YZ450F (05) Dune riding and died??

[neevothespaniel]

I have a 450 and the thing has run perfectly since I bought it about 9 months ago. I took it to the dunes the other day and had a ball untill about 1pm.

The bike was starting to bog and I had a moment on the beach where I couldn't get it started for about 10 minutes.

I decided to call it a day then and when I got it running I went straight back to the car park, although the bike ran perfect all the way back.

Some info: Riding at sea level, fuel was good, air filter had a slight dusting but nothing major.

The only thing I can think of is that the day really started to warm up at about 1pm (midday heat in NSW, Australia). Would this have an affect on the bikes running? Should I be worried at all?

Thanks in advance.

[tnl]

How about some more info? What kind of temp. change did you have, What kind of Bike problems are you having? Is it only starting and bogging issues? Are you up to par on maintenance? Is it in stock cond? Any jetting changes to the bike? Good fuel? Did the bike go down while you were riding? Hot start plunger stuck? Breather tube clean, not full of sand?

[Butta]

I had a similar experience up at 8500 feet in Colorado this summer. I took the 17mm cap off the bottom of the carb bowl to change out the main jet and low and behold the jet and the part the main jet screws into fell out....I was running so rich, like not having a main jet installed. Guess I didn't tighten it enough when I changed the main, 12 hours of riding time ago.

[neevothespaniel]

How about some more info? What kind of temp. change did you have, What kind of Bike problems are you having? Is it only starting and bogging issues? Are you up to par on maintenance? Is it in stock cond? Any jetting changes to the bike? Good fuel? Did the bike go down while you were riding? Hot start plunger stuck? Breather tube clean, not full of sand?

Temp change was probably from 18 C (7am) to about 34 C (1pm).

Just bogging and starting on this one ride.

Maintenance is religiously done. Filter cleaned every ride. Full synthetic oil changed every 2 rides. Oil filter changed every 2 oil changes. Valves checked every 10 hours (shimmed once when I bought the bike, haven't moved since!)

Bike is stock.

I have never touched the carb, ran perfectly in the cooler temps. I have never run it in the full Aussie summer.

Bike stalled in the trails (clutch control probably), struggled to get it going after. Hot start is free and moving, breather hose is clear.

[Yamahafan]

My guess is that your main jet is too rich for the hotter temps and your sparkplug is covered in carbon. Also, a prolonged starting process always seems to cause carbon build-up on the sparkplug. Check your plug and go down at least one size on the main jet. You may want to move the needle clip up one position also.

[tnl]

Temp change was probably from 18 C (7am) to about 34 C (1pm).

Just bogging and starting on this one ride.

Maintenance is religiously done. Filter cleaned every ride. Full synthetic oil changed every 2 rides. Oil filter changed every 2 oil changes. Valves checked every 10 hours (shimmed once when I bought the bike, haven't moved since!)

Bike is stock.

I have never touched the carb, ran perfectly in the cooler temps. I have never run it in the full Aussie summer.

Bike stalled in the trails (clutch control probably), struggled to get it going after. Hot start is free and moving, breather hose is clear.

Even if the bike didn't fall in the sand (which is hard to believe) there is a chance that some sand found it's way into the carb. possibly restricting fuel flow in one of the jets but I would first tweak the fuel/air mixture screw to see if that improves things then the plug (as stated above), then the carb. I have to adjust my fuel/air mixture screw between seasons here in Arizona mainly because the engine pops on decel. I think a bog issue is a result of either not enough air or too much fuel (duh).