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2grimjim

WR471 Stroker

15 posts in this topic

CIMG1103.jpg

Much to my local Yamaha dealers dismay, I decided against buying a new WR450 and instead, spent some time and money rebuilding my trusty '03 WR instead. I'm glad I did. I love the stroker WR! It works fantastic in the gnarliest conditions, wheelies without effort over logs and rocks and runs circles around the newer WR. Here's the short list of what has been done to the bike:

Hot Cranks YFZ Stroker Crank (471cc)

Wiseco HC piston (for YFZ450)

OEM Yamaha '07 WR450 cams

Dyna FS programable ignition

'06 YZ405F Forks w/G2R compression and rebound valves.

'06 WR450 triple clamps, digital display, kickstand, and wiring harness.

'07 WR450 footpegs, brake disks, front axle spacer.

'04 electric starter upgrades.

'04 YFZ450 flywheel.

'06 WR transmission, shift fork, and selector upgrades.

'07 YFZ clutch cover (with piston cooling jet) and oil pump.

13-52 gearing w/Michelin trials tire (summer) 14-49 gearing w/Maxxis Desert IT (winter)

I learned so much info about the small differences between the '03 and '06 models and the YFZ that my brain still hurts. There are some small differences (like the can chain buffer bolts) unique to the '03 WR that can cause some real headaches if you aren't aware of them.

Edited by 2grimjim

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She's no beauty queen. I'd rather spend the money on go-fast goodies than plastic and stickers.

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Would love to see a vid of your bike in action. I rode a mates modified 03 WR450 and boy did it stretch my arms out!

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If I had some hotter cams in it it would be scarry but I used a set of stock '07 WR cams. They have about 1mm less lift than the stock '03 cams. The bike has TONS of bottom end power, but now but it doesn't scream on top like before. That's ok now since I'm old, fat, and out of shape.

I'm contemplating building an engine for my YZ450 with the Hot Cranks stroker crank and a 98mm cylinder (501cc total).

I may just add the cylinder to the WR to ake a WR501!

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I may just add the cylinder to the WR to ake a WR501!

Is 501cc the upper limit of this engine?

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No. You can go MUCH bigger if you want to spend big bucks at Falicon. They make Cylinder/Stroker Crank Kits that get close to 600cc for the Yamaha YZ/WR/YFZ.

501cc is the biggest you can go with commonly available and relatively inexpensive aftermarket parts. Anything over this and you are looking at spend A LOT of money.

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You should have just traded for a whole YFZ instead of buying all those parts. :cheers:

I have a Hotrods stroker crank in my 06 and it's pretty cool. It really woke up the low end but doesn't seem to want to rev as hard as stock. Guess I'll just have to throw a big bore kit at it next.

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You should have just traded for a whole YFZ instead of buying all those parts.

I don't do 4 wheelers. I had a friend once tell me he could take his 4 wheeler anywhere I could ride my bike. When I took him up on his offer I had him on a trail that put his 4 wheeler 100 feet down a hillside with him pinned underneath it. He was ok, but he never offered to go ride with me again.

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Nice....my cousin has a YFZ523 w/ a Max Power Ice Cube cylinder and stroker crank, it runs hard at the dunes....but single track ridin is still my favorite!

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I don't do 4 wheelers. I had a friend once tell me he could take his 4 wheeler anywhere I could ride my bike. When I took him up on his offer I had him on a trail that put his 4 wheeler 100 feet down a hillside with him pinned underneath it. He was ok, but he never offered to go ride with me again.

hahahaha, that's awesome!!!

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I don't dislike 4 wheelers, I just have a problem working on them. When I worked at the local Yamie/Polaris/Suzuki dealer twisting wrenches, about 80% of my work was on ATV's. Most ATV's I had to work on were brought in by the owners completely filthy, in a horse trailer with piles of horse crap still on the floor. When the customer whould come to pay the bill they would always get pissed that I billed them $72 an hour to wash the the filth off. When the service writer sent angry customers to me asking why I charged them to wash their ATV, I would tell them "So I could find the engine". Of course the customer would always say "But the machine sits at a ranch with no water". And my reply was always the same..... "How many car washes did you pass by on the way into town?"

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Well, I have most of a season of riding The Stroker to evaluate it and I'm pretty happy with it.

The bottem end power is WAY better than any WR450 or YZ450 that I've ridden. It's different power from a big-bore. Snappier off the bottom and power flattens out quicker when you get closer to peak RPM's. Still not quite the stump-pulling tractor power like a 525/530 KTM.

Have had no reliability issues and I don't anticipate any since I'm using a YFZ crank/piston with a 20mm wrist pin (vs. the stock 18mm pin) and the oil-jet clutch cover from an '07 YFZ450. Since no issues have cropped up in 2000 miles of riding I'm thinkin' I might go to a 97mm or 98mm big bore and get either 490 or 501cc.

I also have a Hot Cams stage 1 intake sitting unused. I might pick up a matching exhaust cam and try out a cam swap. The cams I have installed now are for a '07+WR450 and I think they are a big cork in the top end power. The stock '03 cams made great top end power but didn't work well with a quiet exhaust. Adding a longer head pipe from a '06 YZ helped bring some life to bottom end power when I had the stock cams and FMF Q exhaust.

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My friend did something pretty similar to his. Pulled like a tractor down low and would run super hard until, like yours, the beginning of higher rpm began. It does surprise a lot of riders though, especially when it's smoother terrain and not so tight. Roll-ons are fun to watch.

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