Flywheel spacing on 07 WR450

[Frostbite]

I'm trying to install the flywheel on my new crank, and have an uneasy feeling about the excessive clearance between the flywheel and the starter gear. The starter gear can float back and forth about 3/16" between the cam gear and the flywheel. Does anyone know if this is normal?

I thought maybe a thrust washer was missing from behind the gear, but checked the slide and there isn't one. I've checked the keyway and torqued the flywheel on a couple of times, but always get the freeplay at the starter gear. Maybe this is normal, but it seems a bit loose for an internal component.

[erickdj]

Why are you installing a new crank? Did the old one crap out?

I wish I could help on this subject, I just worked on those parts about 3 weeks ago, but I can't remember how much freeplay (if any) there was behind the flywheel.

[Frostbite]

Why are you installing a new crank? Did the old one crap out?

I wish I could help on this subject, I just worked on those parts about 3 weeks ago, but I can't remember how much freeplay (if any) there was behind the flywheel.

Yes, the big end bearing started knocking badly. It's the 1st time I've ever had a crank go bad in a 4 stroke. I sold my 99 WR400 last year. Still had the original crank with 15-20 thousand miles at least. I ride hard but stay on top of the maintenance. I run the 450 the same, if not easier, than the 400.

I'm surprised the crank went, but not shocked. 3 reasons I can think of for the crank to go:

1 - I bought the bike used so there could have been damage already. The ODO only read 100 miles, but that could've been wrong, or the bike could've crashed and run on it's side for a while starving for oil. I twisted the crank out of a road race bike like that. Brand new engine, 1st race of the year, guy highsided just as I was passing and I hit his bike and went over the bars. My bike landed throttle barrel down and was on its side WFO. By the time I came to my senses and ran for the bike, the damage was done. The crank seized a few seconds before I got to the kill switch.

2 - 2ce while riding I had one of the valve cover gasket 1/2 moons blow out. The 1st time was only minutes from home, but the 2nd was about 20 miles out on the sea ice and -30. Even though the bike was blowing oil I had to ride because my other options were freeze to death or get eaten by a polar bear. Riding 'till the engine seized seemed to be the best option. I was running in deep snow so I couldn't go easy on the engine. I replaced the gasket and it ran fine for 5 months, then started knocking.

3 - They say these engines shouldn't be lugged, but I do lug it. In winter time I lug the engine sometimes to keep the rear wheel from spinning and digging through the snow. In summer time the land is so rough that I'm in 1st gear on the clutch most of the time so the engine is lugging quite a bit (which is why I bought a trials bike last fall).

I rode the 400 the very same way, so either the 450 is a little fussier about crank oiling, or it was problem 1 or 2, or a combination of any.

I was looking for a stroker crank but couldn't find one for an 07, so I bought a stocker, and an Athena cylinder and piston. Since I had to open it up I thought I'd go a little bigger.

Interesting about the Athena kit, the piston only has 1 compression ring, stock Yamaha has 2. I spent a good while searching for the other ring before I took a close look at the piston. There is a groove where the 2nd ring would go, so at a quick glance it looks like a 2 ring setup, but it's only about 1/2 the depth.

[erickdj]

sucks about that, but it was a better option vs. freezing or the bear hug. Did you happen to take any pictures of the engine teardown? I'd like to see some of the engine apart/cases split, transmission, etc...

[Frostbite]

Did you happen to take any pictures of the engine teardown? I'd like to see some of the engine apart/cases split, transmission, etc...

My spare bedroom yesterday.

[erickdj]

? Oh, man, that's just too many parts together at once! My head is spinning just looking at all that. I don't know if I could put that thing back together....

[Frostbite]

? Oh, man, that's just too many parts together at once! My head is spinning just looking at all that. I don't know if I could put that thing back together....

Haha, you just have to look at it one bolt at a time.