Racing Cam and X-tra Big Bore Carb from AGK install

Tahq said:
If testing goes well is this a product that may be available in the near future? Sounds like it might be a better option for me then the current larger bore carb. I would hate to buy the current carb just to have the improved version offered two weeks later.

AGK seems to be on the ball with the new 4 stroke offerings.
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We will know very soon......just the fact that this has a larger bore than the current one they offer and it is a direct bolt-on with no additional or fabricated linkage needed for the throttle, I would personally wait for the new as I'm sure it's gonna work well ;)

dnut
 
Mac said:
Sign on to follow thread. Scotto- are you using the honda cam AGK sells or is there a new product I haven't seen yet for the HS??

R/Mac
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Sorry I missed this post before Mac.......yes, it's the honda cam AGK sells.

dnut
 
Thanks scotto,
So what are your results with the bored out carb and cam??? worth the investment or just go 99cc?? I love your builds, very clean and accurate... keeps me motor...vated!!

Mac
 
Now it's finally time to test the Keihin big-bore carb offered by AGK. I just got it installed and made a throttle linkage from the governor/throttle assembly that came off of my HF 212cc Predator. Some pics of the linkage installed:

idle position


full throttle position




Took it for a short ride last night and it goes pretty well but I need to play with the jetting today and some other adjustments.

dnut
 
Mac said:
Thanks scotto,
So what are your results with the bored out carb and cam??? worth the investment or just go 99cc?? I love your builds, very clean and accurate... keeps me motor...vated!!

Mac
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I find with the bored carb and cam, better pull through the rpm range and shines more on the top-end than the bottom. It's got stronger pull when your over 5,000rpm and let off on the throttle, and then get back on it. It also gets you a couple more mph over the stock set-up.

This is all well and fine if you are limited to owning a 50cc for legality or race class purposes......but from my perspective if that were not an issue, I would opt for the 99cc if it's really some uummft you're looking for. As it is said, "there is no replacement for dissplacement". For the cost of a big bore carb and cam, you can almost buy a 99cc Predator engine that will perform as well stock as a full blown 49cc race machine in general.

But if ya wanna have the fastest and baddest 49cc 4-stroke around, and you wanna keep it street legal (in most states), every little hop-up part and trick you can do is needed. Keep on motor.....vating!

scotto-
dnut
 
Had a good ride today and determined the jetting needs to be larger than the stock #60 jet that came with the carb. Although the engine was running rather lean, the performance was really good and the throttle linkage worked flawlessly. Here's a vid of the test ride: http://youtu.be/E49nr5W_eiU & http://youtu.be/sdjGXc6E90o
More results tomorrow after enlarging the main jet.....

dnut
 
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Here is where I am today. The stock jet with this big bore carb is a #60 which is .024". I enlarged the jet to .026" and it was much too rich no matter what. The engine ran much better lean so I had to step back to .025" and that seems to be just right. I also removed the limiter cap on the air/fuel mixture screw and it really works on the carb compared to the cheap chinese knock-off carbs.

It's running great right now so I'll be putting some more miles on it and doing mild tweaks as well.

dnut
 
So then it does not direct bolt on with the HS standard linkage throttle, bugger. Still sounds like fun...to mod or not to mod hmm.
 
Tahq said:
So then it does not direct bolt on with the HS standard linkage throttle, bugger. Still sounds like fun...to mod or not to mod hmm.
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The extra large bore (the bored stock carb) that I first tested is a direct bolt on. The current large bore that's available from AGK now (that I just installed) is not.

I'm still trying to determine which one performs better......stay tuned.

dnut
 
Staying tuned and pulling for the direct bolt...though I may soon have a HF 99cc predator taking up a little space in the garage looking for a home, why settle for just one!
 
OK scotto...
Your right, no substitute for cubic inches... I ordered a HF99 yesterday. Not to say I'm done with the HS49.. Crazy as it seems, I plan on dis-assembling the HS, determining TDC head space and valve clearance etc and welding some material(aluminum) on to the piston for increased compression. I'll get into balance later but I have a quart of zinc chromate putty that will work perfect for a before/after mold of combustion chamber shape and volume. I don't expect spectacular results, heck what do I have to loose?? I'll video the first start up(with sound)LOL!!

One question, do you make your own mounting plates or buy 'em ??

R/Mac
 
Mac said:
OK scotto...
Your right, no substitute for cubic inches... I ordered a HF99 yesterday. Not to say I'm done with the HS49.. Crazy as it seems, I plan on dis-assembling the HS, determining TDC head space and valve clearance etc and welding some material(aluminum) on to the piston for increased compression. I'll get into balance later but I have a quart of zinc chromate putty that will work perfect for a before/after mold of combustion chamber shape and volume. I don't expect spectacular results, heck what do I have to loose?? I'll video the first start up(with sound)LOL!!

One question, do you make your own mounting plates or buy 'em ??

R/Mac
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I make and buy them, depends on the application. It is alot easier buying them, just not as cheap as you can make them. The mounts on my current personal builds were bought.

dnut
 
Here's a little update.......I've gone back to the x-tra big bore carb that AGK modified from the stock version. Very comperable in top-end performance, I now find the modified proto-type to be the one that I personally favor. The main reasons are the ease of installation and it's much easier to dial-in than the big Honda Keihin. Overall performance of both is about equal, but the modified shines!

.wee.
 
Hey Scotto-

Thanks for all the great info on this upgrade. I have the Keihin with AGK's throttle linkage (very nice stainless piece). Still building so I haven't fired it up yet. If I am not going with the cam do you think the jetting out of the box will be ok?
 
cdavid67 said:
Hey Scotto-

Thanks for all the great info on this upgrade. I have the Keihin with AGK's throttle linkage (very nice stainless piece). Still building so I haven't fired it up yet. If I am not going with the cam do you think the jetting out of the box will be ok?
Click to expand...

It should be, but you won't know for sure till you fire it up and ride it some.

dnut
 
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