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Can anyone let me know what the base line opening measurement of the carb slide should be on an '04 and if that number is from the engine side or air filter side? When I was cleaning it, I must have messed it up and now I can't get it started.

Also, does the fuel screw at the bottom of the carb have anything to do with starting it or does it just come into play after the bike is running?

I bought this bike earlier this year and it has given me fits all year trying to start it. It was starting at first but then when hot it wouldn't. I did check the valves and will do again to make sure they are still in spec but I think it has to do with the Idle screw/slide opening.

Thanks!!

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it is an FCR. I posted here because it is a KX250F and there are people in here that have written on starting issues of these bikes.

What I am hoping to find out is where the slide and fuel screw should be as a baseline to get it running.

Thanks!

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The fuel screw DOES affect starting. Set it at around 2,5 turns out from fully seated.

The slide plate can be mounted upside down. The cut-out (hole) should be facing down.

The idle speed can´t really be set exactly by chancing a setting.

Just set it so that it doesn´t completely close, then try starting it.

If you can´t get it to start, you can always try jump starting it, then catching with the throttle when it starts, then quickly find the setting with the black knob.

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If im taking a shot in the dark ^^^, I just open the black knob so far, so its going to start and if it starts up and is too fast I shut it off and take out some amount depending on how high it was. so DK even with a 42 pilot I should be out on the FS about 2.5 turns as a base setting? just wondering because Im in the process of having to relearn how to jet this 07 I have and everything I did know is kind of out the window...

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I would say 2 to 2,5 turns out here in Sweden.

Probably less for you in the desert heat. But that´s basically a good base setting for all bikes that are stock.

Btw, I had to go to tech inspection and sound test the bike at the last race I was in.

60 hours on the original packing in the stock silencer.

I turned the fuel screw out half a turn to make it sound more dull.

The guy testing it said that the hour meter interfered with the tach he was using, so he just held it at a steady RPM by ear.

The tester read 91,1 decibels. His jaw dropped and he raised the revs to what I would say was probably close to 6 grand.

It read 93,3, and he said OK and kind of shook his head.:banana:

Later a guy watching the race said my bike was the loudest one:busted:

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The fuel screw DOES affect starting. Set it at around 2,5 turns out from fully seated.

The slide plate can be mounted upside down. The cut-out (hole) should be facing down.

The idle speed can´t really be set exactly by chancing a setting.

Just set it so that it doesn´t completely close, then try starting it.

If you can´t get it to start, you can always try jump starting it, then catching with the throttle when it starts, then quickly find the setting with the black knob.

Thanks for the help. I got it to start last night and even keep it going for a while trying to get it set but it always seems like it is hunting for the idle after I crack the throttle. It will be idleing high and then crack the throttle the idle will fall to point of barely running. It has a 42 pilot in it, engine mods and pipe. The fuel screw is at 2-2.5 turns out. When I do crack the throttle, sometimes the decel popping is there and sometimes not. I also disconnected the TPS to see if there was a change and there wasn't anything I noticed.

I have chased my tail on this all summer and even put in a 45 pilot and it would start most times in 1 or 2 kicks. I even had it running pretty good but it would never start when hot, with or without the hot start. The previous owner says that it started 1-2 kicks with the 42 so that is why I think it is just an adjustment that I am missing.

When it is mid 80s and humid should the choke be used on these bikes? My other bikes all need it but figured I would ask.

Thanks!

Edited by a bad gt
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thats the infamous timing change if you want it to stop unplug the gear position sensor down by the shifter. this s absolutely normal, it wont do it in neutral if you just start it in neutral then rev it, or at least it shouldnt! its the infamous hanging idle, and the bike does this to prevent stalling in slow corners. I cant say ive ever noticed it doing the work for me but Im sure its saved me a few times. Until I figured out what actually caused it I freaked out too, I thought my bike had a problem

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That's the thing it does do it in neutral. It is sitting on the stand. the description I gave above is all on the stand and not riding. I had it pretty warm last night when I was working on it and it would still do it. I don't know if it just isn't warm enough? It was at the boil over point though and i had a fan on it.

When I have rode it with either the 42 or 45 pilot jet, it ran great and the plug looked pretty good. Starting has always been the issue.

Thanks!

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Spray some carb cleaner or ether around the intake boot and carb and check for leaks with the engine running.

Don´t set it on fire though!

If it has a leak it will change the way it runs significantly when spraying over the leak.

Also make sure the 3 parts are in correct order on the fuel screw, spring - washer - oring.

A blown out muffler can make it run erratic too, repack if in doubt.

Try a friends CDI next, see if it makes a difference.

Even if the engine is modified it should not run erratic.

Also check the flywheel sensor. If it comes loose it will run strange before quitting.

And check that the hotstart closes completely.

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I say that your decomp on the exhaust cam is not working properly. would check it next time I check the valves. I would turn the idle up a little more and see what happens just to sure it will idle smoothly, not raspy and rattley.

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I say that your decomp on the exhaust cam is not working properly. would check it next time I check the valves. I would turn the idle up a little more and see what happens just to sure it will idle smoothly, not raspy and rattley.

How do I check the decomp? I should be able to check the valves tomorrow. I shimmed one of the intakes already since getting it in April. I bet I haven't even put 6 hours on it since. If they are out of spec again is that bad? The guy I got it from said the motor was done about 5 hours ago. What is better, to have them a little loose or a little tight? When I say "a little", I mean the feeler gauge fits either easy or hard.

Thanks!

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well its always safe to have them towards the looser side. its prime though really to keep it just a tiny amount tight of middle of specs. If they are already loose, then yes your head/valves have issues. OOPS! IDK if the 04s came with decomps on the exhaust cams. Youll know if it does, there is a jig on gear and a little arm with a spring that easily pulls back. it wont hurt anything to play with it just a little. just make sure the valves are set right!!!

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