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212cc Predator Spark Plug Upgrade

14K views 31 replies 11 participants last post by  GustoGuy 
#1 ·
Hi Guys,

I did the Predator 212cc swap. I see people here make suggestions about installing a better plug than what came with it.

Question: Should I use a NGK- BP6ES

Or, should I use the following;


Autolite Racing Spark Plug

AR3910X Racing Spark Plug - Predator & Honda Clone
Autolite
Our Price: $6.50
Part Number:419357MPN:AR3910xAvailability:Ships same day if ordered before 12PM Eastern time.

PRODUCT DESCRIPTION
This is the spark plug you want for high performance Gasoline or Methanol. We have seen as much as a 3/4 HP gain simply by changing to this plug.

Predator 212cc , Predator 301cc, Predator 420cc

Honda Clone 196cc, GX160, GX200
 
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#2 ·
I use the NGK you mention above. I have been changing it every two years and it works fine. I would be skeptical of the 3/4 HP gain claim with the autolike racing plug on a stock engine. There are go carters that modify the Preditor and supe them up.
 
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#3 ·
If you are using the engine for snowblower use, I would go with the NGK BPR5ES plug. The 5 is a little bit hotter and the R is resistor type, that is a very common plug that works well.
For a small engine, I wouldn't waste the extra money for a "Racing" plug, you wont notice any difference with it, except that it cost you more money and they can foul just as easy as a cheap regular plug.
 
#4 ·
I use the BPR6ES in both of my Predator powered snowblowers and they run great even at 0 F. I also use the same sparkplug in my minibikes with Predator 212cc on them. The Autolite plug reduces the volume of the combustion chamber and at most adds but 1/2 hp. It does this by adding about 3psi or so to the compression. But at $7.00 a sparkplug it doesn't make sense for a snowblower. I have a modified stage 3 Predator with a Mukuni VM22mm in my Rupp Roadster 2 resto-mod and I am using the NGK sparkplug in that engine too.
 
#11 ·
$1000 is actually a decent price for a pretty nice (1972) Rupp Roadster 2. The 1970 Rupp had 10-inch wheels and a different frame and a different fork. 1971 to 1975 were the same frame with the 12 inch spoked wheels but only the 1971 frames were painted the same color as the gas tank and fenders.
 
#10 ·
Hi guys

Thanks for the input on the plug!

That Rupp is very nice. I wanted one when I was 12 yrs old. But at the time I think they were like $199.00, I could be wrong, but my folks said it was to much money at the time.
 
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#12 · (Edited)
I do remember back in the early 70's some people near me had them licensed and rode them on the streets, suburban roads with the 35mph speed limits.
They had brake lights and head and tail lights to make them street legal, the lighting ran off the magneto. They didn't have turn signals back then, they weren't required then, just use hand signals when turning.
I don't know how stable they were at speeds on the road, but the 12 inch wheeled model was a little more stable at speeds and did the speed better.
That was back in the days when some of the smaller 80cc enduro bikes started coming out with lights and were street legal like the Yamaha GT80 and the Honda CT70.
Those were the Evel Knievel days back then.
Mickey Rupp, Mansfield, Ohio, and the snowmobiles and the little dunebuggy and three wheeler, wow, those days were fun for a kid with the toys.
 
#17 ·
You think about it, back then $300 was a lot of money for a mini-bike, but the Rupp was worth it back then, they would blow away all the other mini-bikes from other manufacturers.
The Roadster 2 had the lights and in some states could be made street legal, so it could be used as an on-off road bike, with suspension.
The Black Widow was the off road "Race Bike" mini-bike and those things were fast, a bit too fast for the in-experienced person.
 
#20 ·
Brings back memories... we never had anything that fancy; our stuff was cobbled from stuff we found in the junkyard and the cast-offs of the "big kids".

Sure was fun though, thanks for sharing. 🍻

On topic: I replace those 'Torch' plugs with NGK. So far so good.
 
#21 ·
First off, thank you everyone for the trip down memory lane with all the RUPP stuff.

Look, I've been involved with building high performance car engines. I had a company that designed fuel systems for high HP engines, 500-2000HP. We've tested EVERYTHING. I've seen oil pans vary 50HP.

3/4 HP from a spark plug, not buying it.

Clock the plug to the valve, that will matter far more than brand of plug you are using. That being said, I like the NGK product.
 
#24 ·
The first Predator engine that I ran to break in with the factory Torch plug made me quite nervous when I noticed that the hot porcelain glowed a bright pink. Looked like a Christmas light instead of a spark plug. I replaced the plug with a NGK BP6ES and it has been running normally ever since.

I see no reason to go to a hotter plug in a stock engine.
 
#25 ·
I would judge which heat range to use by how the plug looks. Take it out and look at it after 5 + hours of use. If it is black a hotter plug may make sense. Keep in mind the Preditor is designed for warm weather. It is modified for cold weather use by opening the main jet on the carb. You are running rich or lean? On my machine I run the RPM a bit higher and have a heat box over the carb. All of this makes it not so stock. Also, as mentioned by Yanmar, the gas you use has some effect on this as well. Bottom line, look at the plug after some good run time and judge it by that. I hope this is helpful.
 
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#26 ·
If anything, a so called summer engine would be running lean in cold weather so a hotter plugs seems counter-intuitive to me.
 
#29 ·
Could be a carb adjustment, but carbs aren't adjustable anymore. Keep in mind these things are jetted to run at all altitudes and loads.
So the hundreds of times that members here have stated that Predator swaps need to be rejetted to run correctly in the cold, they were wrong? :devilish:

[Just playing Devil's Advocate here.]
 
#30 ·
So the hundreds of times that members here have stated that Predator swaps need to be rejetted to run correctly in the cold, they were wrong? :devilish:

[Just playing Devil's Advocate here.]
I've had mixed feelings on it but haven't found out for my self yet. I will soon enough though.
A fairly lean (proper lean, not lean lean) running engine will often need partial choke until it gets really good and hot which takes a while.

I've wondered if those that say you need partial choke just assume that and leave it there, or if they have tried opening it fully after loading the engine down good for 10-20 minutes.

But at the same time, cars in the 1970s-80s didn't have "heat stoves" feeding the air filter with a thermostatic valve for no reason, it was to allow them to run leaner in the cold weather. So, there's that too, but there's different levels of "lean" too.

I suspect everyone here has been correct and it's a tad too lean.

For what it's worth, no fixed jet carb can be jetted to run at "all altitudes". Also, my Predator 420 even came with a different jet for higher altitudes.
 
#31 ·
To the original poster: Sorry if I dragged your thread off track.
 
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