2012 Brute Force 750 efi surging at half throttle - MudInMyBlood Forums
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post #1 of 2 Old 07-27-2019, 08:43 PM Thread Starter
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2012 Brute Force 750 efi surging at half throttle

2012 Brute Force 750 surging half throttle
2012 efi Brute Force 750 4000km

swamp exhaust

power commander 5 (custom map vforce john)

Primary Red spring (vforce john)

K&N air filter with breather box hood with fine screen filter


Recently my bike when I go above 1/4 throttle it starts to surge. idle fines and at 1/4 throttle.

I goto half throttle and hold and it starts this consistent surge like its starving for fuel but its not a bog just surges up and down at same rate. I replaced fuel pump and dirty sock at 2500km and installed a tank sock to catch dirt. no issues until 4000km. I just tried 2 sets of plugs and removed the power commander 5 in case its ignition issue but it does not sound like it as stock ignition does exactly same thing. Does exactly same thing PC5 or not. Bought new pump and fuel sock and pressure regulator, still same problem.

I have not done a fuel pressure test but the chances of my 2nd pump and the new one being faulty are very low as they are doing the exact same thing. I have run the bike with fuel cap off and with check valve off tank and no change.

also checked the carbs butterflys valves and they open identically and and seat properly.

I am only left with my injectors,vacuum issue or is there any type of airflow control into the EFI carbs that could be messing this up. bad spark cable or solenoid?



I was told to check upper housing screen inside fuel pump housing..i think i can see a screen inside there but very hard to access as its sealed..it looks dark in colour on both sides but screen is not very visible. I am assuming I have proper fule pressure but this screen could inhibit proper volume too.

The surge has no bog out which tells me it seems to be getting enough fuel so is it ignition solenoid or bad cable as well. any help would be great.
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post #2 of 2 Old 09-21-2019, 05:24 PM
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Join Date: Jan 2018
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There is a vacuum equalization adjustment on those throttle bodies but I doubt that is you problem.

Have you checked your TPS with an DMM?


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