416EX build -- Won't Start --

[Keats]

I just completed my rebuilt to a 416, hooked everything up, turned the key, hit the button and she turns but won't quite start. Pops good, has spark, fuel, and good compression. Sounds like it does when the run/kill slider is slid into kill mode. Charged battery, poured gas on the cylinder, heated the spark plug, tried bump starting, changed gas, etc. It backfired, so I was thinking timing, not sure though. could we have mixed up the timing during the rebuild?? Could the cam/cam chain bet out of sync??

I'm calling it a night and am getting up tomorrow to make it run for sunday, just thought i'd post up my problem to see if anyone has experienced this and can save me some time...

thanks!
-Keats

[JOEX]

Stock cam? If so did you put the decompression spring and plunger back in?

[Keats]

Yes, im pretty sure we did. I would be completely sure, but it wont start so i guess we could have missed it, it its worth a shot. looks like we might be doing more tearing down tomorrow, thanks alot we'll check it for sure!!

anything else?

I also got a new clutch and perch, and while browsing the forums I saw something about some clutch levers not working with electric start??

[JOEX]

It could be something else so i'd wait before tearing it apart just yet.

As for the clutch lever.. I want to say it wont turn over at all without the neutral safety switch but i'm only 50-50 on that at best:p

[Keats]

OK i'll try doin a search on it here on the forums...thanks for the fast response!

[dariusld]

Originally posted by JOEX
I want to say it wont turn over at all without the neutral safety switch but i'm only 50-50 on that at best:p Your 100% right.

[Sparky_20]

if its popping then its getting spark, just sounds like at the wrong time. If the neutral safety was engaged then it wouldnt even turn over am i right? I would check your cam timing, just hope you didnt bend any valves if its 180 out! good luck

[AJ's Blaster]

about the clutch perch just take the wires off teh sapety switch thing and hotwire them together, I did that and now I can even start in gear with the clutch out.

[400exrider707]

Originally posted by Sparky_20
if its popping then its getting spark, just sounds like at the wrong time. If the neutral safety was engaged then it wouldnt even turn over am i right? I would check your cam timing, just hope you didnt bend any valves if its 180 out! good luck

The 400ex motor cant be 180 out, its impossible.

Are you in fact running the stock cam? If you are that plunger and spring needs to be there.

[Sparky_20]

how cant it be 180?

[GPracer2500]

Originally posted by Sparky_20
how cant it be 180?

Rotating the cam exactly 180 degrees will just flip-flop the exhaust stroke with the compression stroke. Since the spark plug fires at both TDC's, it doesn't matter which is which. Remember that the cam spins at exactly 1/2 the speed of the crank. So, every time the crank spins 360 degrees the cam spins 180 degrees.

--Put the piston at TDC on the compression stroke.
--Flip the cam 180 degrees.
--Now you're at TDC on the exhaust stroke.
--Spin the crank 360 degrees.
--Now you're right back where you started: TDC on the compression stroke. Everything is still perfectly in time even though you turned the cam 180 degrees.

Really, the maximum number of degrees you can be out of time is 90 degrees. As soon as you get to 91 degrees you're really now at 89 degrees out. Go to 92 degrees and you're really at 88 degrees out. The further you go past 90 the closer you get to 180 which is actually taking you back towards being in time. The only thing that's changing is the strokes are flip-flopping, which is of zero consequence.

[Sparky_20]

cool gp, thanks for explainig it. I know feel like timmeh :cool:

[Keats]

Thanks for the help fella's...I took off the head, checked the timing and it was all good, i reset the valves which were fine already, and reassembled the head and now she fires right up. Now it's got an awful tick to it, but I've already got 6 hours on it, so it can't be too bad for it...