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2004 Arctic Cat 400
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Discussion Starter · #1 ·
I recently did a pile of work on my machine, trying to test ride it felt like my rpm was capped around 3400 and it was cycle revving up and down.

Cleaned carb . Still there. Looked back at airbox and air duct from carb to filter had raw fuel in it.

Adjusted my intake valves and it still seems like I have airflow backwards out of the carb.

Is it normal to have a bit of fuel/air backflow from carb at rpm?

When I had the head off the valves seemed Clean and seated...

Any suggestions? Could my timing be off by 1 tooth on the cam?
 

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Did you set the valves on the compression stroke? Two timing marks in the inspection hole
 

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2004 Arctic Cat 400
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Discussion Starter · #3 ·
Got valves tuned in.... Now have an imaginary rev limiter with the airbox on I'm rev limited to 33-3800.. off no issues, nothing wrong in carb.. might be electrical, coil is showing wild numbers on a multimeter... I'll need to hook my computer up to provide details tonight
 

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Discussion Starter · #4 ·
Ok, so I set the valves correctly and they were a little bit out of spec, I set them on the compression stroke, TDC. (intake open and close, keep turning till timing mark, stop immediately). The engine sounds a bit happier now.

I'm not sure if I'm having a breathing problem or an electrical problem now, I'm still hitting this false rev limiter.

Here is a list of what I know so far:

With my muffler off but airbox on my rev cap moved up to 4k RPM from 33-3400rpm, blew out the head pipe as best as I could to ensure nothing was living in there, the muffler obviously chokes it down a bit to be better for scavenging and to make it manageable to be around.

With my airbox off but muffler on, no problems revs out to 5-6k no problem.

I started thinking it was electrical so I pressed reverse over-ride switch while revving in neutral, no change.

We put a multimeter on my coil (not sure I trust the meter) I had 200 DCV setting, on the white and blue wire while disconnected from the coil with the machine keyed on not running, meter out ranged (supposed to be 36V I think? unless it needs connected to coil to show that, while connected to coil it showed nil/outrange still)

With the meter on and pressing the starter for a second, meter outranged as the charge began to dissipate through the meter after this, waiting 15-20 seconds the DC-V would read 200V.. 195 190 ...... and slowly ticked down until it was fully dissipated.

Things I want to check tonight-

I want to remove my carb vent from the carb and try to push air through it... I might have compressed it with a zip-tie while re-securing all the wiring I had to loose in order to do all the work I did.
My theory behind this is, with the airbox off the carb opens all the way gets full travel and full RPM, there is a high enough volume of air available that it can compress the vacuum piston up. with the air filter on the air volume is reduced meaning not enough pressure to compress the vacuum piston IF the vent line is plugged.

I'm not 100% sure I was testing the coil correctly (should the wire have been connected to the coil while testing the terminal?)

Things I feel I've eliminated-

I feel after spending 2+ hours carefully setting the valves that they are removed from cause.

I've cleaned my carb thoroughly I feel like I've reduced/removed the chance my carb is clogged.

Fuel is fully available, new, clear fuel filter shows good flow

Spark plug is new


Things I hope it isn't but fear-

  • CDI
  • Coil
  • Timing mistake while reinstalling cam-shaft.

My friends are all pretty certain that I couldn't have been a tooth off on my cam timing because it wouldn't run/idle as well as it does currently, it idles great, 12-1400 rpm no issues. also with 1 tooth off it should have been noticeably out of plane with the top of the head.
 

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Discussion Starter · #5 ·
Confirmed I was testing the white and blue wire to the coil correctly, should have 36V key on, 136V key on starter depressed. I have 150v and 450v respectively. Is this a direct indicator my CDI is toast?

Carb vent wasn't plugged, revved out good on the first start, as the engine got a bit warmer it started revving out a bit less and less.. frustrating.

Rammed a borescope up it's intake to watch the carb slide move correctly, seems like carb is fine.

Scared it's my CDI and can't find a known good one to test before I spend $600 on a new one....
 
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