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XR650R Holes in airfilter cover

By Tom81,
in XR600R & XR650R/L

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Grand Master

qadsan

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Dyno charts for this mod have been posted on this and other forums in the past quite a ways back. Whether they still exist on this or other forums anymore after all this time I don't know, but facts are facts and you can easily prove this yourself for very little money. If you're lucky, maybe somebody still has a before / after dyno chart that they can post.

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Grand Master

qadsan

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That's what I thought. I wonder why Precision Concepts would tell me that it was a waste with a stock motor, I was all set to buy a modified side panel from them. I did think it was pretty cool of them not to just take my money.

I wonder why they'd tell you that too, especially when the proof is with the dyno. Nobody here owes you any proof. You can take advice and run with it and prove it to yourself like some people do with a simple dyno session or believe everything your told as fact.

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Grand Master

BWB63

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It only works if you jet for it. It is also better if you let more flow out of the engine system to make it work better. More air in you need more fuel = more power. You are just taking the uncork idea to the next level. You knock out the air box restricter for more air, you are just allowing more air directly to the air filter.

http://www.borynack.com/Bruce/XR650R/dynocharts.htm

http://www.borynack.com/Bruce/XR650R/HorsePowerMods.htm

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Grand Master

qadsan

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Hey, this is all fun for me so I don't have to take anything and run with it OK? Just interesting that the shop that builds the bikes that kick everyones ass would say that. You probably know more than them.

I don't have to know more than PC to know it works when I've seen the dyno testing first hand. It costs ~$5 for the #30 stainless screen and most people have the tools to do the simple cutout themselves as opposed to spending $100+ for a modified side panel.

If more people cut the courses like team Honda did in previous races, they may not have had as many wins. If team Kawi would have been in the Baja picture these last many years after Danny Hamel was killed, then team Honda would probably not have had as many wins. The 650R is a good bike and PC is a good shop, but it's not just the bike or PC that's kicking everyones ass.

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Proficient

oldturtle

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I was told by Precision Concepts that the airbox mod does not make any difference on a motor with the stock cam. Anybody with some imput on this?

Yes, I was told the same thing by owner of Berkeley Honda and regular Baja racer Scott Dunlevy. Both the airbox cover mod and larger header pipes will have very little benefit unless internal motor mods go along at same time. These mods will have benefit over entire powerband when go along with correct motor mods. But by themself these mods will loose substantially from low to mid that they are not worthwhile. Many will continue to do a full exhaust and air box cover holes/screen just for the way cool effect that actually does about as much good as race gas in stock engine.

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Grand Master

BWB63

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The whole air box on the XR650R has small issues. Some use a batwing to help also. It isn't about PC and what they run on Jimmy's bike. We are talking about allowing more air into the bike so, some that more fuel can be mixed with it. Fact: running no side cover, no air filter, a better flowing exhaust, then jetting for it will make more Horsepower. That is a fact but, that does not make it a good idea. Running no air filter, with no side cover and jetting for it is 2 peak horsepower gain. I have done it on the dyno on a built motor. Holes in the side cover on a stock bike is not going to make .25 peak hp difference but, it will allow the peak horsepower to last longer up the RPM curve. So, on a stock bike (uncorked) there is little difference to none for the average rider.

This is where holes in the air box help the most when added with other fuel and exhaust mod's. Lets say I add a header/muffler setup (XR's only header/R4 muffler) and Mikuni pumper carburetor. Each is good for about 1+hp on there own. I added 2hp....not much for the money. Adding holes in the air filter cover, a UNI and jetted air filter I get another full horse maybe a tad more. So, carb, header/muffler I get maybe 2.5hp and the Uni, and holes I get about 4hp. You are right holes alone does little for the average rider but, it does allot if you are looking for that little bit more in the higher RPM's.

Bringing me to a point that most over look when looking at Horsepower numbers. Peak horsepower is not the whole story! Adding a header/muffler setup may only give you 2~3 peak horsepower but, at 6,800rpm it gives you a seven horsepower gain over stock and holds that gain to 8,200rpm. Sometimes it's not how much peak horsepower but, how much you get, where.

Team Honda does not win over everyone or all the time. Baja is going to be a lot tougher to win now that cheating is being slowed down.

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Experienced

Supplicate

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The whole air box on the XR650R has small issues. Some use a batwing to help also. It isn't about PC and what they run on Jimmy's bike. We are talking about allowing more air into the bike so, some that more fuel can be mixed with it. Fact: running no side cover, no air filter, a better flowing exhaust, then jetting for it will make more Horsepower. That is a fact but, that does not make it a good idea. Running no air filter, with no side cover and jetting for it is 2 peak horsepower gain. I have done it on the dyno on a built motor. Holes in the side cover on a stock bike is not going to make .25 peak hp difference but, it will allow the peak horsepower to last longer up the RPM curve. So, on a stock bike (uncorked) there is little difference to none for the average rider.

This is where holes in the air box help the most when added with other fuel and exhaust mod's. Lets say I add a header/muffler setup (XR's only header/R4 muffler) and Mikuni pumper carburetor. Each is good for about 1+hp on there own. I added 2hp....not much for the money. Adding holes in the air filter cover, a UNI and jetted air filter I get another full horse maybe a tad more. So, carb, header/muffler I get maybe 2.5hp and the Uni, and holes I get about 4hp. You are right holes alone does little for the average rider but, it does allot if you are looking for that little bit more in the higher RPM's.

Bringing me to a point that most over look when looking at Horsepower numbers. Peak horsepower is not the whole story! Adding a header/muffler setup may only give you 2~3 peak horsepower but, at 6,800rpm it gives you a seven horsepower gain over stock and holds that gain to 8,200rpm. Sometimes it's not how much peak horsepower but, how much you get, where.

Team Honda does not win over everyone or all the time. Baja is going to be a lot tougher to win now that cheating is being slowed down.

:banghead::banghead:

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Enthusiast

Tom81

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Now I'm a little confused.

My pig is stock uncorked with a WB E2 exhaust, W/O spark arrestor. 68s, 175 jets. and b53e needle in 3rd groove. I know it is running a bit rich, so I was thinking that the airbox mod would do the trick.

It must be running rich when I can start without choke almost all the time, right??

Do I have to buy bigger header and pumper carb to gain anything from this mod or....???

thanks... :-)

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