# 212cc Predator Spark Plug Upgrade



## Ariensboy (Apr 2, 2019)

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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## Toro-8-2-4 (Dec 28, 2013)

Ariensboy said:


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



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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## ST1100A (Feb 7, 2015)

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.


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## GustoGuy (Nov 19, 2012)

ST1100A said:


> 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.


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.


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## ST1100A (Feb 7, 2015)

GustoGuy said:


> 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.


Hi Gusto. I remember those old Roadster 2's. I had the Black Widow when I was younger, those old mini-bikes were a blast back then.
The old Rupp's are worth money today if they are original.
I guess with a highly modified engine the plug would make a little bit of a difference, but not enough on a stock engine to justify the extra cost.
I normally use the BPR5ES on everything, winter and summer, a common plug for my Honda equipment. I stick with the NGK plugs, they always worked better for me.
Have to see some pictures of your Roadster some time. They were high tech in their time with the belt torque converter set-up, bigger spoked wheels, and lights on the Roadster all on the old pull-start mini-bikes.
I think they were rated at 4 H.P. back then stock, I remember all the tricked out parts you could get for the Widow, back then they may have been 5 hp with the straight pipe and Del Orto carburetor and a hotter cam.
I remember the Widow's used to blow the engines a lot from revving them so high for a flathead without the governor,but that was part of the fun of it with them, and replacement engines were not expensive back then.


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## GustoGuy (Nov 19, 2012)

ST1100A said:


> Hi Gusto. I remember those old Roadster 2's. I had the Black Widow when I was younger, those old mini-bikes were a blast back then.
> The old Rupp's are worth money today if they are original.
> I guess with a highly modified engine the plug would make a little bit of a difference, but not enough on a stock engine to justify the extra cost.
> I normally use the BPR5ES on everything, winter and summer, a common plug for my Honda equipment. I stick with the NGK plugs, they always worked better for me.
> ...


Here is a picture of my bike with the Predator. I estimate my bike to have at least 12 to 13HP with the stage 3 NR racing kit in it with 22lb valve springs and the low restriction exhaust. The BlackWidow is a highly collectible bike and with the Del Orto carburetor added about an additional 1hp to the bike performance and the HS40 were basically ungoverned with this carburetor and quite a few of them ended up blowing connecting rods especially if people wound them up while going downhill they could get the RPMs too high causing the connecting rod to fail. I have a 1971 Rupp catalog and it said right in the manual that there is no warranty with the BlackWidow. The BlackWidows were about 7 to 8mph faster than the Roadsters since the engine would rev higher being that they were ungoverned with the Del Orto carburetors. I have an ARC billet rod with forced oiling passage on the dipper and an ARC billet flywheel rated for 8000 RPMs. My bike reves to about 5700 to 5800 RPMs and I clocked it at 52 mph with my GPS app on my Samsung Galaxy S 9+ smartphone on a level section of road. I bet on a section going downhill I could get it to approach 60mph which is quite scary fast on a little bike like a Rupp Roadster 2. Other than a souped-up Predator the bike is mostly stock except for a Comet steel primary and comet steel secondary which is better TAV than the stock Rupp aluminum secondary was. I bought a 25lb bag of lead shot and ended up putting 6lbs in the frame tube right in the front of the engine and 4 extra pounds into the handlebars to tame the wheelies since it has 3 times the hp it did when stock. Here is a picture of what my bike would have looked like stock with a period-correct HS40. It is not my bike since mine was an engineless roller that I bought on Craigslist for $100 without the period-correct HS40 see picture of the red Rupp Roller.

I also attached the Rupp Catalog from 1971 too since you are a fan of Rupp mini-cycles. I could not upload the Rupp catalog for some reason. I have 3 mini bikes 1971 Arctic Cat and a Predator powered DB30 as well as my Rupp resto-mod, I also own 3 snowmobiles a boat and a personal watercraft too. I really enjoy my toys and they are fun to ride and I do most of my riding at my cabin since I have miles of low maintenance gravel roads to ride my mini bikes on.


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## ST1100A (Feb 7, 2015)

GustoGuy said:


> Here is a picture of my bike with the Predator. I estimate my bike to have at least 12 to 13HP with the stage 3 NR racing kit in it with 22lb valve springs and the low restriction exhaust. The BlackWidow is a highly collectible bike and with the Del Orto carburetor added about an additional 1hp to the bike performance and the HS40 were basically ungoverned with this carburetor and quite a few of them ended up blowing connecting rods especially if people wound them up while going downhill they could get the RPMs too high causing the connecting rod to fail. I have a 1971 Rupp catalog and it said right in the manual that there is no warranty with the BlackWidow. The BlackWidows were about 7 to 8mph faster than the Roadsters since the engine would rev higher being that they were ungoverned with the Del Orto carburetors. I have an ARC billet rod with forced oiling passage on the dipper and an ARC billet flywheel rated for 8000 RPMs. My bike reves to about 5700 to 5800 RPMs and I clocked it at 52 mph with my GPS app on my Samsung Galaxy S 9+ smartphone on a level section of road. I bet on a section going downhill I could get it to approach 60mph which is quite scary fast on a little bike like a Rupp Roadster 2. Other than a souped-up Predator the bike is mostly stock except for a Comet steel primary and comet steel secondary which is better TAV than the stock Rupp aluminum secondary was. I bought a 25lb bag of lead shot and ended up putting 6lbs in the frame tube right in the front of the engine and 4 extra pounds into the handlebars to tame the wheelies since it has 3 times the hp it did when stock. Here is a picture of what my bike would have looked like stock with a period-correct HS40. It is not my bike since mine was an engineless roller that I bought on Craigslist for $100 without the period-correct HS40 see picture of the red Rupp Roller.
> 
> I also attached the Rupp Catalog from 1971 too since you are a fan of Rupp mini-cycles. I could not upload the Rupp catalog for some reason. I have 3 mini bikes 1971 Arctic Cat and a Predator powered DB30 as well as my Rupp resto-mod, I also own 3 snowmobiles a boat and a personal watercraft too. I really enjoy my toys and they are fun to ride and I do most of my riding at my cabin since I have miles of low maintenance gravel roads to ride my mini bikes on.


NICE BIKE !!!
I miss those old Rupp's. They were fast in their day, a little bit too fast for most people.
Thank you for sharing the pictures. They bring back a lot of memories.
Back in the Evil Knevil days !!!
You are correct about the speed those things did, that was too fast for a little mini-bike, but as kids we were indestructible back then.
I remember the Widow going faster than the Yamaha 175 enduro back then on the trails we had, and to think the Rupp even had suspension, unheard of for a pull start mini-bike back then, most were the rigid frame models that were available everywhere.
They had that special custom intake manifold, made just for the Rupp mini-bike because of the engine tilt in the frame.
Those intake manifolds are hard to get. If you have the original manifold, hang on to it, they are hard to find and worth money.
I remember them wearing out the pulley sheaves and bushings on the primary and secondary clutches, the steel sheaves were a lot better than the aluminum ones, and people used to change the springs and weights to make them engage at higher speeds on some of them.


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## GustoGuy (Nov 19, 2012)

ST1100A said:


> NICE BIKE !!!
> I miss those old Rupp's. *They were fast in their day, a little bit too fast for most people.*
> Thank you for sharing the pictures. They bring back a lot of memories.


LOL As to being a little bit too fast (Stock Rupp Roadster 2's were capable of about 28-32 mph and stock Black Widows could go about 35-40 mph) this bike with about 3 times as much HP as stock is more like *"a lot too fast"*. I will not let anyone younger than 18 years old ride it since it could mess you up if you are not careful plus a helmet is not considered optional on this bike. If you were to whiskey throttle it from a stop it could literally jump out from between your legs. I take off easy and carefully throttle it up and it is plenty quick. I will be mounting a GPS powered speedometer on it too. I also have a Daymaker clone 35W high powered LED headlight which I will be getting a high capacity 12 Volt rechargeable battery to power it so I can ride it at night. It will also have brake light and rear running light on it too when I am done with it. I am a bit afraid of it and it definitely commands your undivided attention when riding it. I have yet to ride it on gravel roads since it is still at home in my garage and I took it for a short just over 1 mile ride on the paved road with my smartphone in my front jean pocket with the GPS speedometer app on and it registered a top max speed of 52 mph with an average speed 43 mph on my ride which occurred on a section of level straight road less than 1/2 mile from my house and I believe I could have easily gotten a few more mph out of it. Plus it isn't street legal either although it is possible to register a Rupp to be street legal if you have a title for it which I do not. It will be legally ridden most of the time off the highways on gravel roads at my cabin and I don't know how stable this bike will be at higher speeds on gravel roads either and I do not want to push it and end up with a bad case of road rash. On the paved road, it seemed stable and pretty easy to ride and my other Predator powered mini bike (Baja DB30) has a top speed of about 40mph which I have actually done on the gravel roads around my cabin and it is sort of questionable at that speed on gravel let alone going another 10+ mph faster which this bike is capable of.


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## legarem (Sep 9, 2017)

Hello Rupp Guys. Look at that here. It is in stock condition near my city. Stock condition.

https://www.facebook.com/marketplace/item/467241150559431/


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## Ariensboy (Apr 2, 2019)

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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## GustoGuy (Nov 19, 2012)

legarem said:


> Hello Rupp Guys. Look at that here. It is in stock condition near my city. Stock condition.
> 
> https://www.facebook.com/marketplace/item/467241150559431/


$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.


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## ST1100A (Feb 7, 2015)

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.


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## Kiss4aFrog (Nov 3, 2013)

legarem said:


> Hello Rupp Guys. Look at that here. It is in stock condition near my city. Stock condition.
> 
> Adding your location to your profile would be helpful :wink2:
> 
> .


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## legarem (Sep 9, 2017)

Kiss4aFrog said:


> Adding your location to your profile would be helpful :wink2:


Done


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## GustoGuy (Nov 19, 2012)

Ariensboy said:


> 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.


Back in 1971 Rupp Roadster 2 was $299.99 or about $1860 bucks in today's dollars adjusted for inflation. The Rupp Roadster 2 was the top of the line Mini cycle back then


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## Ariensboy (Apr 2, 2019)

See, I had the eye for quality back then at 13 years old! But now I know why I didn't t get it......$1860

You have made awesome upgrades to that Rupp Roadster 2


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## ST1100A (Feb 7, 2015)

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.


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## Toro-8-2-4 (Dec 28, 2013)

ST1100A said:


> 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.



Thanks for that feedback. Like I said I have had good results with the 6ES but it does tend to get a bit black which I attribute to a larger jet for winter use. I do have some trouble starting when the machine sits for a long period. I usually have to pull it 7 or 8 times. I just attributed that to the fact that it does not have a primer and it is cold out when I use it. Maybe the 5ES will help with that.


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## GustoGuy (Nov 19, 2012)

GustoGuy said:


> LOL As to being a little bit too fast (Stock Rupp Roadster 2's were capable of about 28-32 mph and stock Black Widows could go about 35-40 mph) this bike with about 3 times as much HP as stock is more like *"a lot too fast"*. I will not let anyone younger than 18 years old ride it since it could mess you up if you are not careful plus a helmet is not considered optional on this bike. If you were to whiskey throttle it from a stop it could literally jump out from between your legs. I take off easy and carefully throttle it up and it is plenty quick. I will be mounting a GPS powered speedometer on it too. I also have a Daymaker clone 35W high powered LED headlight which I will be getting a high capacity 12 Volt rechargeable battery to power it so I can ride it at night. It will also have brake light and rear running light on it too when I am done with it. I am a bit afraid of it and it definitely commands your undivided attention when riding it. I have yet to ride it on gravel roads since it is still at home in my garage and I took it for a short just over 1 mile ride on the paved road with my smartphone in my front jean pocket with the GPS speedometer app on and it registered a top max speed of 52 mph with an average speed 43 mph on my ride which occurred on a section of level straight road less than 1/2 mile from my house and I believe I could have easily gotten a few more mph out of it. Plus it isn't street legal either although it is possible to register a Rupp to be street legal if you have a title for it which I do not. It will be legally ridden most of the time off the highways on gravel roads at my cabin and I don't know how stable this bike will be at higher speeds on gravel roads either and I do not want to push it and end up with a bad case of road rash. On the paved road, it seemed stable and pretty easy to ride and my other Predator powered mini bike (Baja DB30) has a top speed of about 40mph which I have actually done on the gravel roads around my cabin and it is sort of questionable at that speed on gravel let alone going another 10+ mph faster which this bike is capable of.



Here is a YouTube video of me riding my Resto-mod Rupp. 









Riding my Resto-mod Rupp 😎







youtube.com


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## Yanmar Ronin (Jan 31, 2015)

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.


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## jsup (Nov 19, 2017)

Ariensboy said:


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


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.


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## jsup (Nov 19, 2017)

Toro-8-2-4 said:


> Thanks for that feedback. Like I said I have had good results with the 6ES but it does tend to get a bit black which I attribute to a larger jet for winter use. I do have some trouble starting when the machine sits for a long period. I usually have to pull it 7 or 8 times. I just attributed that to the fact that it does not have a primer and it is cold out when I use it. Maybe the 5ES will help with that.


The 5 is a hotter plug than a 6, just for people who don't know. The 5 should do it..


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## Yanmar Ronin (Jan 31, 2015)

Depending on the fuel you run I conditionally agree... I have switched to a warmer plug on occasion with good results. You can always go back.


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## deezlfan (Nov 8, 2017)

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.


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## Toro-8-2-4 (Dec 28, 2013)

deezlfan said:


> 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.


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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## deezlfan (Nov 8, 2017)

If anything, a so called summer engine would be running lean in cold weather so a hotter plugs seems counter-intuitive to me.


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## jsup (Nov 19, 2017)

deezlfan said:


> If anything, a so called summer engine would be running lean in cold weather so a hotter plugs seems counter-intuitive to me.


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.


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## orangputeh (Nov 24, 2016)

5


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## deezlfan (Nov 8, 2017)

> 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? 

[Just playing Devil's Advocate here.]


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## ChrisJ (Nov 27, 2014)

deezlfan said:


> 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?
> 
> [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.


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## deezlfan (Nov 8, 2017)

To the original poster: Sorry if I dragged your thread off track.


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## GustoGuy (Nov 19, 2012)

jsup said:


> 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.


The jets are easily replaceable and available since they are the same sized jets used in the Honda small engines. As to high altitude beyond 10,000 feet is were a carburetor starts to run rich. A slightly smaller jet will help the engine run better. Likewise in the winter a slightly larger jet will richen the fuel air mixture and help to prevent lean surging.


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