Uncorked 650R, hard starting, backfiring...Help Please!

8 replies to this topic
  • NorthVanRider

Posted August 09, 2007 - 12:05 PM


Hi All, Just looking for some advice on setting up my 2006 650R...

My current set up is the regular uncorking- 68S pilot, B53E needle with clip in 3rd position, 175 main. Airbox back plastic is removed, however the side cover is not drilled or modded, and I am running a Unifilter with the backfire screen removed. I had been running the bike with the exhaust tip removed as I'm waiting on my HRC tip to arrive...

I live on the west coast of British Columbia and we ride mainly 0-5000ft.

The problem is, although the bike starts easily when we first go out, it seems to get very hard to start when hot and seems to flood very easily. Also when starting hot it backfires almost everytime. As a result when i took my filter out to clean it, i found that it completely burned with large holes in it!

Now to be honest, I do ride this bike in single track trails it was never meant for and i do dump it at least once a ride:crazy:

So before I go and drop the $$ on a new unifilter I want to make sure I get this sorted out before i burn up another one.

I love the bike, but I have been really dissapointed with the extremely hard starts. I ride mainly with 450R's and everybody gets annoyed when I have to back my bike down to the bottom of a hill then kick for 20mins before the damn thing fires.

I am aware of the edelbrock carb and will probably invest in it shortly, but in the mean time i'd like to get the stock carb set up best as possible.

All thoughts/advice welcome.... Thanks in advance!:thumbsup:

  • metisse

Posted August 09, 2007 - 02:43 PM


On both my 650r and 600r, the edelbrock completly and absolutely cured the hard starting and flooding. Worth every penny and no need for the button.

  • JohnnyAirtime

Posted August 09, 2007 - 03:28 PM


Sounds like your sights on the Eddy may be needed sooner, than later. A wise investment and you'll wonder why you didn't do it sooner.

Do you 'clear out' the carb when trying to start it?? Ya know... Compression lever in, hand on kill switch (this is possible cause for fire if you don't), throttle wide open, gas off.... like, after you've dumped it?! Or is this a problem a 'hot start' would cure??

Jetting sounds pretty darn good (excuse me for not knowing perfect specs... I don't own an XR anymore)... but your either too lean, or too rich on the pilot side or air/fuel screw.

How many turns out on the screw??

  • martinfan30

Posted August 09, 2007 - 04:04 PM


backfiring is almost always a sign of a lean condition. is it possible that something is making the mixture way too lean on hot starts? back firing thru the carb can be sign of timing issues(at least in auto applications). just a couple thoughts.

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  • NorthVanRider

Posted August 09, 2007 - 04:41 PM


Thanks for all the replies... I am definitely getting the edelbrock eventually but I just dropped a bunch of $$$ buying all my dualsport parts and DOT tires.

I don't think the bike is jetted on the lean side, if anything I think I might be rich, but I have been running it with no exhaust tip so maybe the complete lack of back pressure has something to do with it?

I do clear my carb out by pulling in the decomp lever, but I haven't been holding down the kill switch:bonk: That probably explains the back firing...

Anyone know the correct setting for the idle/air screw?

  • JohnnyAirtime

Posted August 09, 2007 - 05:25 PM


With that... sounds like just the removal of your end cap gave you the 'pop' on decel problem. ...very common, and you need to be a bit richer for it to stop.

  • martinfan30

Posted August 09, 2007 - 06:00 PM


+1 on that. if it is free flowing uncorked exhaust it is now running even leaner. this will cause the backfire/popping on decel. time to rejet.

  • Thorpey

Posted August 09, 2007 - 06:48 PM


Have you checked your valves? Valves heats up, clearance goes away, intake valve open a little at TDC. BAM! Might want to checkum. Easy to start cold, hard to start hot + backfiring could be valves. Make sure you are off the auto decompressor if you do. Jetting sounds right on.

Here's a link if you've never done them: http://www.xr650r.us/tech/valves.pdf

  • NorthVanRider

Posted October 05, 2007 - 04:32 PM


Thanks for all the replies! I have installed the edelbrock, but am running the stock airfilter and backfire screen, but opened up the back panel of the airbox. I am also running the stock exhaust with stock tip as I have the bike dualsported and need to keep it relatively quiet as I live in a residential area. I am now running the 17E needle about 8 clicks out (counter clockwise) from full in.

Anyone know if this is near what I should be running for 0 - 3500ft elevation with this set up?

It will pull the front end up easily with no clutch and starts soooooo easily!! Which leads me to believe I must have it reasonably close to dialed in, but I would like some input....

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