jetting after air box modifications


17 replies to this topic
  • Roll_it_on

Posted March 10, 2004 - 08:22 PM

#1

After reading all the stuff about modifying the air box cover to allow more air I have decided to give it a go. I was wondering what main jet size to go with as a starter? I am currently running the 175 main, 68s pilot, HRC tip, uni filter, 500 to 3,000 feet elevation riding area, 50 to 85 degrees temp. I originaly thought about a 172 based on the info above before doing the modifications after looking at the jetting charts but I decided to go with the 175 to be on the safe side. Any of you guys done this and just how much richer do I need to go after doing the side plate modification or will the 175 perhaps be OK since I may be a bit rich now as it is :)

  • jws

Posted March 11, 2004 - 02:48 AM

#2

i run a 175 main and a 68s with my airbox opened up - before i did the airbox mod i played around with 172 and 175 - after i did it i went to a 178 main but i think it runs the best with a 175 :) and the plug looks good :D
i ride 0 to 4000ft


jeff :D

  • Rokatt88

Posted March 11, 2004 - 06:47 AM

#3

Ok, you beat me to the post! I was thinking of posting the same questions. What I want to know is if anyone has had any issues with the stock carb and the opened air box? I know that the guys with the Edelbrocks can ride from the bottom of the Abyss to the top of Mt. Everest upside down and not have any problems or burps. What I don't want to have happen is to have carb/jetting issues. I'm having too much fun RIDING! :)

  • qadsan

Posted March 11, 2004 - 08:52 AM

#4

I'm having too much fun RIDING!



I think it was Dave in another thread who said to try out someone elses side cover first, which is excellent advice because you will have to spend time fiddeling with your bike to get minimize the off idle hesitation once the holes are cut, but it's worth it in my opinion.

OK, here's an idea to ponder...:D

XR650R new price = $6,000
XR650R = 44HP
$6,000 / 44 HP = $136.36/HP

Edelbrock + side cover = $400
Edelbrock + side cover = ~4+HP
$400 / 4+HP = $100/HP

XR650R + Edelbrock + side cover = ~48+HP :D

More importantly, XR650R + Edelbrock + side cover = more power throughout the cruve, no more off idle hesitation, simple tuning, one kick starting when you dump the bike and you can ride upside down on Mount Everest :)

  • Rokatt88

Posted March 11, 2004 - 10:40 AM

#5


XR650R + Edelbrock + side cover = ~48+HP :D

More importantly, XR650R + Edelbrock + side cover = more power throughout the cruve, no more off idle hesitation, simple tuning, one kick starting when you dump the bike and you can ride upside down on Mount Everest :D



:busted:FOUR MORE HORSEPOWER??? :D

That DOES change things!!! :D

To be honest, all I have ever heard about the benefits of the Edelbrock are the starting (never been an issue for me), Drooling (I drool too so we're in good company), Tune-ability (you can tune a piano but you can't tuna fish), but a 4 HP increase??? Jumpin' Jehosafats; Yeeha! Might just have to give 'ol Mr. Barnum a call after all! :)

  • Roll_it_on

Posted March 11, 2004 - 11:00 AM

#6

Well my birthday is coming up so perhaps the wife will take pitty on me and get me what I really want (pumper carb) :) and not what she thinks I need :D

Jeff ...Did you notice a difference after the mod with given your setup?

  • Rokatt88

Posted March 11, 2004 - 02:59 PM

#7

Man, this is getting interesting. Went to the source and talked with Mr Barnum. What a great guy. Very cool and a wealth of knowledge. He explained what I needed to know and now I am looking at getting the Edelbrock. Appears to be one of those Bang for the Bucks that will really pay off. Hmmmm. Kids, you don't need new shoes and clothes right? :)

I'm so Bad! :D

  • jws

Posted March 11, 2004 - 03:03 PM

#8

Jeff ...Did you notice a difference after the mod with given your setup?


yes - but i also got rid of the baja designs quiet baffle i was running at the same time :)

i think i need to call rob :D


jeff :D

  • mmxr650r

Posted March 11, 2004 - 07:12 PM

#9

All,
I did the airbox cuts (like Team Honda - Campbell, Hengeveld) and ran the #185 main, as recommended by Honda (http://www.4strokes....h/honda/airbox/)...Quick snap to throttle would result in bogging, so I scaled back to a #180 main, and am very pleased now.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • irondude

Posted March 11, 2004 - 10:52 PM

#10

scale back to a 175 main, and it'll hit even better, plus be easier to start...and then write Honda and tell them how stupid they are...185 main jet? smokin more crack....

I have done a lot of testing with the Edelbrock-and for sure it is a fantastic addition to the BRP-all the new four banger Hondas come with pumper carbs...whats that tell ya?!but i have also done my homework with the re-jetted Keihin-and i take it to the races as a backup-in fact i have raced some major races with the Keihin; Always with the cut out airbox. Both with and without the stock cam, both with and without stock header and pipe, both with and without various other engine mods---the cut out airbox cover is ALWAYS a good fix. The ONLY major issue i have come up with is if you crash into very thick talc like powder--the talc will get sucked right thru that cut out and completely cover the airfiter--chocking the motor off instantly. In fact several bikes DNFed the Vegas to Reno just from that situation! I carry an extra airfilter in my backpack for just such scenarios when racing in alkali Nevada or some sections in Baja!
ps-after testing numerous filters--the No Toil filter is the best one...

SO feel good about cutting out the side cover. Some guys just drill a series of holes, others cut out two triangles and epoxy some screen over it. Cambell has experimented with some much larger cut outs--nearly the entire area over the filter-but Team Honda has gone back to the two triangles...Rob has the cut out kits for sale, or there are diy articles on the other BRP sites. Its a great, safe, easy upgrade that will be very noticable everywhere on the RPM range...

  • jws

Posted March 12, 2004 - 02:52 AM

#11




XR650R + Edelbrock + side cover = ~48+HP :D

More importantly, XR650R + Edelbrock + side cover = more power throughout the cruve, no more off idle hesitation, simple tuning, one kick starting when you dump the bike and you can ride upside down on Mount Everest :D






done deal - i called rob barnum last night :) new carb, dampner, tripple clamp and bars are on the way :D


jeff :D

  • motart

Posted March 12, 2004 - 03:45 AM

#12

is anyone running the mikuni and airbox mod combo? curious of their jetting

  • J_T

Posted March 12, 2004 - 07:37 AM

#13

done deal - i called rob barnum last night new carb, dampner, tripple clamp and bars are on the way




Wow if your on a spending spree I could use some triple clamps, Stabilizer, Tires, and a Suspension reworking!! :)

Oh yea! I'd love to try one of the SRCinc.net hydraulic Clutch pulls as well!!

Anyone else have any orders to place? :D

  • Rokatt88

Posted March 12, 2004 - 10:48 AM

#14




XR650R + Edelbrock + side cover = ~48+HP :usa:

More importantly, XR650R + Edelbrock + side cover = more power throughout the cruve, no more off idle hesitation, simple tuning, one kick starting when you dump the bike and you can ride upside down on Mount Everest :D






done deal - i called rob barnum last night :) new carb, dampner, tripple clamp and bars are on the way :D


jeff :D










Rob is having a good week! Just ordered 3 Edelbrocks for me and 2 other riding budz.

Yah...diss ess Hans uhnt Franz uhnt Deiter...We're heeya to Pomp Chew Up! You can ride chor leetle girly bikes. We will crush dem and make you cry like a leetle gurl :D

  • BWB63

Posted March 13, 2004 - 09:13 AM

#15

I am running the TM40, Uni air filter, Holes in the air filter cover, no back fire screen, XR Only's header, WB R4, and have a 140 main, 27.5 pilot, 1.2 air jet, Y-4 needle jet, 4th pos. on the 90IJ-1 needle, Stock Carburetor was--185main, 70s pilot, power-up needle 4th pos. If you have a header, and free flowing muffler, Uni, holes in the cover, you do need a 185 main! 178~180 main if you have stock header and free flowing muffler (R4, Open 'E' series, T4). 175~178 if you have the stock muffler with HRC Tip.

  • XRMANU

Posted March 15, 2004 - 10:56 AM

#16

is anyone running the mikuni and airbox mod combo? curious of their jetting


look here: http://www.visordown...threadid=120741

http://www.endurofre...onda/mikuni.htm :)

  • tirebiter

Posted April 01, 2004 - 11:41 AM

#17

Roll_it_on, Are you the guy I met last sunday up at Cow Mountain? I was wearing a red aloha shirt. If that was you, nice to meet ya! Dan

  • Roll_it_on

Posted April 01, 2004 - 04:02 PM

#18

Dan,

Yes that was me. Small world sometimes. What a nice day to be up there last Sunday. Nice to meet ya :)

Jack





Related Content

 
x

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.