First of all let me say hi, glad to be a part of this forum.

I have a 1998 CBR 600F3. I am a noob, learned everything I know via youtube so I can use all the advice I can get. When I first got the bike it didnt run, ended up taking the carbs entirely apart and cleaning/adjusting them based on youtube videos. After that the bike ran . Runs decent actually. The issues I would like help with are that while riding at higher RPMS when I let off the gas the bike backfires pretty badly. Only things I have changed on the bike is putting on a little shorty exhaust tip (which im not a big fan of). I am looking on ebay and trying to shop around for a carb kit, jet kit, or a new air filter. Dont know which direction I should start with to get the backfiring to stop. Another note, the bike has great top end speed but low end speed (particularly 1st gear) is not so great. Thanks in advance!

 

Hi mate
Not knowing where you are but well done for first up getting the bike but secondly getting the hands dirty in trying to fix stuff.
I'd be really hunting down that car you kit mate but in the interim run a really heavy dose of carby/injector cleaner through it. Start with basics and make sure air filters, fuel filters are all good, check all of your plug leads as well as plugs,
Do you know off hand if anyone had played with or messed around with cam timing. Could even be possible if someone at some stage had replaced the cam chain and possibly got it a tooth out.
You can't as such changed ignition timing on these I don't think as I think on that bike the ignition timing would be governed by the ecu controlled by signal from crank position sensor.
If your in an area where you have other members from here that have some good hands on knowledge, put a few beers and a barbecue on and see if you can get a couple of blokes that know a bit to call in and give you a hand.
I know over here in Aus, quite often we will chip in and help out others in need just for the enjoyment of it so I would imagine there would be some good hearted blokes close by that would offer a hand rather than you pulling things further apart and possibly getting further away from optimised performance

 

I would venture to say the carbs need fine tuned. You could check the timing chain thing by undoing the cap on the "pulse generator cover" line up the marks, pull the cam cover to see if the cam sprocket marks are lined up with the top of the head surface AND count the links inbetween the two. It says how to do this in the manual, buy one or download it. Oh, get rid of the shorty muffler, get a real one. Maybe just for the hell of it remove your air filter and take it for a spin, if the bike runs better your jetting is too rich. Does it run better when the bike is cold, if so, its rich.

 

The deceleration back firing is most likely the pilot circuit is lean.. when you did the carbs do you remember where you set your mixture screws at??

 

Thank you all for the replies!
@Gazz:I live at about 7000ft elevation if that plays a big part in it? I also have never changed the air filter because I wasnt sure if I should just go OEM, or a higher flow one? I read somewhere that you dont go higher air flow unless you have some mods in place like a jet kit? I am located in Arizona, not sure if you know any other members here?

@coalminer frank: I am almost positive my carbs do in fact need to be fine tuned. Is it worth it to have a professional do it or can I with some guidance? Also would it be best to just start by having them tune it as is or should I go buy that carb kit and give it to them and have them install it?

@squale147: When I cleaned my carbs I believe I screwed all of the mixture screws all the way in and then (I dont remember exactly) I read you unscrew them like 1.5 turns or something like that somewhere and that was a good ball park so thats what I did.... How crucial is it that those are set to the correct mixture? I do remember when I took the carbs out, (I think there were four of them in a row) they had a metal cover on one side of each of them that housed like float and what not and due to somebody stripping the screws on them previously, I wasnt able to get to one of those chambers and clean it out so I just cleaned out the other 3.

 

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Here is a pic of my bike now just for fun.

 

First up mate grab a hard copy of the workshop manual. Haynes by far is the better quality with clearer pictures and even better quality paper. Most of ours are Haynes and after buying one clymer recently I can say I won't be buying another as even the paper feels like the poorest of qualities and photos look like poor photocopies. The other thing we have done and mind you it has taken a bit but we found a cheap tv I think it 38 inches but we can hook up the laptop to it and save YouTube movies etc of how to do particular things and its in the garage so when we want to do something that we have no clue about, we first and foremost read the workshop manual then when you have read it, read it again and then again. Then we can have workshop manual and computer hooked up to a good size tv and watch in real time close to actual size what we are attempting.
The tv was only a cheap one from gumtree but it works a treat.

Our experience with shops is that you pay through the nose for poor workmanship, lots of bullsh....t and sometimes even damage.
If you take it slow, be well prepared and again I stress have read your manual then you can always seek further help if what you do doesn't work.

Newer bikes certainly need shops and expensive gear but older bikes you can get away with tools, hands and research , experience comes from the accumulation of using those three things.

You mention screws are damaged and you can't get one apart, remember you might even pick up another set somewhere reasonably cheap.

I not long ago picked up a full 1000 cc running no dramas just ratings bashed up beyond repair for $400 so that's a lot of spare parts if you look at it that way.

It is always good to get a few parts as they become available just I case you need them.

I picked up a set of stainless steel laser exhausts excellent condition for $100 that's the type of stuff you keep your eye out for., put it on a wanted ad somewhere and just let it sit and you will be amazed at what comes out of the woodwork over time

Best of luck mate

 

Thanks for the info. I already have a similar setup in my garage, with a large tv setup to computer so I will be sure to utilize that. I will also try and get my hands on a Haynes manual.