Hyper .21 Carb Upgrade (O.S. Carb 20e)

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RobH

Gone - bye bye.
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I wish I had a pic of my Hyper .21 8-Port Race with the O.S. 20e carb on it, but I don't. You’ll just have to use your IMAAAGINAAAATION.

The Hyper .21 engines are known for a lot of power for not a lot of green. The downside to the Hyper .21 series is the difficulty so many people have with tuning these engines. I read a rumor on the OFNA boards that the OS 20e carb is a direct fit on the Hyper .21.

I run a Hyper .21 8-Port Race in my 1/8 buggy. I purchased an OS 20e carb from a guy locally. The other night, I tested the rumor about the 20e carb. It fits like a dream! I didn’t get an o-ring with my used carb, but borrowing the o-ring from the stock carb was not a problem. Two nights ago, I re-tuned my engine for the new carb. Wow, does the new carb make a difference! Even with my rough, novice tuning skills, I had it dialed in no time. It has better bottom end now, but I think that was a tuning error on my part with the old carb.

If all of the Hyper .21 engines have the same stock carb and hence the same diameter “carb hole” in the crankcase, anyone that has a Hyper .21 can use the OS 20e carb. I can not verify that, but my gut tells me this is more than likely the case. Take that advice anyway you like.

A few things to remember before you slap the 20e on your Hyper .21:

Make sure you have an o-ring to seal the carb to the engine. If you don’t, do like I did and borrow the o-ring from the stock carb. You can also use a carb sealer. I have this stuff called “Air Seal” which will seal the carb too. I didn’t use it, but it doesn’t seem I have any air leaks anyway (not over heating or anything).

YOU MUST RE-TUNE YOUR ENGINE. (duh?)

VERY IMPORTANT: Your old carb settings (5-6 turns out for break in, blah blah blah) no longer apply. In order to use your new carb properly, you must download, and read the manual for O.S. max-21RG engine:

http://www.osengines.com/manuals/21rg-manual.pdf

20e Carb Settings Summary:

Base-Line HSN Setting: 3 turns counter clockwise from lightly seated
Base-Line LSN Setting: 1 turn clockwise from flush with the carb housing
(This is a two-needle carb and the LSN adjustment is now where the old mid range needle was on the Hyper .21’s carb. It’s also called “Mixture Control Value”, but same difference.)

You really should read the manual for the full details. It gives some top-notch tuning advice, which helped out this newbie tuner a lot.

How much is this going to run me, you ask? Well, if you buy a new OS 20e, you’re looking at $70. That sucks when it’s a bargain engine to begin with. You can get them on ebay from time to time for $30. Also, the guy I bought my 20e from said he has a couple more he could sell. I think you’d be less than $30 after shipping. Send me a PM if you’d like me to hook you up with his email.

-Rob
 
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Good info Rob:clap: The was very well written and comprehensive. You defintely need to change your name if you are going to start posting awesome threads like this!
 
Originally posted by humboldtblazer
Good info Rob:clap: The was very well written and comprehensive. You defintely need to change your name if you are going to start posting awesome threads like this!

Thank you, Sir. I was kind of leary about buying the 20e if it didn't work. I figured I'd share my success with the other guys on the board that have this engine. It's a great hopup, if you can get one cheap.

I could measure the neck on my old carb for others to compare with, but I don't have calipers. :(
 
I need to buy a caliper also. I think thats when you know your really getting into it is when you need a caliper.
 
Good info. I found that my OS20E doesn't fit the hpi stock 21BB (bummer) but will try it when I can afford to buy a Hyper 8 port for my Savage MT. The O.S. carbs have always been know for their easy tunning qualities. I slapped an OS 10E on my HPI NRS4-3 SS before I ever even tried to start it. Beakin and tuning was simple (as that stuff goes). I've always had good results with the OS carbs as compaired to other manufacture's carbs that I have tried to tune. HPI has a midrange needle and tells you it is not recommended to change it, so why did they even out it there? Good question, I don't know. I do know I'm having all kinds of problems with my 21BB and stock carb.
 
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