Join Date: Sep 2017
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05 Brute Force 750 wont rev up.
Hey, i had an account here years ago but haven't used it in a few years so it was deactivated/removed i guess. =(
So a few weeks ago my father dropped off his 05 Brute force 750 and said it just stopped running. Quickly figuring out the valve head broke off and is in the cylinder. so i pulled the motor apart, got a used cylinder head, valves and springs from a local shop. took it apart, lapped the valves and "redneck leak tested it".
because my dads on a bit of a budget, and there was no damage to the piston, Cylinders or rings I decided not to replace the piston/rings.(a few small light gouges to the top of the piston head. 8 sec with a small flap disc smoothed it right out). I gave the carb a quick wash down with carb cleaner and put it back together. Upon first start up i was getting spitting out the front cylinder just before ignition, so i assumed i did a bad job laping the valves or the timing was off 1 tooth. So i pulled the motor apart again and re-laped the valves and reset the timing. I pulled bolth carbs apart cleaned and inspected them. after putting it all back together it runs and idles fine. but when i try to rev it up it wont rev up and lacks power. I let the bike run idle in the back yard for 1/2 hour while i filled the coolant. after the bike is warm it will rev up quite a bit more but still not like it should. it also backfires every time i give it more then 1/2 throttle.
I checked the rubber boots and everything is fine. The diaphragm and CV valve(I think its called) are in good condition. no wear, cracks or damage.
If anyone has any insight to what the problem might be, i'm open to suggestions. Thanks
20 sec video of the issue i'm having.