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Krannie McKranface

Rev boxes: do they help top end?

10 posts in this topic

Looking to gain a bit on top that was lost by the Edlebrock. Does anyone have experience with any brand/model, and do you reccomend?

Thanks

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In your situation I really doubt it will help at all. Extra RPMs will only help if the intake, exhaust , and cam are setup to allow for higher revs. You are already down on torque at the top end. It's just going to extend a little more in revs, but not help at all on torque. You have to remember that extra RPMs mean extra wear. It's not dramatic like an extra 750 RPM will wear it out in 50 hours, but it is an exponential increase in wear. At some point catastrophic damage occurs when valve meets piston from valve float.

Why do the Edlebrock's lose top end anyway. Is it an airflow limitation or a fuel mixture problem at max flow?

You might want to sell that carb and replace it with a unit more oriented to high end power. Check out the FCR vs. Edlebrock thread http://www.thumpertalk.com/forum/showthread.php?t=581146

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In your situation I really doubt it will help at all.

You might want to sell that carb and replace it with a unit more oriented to high end power. Check out the FCR vs. Edlebrock thread http://www.thumpertalk.com/forum/showthread.php?t=581146

Yeah, I've followed that thread. I am not willing to give up the easy starting and non-flood-a-bility of the Edle. I just want the XR to have the top end pull it had with the stock carb, if possible, using the Edle.

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What bike do you have? What mod's do you have? I'll assume it is a XR650R for now. Are you still running the stock exhaust header, air filter? How many clicks out from full rich and what needle number are you running? Boring the edelbrock will give you more top end then the stock carb. could give you, But, to use it you will have to have a freeflowing exhaust. If you are still running stock exhaust header I would say it isn't tuned to pull top rpm's. Edelbrock carb. is more then enough to feed a stock uncorked bike to 100mph and 45rwhp @ 6800, 40~42rwhp @ 8200rpm with a freeflowing exhaust, Uni air filter, valves adjusted right but, the stock will do better with the same setup. The problem is if you set the needle to run right up top you get a dip around 2500~3200rpm on the edelbrock. I am not the only one that runs a bored Edelbrock on the BRP. Barnum, Jay lewis, I think David Gray, it is a nice upgrade. The needle jet, pump squirter jet, slide come out and you bore it out. Edelbrock doesn't have to do it others can. Simple tools to remove every thing to bore it. Needle nose pliers, screw driver, stuff like that. I have two that were bored while I watch at Edelbrock in San Jacinto.

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What bike do you have? What mod's do you have? I'll assume it is a XR650R for now. Are you still running the stock exhaust header, air filter? How many clicks out from full rich and what needle number are you running? Boring the edelbrock will give you more top end then the stock carb. could give you, But, to use it you will have to have a freeflowing exhaust. If you are still running stock exhaust header I would say it isn't tuned to pull top rpm's. Edelbrock carb. is more then enough to feed a stock uncorked bike to 100mph and 45rwhp @ 6800, 40~42rwhp @ 8200rpm with a freeflowing exhaust, Uni air filter, valves adjusted right but, the stock will do better with the same setup. The problem is if you set the needle to run right up top you get a dip around 2500~3200rpm on the edelbrock. I am not the only one that runs a bored Edelbrock on the BRP. Barnum, Jay lewis, I think David Gray, it is a nice upgrade. The needle jet, pump squirter jet, slide come out and you bore it out. Edelbrock doesn't have to do it others can. Simple tools to remove every thing to bore it. Needle nose pliers, screw driver, stuff like that. I have two that were bored while I watch at Edelbrock in San Jacinto.

'01 XR650R:

- Edle #19e 20 clicks

- Uni with opened side panel

- stock header

- FMF Core 4 slip-on

I am thinking of adding the FMF 'free-flow' header.

I clicked the Edle three more clicks out today, and got much more top end, and eliminated the 'decel pop' at the same time. Now I don't feel 'strangled' above the midrange.

Also: the fuel hose is important. I had a piece of 1/4" ID hose running to the edlebrock, and after changing to 5/16 it seems much better running, and no more 'balking' at full honk of the throttle.

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Another question: What do you mean by "balking"? I´m from Sweden and my English sucks every now and then.

/ Christer

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Another question: What do you mean by "balking"? I´m from Sweden and my English sucks every now and then.

/ Christer

From dictionary.com:

2. "something immaterial that interferes with or delays action or progress"

In other words, a momentary stall, or interuption in power.

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i would say you wont really gain anything noticeable with a rev box, put one on a 400ex and i couldnt tell crap $50 waste

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