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Author Topic: spark plug upgrade  (Read 10891 times)

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Offline Lord Icon

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spark plug upgrade
« on: August 26, 2012, 08:26:53 AM »
I have been lurking in the go-kart web sites for a while. One of the major improvements to a small engine is compression ratio. The autolite sparkplug designed for Nascar works well in both engines, and all clones. Autolite AR3910x. Don't bother the local guy , nobody stocks them. Most can't even look it up in the books. I ordered mine from e-bay. I got 4 , one for each of my boats, and two spares.
Don't get confused with the cheaper and less useful AR3910. You need the "X" . The plug sits into the combustion chamber further than the normal plug. Therefore removing precious space from an already small area, increasing the compression ratio. The gain is 5-10 % .... just for the plug.
The X plug has no grounding electrode to get in the way and be hit by the piston.
 >:D    Now to find a way to use the hp .... some type of gear upgrade. The engine only turns ay 3600 4000 ... no matter what hp you have. But if I add a in line gear , like a torque doubler only backwards.. Engine runs at 2500, and turbine runs at 5000,,,,, more water out the tail pipe, more speed.
 

Offline Painlesstom

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Re: spark plug upgrade
« Reply #1 on: August 26, 2012, 09:45:35 AM »
You are correct in that being a better plug, I've been running one in my GX200 for some time now. It doesn't give you the increase in power you are expecting though. I looks neat, and made me feel better knowing it was in there, but I can't say I really felt a difference in performance.

If you want more speed, you need a lot more torque to get the rpm's up. Using gearing to overdrive the pump will add weight and put an end to the easy motor or pump removal process and the motor wouldn't have enough torque to really give you enough extra rpm to make it worth all the trouble. Not saying it cannot be done, just that you aren't going to achieve the warp speed and beyond we'd all love to have.

Work on the motor, or find a KX21 motor.. More compression, bigger carb, camshaft, pull the governor etc...  That is where you will find your speed! It's a balance between performance and reliability, nothing would be less fun than going out at warp speed only to paddle back, or be stranded somewhere.  :( 
Tom

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Offline Lord Icon

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Re: spark plug upgrade
« Reply #2 on: August 26, 2012, 10:11:37 PM »
Added it to the wife's 2003 with Honda. Woke it right up.

Offline Hillbilly

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Re: spark plug upgrade
« Reply #3 on: August 27, 2012, 07:12:44 AM »
This is a good addition for the GC190 thread

Offline Hillbilly

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Re: spark plug upgrade
« Reply #4 on: September 09, 2012, 10:29:04 AM »
This same plug is sold by ARC racing as an upgrade for the GX200 and clone, with anecdotal claim of 3/4 hp increase in the clone from the plug itself.  Wonder if it fits the EX or K motor?

Offline Hillbilly

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Re: spark plug upgrade
« Reply #5 on: September 09, 2012, 11:03:48 AM »
This plug sells for $7 at ARC Racing.  They recommend to run the motor hot. They don't mention the GX200 specifically but if it works in the clone  . . .  What better for a Mokai.  I'm going to get one for my clone and another to try in the Robin.

Offline Painlesstom

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Re: spark plug upgrade
« Reply #6 on: September 09, 2012, 11:08:36 AM »
Should work fine, works great in my GX200. "Plug and Play" (pun intended)  ;D

Definitely helps prevent fouling.
Tom

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Offline Hillbilly

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Re: spark plug upgrade
« Reply #7 on: September 09, 2012, 12:41:55 PM »
Did you feel any difference from old plug?

Offline Painlesstom

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Re: spark plug upgrade
« Reply #8 on: September 09, 2012, 12:54:05 PM »
I'd like to say I did but I think most of it was psychological, starting seemed easier and I want to say WOT was more consistent. There was no increase in speed on GPS or anything substantial. I like the fact there is no electrode that needs to be gaped, it is less likely to foul, and it won't  erode.  So I'd say it's definitely worth it, one of those improvements that would require a dyno to confirm any performance gains though.

I'm getting ready to so some upgrades that should bump performance though.. .020 over billet rod, 252 marine cam, 2 advance key, and a .010 head gasket. Should put my compression up a point and let the new cam make some more torque. We'll see!  ;D
Tom

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Offline SDonker

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Re: spark plug upgrade
« Reply #9 on: September 17, 2012, 01:43:50 PM »
I bought 2 of the AR390X plugs and they are 6 mm's longer.

I checked and the plug gets really close to the piston @ TDC so I just put the standard plug back in.

Offline Hillbilly

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Re: spark plug upgrade
« Reply #10 on: September 18, 2012, 08:03:09 AM »
What motor did you put the new plug in?

Offline Hersh

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Re: spark plug upgrade
« Reply #11 on: September 18, 2012, 09:16:14 AM »
I bought the same plugs for my two Mokais but I'm concerned about the same thing(to close to the piston head). Mine are the 2011 Subaru engines.

Offline SDonker

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Re: spark plug upgrade
« Reply #12 on: September 18, 2012, 12:06:24 PM »
I have a 2011 and a 2010 Mokai both with Subaru motors.

Offline Hillbilly

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Re: spark plug upgrade
« Reply #13 on: September 19, 2012, 10:16:03 AM »
Thanks.  Saves me from buying and trying in my Sub's.  May still try one in my clone.

Offline Lord Icon

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Re: spark plug upgrade
« Reply #14 on: September 21, 2012, 01:04:14 PM »
I added the plug to my 2003other with the honda 5 hp. Works great. No issues and starts easier.  Even hot starts seem to be no problem. As it is the wife's boat. I would have been told of any issues right away... haven't put it in the 2012 boat yet.