Too Rich?

6 replies to this topic
  • redmanrandyed

Posted September 25, 2003 - 10:56 AM


My BRP boggs down really badly at higher elevations. :D I have recently uncorked it. I was running a 172 Main, changed it to a 170 Main and did not notice any difference. I then changed the Main to a 165. There is still no difference pertaining to the bogg factor.
Up to 1/4 throttle it runs great. I can tractor up any hill, but when I open it up, 1/4 throttle on, it boggs down like it is getting drowned with fuel. At 4500' in elevation the bike runs great and the plug looks beautiful. It is only when the bike is ridden at 6500' plus that it boggs down.
I am thinking about changing the clip on the needle to lean it out some but wanted to ask you guys first. I am currently running the upgrade (power up) needle with clip in 3rd position. Should I change that or continue to lessen the Main jet? Is there anything else that could be causing the frustrating bogg? It sounds like it is running under water. :)
Any suggestons would be greatly appreciated.

Thanks in advance :D

  • J_T

Posted September 25, 2003 - 12:31 PM


Now I am fuzzy on this because since I bought the Edelbrock I haven't had to worry with jets. But I'd Try lowering the needle position a notch before you keep lowering the main jets or it may be a combination of the both. I Thought this is how it worked out; Pilot jet = idle, Slide is 1/8-1/4 throttle, needle size/position is 1/4-3/4 throttle, and Main jet is Wide Open Throttle (WOT). And trouble in these particular areas tells you where you need to look to adjust. Now please correct me if I'm wrong b/c like I said I'm fuzzy on this. So I'd lower the needle a notch and you may find that you didn't need to decrease the main jet as much but I'm not sure what jet works best at what altitude. But since I try to do the things that don't cost me first that is my first suggestion. I have run across many post of where people ask comments of particular jet sizes at certain altitudes so you may be able to find something more specific and I'm sure you will get more suggestions from here! I hope you get it figured out soon b/c it suxs to be riding an ill-running Pig!


PS one more thing b/c it'd be something I'd forget to check would be make sure the air filter is clean!

  • qadsan

Posted September 25, 2003 - 01:25 PM


Hopefully someone here rides at the same elevation & temperatures you're planning to, but here's where I'd start as a general starting point to work from if I had nothing else to go by. The following starting point assumes a stock uncorked bike for about 6,000 ft altitude and +70F temps. The higher you go in altitude, the leaner your jetting will need to be for optimum performance. If the temps are +20F colder than +70F, then I'd try the next step up toward richer jetting for the pilot and main jets than what I listed. If the temps will be +20F warmer, then I'd try the next step down for a slightly leaner jetting than listed for just the pilot and main jets. You could probably leave the needle alone a the 2nd position from the top, but the 3rd is probably too rich for riding at 6,000+ for the best performance. Here's my recommended starting point / guesstimate.

Main Jet = 162
Needle clip = 2nd position from the top
Pilot = 65s

It's hard to give an exact number on the jetting, because of various factors about a given bike and there are also machining & tolerance differences between the jets when they are made. In other words, all 170 jets are not created equal. If you had a bag of a dozen 170 jets and flow tested them all, you might find that some flow like a 170, some like a 172, some like a 174, some like 168, etc.

Don't forget to adjust your pilot/fuel screw afterwards because that will affect your off idle performance and whether it feels sluggish or not down low. In terms of adjusting your pilot/fuel screw, make sure your engine is fully warmed up and set the pilot screw to 1.5 turns out. Then turn the pilot screw clockwise until the idle slows. Then turn the pilot screw counterclockwise until the idle slows again. Make a mental note of how many turns you made in between the low idle points. Then turn the pilot screw half way between the low idle points to finish the adjustment. If you turn the adjuster counterclockwise and the idle doesn't drop down, then you need a larger pilot jet. If you turn the pilot screw clockwise and the idle doesn't drop down, then you need a smaller pilot jet. After adjusting your pilot circuit, re-adjust your idle speed if necessary. Don't crank down on the pilot screw when it closes or you'll damage the seat, so be gentle when it stops or becomes harder to turn turning.

Even with the proper jetting, you'll still loose about ~20% of the relative HP at 6,000 ft when compared to sea level due to differences in air density, but it should still be fairly responsive and not terribly sluggish with the proper jetting.

Also, make sure you're running a good fuel and not AV Gas or something else that might contribute to lazy low end throttle response.

If you come down in elevation too much such as at sea level, make sure to enrich the jetting or else you might be running too lean.

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  • J_T

Posted September 25, 2003 - 01:58 PM


Qadsan, You have an edelbrock, how does it do with varying altitudes. I am at 300 MSL but looking at taking my BRP with the edelbrock with us on a road trip out west. I haven't decided yet but the question has been in the back of my mind about if I'd needed to adjust much?


  • qadsan

Posted September 25, 2003 - 03:06 PM


I've been from 0 to ~7,000 ft without any adjustments and found the performance acceptable where as before I was having to rejet the stock carb to get the most from it. I've heard of other people riding from 1,500 to 12,000+ ft without any adjustments and they also found performance acceptable, but said it could have been better with a leaner needle at the higher altitudes. The dual vent design seems to work and I'm quite happy not having to mess with the carb like I used to when riding at different locations, but I'm still stuck rejetting a XR100, a XR200 and a TR200 when we significantly change our riding environment. I never have to mess with my sons XR250 & my XR650R that have Edelbrocks on them.

  • redmanrandyed

Posted September 26, 2003 - 05:32 AM


Thanks a ton! I will try what is suggested before my next ride which is hopefully very soon. As far as the Edelbrock carb, that sounds like a pretty good investment. Where's the best place to pick one up?
Thanks again for taking the time to help me out on this. I really appreciate it. :)

  • J_T

Posted September 26, 2003 - 11:31 AM


Take a look at this post pumper carbs ?? b/c it tells you something about the carbs but there have been tons of other post about the Edelbrock with a simple search. As for places to order, Rob Barnum owner of is known for excelent customer service and I was able to purchase the carb from them for under $400 with s/h. I bolted it on while the bike had been sitting for one year with out cranking, put fresh gas in the tank, changed the oil and it started w/in 5 kicks but starts w/in 1-2 normally. I also was loading it in the back of the truck after a ride and already had my boots off and I was able to kick it Bare-footed which I would have never tried previously! Also the response is quick with no hesitation! Its great, But don't take my word for it b/c there are tons of post about it and see what others are saying!

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