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Predator 670 motor help needed
http://www.mudmotortalk.com/mmt_v2/viewtopic.php?f=3&t=68566
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Author:  bigticket [ Fri Oct 07, 2016 12:46 pm ]
Post subject:  Predator 670 motor help needed

Ok motor guys I got a condition going on I thought I burnt a exhaust valve but I pulled both heads and valves they look fine,no holes chips or Burt metal but the dam thing just recently started popping and shooting a 3 inch flame @ wot or when revving and letting off throttle on cyl 1 or left cyl , rough idle etc but runs like a scalded dog at wot till hot then acts like it's dropping a cylinder.

during dove season it barely got me home down red river.
I built a custom exhaust and went up 2 jet sizes but that was done a long time before this started, I flipped heads over and filled with some gas to check for a leakdown and 30 mins later they are still full.
Could it be a coil pack failing when hot? IMAG0102.jpgIMAG0103.jpg

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Author:  Will C [ Fri Oct 07, 2016 1:08 pm ]
Post subject:  Re: Predator 670 motor help needed

Sure it could be ignition. Could also have been a valve adjusted too tight

Author:  Fowlintentions247 [ Sat Jan 07, 2017 12:47 am ]
Post subject:  Re: Predator 670 motor help needed

Hey I'm curious where you got the different jets for this motor? How do you like it thanks

Author:  bigticket [ Fri Jan 13, 2017 2:01 am ]
Post subject:  Re: Predator 670 motor help needed

Thank you guys for all the questions I never check my email,been busy hunting....

im gonna throw some info out hopefully i awnser your questions.

I honestly couldn't find any ,I did however drill out my high altitude jets that came with motor (extras) 2 sizes over the stock jet size or 3 sizes over on high altitude jet size.

I have to double check and please do this at your own risk....

if your going to try it start a size just above the stock and go up in steps until it's tuned in.

As best as i can remember...
Original size jet # 105-106 L #110-111 R

new jet size # 120-119 L / 119 R - #56 drill bit.

It's been a while over a year ago since I did this so I could be off on my #'s without pulling carb and double checking everything so just use as a reference to give ideas.

i did save my original jets i pulled out and didnt drill them in case i needed to go back down a size or back to normal.

I think and im guessing they use 2 different jet sizes because of the way the stock muffler is made ,short side has a bigger jet to stop it from running lean (right) and of course smaller jet on long side of muffler(left) .

I drilled both jets same size,it starts super easy no choke and idles great,used to not crank without choke on hot or cold motor.

i also got rid of the crappy stock airfilter and used the stock air filter frame after i cut the paper out of it,and put a shopvac filter around it like a sleeve (kinda a cheap k&n) to help it from running too rich with the jetting, works great and fits perfect,I couldn't find any kind of filter to replace it there just is nothing out there for stock.




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Author:  bigticket [ Fri Jan 13, 2017 2:16 am ]
Post subject:  Re: Predator 670 motor help needed

And yes it was a coil pack failing I got it changed and its running like a scalded dog.

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Author:  bigticket [ Fri Jan 13, 2017 2:19 am ]
Post subject:  Re: Predator 670 motor help needed

Here is a link to the site I got some info from,there isn't much out there

If the link gives a 404 error just click link on their page to see the full article.

http://www.affordablegokarts.com/Drilling%20Main%20Jets







Test running on the river after I got the coil fixed.



It's a trial and error on the jetting I just went up a size at a time until I got the right plug color( chocolaty color ) the carb has no adjustments for rich or lean they are capped off. And yes I'm running the stock governor setup that came with it and 9x6 go devil cupped prop.

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Author:  jpo_land_man [ Wed Jan 18, 2017 7:59 am ]
Post subject:  Re: Predator 670 motor help needed

I'm not mechanically inclined when it comes to carbs for sure. I was thinking of just buying a stock Honda carb and bolting it on. Do you think I'd see any gains from this?

Author:  bigticket [ Thu Jan 19, 2017 11:53 am ]
Post subject:  Re: Predator 670 motor help needed

You may be better off getting a Honda carb,i'dk about gains but it has to be better than the stock clone.

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Author:  sleepy_sleeper [ Tue Feb 14, 2017 5:43 am ]
Post subject:  Re: Predator 670 motor help needed

How fast is "scalded dog"? I just got a GD frame with a Predator 22 on it. The SN starts with BS16 so I assume it's a build just like yours. It currently has a 9x5 prop but I plan to do these mods once it is all setup on my 1548 Weldcraft.

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