5 replies to this topic

Posted December 17, 2003 - 10:14 AM


I just purchased a new 2002 650r and I uncorked it, removed
the smog, rejetted it to accommodate the free flowing baffle
with the stock exhaust. It has a 175 main, 75 pilot, the
needle is a B53E and it's in the 3rd (middle) position. My
problem is that it doesn't run well at 3/4 throttle and above (in any gear). The bike starts missing and feels like
it's not getting any fuel. I also have 2000 650r with the
exact same jetting and I swapped the carbs and it ran fine
with the old carb. If it makes a difference, I am using a
stock air filter on the bike. I would appreciate any help
or advice.

  • qadsan

Posted December 17, 2003 - 11:34 AM


I swapped the carbs and it ran fine
with the old carb.

If that's the case, then something is wrong with the new carb, the new jets or there's an installation issue.

Make sure you installed the new needle down through the top of the slide and not from the bottom of the slide where it can't be properly adjusted. In regards to the needle seat where the needle seats into the jet, the side that should be facing the top should have a wider opening than the side facing the bottom.

Make certain that your float heights are the same between the two carbs. The 75 pilot seems awefully rich, but that won't cause this problem.

The only other thing that comes to mind is that not all jets are created equal. It's quite possible to have a 175 main jet that flows like a 170 or 180 due to tolerance issues, so as another option, simply swap the main jet from the old working carb into the new carb and see if that takes care of your issue. Let us know what you find :)

Good luck!


Posted December 17, 2003 - 12:06 PM


I installed the needle from the top and I tried running a 170 main and 70 pilot and it had the same problems.
When I installed the needle seat, I put the thinner, tapered side pointing up towards the needle (that's the
way it is on the old carb). How do I check the float levels?

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  • qadsan

Posted December 17, 2003 - 12:28 PM


The service manual has all the specs and details on how to check/adjust the float level. It's pretty easy to do if you've never done it before, but I don't recall the exact values off the top of my head since I don't have a service manual sitting in front of me right now.

Here's a link that will give you a basic idea of the procedure, but you'll need the float drop specs specifically for the XR650R.


Also make certain that your carb still has the white plastic shroud around the main jet cause they fall off quite easily and are easy to loose.


Posted December 17, 2003 - 01:07 PM


Thanks for the tips...I'll check my manual tonight. I don't what plastic shroud you are talking about. There
is a brass cup that surrounds the main jet.

  • qadsan

Posted December 17, 2003 - 01:23 PM


Hmmm, maybe the 650R has a brass jet holder instead of the white plastic shroud :) Many other XR models have a white plastic shroud around the main jet that's supposed to keep the main jet supplied with fuel under hard acceleration or on rough terrain under WOT. It's been years since I seen my stock carb which is long gone, so my memory of it is a bit fuzzy. If there's a brass cup around the main jet, then you won't have the white plastic shroud like other XR's (XR250, XR400, etc).

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