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Discussion Starter #1
Hi, new member here, here's my story and I really appreciate your help:
Bought a 2009 Thundercat 1000 H2 with engine in a box, it was submerged in mud, so I rebuilt the whole engine, new crankshaft, rods, pistons+rings, ....; cleaned the whole engine and put back together to factory specs.
Run it the first time and found out that I had fuel issues, changed the pump and it worked fine for a while then same issue happened, opened the tank and found out that the little hose piece between the pump and the assembly had cracked. In the meantime I had ordered the Ford Mustang pump that everyone swears about it works for the thundercats. installed the new pump, bike start and runs, but sputters and back fires at mid throttle and won't accelerate. It acts as if it is in limb mode.
Brief history: installed new injectors, new tps and adjusted it, new spark plug when finished the rebuild a few months ago, new air sensor, rechecked the valves timing and it was to specs, no codes displayed on the pod.

I'm asking all you experienced arctic cat gurus to help solve this issue.

Thank you so much.
 

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Is one cylinder cutting out? Also check the diodes in your fuse box to make sure they are all pointing in the right direction. Have you tried new plugs ?
 

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Discussion Starter #3
None of the cylinders is cutting out; I suspected the diodes earlier and changed them with new ones, no help.
Thank for your input
 

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Discussion Starter #4
I will try new plug tomorrow and feedback; I have NGK installed when the engine was rebuild.
 

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Discussion Starter #5
Update:
Got my spark plug today, had to order them cause none of the auto parts stores had them in stock.
Got the NGK CR8EIX (iridium), gapped them to 0.024 and installed them, started the monster and it sounded better, i was excited, but the issue of backfiring still there at mid throttle or higher.
Measured the primary ignition coil found 4.75 ohm, the secondary was 3200 ohm, the previous owner had installed aftermarket spark plug wires.
my old regular NGK plug were black like the bike was running rich or something, the gap was on the lower side value.
Any help would be appreciated.
 

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Have you reset your IAC ?
 

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Discussion Starter #8
Yes I did that after installing and setting the new tps, thank you.
I have no codes (only AC-00).
 

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Check the wires right where they enter the throttle body. They break right there inside the outer coating sometimes. Is your tilt sensor working correctly ?
 

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Discussion Starter #10
ok will check them.
Just for info, this bike had snorkels and hmf exhaust installed before I got it, I removed them and installed stock muffler and everything else is stock now.
Also noticed when I switch the pod to rpm, the needle doesn't move, but work fine in mph when I'm riding it, could that be related to my issue?!

Thank you, I really appreciate your help.
 

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Yes it almost sounds a shorted wire somewhere
 

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Discussion Starter #12
Yes it could be; do you know where the rpm signal is picked up from?
A wiring diagram will help too, do happen you to have one?
I will go through all connections this weekend since it gets dark when I get home from work. I also bought another spark plug wire and will replace the existing ones just to make sure the ignition circuit is good.
Do you think a ecu re-flash would be necessary in case everything else fail? it make me thinks the previous owner might have played with it, since he had the snorkels and the hmf exhaust installed; do you anyone who can do the re-flash for a reasonable price. It looks like there are no real Cat dealers here in the ATL area!
Thank you.
 

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You can get a free downloadable service manual and wiring diagrams at countrycat.com under technical.
 

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Discussion Starter #14
Update:
Checked all connections and sprayed wd40 in connectors just to make sure there's a good pin contacts, checked for broken wires, none found.
Changed spark plug wires with brand new ones, now the secondary resistance is barely 2,500 ohms, also re-gapped the plugs to 0.030 inch, the bike idles smooth and start right up, but the mid-throttle issue is still there.
Decided to check the fuel pressure just for the heck of it; the pump shoots 45 psi when you turn the key, also changed the inline filter with a transparent one, just to see the fuel flowing, that's when I noticed something strange.
When the key is turned to on, the fuel rushes through the filter, when the bike is running I still can see the fuel in the filter, but noticed that there's no rush when I hit the gas especially at mid throttle when it start sputtering and backfiring; so I decided to pry open the fuel pump, lifted it from the fuel tank and noticed that it is bypassing like crazy, when I hit the throttle the flow is insane inside the tank, but not through the hose/filter. I think I found my problem!
Took the pump out the tank, noticed the regulator has some kind of rust on the metal part (white coat), disconnected it from the pump, the o rings look good, but i have no way of testing it, so I ordered a new one from Quantum fuel systems, I should get it by Thursday or Friday and hope this will fix the issue.
Any thoughts on this and if you guys have any suggestions i should try.

Thank you guys for your help.
 

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You got it!
 

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Discussion Starter #17
Well bummer, I installed the new fuel regulator and wished that's it I got this monster fixed, but no still has the same mid throttle backfiring problem.
I would like to have the ecu remapped, because this atv had snorkels and hmf muffler installed before, it leads me to thinking this the previous owner may have modified it.
Any idea who can do it correctly?
Any other idea I should try to get this thing going?

Thank you all for your help.
 

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Backfiring is a lean condition and would have been worse with a HMF and snorkels.

Did you check the intake boots? for leaks and cracks? Sorry if you already posted that info.
 

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Discussion Starter #19
Yes I did, no cracks or leaks; I even tried to put my hand and partially block the intake just to limit the air going through, but still the same result. Any other suggestions?
 
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