XL600R minor bog when throttle is snapped open

10 replies to this topic
  • NY_SXR700

Posted July 08, 2007 - 12:15 PM


I have a 1986 XL600R that runs great (since I replaced the stator). I have only one issue left to fix. When you snap the throttle to wheelie or go over a log it bogs for a quick sec. It will toss you to the bars if your not ready for it. It's much better when it's warmed up good. The former owner calls it the "honda kill switch". He said that bike has been like that since the mid 90's when he bought it. It has just over 10k on the odo and the compression is over 175 liek the book calls for. I tore the carbs apart and noticed that the jets are much fatter than stock. I don't have the jet numbers off the top of my head but it's fatter. I just cleaned the air filter and decided to run it with no filter to see if the bog was still there. It's much worse and it has a lean backfire with no filter installed. This leans me to believe the jetting is good. The plug read is good also and I am getting 53.5 mpg on avg. It has 2 carbs and I am wondering if the second carb is not comming in at the right time. Anyone with any knowledge on this bike with dual carbs have any ideas. This is my first bike but I have been wrenching on sleds and jetskis for most my life. This bike is also geared lower for trail if that makes a difference. tks doug

  • NY_SXR700

Posted July 11, 2007 - 05:47 PM


36 views and no replies. Someone must have some background with the dual carbed 86' XL600R. tks doug

  • Kawabuggy

Posted July 12, 2007 - 06:50 AM


If you are getting 53 MPG I would have to guess that the jetting is lean. I am lucky if I get 35 on my XR600. The other thing is you mention that the jets are fatter than stock.. You have checked to see what stock is and know for sure that they are larger???? Have you cleaned the carbs thoroughly to insure that there is no debris plugging up the air bleeds, or the fuel jets? How about the pilot/fuel adjustment screw? My bike (single carb) has one and it has to be adjusted right for low speed operation to work. If your carb has one, try backing it out one more complete turn and then see what that does.

The other thing is how much are you whacking the throttle open when you are attempting to wheelie? If more than half way all at once, you are going to get a momentary bog because there will be a temporary lean spot when you do that. That's why there are pumper carbs to over-come that initial bog. And NO! I am not recommending that you switch to a pumper carb. I don't have one, and will probably never get one because my stock carb (tuned fairly well for my bike) works pretty damn well as is.

Lastly, and it should probably be first-have you pulled the plug to confirm how rich/lean the motor is running? Do that before you do anything else.

  • NY_SXR700

Posted July 13, 2007 - 04:07 AM


Thanks for the reply. My plug does look good and tan. The stock jets should have 118 main on the pri carb and 115 on the sec carb, mine are 122 and 118. I should also have a 62 pilot and I have a 65. The screw was missing the o-ring and washer I replaced that. If I turn the screw all the way in I would think the bike would die. It does not and only runs rough. The book calls for 1.5 turns out. I have tried that and 2.5 out not much difference. I am also thinking it's a lean bog as that is most common with my sleds on a snapped throttle with a bog. When I snap it, I am going WFO, this being my first bike I guess I need to learn not to do that. The only thing I have not checked is when the second card kicks in. So, I was wondering if that could be an issue. I also know that the valves have not been looked at on this bike in over 10 years or about 3000 miles. Is this important to keep an eye on it? Thanks Doug

  • Kawabuggy

Posted July 13, 2007 - 05:08 AM


Yes, very important to keep the valves adjusted, but I don't think valves out of adjustment will cause the bog that you are experiencing. Normally valves out of adjustment make for hard starting, or in extreme cases popping back through the intake or exhaust due to a non-sealing valve during the firing event.

If the bike is running properly, there should never be a time that you can give it full throttle in the lower gears (1st, 2nd possibly 3rd) unless you have no traction. Otherwise full throttle with traction while moving slowly should flip the bike over backwards.

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  • pcmartin

Posted July 13, 2007 - 05:49 AM


There is a "U" shaped part that the linkage from the secondary carb hooks too. If you want the secondary carb to open sooner you squeeze the "U" a little at a time at the top of the "U". The easist way to do this is with the carbs off and the throttle wide open. Then you squeeze the "U" together until the secondary slide starts to drop. At that point you open the "U" back up a tiny bit. This lets the secondary carb open fully and asap. And your jetting sounds about right. We would take the primary main jet and put it in the secondary carb. Then go 1 up on the primary and idle jets.

  • surveyman

Posted August 20, 2007 - 10:52 AM


I have a "86" xl600r and am having even worse bogging problems. Mine will almost cut off and start backfiring, like it is running lean. I have put a new coil in as recommended and checked the choke for sticking. I have not replaced the CDI unit yet. I checked the micro fuel screen at the fuel petcock, nothing there either. I struggle to get above 55mph and have to work at it to get to 70mph. I am leaning toward carb work. One person said take the air filter out and see how it runs as you did. Any help I would appreciate as you because I want to get it on the road soon, for fun and gas mileage.

  • asf

Posted August 20, 2007 - 10:16 PM


you need a pumper carb. Gigantic single cylinder requires lots **NOW** of gas if you crack open the throttle. A non pumper carb requires gas vacuum to pull in the gas, but guess what, air will make it there well before the gasoline for that first burst. A pumper eill inject gas mechanically before the vacuum builds to eliminate the bog.

  • martinfan30

Posted August 21, 2007 - 02:50 PM


+1 on asf's post.

  • pcmartin

Posted August 21, 2007 - 07:56 PM


Yeah pumper carb great idea, except it's a twin carb motor!

  • martinfan30

Posted August 21, 2007 - 09:16 PM


how about twin squirters!LOL!:applause: :busted:

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