Anyone following Supercross This Year?

[Randy]

R.C. bailed and went to the pits. Stewart could have coasted his way to 3rd and left St. Louis with the points lead, but, he caught a rut and the rest is history.

Anyone know why these bikes are so hard to start? When roadrace bikes crash, as long as they are intact, they almost always start. This past weekend, RC couldn't get his refired and then Stewart had the same problem. If they're that hard to kick over, why not put a small battery and a starter motor on it? Wouldn't need a charging system, just have enough juice in the battery to turn the starter over.

 

[markjenn]

Anyone know why these bikes are so hard to start? When roadrace bikes crash, as long as they are intact, they almost always start.

Big, highly-tuned, carb'ed four-stroke singles have always been difficult to start, worse when they're hot. And if the bike has landed upside down, that just adds another variable. Roadracing just has dramatically different engines (now typically FI'ed) and a restarted bike usually hasn't tumbled.

A starter and battery is going to run 10-lbs or so. The difference between a 215-lb and a 225-lb MX bike is pretty dramatic, especially in the whoops, and no one is willing to pay the performance hit to fit a button start. And a button doesn't guarantee the thing will start... if you kick for 25 secs to light a fire, you may be grinding the starter for nearly as long IF the battery lasts that long.

- Mark

 

[sparky3008]

12:5:1 Compression!!!

If you think they look hard to start now you should try a bike with out a autodecompression cam and a hot start button.

These two things make the difference in getting them to start during the race or never.

 

[sparky3008]

If they're that hard to kick over, why not put a small battery and a starter motor on it? Wouldn't need a charging system, just have enough juice in the battery to turn the starter over.

Funny, the YZ250F is considered the MX bike for many reasons. Different transmission gearing, different emission standards so different exhaust, different timing on cam.

Anyway the WR250F is the same engine basically but it has a headlight, brakelight, e-start and meets many of the strict emission standards so people can ride in State parks and such.

As a result the exhaust is extremely restrictive and is almost everyones first mod.

There is a wire that gets cut to change the timing in the mid range to really open them up and the wr's have the throttle restricted and the yz doesn't.

Anyway many buy the wr and one of the first things they do is remove the lights and battery because of the weight. It may not sound like much but throwing these already 250lb bikes around all day is a job in and of itself and many of these guys/girls are average 150lbs or smaller themselves. That battery does make a big difference.

Endurance is a big deal for this sport when you have several qualifying races just to get to the main.

These guys aren't some of the most athletically fit guys in the world behind soccer for no reason...

I have ridden at times so hard that getting off I have fallen flat on my face because my legs were so tired.

Awesome ride though, wouldn't change it for the world...

 

[Randy]

Regarding the weight, isn't there a minimum weight for supercross? If so, do you know if they are normally adding ballast to get up to that weight or scraping every ounce they can to get as close to that weight as possible?

 

[sparky3008]

Regarding the weight, isn't there a minimum weight for supercross?  If so, do you know if they are normally adding ballast to get up to that weight or scraping every ounce they can to get as close to that weight as possible?

I found a .pdf online (don't know how old it is) that says weight requirement is minimum of 216lbs for supercross.

https://www.amaproracing.com/prorace/pdf/mx...%20Rulebook.pdf

Reading the first page it was for the 2006 season...

Side not, as on our bikes unlike cars, their is not a lot of fat on these bikes. Everything is already plastic or bare minimum. Aftermarket cans saves a few pounds but not much....

 

[MrT]

I'm guessing those race engines foul a sparkplug pretty fast.

Here's the spec page for Chad Reed's Yamaha:

https://www.chadreedracing.com/bike.asp

 

[dcarver]

I'm guessing those race engines foul a sparkplug pretty fast.

Actually, even the 2-stroke motors rarely foul plugs. The 4 strokers never do. Better ignition systems (mapped with TPS), better fuel/air distrubition in the head, etc etc. And they are bullet proof.

 

[sparky3008]

I'm guessing those race engines foul a sparkplug pretty fast.
Here's the spec page for Chad Reed's Yamaha:

https://www.chadreedracing.com/bike.asp

On my old Yz250 2 stroke I ran 32:1 oil and as long as I didn't try to pretend it was a 4 stroke and putt around I never fouled plugs. Now if I let some beginner ride it would foul but most beginners didn't want on that bike for very long. The powerband on that bike came on like a bullet and if you weren't ready you were, well on your ass

Proper jetting is crucial to these bikes for performance and reliability. If you ride in the same place all the time fouling plugs is very rare. Going from summer to cold or dry to humid has a great affect on these smaller engines and knowing how to change the jets is important for the engine to perform correctly. Main jet and maybe a clip on the needle is about all I ever adjust once it is dialed in.

Example:

Stock wr250f jetting:Very lean

Main #168

Pilot Jet #40

Leak Jet #95

Pilot Screw out 1 3/4

Modified Jetting

Main #180 Summer #185 Winter

Pilot Jet #42

Leak Jet (Either #40 or #65 for some)

Some block the leak jet off entirely to eliminate low end bog

Pilot Screw is adjusted based on how far out it is before it starts to run poorly and then screw it back in. If you are out past 2 turns or so that is where a bigger Pilot Jet comes in.

Open Air and stock exhaust on the wr is extremely restricted. Aftermarket exhaust or the stock yz exhaust is common. Removing the stock baffle helps too.

I have had to do this type of stuff with every dirt bike I have ever owned. The stock setup is extremely lean, bike pops like crazy and doesn't run near its potential.

The WR even has the timing restricted via a grey wire that once clipped opens up the mid range a good bit.

EPA is hell on these bikes.

The YZ is less restricted as it is meant for track only and will most likely not make it into any parks without a spark arrestor and some type of silencer...

 

[yamaholic]

I used to have a WR400...setup like a YZ400 as far as jetting, timing, etc. It was a bitch to start after crashing. If you didn't do "the drill" just right, you could pretty much forget about starting it for at least 10 mins. Maybe longer.

Oh, and I used to foul plugs ALL THE TIME until I was familiar enough with it to stop doing the things that made it foul (like blipping the thottle when off/cold, turn off gas during transport). Racing bikes are not always user-friendly.

My newer YZ250F is hard to start when bone cold, but no problem when warm. Usually 1 or 2 kicks. But, I only have about 9 hours on it, all cold weather, so not sure how it will react when hot. I'm using the JD jet kit.

The motors the pro's use are similar, but they are jetted differently. For one..race gas is used. Two, they run a little on the lean side for more power. Lean bikes are hard to start when hot.

Batteries and starters are not going to be accepted by the MX community. I think Fuel Injection would be accepted, but to add weight is going to be a tough sell.

For "racing type" trail bikes like the WR, I think electric start is waaay cool. I personally don't mind kicking to save the weight. But as I grow older my opinion will probably change.

It was funny as hell watching a friend with an XR200 try to start my old 400.

 

[sparky3008]

I used to have a WR400...setup like a YZ400 as far as jetting, timing, etc. It was a bitch to start after crashing. If you didn't do "the drill" just right, you could pretty much forget about starting it for at least 10 mins. Maybe longer.
Oh, and I used to foul plugs ALL THE TIME until I was familiar enough with it to stop doing the things that made it foul (like blipping the thottle when off/cold, turn off gas during transport). Racing bikes are not always user-friendly.

My newer YZ250F is hard to start when bone cold, but no problem when warm. Usually 1 or 2 kicks. But, I only have about 9 hours on it, all cold weather, so not sure how it will react when hot. I'm using the JD jet kit.

The motors the pro's use are similar, but they are jetted differently. For one..race gas is used. Two, they run a little on the lean side for more power. Lean bikes are hard to start when hot.

Batteries and starters are not going to be accepted by the MX community. I think Fuel Injection would be accepted, but to add weight is going to be a tough sell.

For "racing type" trail bikes like the WR, I think electric start is waaay cool. I personally don't mind kicking to save the weight. But as I grow older my opinion will probably change.

It was funny as hell watching a friend with an XR200 try to start my old 400.

I have a friend that has a lot of land and we use to ride at his house a lot years ago. He had a bike that sometimes people who didn't have a bike would ask if they could ride it.

His standard comment was, "Sure, if you can start it you can ride it".

I never saw someone successfully start it.

However if he did ever decide to come out and ride with us, he could start that thing in just a few kicks.

He knew exactly what it took, always killed me as I could never start that thing either...

 

[FJRandy]

I've got a WR250F, and love it. I used the YZ can with the aluminum end cap so I can remove the quiet core for hare scrambles.

I'm about to re-do the whole motor with a 290cc kit, Hot Cams, HD rod kit, etc etc. Since I can't afford new, I might as well build this one up considering I FINALLY dialed in the suspension for the rocks here in the northeast. Funny, I haven't wanted for the magic button yet. Mine starts tough in the morning, but it'll start right back up when hot. I pull the hot start lever and kick. Fires right back up. Also, the '03 cam swap made a HUGE difference in just how easily it fires up now.

But isn't this a thread about who's following supercross? RC is kickin' ass! He shoved right in Bubba's face by lapping him at Daytona. Go Ricky!!