Bike hard to start after stalled?

I have a 2007 Yz250F. I just recently rebuilt my motor and it runs fantastic. Not too rich or lean, thats all dialed in. It starts in 1-3 kicks every time. However, it only starts that easily when I shut down the motor appropriately (i.e. hit the red OFF button). Even cold, the motor will start that easy if I shut it down correctly. However, there is one big problem I am having. It is an absolute PITA to start if it has been stalled. After a couple laps around the track I stalled it in second gear in a tight corner. I kicked and kicked, and eventually had to pull it off the track. I tried to start it intermittently for about 10 minutes, catching my breath in between kicking intervals. After that, it finally started back up with 5 hard kicks in very quick succession. This whole ordeal actually happened twice, because to be honest I'm not a very good rider so I ended up stallling it twice in the same corner on different laps.


I really don't think flooding is the issue, because I am aware of how much kicking is too much, and know when to give it a break. It also leaks gas when it is flooded, and it wasn't doing that. And yes, I was trying out the hotstart, which didnt help one bit. And since it starts so easily otherwise, I really have no idea what it could be. I do have a hunch though. My motor is a race built monster, and in general, there is not much left on the bike itself that is stock. Stage 1 hotcams, 13.5 comp wiseco piston, full titanium 4.1 exhaust with powerbomb, pro-x steel valves (with tougher springs) on a rebuilt head, along with many, many other things that dont affect HP performance, like boyesen supercooler, aftermarket radiator, hinson clutch, etc etc. It flies when you really want it to. I am also running 100 octane AVGAS, and it seems to be working really well.

Now, I do know that the more powerful you make a motor, the more tempermental and harder to start it will become..right? So can the fact that the motor is so full of aftermarket parts cause it to be such a PITA to start after it has been stalled? Is there anything I can do to fix it...besides not stalling? The only thing I didnt try was the choke, but it wouldnt make any sense to put the choke on to start an already hot motor.
 
My experience motorcycles are like women. They all have their own attitudes and you have to learn what it likes, because every one is different.

First off I find it much easier to start when it is in neutral. when I stall my bike I always just give it one or two baby kicks to try and clean out the cylinder. Then I kick it like I mean it. Sometimes mine starts with the hot start and sometimes it doesn't.

Just know that you are experiencing a common problem with the early year four strokes. They run like a raped ape but god love you if you stall it. I also found that if you are in hurry that bike will take 50 kicks to start. If you take your time and remain calm it is only 3 or 4 kicks.
 
Do what a wise man once told me......... DONT STALL IT MAN!...:smirk:


Is it you stalling it? Or the bike stalling for somereason? If its stalling it could be a issue of the fuel getting too hot and vapor locking. Never really heard of it on bikes. But its a problem that i've ran into in auto's.

Other than that thats all i know off the top of my head.

If anyone ask me why there modern 4stroke isn't starting right, I tell them to check there valves.
 
+1 on what PSJBrock said. You ever watch supercross? A few years ago when a rider would stall, they would take forever to start back up as they kick and kick. They would always mention that these race motors are a bitch to start when they are hot and stall out.
 
Avgas as in aviation fuel? I think that works better in lower compression bikes than "race" gas. Since its leaded, have you noticed any buildup on your spark plugs? I would suggest running race gas and mixing it 50/50 with super unleaded and see it that helps. Just try a couple of tanks with it.
 

James

Staff member
This whole ordeal actually happened twice, because to be honest I'm not a very good rider so I ended up stallling it twice in the same corner on different laps.

Sounds like you have your idle speed set too low. If memory serves me right most are supposed to be around ~2,000 rpm. Which is higher than what a lot of people think (it's not your car).
 
+1 on what PSJBrock said. You ever watch supercross? A few years ago when a rider would stall, they would take forever to start back up as they kick and kick. They would always mention that these race motors are a bitch to start when they are hot and stall out.
That's becase they were running with leaded gas (ie - AVGAS):devil:
 
bobkyle2, it is definitely me stalling it, not the bike. And James, the idle is set just right. The reason it stalled was because I was traveling at 1st gear speeds in 2nd gear. The reason I was doing that is because I was taking a tight corner right before a large jump, and I'm still trying to learn how to carry my speed through rutted turns. Point is, it's me.

As for the leaded gas, TurtleShifter, I doubt thats the problem. First off, race gas and 90 supreme (highest octane pump gas here) 50/50 mix would be more expensive, and I don't think the cost justifies the means. Basically, I don't stall it very often, and unless the lead is coating my spark plug and other engine parts (which if it was, would definitely justify the cost of going 50/50) it doesn't seem like it would be worth it. Plus, I don't really see how the lead would be making it hard to start only after it has been stalled. That doesn't really make sense, unless lead or something in the AVGAS somehow reacts with extreme heat in a negative way. That is why I am thinking it is something else, such as the engine being worked. However, somebody else told me that it has nothing to do with the engine being worked. So I'm kind of at a loss.
 
I just noticed that you said you tried the hot start lever... Sounds to me like it is not operating correctly, especially since it starts up after you let it cool down. I would check the cable.
 

James

Staff member
BTW unless you're knocking with 90 octane, there's no advantage to running race gas, if anything it'll be a disadvantage. Especially if you're not running a high compression setup.
 
BTW unless you're knocking with 90 octane, there's no advantage to running race gas, if anything it'll be a disadvantage. Especially if you're not running a high compression setup.
Race gas and Avgas have such a variance in additives that they should not be compared. Avgas has de-icing additives in it...

This may not be the source of your specific issue but I would just suggest you don't run Aviation fuel in your bike.
 
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