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2grimjim

Project YZ306WR

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Ok. So I picked up a nice, clean 2005 YZ250F that needs valves for $700. I also have a huge pile of parts sitting in my shop for various YZ and WR 250's and 450's from 2002 to 2007. Among them is a 2002 WR250F bottom end, a Clarke 2.8 gallon tank, a brand new Dyna programmable CDI, a new set of 18" and 21" Tubliss inserts, and who knows what else.

I have a 2006 YZ450 that I put a WR tranny in and I love it! The bike is a lot more fun to ride off-road (thats a good thing since I'm surrounded by BLM land) and I'm thinkin' I'll do the same thing with the 250 for the high country.

The YZ with the WR tranny is still a handfull in the mountains when the fastest you can go for 10 miles at a time is 5mph.

I know, I know....everyone is gonna rag on me 'why don't you just buy a WR?'.

I already have 2, a 2007 250 (my wifes actually) and a much modified 2003 450. I like my WR's but I also like the 30 missing pounds on my YZ...a lot! Giant sand woops at 60 mph are no fun on my WR and the extra 30 lbs feels like 300 lbs at the end of a long ride after you drop the bike off the side of a trail above 11,000 ft.

So, the plan is;

Put the WR tranny in the YZ

Go to a Hot Cranks stroker crank with an 83mm big bore for 306cc

Stage 1 Hot Cams intake and exhaust cams

Kibblewhite stainless valves with spring kit

Use the Clarke 2.8 gal tank

Use the WR flywheel, lighting coil, mag cover, and the Dyna CDI

Lace up a 2.15x18 rim for the rear and use a trials tire with the Tubliss insert

Revalve and respring the suspension (maybe swap fork internals for a 2006)

Use a a set of 2006 YZ triple clamps

Make a set of 2007 WR radiators work

Scour up a set of '07 or later footpegs (stock Ti ones are cool, but bend easy)

I have $3500 budgeted for the cost of this endevour (including the cost of the bike) and would like to have it done before June. Should be enough money to rebuild of replace damn near everything on the bike. If the end product is under 220 lbs that would be sweet!

I'll add pics to this post as the project gets under way, but for now I'll just have to be content shopping on eBay for bargains (I still need an exhaust) and rehab my back from recent surgury.

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Sounds like one hell of an off-road machine :bonk: When you get it together, get the bike over to a dyno to get the jetting squared away and be done with it, that large of a motor change could be a pain to find the best jetting.

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A few trips up and down the ally behind my house is all I need to get the jetting dialed in. Even with the big changes I made with my WR450 engine, the jetting wasn't too far off. I've had to make bigger jetting changes just by switching fuel (to Avgas or race gas) then any major engine mods. I've done about a half dozen 290 kits (2 with cam swaps) and the jetting doesn't change a whole lot. Where I live at, altitude changes wreck havoc on carb jetting more than anything else. It's not uncommon for a ride to start at 4,500ft go to 10,000+ and back to 4,500 in under 20 miles.

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Good luck man!! Post pics and info on the build. My plans for a build would never get past the approval of the ol' lady. I envy you!!

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Good luck man!! Post pics and info on the build. My plans for a build would never get past the approval of the ol' lady. I envy you!!

I'm one lucky S.O.B. My wife is my enabler. It also doesn't hurt that she work's at the parts counter at my local Yamaha shop!

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I'm one lucky S.O.B. My wife is my enabler. It also doesn't hurt that she work's at the parts counter at my local Yamaha shop!

This sounds like it could turn into a "How I met your mother" post!

I have the same plans for my YZ-F but am trying to justify putting $1500 into a six year old bike. I want to race HS this up coming year and would love to hear how your build turns out :bonk:

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I'm interested in why your doing the crank and the cams. Looking into this myself. Obviously your looking for a torque beast. Are you afraid of loosing overrev? It looks to me that those cams dont give you more juice and cost at least as much up top as they give down low. are you afraid of a balance problem with the crank and 290?

my 290 yz is a beast for enduro and as much as I'd like to stroke and stage 1 cam it it looks to me like I would loose top end and have too explosive bottom. has anyone done this to know? seems like people stage 2 cam these 290's to make a better balance?

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I'm interested in why your doing the crank and the cams. Looking into this myself. Obviously your looking for a torque beast. Are you afraid of loosing overrev? It looks to me that those cams dont give you more juice and cost at least as much up top as they give down low. are you afraid of a balance problem with the crank and 290?

my 290 yz is a beast for enduro and as much as I'd like to stroke and stage 1 cam it it looks to me like I would loose top end and have too explosive bottom. has anyone done this to know? seems like people stage 2 cam these 290's to make a better balance?

I built a few WR's with the Athena 290 kit with no other changes but exhaust and jetting. I was really impressed with the increase in bottom end power. I'm not really concerned with losing top end. For the type of riding I plan on using this machine for, losing some overrev isn't going to be noticed.

The key elements for this build (for me, anyway) are plentiful, smooth power at low and mid RPM's but not so much that it can't metered easily in small amounts. Ideally, just enough power to pop the front over large obsticals, but so so much that I'm struggling throttle controll when things get really slippery. Low weight is the other objective. As I stated before, bikes under 220lbs are a blast to ride, even if they are underpowered. There's a lot of situations where you can physically muscle the bike around without paying the penality of hastened physical exhaustion during your ride. This bike is intended for tight, twisty, steep, rocky, slimy, mountain riding.

Scorpa made a Yamaha WR250 powered bike called the 'T-Ride' a few years back. I don't know if any were actually imported into the US, but I sure wanted one. They were kind of a cross between a trials bike and dirt bike (similar to a GasGas Pampera). When I'm done, I hope to have something almost like a T-Ride.

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my concern is that point of metered easily in small amounts. Im heading the same direction as you but i'm still scared of an explosive range about 4k to 7k. have you heard of this combination before to know what to expect? I realize the cams and stroker will probably not come close to equaling what the 290 did. I'm pretty anxious to hear someones conclusion,, when is yours going to be done? Your not balancing that crank?

Thanks,

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my concern is that point of metered easily in small amounts. Im heading the same direction as you but i'm still scared of an explosive range about 4k to 7k. have you heard of this combination before to know what to expect? I realize the cams and stroker will probably not come close to equaling what the 290 did. I'm pretty anxious to hear someones conclusion,, when is yours going to be done? Your not balancing that crank?

Thanks,

That's where the Dyna programable ignition comes into play. If you aren't familiar with it, it's a user programmable CDI, unlike the Vortex unit. The Vortex is slick because is comes preloaded with 10 maps and alows the rider to select between the stock timing curve or one of the 10 presets on-the-fly. But, if you don't like any of the programs in the box, you have to send it back to MT Racing to be re-programmed. The Dyna, on the other hand, only holds one program, but you can make and store as many timing maps on a laptop and re-flash thr CDI on the bike.

The timing map has a pretty big impact on how hard the power hits and I'm fairly confident I can get what I'm looking for without too much trouble.

The Stage 1 Hot-Cams will tame the hit to some degree. Remember, I also plan on using the WR flywheel as well.

I'm not overly concerned about crank balance either. I have an '03 WR450 with a stroker crank for a YFZ 450 in it and there is a little more vibration at lower RPM's, but nothing I can't live with.

As I stated before, I will be using the stroker crank with a 290 big bore (The 83mm bore). Adding displacement, without porting or the addition of bigger valves, is going to provide a bigger increase in torque than horsepower. Exactly what I'm looking for.

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Thanks so much! Your OK with an 05? Do you feel that you would gain much with a newer bike to start with? do the 06 triple clamps change offset at all or are you just trying to get the ability to mount the SS forks?

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I think anything '03 and up would be a good choice for a starting point. Obviously, if you start with an '03 or '04, you'll want to upgrade to a set of newer forks. But, if you find a'03-'04 cheap enough, you can afford those type of upgrades.

The only reason for the swap to the '06 triple clamps is because the stock '05 clamps won't accept 1 1/8" handlebars (and I have a set sitting around).

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I thought you couldn't just bolt up WR flywheels and stators to a YZ250F? I thought you had to buy entire WR case halves to make this work?

Lemme know how it goes! My YZ250F has 190 hours on it and still cranking. Tried to sell it after getting this CR but nobody will pay more than $2K for a 2007. :smirk:

I have HotCams Stage 1 intake/exhaust and I have all kind of low end torque power.

I had a Scorpa SY250 (actual trials two stroke) and liked it but would LOVE to have that long ride 250F version. I've WR'd mine out pretty heavily save for lights and WR gears though. :bonk:

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I thought you couldn't just bolt up WR flywheels and stators to a YZ250F? I thought you had to buy entire WR case halves to make this work?

'03 and later electric start WR's have different cases, cranks, stators, etc from the YZ's.

'01-'02 YZ's and WR's were identical cases and crankshafts. The part number for the YZ stator is the same from '01 to '05 (5XD-00-00).

The difference between the '02 and '03+ YZ crank is the crank pin is 2mm bigger. If I rember right, the '01-'02 WR stator and flywheel will fit on all YZ's to '09.

The magneto cover and gasket will interchange on all YZ's '01-'09 and WR's '01-'02.

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If I rember right, the '01-'02 WR stator and flywheel will fit on all YZ's to '09.

The magneto cover and gasket will interchange on all YZ's '01-'09 and WR's '01-'02.

So I could buy a 01-02 WR250F stator and flywheel and it would work for my bike (i.e., add lights)? Would it change the ignition curve?

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So I could buy a 01-02 WR250F stator and flywheel and it would work for my bike (i.e., add lights)? Would it change the ignition curve?

Give me a few days to get the '02 parts motor tore down and make sure all of the mag parts will swap to the '05, but I'm pretty sure they will. The only thing I'm not 100% certain at the moment is if the taper and diameter is the same on the left side of the crank from '02 to '03, but I know the stator and cover will swap.

Since you aren't changing the CDI box, it wouldn't change the timing map, but the initial, or 'static' timing may de a few degrees different.

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Just double-checked part numbers on stators and the '06 and later is different, however I think the difference is in the connector and not the stator itself. As soon as I can get my hands on a '07+ YZ I'll verify this.

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