Gwbarm

I jut re read your post and missed the part where you had already pulled the head and leak tested your valves, check to see if your getting any weird suction feeling at the spark plug hole with your finger it just won't feel right, the only thing I can think of that could cause this is valve timing, when you check the timing make sure you are on the compression stroke, not likely, but you could be 180 off and marks still line up.

You definitely should clean the carb if for no other reason peace of mind, you might try turning your petcock to prime and running it ,sometimes the vacuum petcocks go bad and you can't tell if its getting gas without the engine running.

You have been very thorough with your diagnosis, but if you are getting suction from the exhaust there has to be something not right with the valves, I would work with it a little more to see if exhaust valve is sticking before I take the head off.

New carb is flooding ,black plugs, you need to dial in the fuel air mixture if you can, I v had some trouble dialing in aftermarkets . also if the air filter is not stock aftermarkets can be rather dense and cause some degree of flooding.

I agree with mech compression is low, borderline to even run, should be 140 or higher.

Sounds like the timing advance is not functioning correctly, so I would also guess CDI , a little confused at what you are trying to bypass.

Good you got it running and driving, I would definitely get the boot fixed as soon as possible, if its been broken for a while that axle may be where your noise is coming from and may need to be replaced.

Im good, I have a box of them, they work good for a few months then I end up spending lots for a good one, you would think I would learn my lesson after a couple of tries.

I would pull your nice Mikuni carb off it actually looks very clean on the outside, certainly not 20 years of doing nothing to it, and make sure its clean on the inside. If its a manual petcock just needs new rubber there is a kit for that, if it is a vacuum petcock it will have a prime setting on it iv not had much luck at rebuilding those just replace.

If it has the original Mikuni on it I would rebuild it with a OEM kit.

Good advice mech, the only thing I might add is the float pins get gummy after a while especially if it been sitting, with out taking it apart I might add a little Berryman carb cleaner to gas it will help and might even fix your problem , best to do the easiest things first.

Make sure the master cylinder is creating pressure, look for leaks and make sure it has plenty of fluid, not much fluid in reservoir.

I did check after I changed the filter and it did have oil in it but not a lot like I expected i will check it again after I get it good and warmed up. Thanks!

Sounds like your air filter is clogged causing it to flood badly. Carb could be partially clogged also. I would get a new air filter make sure all the air passages are clear no mouse nest and clean and adjust the carb. I just noticed you said the carb was new so may not need cleaning.

Tire pressure from my owners manual 4.7PSI front 4.4 PSI rear, so 5 sounds good to me.

I think my Eiger has the same 400 engine as your Arctic Cat, this is what I used, not saying its better than synthetic, I used Suzuki Ecstar R5000 10W-40 mineral oil. I also used the compatable suzuki oil filter, and this is why, I went to change the oil and it had a Fram filter, when I pulled the filter it concerned me that there was no oil in the filter, I assumed it had drained back down, maybe the Fram doesn't have a check valve to keep that from happening. Not sure of that I just ordered the correct Suzuki filter.

I just looked yesterday all of the ones I listed looked the same tank and I figured they will all fit your model, but your repair should work fine.

Had one listed for 2002 it was 199 a couple listed for 2003 I think 150 and a 2005 for 125

I did see 1 I think it was 199 not sure if I got your year and model right

Gas tank is easily repairable , with epoxy putty, but you can get new for about 225.00 and they are on eBay but I would buy new before I paid their prices. Tank cover is 110 for new, but I did see one on eBay that needs refinishing for 10.00 so you really have to look, and decide how much work you want to do plus the materials to refinish aren't cheap. Gas gauge new is about 100 , amazon might have an aftermarket that will fit. Just my experience from buying parts.

Sounds like your not getting a signal from main controller , I would check al connections for corrosion and loose contacts and wires.

My guess as well ! Sometimes they are hidden and easy to overlook when cleaning, Which carb OEM or aftermarket. The only thing I like to do also is take the emulsion tube out that runs from Venturi to main jet, they get dirty, if it won't come out use something like Berryman carb cleaner in an ultrasonic for about 20 minutes that should clean it well enough.

It sounds like a CVT transmission rattle, check pulleys and belt for wear and correct alignment.

What your doing is good all this needs to be done as a process of elimination. Next I would probably change plug and check for consistent spark., but I still think its fuel related, may need a carb replaced.

What I do know about lithium batteries, if you run the battery down to much the charger sees it as bad and won't charge it, hence you have to put voltage back in it from another battery, then the charger will recognize it as good and charge it up.