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Discussion Starter #1 (Edited)
Thought it might be helpful to make a list of the most COMMON mechanical problems/weaknesses that occur on the BF750i and BF650i. (NOT including the BF650sra b/c that is a separate list). This list could be helpful for new BF 750i and BF650i owners and/or someone interested in buying one.

I'll start the list (in no particular order)...please post below with any suggestions you have to add to this list.


BRUTE FORCE COMMON MECHANICAL PROBLEMS:

1) Stock oil seals on engine and front/rear diff tend to leak; Fix: Keep an eye on them and replace as needed (no aftermarket seals available at this time)

2) Stock front and rear shocks are too soft for fast-paced riding; Fix: replace with aftermarket shocks

3) Stock CDI is very restricted on carb'd models; Fix: replace with aftermarket CDI to eliminate low speed and top speed retarded ignition timing and to increase maximum ignition timing

4) Stock radiator tends to plug up with dirt/mud and cause engine overheating; Fix: Thoroughly clean the radiator fins with a water hose on a frequent basis (don't use a pressure washer), especially needed after a muddy or dusty ride. Some folks install a fan switch and operate the fan continuously during rides.

5) Stock bushings on front and rear a-arms wear out fast/have no grease zerks; Fix: Replace with aftermarket bushings

6) Stock actuators for the KEBC and 2wd/4wd tend to fail within a few years; Fix: Some folks remove the KEBC actuator and fork and live without the KEBC function. A few folks have also removed the 2wd/4wd actuator and modified it to function manually via a choke cable set-up. If you don't want to make those changes, you can occasionally disassemble the stock actuators to clean, lubricate and reseal with silicone/gasket maker.

7) Stock radiator fan breaker tends to malfunction; Fix: Replace with inline fuse.

8) Pre-2007 BF750i stock front a-arms cause hard steering; Fix: reduce castor angle or replace the upper and lower the stock a-arms with later model BF750i a-arms.

9) Stock front diff may break/lock-up, especially if jumping while in 4wd or if one of the oil seals leaks; Fix: Avoid jumping while in 4wd, change the front diff oil as recommended, and keep an eye on the oil seals.

10) 2007-10 BF750i rear differential ring and pinion locking nut sometimes comes loose; Fix: Apply red loctite to the nut and torq to spec

11) Stock Airbox intake snorkel needs better splash protection to prevent water from entering the airbox during shallow water crossings; Fix: Install EHS Mudder Lid or install full snorkels.

12) 2005 & 2006 BF750i had buss connectors that would sometimes cause odd electrical problems; Fix: Cut the wires and solder all the white wire together and all of the black wires together.

13) Stock tie rods bend too easily; Fix: Replace with stronger aftermarket tie rods.

14) ANYTHING ELSE ???
 

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Discussion Starter #3
Possibly, but I would still like to complete this list for all of those who already bought and/or are considering buying in the future a pre-2012 model BF.

Thanks.
 

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Just the poor bushing setups on the front and rear a-arms that have no grease zerks.
 

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The KEBC acting up, I removed my fork and am happy with it :) The rear brake cable freezing up in winter. Some cable lube and the cable lube tool is a quick fix.

Mikeyboy is the Moose Module assocciated with the CDI or ECU??? , reason i ask is because I have one and it didn't do a thing. Everyone else claims their's is a wheelie monster with one.
 

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Discussion Starter #6
TStubb,
The Moose module (not same thing as Moose brand CDI...which is actually a Dyna CDI with Moose label) is not as good as an aftermarket CDI. The Moose module (or any other brand module) only eliminates the low end retarded timing and does not increase the max ignition timing or eliminate the top end retarded timing.
 

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So the CDI gets rid of the rev limiter?
 

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Discussion Starter #8 (Edited)
TStubb,
The aftermarket CDI still has a rev limiter (which may or may not be higher than stock), but that is not what I meant above when I said it removes the top-speed retarded timing. What I meant was that the STOCK CDI retards the ignition timing at idle (upto a certain speed - say 10mph) and slowly increases to a max of 28 degrees ignition timing, then the ignition timing goes down when it reaches a certain rpm or speed (say above 60mph). The result is an ignition timing chart looks like a bell curve.

On the other hand, an aftermarket CDI (like the Dyna CDI) will have a higher ignition timing at idle and reach max ignitition timing sooner (say 33 degrees) and hold that ignitition timing until it hits the rev limiter. The result is that you take-off quicker (assuming you have good traction), have more throttle response in the mid-range and have a higher top-speed (typically 3 to 5 mph more).

Someone please correct me if I misstated anything above...I'm going off my memory from a long time ago.

Thanks,
 

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I've always thought the CDI gets rid of the rev limiter or increases it to a point that it is a risk or possiblity of blowing the motor up, that's why I stayed away. Advancing the timing, does that hurt it at all? And can this be ran with the moose module?

Any one got one for sale?

Just read online you need to rejet with a CDI, well that sucks
 

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"2) Stock front and rear shocks are too soft for fast-paced riding; Fix: replace with aftermarket shocks"

Alternative might be using other factory shocks from different ATV manufacturers. I'de be interested in finding out which ones fit our ATVs.
I know the Grizzly front Shocks work for the rears on the Brutes. But are there Any alternatives other then the grizzly and what about the fronts?

thanks Dave F.
 

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Discussion Starter #11
Starting to get off topic here, but I'll try to answer your questions one last time.

1) The aftermarket CDI's might raise the rev limiter some, but not enuf to worry about blowing the motor up. Remember, we have CVT transmissions and its very unlikely you will reach high rpms unless you also have nitrous, big bore kit, etc.

2) Advancing the timing to 33 degrees (as is the case for the non-programmable Dyna CDI) is usually a good thing...too much timing might hurt the engine, but 33 degrees should be safe for most anyone.

3) Post an ad in the WANTED section of this forum and do a search thru the FOR SALE section for a Dyna CDI.

4) Unless you do other mods (drill holes in the airbox, add an aftermarket exhaust), there is probably no need to rejet if all you do is install a Dyna CDI. At least that was true for me and I've used the Dyna CDI on all of my Prairies with no need to rejet.

5) If you install an aftermarket CDI while the Moose module is connected, it won't hurt anything. However, the aftermarket CDI will ignore the Moose module so you will see zero benefit from the Moose module. That being the case, I recommend that you sell the Moose Module and buy a Dyna CDI.
 

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One more: Super Unleaded, need w/ the CDI or would Unleaded work?

I think some have used the YFZ's front shocks in the front of the brute but I could be wrong.
 

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Discussion Starter #13
I have always used superunleaded in my ATVs (except when I ran nitrous - in which case I used a 50/50 mix of superunleaded and race gas). I don't know if its required, but its probably a good idea to use superunleaded whenever you install an aftermarket CDI (that increases the max ignition timing) so as to prevent pre-detonation.
 

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for the 2012 750i, here is my 10 cents worth::::
#1 stock tires are crap
#2 the rad is located higher than previous years so unless doing extreme mud riding, you should be ok..plus larger fan and rad size helps w/over heating issues
#3 CHECK BELT DEFLECTION...IT "WILL" be loose from factory!!!!
#4..did I mention sock tires suck??
#5 stock shocks still are lacking
#6 skid plates are still sub par, only covering some of your under belly
 

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Someone should make this a sticky
 

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Discussion Starter #16
I'm planning to make it a sticky after the list is complete. Does anyone else have any suggestions for this list?
 

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maybe fan breaker going out. replace with inline fuse.
 

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Discussion Starter #18
Thanks BFttu.

Anyone else have suggestions for this list?
 

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Stock bf flywheels (or starter gears) are weak in the older brutes and can strip with the addition of an aftermarket cdi box. FIX get a flywheel from a 2012 brute that is thicker.:D
 

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What about the main buss connector on the 05 brutes? Shouldn't that be in this list?
 
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