Mud in My Blood Forum banner

1 - 20 of 26 Posts

·
Registered
Joined
·
11 Posts
Discussion Starter #1
I have this 2007 brute force 750.. carbureted quad.. it was running great and we got home and turned it off and it never started again. It has weak spark its seems. We have good fuel, cleaned the carbs, tested the stator, brand new rectifier, tested the rollover switch... to no avail. Any input would be appreciated
 

·
Premium Member
Joined
·
24 Posts
What's the weak spark source? Is it on one cylinder or both?

You have your plugs, coils, and stator to suspect. Start with the easy, what do your plugs tell you? Are they fouled, are the gaps correct, etc?



Sent from my SM-N950W using Tapatalk
 

·
Registered
Joined
·
11 Posts
Discussion Starter #3
Thank you for the response. My plugs were wet which I assume was from all the cranking. Put new plugs in it and just grounded it and its a small yellowish spark out of them. Much weaker than I ever had before.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #4
In both cylinders also... checked compression for giggles and its 60psi in both cylinders which is on par with the manual according to other posts on this forum
 

·
Registered
Joined
·
11 Posts
Discussion Starter #6
Yes both ngk plugs. I was just poking around just now and found there is continuity to ground on both sides of the coil... is that normal?
 

·
Premium Member
Joined
·
24 Posts
Yes both ngk plugs. I was just poking around just now and found there is continuity to ground on both sides of the coil... is that normal?
You have a primary and secondary resistance, they should be very different values. The primary should be really low and the secondary significantly higher.

My manual also suggests a low battery will give a weak spark condition.

Sent from my SM-N950W using Tapatalk
 

·
Registered
Joined
·
11 Posts
Discussion Starter #8
We have the battery at 13.6 volts. Let me check the coil resistance. I'm trying to look that up. I bought a manual but it hasn't come in yet
 

·
Premium Member
Joined
·
24 Posts
Stator coil 0.29 - 0.43
Primary 0.09 - 0.13
Secondary 3.8k - 5.8k
Crank Sensor 423 - 517

Sent from my SM-N950W using Tapatalk
 

·
Registered
Joined
·
11 Posts
Discussion Starter #11
Ok my ohm readings seem to be in spec everywhere except coil #2. It has ground on both sides of the coil.. the other coil does not. Wondering if that is the issue. Not sure how it's supposed to be but seems funky
 

·
Premium Member
Joined
·
24 Posts
Ok my ohm readings seem to be in spec everywhere except coil #2. It has ground on both sides of the coil.. the other coil does not. Wondering if that is the issue. Not sure how it's supposed to be but seems funky
Sounds like it went south; unplug it and you get a strong spark again on #1?

Sent from my SM-N950W using Tapatalk
 

·
Registered
Joined
·
11 Posts
Discussion Starter #13
also... you can crank and crank and then a loud a$$ backfire out of the exhaust like clockwork. Just trying to give you everything I know
 

·
Registered
Joined
·
11 Posts
Discussion Starter #14
Made a discovery. The rollover switch only has a 5 volt reference when i lay it on its side. I shook the piss out of it and its still the same.
 

·
Premium Member
Joined
·
24 Posts
Made a discovery. The rollover switch only has a 5 volt reference when i lay it on its side. I shook the piss out of it and its still the same.
It is a Hall Effect sensor, it doesnt work like you are expecting it to (you are describing a mercury or weighted reed type switch)..



Sent from my SM-N950W using Tapatalk
 

·
Registered
Joined
·
11 Posts
Discussion Starter #16
Laying on its side it just started... up until now it would do as much as try to start
 

·
Premium Member
Joined
·
24 Posts
Laying on its side it just started... up until now it would do as much as try to start
Is the spark stronger?

In general that sensor does not affect the coils and is likely unrelated.

Quite more probable is that your wiring harness is wore through in one of the two spots that are near the electrical tray where mine AND the second harness I have showed wear.

I'll try and see if I have an image in a bit.

Sent from my SM-N950W using Tapatalk
 

·
Premium Member
Joined
·
24 Posts
One is of the spot in the spare harness, and then it is approximately in position so you know where to look.

Those wires all go towards those rear sensors.

While I think about it, I'd recommend anyone reading this to pick up a spare parts harness and a set of connector pin tools. Most of the harness you can pull the pins and wires you need and just tape them to the existing harness instead of cutting and splice (just remove the bad pins or tape them into the harness as well, never know if you might need em).

When the harness went back in we used a section of the plastic guard from the spare harness to stop that section (and a couple other spots) from rubbing against the frame. You will see where the tape is worn through.


Sent from my SM-N950W using Tapatalk
 

·
Registered
Joined
·
73 Posts
Can I suggest this?


It is very inexpensive, easy to get, and does a great job protecting wiring. When I did all the wiring on my RZR, I used this stuff on ALL wires. It comes in a lot of different sizes, and it is fairly easy to install. This stuff is an ATV Electrician's best friend.
 
1 - 20 of 26 Posts
Top