How do you bump start a thumper?



11 replies to this topic
  • Pooley

Posted June 09, 2003 - 04:12 PM

#1

The last time I went riding with my 2-smoke buddy his kickstarter fell off on the trail. We would run with the bike in 2nd gear, clutch in and he would simultaneously jump on the seat for more traction, pop the clutch and start the bike. How would you accomplish this with the thumper due to the manual decompression (without doing the cam swap)? Assume I am on a trail without the ability to be towed. Hopefully I will never have to do this but I should know how at least.

Thanks

  • tctrailrider

Posted June 09, 2003 - 04:20 PM

#2

Pooley,
Pull in the clutch and compression release. Let out the clutch and then comp. release. Wroom. A bit tricky but it works.

  • Eddie Sisneros

Posted June 09, 2003 - 04:28 PM

#3

put it in gear and pull the bike back.put bike in 3rd gear push like hell and hop on the seat and let out the clutch.it will fire right off.

pulling the bike back in gear puts the piston right after tdc.this is how we start our push start only dirt trackers.

  • Indy_WR450

Posted June 09, 2003 - 05:35 PM

#4

The WR450 has the auto decompression feature so if you stall going in to a corner with to much rear it hooks up and restarts the engine. Not quite as easy as a 2 stroke but with good traction it is rather easy. Downhills are the same. but four strokes demand better traction conditions to reliably pull it off. Some people have added the 450 cams on their earlier versions because of this great feature.

  • Hick

Posted June 09, 2003 - 05:42 PM

#5

Hopefully I will never have to do this but I should know how at least.

Thanks


I became quite adept at bump starting my 426, this saved my ass more than once in a race when I had brake-stalled my bike. I had a GYT-R thumb-lever compression release, and this made it even easier and more natural to just feather the lever the instant I stalled the bike (no clutch needed if you are already in motion). The motor pretty much always stops with the piston at TDC-compression, so you just need to let the piston get beyond that and allow it to come back around two strokes later on compression again w/ the compression "on." On one occasion I restarted my bike in some deep braking bumps, in second gear, barely moving, and preserved a tenth place finish (whoopee).

Anyway, if you need to bump a 426, do like was already advised. Second gear, clutch and decomp in, release clutch then decomp. If the rear tire drags just "slip" the decomp lever, allowing the motor to just get past TDC-compression, and hope it lights the next time around (just as you would if kickstarting it).

Hope this helps.

  • The_Missile

Posted June 10, 2003 - 02:57 AM

#6

keep it in gear and chug along with the decomp lever pulled. Then let go the lever. Starts any time any gear providing gearing is matched with your speed. ie bad idea if you ar going 60kmh and bumpit in 1'st gear but good if you bump it in 3'rd.

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  • John_H

Posted June 10, 2003 - 08:24 PM

#7

decomp lever really comes in handy. Especially if you catch it early, just after stall when you're still moving.

Usually fires right back up...

  • ZEKEDAWG

Posted June 11, 2003 - 04:50 AM

#8

Mine will bump start without the decompression lever trick. Should I be using it or is it ok if the bike starts without it. I don't want to cause and problems later. I would not think it would matter but you never know.

  • Hick

Posted June 11, 2003 - 07:39 AM

#9

Mine will bump start without the decompression lever trick.


Hmmm. I doubt it would every time.

Using, or not using, whatever, the decomp lever will not hurt anything.

  • ZEKEDAWG

Posted June 11, 2003 - 08:55 AM

#10

So far I haven't had too much trouble, granted I need at least 10 mph and good traction but I will try with the lever it should make it easier. The only time I do it is at the end of the day and I am tired.

  • brentcarl84

Posted June 11, 2003 - 10:46 AM

#11

I just put it in 1st, pull in the clutch lever, push and get it going as fast as I can and then jump on and release the clutch. Going down hill works better. I'v had it stall before letting out the clutch to fast and not giving it enough throttle and i can pull the clutch in and let it out and it will start.

Carl

2003 WR450

  • Hick

Posted June 11, 2003 - 01:37 PM

#12

I just put it in 1st, pull in the clutch lever, push and get it going as fast as I can and then jump on and release the clutch. Going down hill works better. I'v had it stall before letting out the clutch to fast and not giving it enough throttle and i can pull the clutch in and let it out and it will start.

Carl

2003 WR450


No fair, you have an automatic decompression mechanism.




 
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