can supply the 265 and 275 pistons, but not the 285.. MP only... Which reminds me, I need to call and order another.. Its almost time :D

When you see the cylinder, you will be scared to put it together.. Look at your stock cylinder, you'll see you have approx 3 mm between the cylinder wall and the water jackets.. Now, keep in mind, we go from a 69.4 mm piston (stock, I think) to a 73.44 MP piston.. Thats two mm per side, when you are working with 3 or so to begin with.. Thin Thin Thin, but I assure you guys, I abuse my motor and it has given me no problems.. It probably has 50 hours on it, with no ring or gasket replacement..

I know I know, shame on ME Bikedude :)

Does anybody make a 285 kit for an older YZ like mine('98)?

Does anybody make a 285 kit for an older YZ like mine('98)?

As far as the cylinder goes, just send it out to EGorr and have the work done.. But get in touch with MaxPower and see if they have the piston available.. :) They have a patent on them as far as I know..

http://www.maxpower-engines.com/

There is their homepage, just contact them and ask if they have a 285 cc piston for your scooter.. :D

Braaaaap!! Going moto trackin tonight.. Maybe, just maybe, you'll get lucky in the next few days!!!

make it so, bikey dude!

:):D:worthy::ride::banghead:

As far as the cylinder goes, just send it out to EGorr and have the work done.. But get in touch with MaxPower and see if they have the piston available.. :) They have a patent on them as far as I know..

http://www.maxpower-engines.com/

There is their homepage, just contact them and ask if they have a 285 cc piston for your scooter.. :D

I think I talked to them about a year ago. They wanted $1300 for a 285 kit. Just wondering if anybody else was making them? It sounded like he didnt want to sell me just a piston, he said without him doing the entire motor he wouldnt stand behind it. I wouldnt expect him to if I did all the work. Plus he wanted to modify my stock head for the kit, which is pointless, because I plan on building my own billet head.

Does anybody make a 285 kit for an older YZ like mine('98)?

Welcome...Yes, there are oversize pistons available for your bike. I actually owned a 310 cc kit for mine. That was too big and it did not leave enough fo the powervalve in place.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now