HELP! I'm a desperate!!!

7 replies to this topic
  • jclaus98

Posted February 07, 2008 - 04:59 PM


1993 XR600R having issues, nothing detrimental, but just enough to really, irritate the hell out of me. Ok, so this is gonna be long winded, but bear with me, I wanna make sure I provide as much info as possible. So, here's the deal, I just finished rebuilding the top end completely: rings, cam, rockers, valves, the whole nine yards. Everything went back together smoothly, and it runs great, but it is unbelievably hard to start now. Before, first or second kick everytime, whether it was 40 degrees or 90. Now it takes 20-25 kicks, using the decompressor intermittently, to get it to even start to think about running and it won't start at all with the choke on. Its got to be some sort of carb issue, but I'm at my whits end trying to figure out what. I mean, I did nothing to the carb during the rebuild, and everything ran fine before? It runs great once its warmed up, idles fine and has great power. I did have to jet it up after the rebulid, with a Mikuni flatside, non-pumper, it came with a 240 main jet, but with that after the rebuild it was popping on decel. So, its up to a 270 now and its not popping anymore. But, there is one more issue, I race it alot and in order to pass the sound test, I'm always right on the line and the ranger will always say, "you know that popping is why its so close, if you get it jetted right, it won't do that and you wont have any problem passing." So, what I'm saying is when I open the throttle up about half way, under no load, it wants to pop a little even still. Does anyone have any idea where I should start? :busted: I haven't had the carb apart in a while, I suppose that would be a good place to start, but I wanna see if there's anything obvious I'm missing before I tear the whole thing apart.

  • cleonard

Posted February 07, 2008 - 05:05 PM


Sounds like a classic case of a clogged pilot circuit. Blast everything with carb cleaner and make sure you can see it get through everywhere.

  • JohnnyAirtime

Posted February 07, 2008 - 05:26 PM


If it starts okay... pilot isn't clogged necessarily.

But, to remove the popping... there could be several issues.

1- Air leak at carb or manifold.
2- Pilot jet too small (richen pilot)
3- Fuel screw incorrectly set (start at stock setting - 1 1/2 turns out maybe)

Your main jet only works on 3/4 to full throttle... with the needle working just after 1/4 up just passed 3/4. And the pilot taking over from 1/4 and below.

Also, if the floats aren't set correctly... starting can be a biotch, as most bikes will fload if the floats allow too much fuel. Or too less fuel and you'll starve when wide open for long periods.

Clean the pilot and make sure you've gone up a couple sizes, set the fuel screw, and start'er up! I nearly take my pilot up big enough it's rare I have to use the choke to start'er up from cold. Do you always have to use the choke when first starting the bike?


  • jclaus98

Posted February 07, 2008 - 06:12 PM


Before the rebuild, I always used the choke, it would never start without using the choke. I'd turn the choke on, kick it once, maybe twice, and brraap! She'd take right off. Leave the choke on no more than a minute and let her warm up. Standard procedure. Never tried without the choke come to think of it. So, I guess I'll just have to tear it apart and clena everything out real well and we'll go from there. Thanks guys.

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  • captb

Posted February 07, 2008 - 06:49 PM


Are you sure the cam timing is on the mark?

  • jclaus98

Posted February 07, 2008 - 07:45 PM


Are you sure the cam timing is on the mark?

You know that nightmare crossed my mind a time or two, I got it as close to lined up as I could, but with the teeth on the sprocket as close together as they are, its possible it could be one tooth off? But, wouldn't it run crappy if that were the case? It runs great once its warmed up, just seems that if the timing were off, it would run worse. I REALLY don't wanna take that cover back off to realign the freakin' cam, I was just waiting for someone to suggest timing.

  • creeky

Posted February 08, 2008 - 04:53 AM


Sounds like a classic case of a clogged pilot circuit. Blast everything with carb cleaner and make sure you can see it get through everywhere.

Good advice, try this first. Sometimes it is necessary to run a fine wire through the pilot to get the crap out of it, a bristle pulled from a wire brush works pretty good.

  • Motosprtman

Posted February 08, 2008 - 07:55 AM


I agree odds are a clogged or lean pilot jet and or float lveel and or valves are set too tight.

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