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a.k.a Mark
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85 Posts
Discussion Starter · #1 ·
Is anyone using Zipper's Oversize throttle body? Does it work well on a stock engine with simple mods like ..topless, pipes, PCIII or R/T?
 

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Premium Member
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1,777 Posts
Unless you at least port the heads & possibly chg your cams, I am not sure how much you will gain with the larger throttle body accept a drop in gas mileage.

I am quiet sure the more knowledgable will chime in soon (Rick N., Kaz, Max, UPSMan ...)
 

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a.k.a Mark
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85 Posts
Discussion Starter · #3 ·
Zipper's website says it provides excellent results in stock OR modified engines. The throttle body is increased from 53mm to 58mm.
 

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Premium Member
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I guess my question would be how much improved HP could you expect to get? I dont doubt that it improves HP but by how much being that your heads and cams are stock. Would they be fully utilizing the extra airflow and my guess is, they wouldnt.

But you can always try they them, I am sure others on here would like to know the same answer you are looking for. IN any case it is a step forward to future power upgrades that you would have done.
 

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FASTESTSTKBLTDRV
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1,267 Posts
rmmccon said:
Zipper's website says it provides excellent results in stock OR modified engines. The throttle body is increased from 53mm to 58mm.
INTERESTING QUESTION,I'AM SURE IT HELPS AT THE TOP OF THE RPM BAND.
I'LL HAVE TO BOLT MINE ON A STOCKER WHILE IT'S APART AND POST THE
RESULTS.
 

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Greg/Moderator
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18,951 Posts
Rick.... I curious to see what you come up with, maybe a better flowing exhaust system with the larger TB and some dyno time would help.
 

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Caretaker for BADROD
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293 Posts
Rick,
Don't waste your time changing throttle body on stock displacment motor. No gain. We also used ported heads with 40/34 mm valves on stock dis. with diff. cam timing on stock cams and still no real gain. I think that the stock T.B. is large enough it stock RPM. I have tested a modified engine that was still stock Dis. but turning it way past the normal RPM in that case the bigger T.B. made a big difference.
 

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1,493 Posts
Paul:

I missed you at the Breathless tent during Biketoberfest.

In any event I had 2 questions:

WITH A Weisco BIG BORE kit, 58MM INJECTORS, VELOCITY STACKS, ZIPPERS CAMS AND A SPRING AND RETAINER KIT;

1. What would the incremental HP AN TORQUE difference be if CNC heads were added (I cleaned mine up some and left the valves stock)?

2. What is your recommended street pipe configuration?

3. Is the incremental change worth the expense in your opinion?

My goal is a streetable motor that runs well.

Regards.
 

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Loud and Proud
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628 Posts
Paul Diener said:
Rick,
Don't waste your time changing throttle body on stock displacment motor. No gain. We also used ported heads with 40/34 mm valves on stock dis. with diff. cam timing on stock cams and still no real gain. I think that the stock T.B. is large enough it stock RPM. I have tested a modified engine that was still stock Dis. but turning it way past the normal RPM in that case the bigger T.B. made a big difference.
It all comes down to what is the weakest link. How about just changing the CAMS on a stock motor? Any gains?
 

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Wild Bill said:
It all comes down to what the is the weakest link. How about just changing the CAMS on a stock motor? Any gains?

That was the first thing I did to mine way back when. I believe I saw about about 4-7hp along with going topless then. Was it worth the $$ figure $600 + labor = $1k approx..... waiting and doing at least head porting at same time will probably result in better bang for the buck.
 

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Loud and Proud
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brent_walkoviak said:
That was the first thing I did to mine way back when. I believe I saw about about 4-7hp along with going topless then. Was it worth the $$ figure $600 + labor = $1k approx..... waiting and doing at least head porting at same time will probably result in better bang for the buck.
By the time you do all that, you might as well do the big bore kit.
 

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626 Posts
Am I wrong or would the way to tell if you need Oversized throttlebodies is to have the bike tuned. If the bike is still running lean, then larger throttlebodies would help.

If the bike is mapped good with the 53mm throttlebodies, why change them?

Or am I missing something?

Mine is still running slightly lean with the SE 1250 Kit. Megacycle Cams and 58mm TB's will be my next upgrade.
 
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