When I first saw it in Pit Bits I thought "that's neat". But after actually thinking about how carbs/efi work, and seeing Ken struggle a couple times to kickstart during qualifying, I think their hot start lever might be an unnecessary distraction.
Often a bike is stalled in a way that leaves excess fuel in the engine that needs to be cleared. You could just crack the throttle open, but with a carburetor there's an accelerator pump that will shoot fuel. One way around this is the hot start bypass circuit. (The other way is to open the throttle VERY slowly so the pump shot bleeds out the leak jet)
Efi doesn't use an accelerator pump. You can just crack the throttle open. Also, I don't know about EFI MX bikes, but most automotive ECUs have a flood-clear mode, where if the throttle is opened past a certain point, no fuel will be injected while starting.
I noticed the couple times when Ken was trying to start his bike in qualifying, he had trouble finding neutral and it would lurch forward. At first I though the clutch was dragging, but then I realized he wasn't pulling the clutch in at all and instead concentrating on pulling the "hot start" lever. More often than not, my bikes start just fine even in gear, so long as the clutch isn't dragging too much (but I don't abuse the clutch like the pros do either).
I can't help but wonder if the "hot start" lever on an efi bike does nothing, is a distraction, and should be ditched. Thanks for attending my TEDtalk.
As a 50+ C rider I am not in any position to question the decisions of Roczen/HEP Suzuki....
Roczen is one of the pickiest riders in the sport. If that lever wasn’t necessary it wouldn’t be on the bike.
Electric start bikes have the luxury of the computer knowing when it’s trying to start because your already pushing a button. This can change maps or whatever is necessary to make starting easier. Street bikes often used a the clutch safety switch to switch to a different map when starting. The button most likely just tells the computer it’s going to try to start and let the it decide what’s the best changes to make for the current engine conditions which could be anything from fueling changes to timing changes which you can’t do on your own
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The ECUs I have experience with differentiate run mode from start mode by engine rpm. For instance, on my car. Idle is 850, cranks @ ~150, threshold set to 300.
Edit: Also, I think I remember an interview where they said it's tied into the high idle plunger. Basically the same thing as the hot start circuit
I won't disagree on Roczen seeming to be picky. But maybe that's exactly why it might be there unnecessarily. Maybe he wanted it and the team is appeasing him. Who knows, I could be completely wrong about the whole thing.
Sign should say Deegan.
The hot start has to be on there I can almost gurantee that.
I have a 2011 suzuki and rode a few newer ones. They will not start unless they are in neutral and hot start lever engaged.
I have tried adjusting my clutch new clutch etc. Just one of those things these bikes are known for.
Roczen probably got so used to an electric start being able to get enough rpm to get the bike to start in gear that he doesn't even think about putting it into neutral until he struggles to start the bike.
Funny you say that about the 2011....
I've had many RMZ450's over the years and the 2011 was the only year of them all that I could consistently start while in gear!
If Deegan Jr's career ever has him on a bike with a kickstarter or swinging by Aldon Baker's place, I hope the servers here are up to the job 😬
Kickstart/EFI bikes like the Suzuki "know" when the bike is starting versus when it is running. They have to because there is a different path for power to the injector (condensor for starting, stator when running) and the ECU controls this. Not sure how much it adjusts the mapping for starting vs running based on this, but it likely does.
It definitely adjusts the mapping somewhat. When I had my 14' RM-Z 250 brand new I remember that one of the changes over the 13' was that it would only fire the plug on the compression stroke while being started and then after it was running, switch to wasted-spark vs the 13' and older which fired wasted spark all the time. I think they claimed it was supposed to help keep it from kicking back while starting or something. But that bike also had a Hot Start from the factory and it seemed to help it start sometimes too. My 18' RM-Z 450 starts like shit when it's hot all the time so maybe it really would help, who knows?
Didn't know Suzuki had a hot start circuit on their early EFI bikes. Looks like through 2014. Any other brands do that? Still think it's unnecessary when you can just crack the throttle for a kick or two and achieve the same thing. It's just a plunger in an air passage. Had the hot start plunger seize up on an old kawi and cracking the throttle worked just fine till I got that fixed
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