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Hard to start and exhaust glows red quickly

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Hello Folks,  I recently finished up some work on my bike (Changed the decompression shaft and plunger, adjusted the valves to within spec).  I set the timing as per the dot on the crank and also the arrow was matched up with the line on the cam gear.  I was hoping that it would fire right up, however, it took quite a while to get it going.  Once it fired up, the exhaust header heated up really quickly and began glowing red. 

Prior to doing this work, the bike ran fine, was just a huge pain to kick over as the decompression shaft had the bent pin problem.  

Anyway.. Does this sound like I perhaps ended up being a tooth off on the timing, or is there a possibility that I set the crank dot on the exhaust stroke instead of compression TDC ? (not sure how this would be possible as with the marks lined up, I confirmed that the piston was at TDC) Alternatively, now that I have the valves shimmed properly, is it possible that the bike is now running lean ?  I bought the bike used and am not sure what the previous owner had done to it... 

Any guidance would be greatly appreciated ! 

Regards, 

Rod

 2008 CRF 450x

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24 minutes ago, Rod St. John said:

Hello Folks,  I recently finished up some work on my bike (Changed the decompression shaft and plunger, adjusted the valves to within spec).  I set the timing as per the dot on the crank and also the arrow was matched up with the line on the cam gear.  I was hoping that it would fire right up, however, it took quite a while to get it going.  Once it fired up, the exhaust header heated up really quickly and began glowing red. 

Prior to doing this work, the bike ran fine, was just a huge pain to kick over as the decompression shaft had the bent pin problem.  

Anyway.. Does this sound like I perhaps ended up being a tooth off on the timing, or is there a possibility that I set the crank dot on the exhaust stroke instead of compression TDC ? (not sure how this would be possible as with the marks lined up, I confirmed that the piston was at TDC) Alternatively, now that I have the valves shimmed properly, is it possible that the bike is now running lean ?  I bought the bike used and am not sure what the previous owner had done to it... 

Any guidance would be greatly appreciated ! 

Regards, 

Rod

 2008 CRF 450x

When setting the piston at TDC with the cam out of the head, it doesn’t know which stroke it is on; it’s either at TDC or it’s not. The cam’s position is really what sets which stroke it is in. Usually, if you are off a tooth, the bike will just run poorly. 

Is it possible that you left one of the boots on either side of the carb loose? Forget to install the hot start back on the carb perhaps? Is it easier to start with the choke on? 

Edited by CSAR FE

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 I was hoping that it would fire right up, however, it took quite a while to get it going.  Once it fired up, the exhaust header heated up really quickly and began glowing red.

That's a sign it's running lean....as CSAR FE said, check everything over, including the hot start.   Make sure it's not cracked and that the hot start is not hung up.  Make sure the band clamps on the boot between the carb and the engine are tight. 

The hard starting may or may not be related to running lean (assuming you started with choke) and there, I would double check the valve lash.

Jim.

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One thing I should add; these motors are jetted very lean from the factory.    If it's never been re-jetted, there may be nothing wrong.

With stock jetting the header will glow, which is especially noticeable at night.

Jim.

Edited by Jim Dettman
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If it didn't run lean and glow before, then yes you are most likely advanced a tooth... also makes it hard starting, but will run fine once started.

Use the viewing port on the ignition cover and flywheel, not the dot on the primary gear... too easy to make a mistake.

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Hello Gents,   Thanks for the info !  The bike was running decently before and I didn't touch the hot start or the carb, so I'm hoping that I can rule that out.  I'll give it a once over to be sure though..   from the sounds of things, I'll have to double check the valve timing.  I really thought that I had the index mark on the cam gear lined up with the arrow on the cam holder, however, it was really hard to see through the hole in the gear, so perhaps I messed that up.  I'll pull the cam cover, line the crank up at TDC using the flywheel as suggested and take another look.   

On another note.. when I was putting it back together, I noted that there were 2 hoses just under the gas tank that didn't seem to go anywhere... I couldn't find any diagrams for them in the manual, so thought that perhaps these were vent hoses.  When I pull the tank to check the timing, I'll take a better look and maybe post a pic of them.  I suspect that if these are supposed to actually be connected somewhere, that could be a big vacuum leak and explain my lean condition.

Regards,

Rod

  

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 so thought that perhaps these were vent hoses.

They are.  They are routed up high so water can't get in them.  Might be related to the PAIR valve though, so post a pic.

Edited by Jim Dettman

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Hi Folks, 

Thank you for all the helpful tips !!  Doc - you were spot on.  I aligned the flywheel to the 2nd mark, also confirmed that the dot on the right side was aligned and lo and behold, my cam gear was 1 tooth off,.. I found that I needed to put a spotlight shining down from the cam in order to properly see the cam carrier mark through the hole in the cam sprocket.  Anyway.. moved the sprocket 1 tooth and all 3 reference points were lined up perfectly.  After it was all together, it started on the 2nd kick !  I'm a happy guy once again.  Now I'm looking at a timbersled kit so I can run the bike all year !!! 

Thanks again for all your help ! 

Regards, 

Rod

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