Thanks R1000! Well, I know I was unclear, can´t really explain in english how it runs, but at the 3000-6000 RPM range it doesn´t run even. It almost sounds like an V-engine... If it was an 2-stroke engine I would say it "four-stroked".
It can´t be running rich with such whiteish spark plugs, I held it at ~4500-5000 rpm standing still for a while and then shut it of and checked the plugs. They were whiteyellow on the elektrodes and the bottom egde of the coils was black.
Is the choke adding fuel on these carbs, or just choking air? Or does it just apply throttle? I will check the service manual myself, but does anything need to be assembled to adjust the fuel mixture screws or raise the needles? I´ve never fiddled with motorcycle-carbs before so...

 

Hey:

It sounds like water in the fuel, as 4-6000 is where that would be affected the most. Also how does it
idle off choke, Don't drain tank just yet, get some fuel water remover and add some fuel stabilyzer after
draining the carb bowls, you can sometimes save a tank of fuel, if the carbs are not gummed up. Do you
have an inline fuel filter? If so try bypassing it, or routing thru a new one. Plug idications will not show any
thing on the correct carb adjustments at middle rpm, and mostly not when there is moisture in the fuel.
How did it run when you put it away and was the tank full and or treated with an storage stabilyzer?
Just some things to ponder.

Dub

 

OK, but still try with some choke to seehow midrange is affected; it is importantthat thecause is diagnosed before you do adjustments so you don’t end up with severalfaults on top of each other. If it runs better with choke, it runs to lean since the choke adds fuel and the first thing would be to rise the needles and see where that leads. The pilot jets don’t have a great effect at 6000 rpm, so if it runs lean you have to raise the needles anyway. You need to remove the side fairings and the gas tank to get access to the carbs. The pilot screws are on side of each carb and are not easy to adjust since the space is almost zero to the mid carbs. I've adjusted them once onmine Hurricane when the carbs was off, but it should be possible with a long screwdriver, or better a small gear driven angle tool. You can see what I mean on http://www.carbtune.com/bevel.html

To raise the needles you nead to remove the top cover of the carbs and lift up the throttle assembly. This is quite easy to do. The problemmay be toget the vacuum membranes right at assembly, which is far easier if you put some heavy grease in the carb groove where the membrane shall be.

Just a control question, I guess you didn'tget the possibility to run the bike with the new exhaust last year, right? If you did and it runned well on road at that time, you should not adjust anything, just change fuel and clean the carbs if that is needed too.

 

Thanks both to R1000 and CBR1988 for the answers!
CBR1988: Do you mean idle without choke? In that case, it idles smooth at slightly over 1000 RPM. Yeah, saving gas is always an issue in gas-expensive Sweden, but if it´s the gas causing the problem it´s worth it to fix the problem. I have slightly under half tank now, and I have an additive that´s supposed to break down water into much smaller drops making it boil out easier when the fuel burns (it seemed to work in my snowmobile). Should I try filling up and put in that additive in the gas? If there is a inline filter from factory I have one, otherwise not. It runned fine before storage, but I have installed the slip-on since then as mentioned. Sorry to say, had half tank and no storage stabilizer. Carbs were drained though.

R1000: I will eliminate water-in-gas problem first, then run it and see if it still misses. If it does, I will try with the choke. But still, it must be running lean since last year also since even the mecanic pointed it out in august last year. Rode it in highway-speed (130+ km/h) to the shop were they serviced it, so it most probably needs more fuel somehow...
Thanks for the how-to. And no, didn´t ride it last year with the new exhaust.

 

Hey:

I guess it depends on how much the fuel water remover cost, if its cheap add it to see if it helps
but don't add more fuel unless you have an lawn mower or something else that you will use soon to put
it in. maybe drain the sleds fuel unless its 2 cycle premix, and put in the bike to help troubleshoot the
problem. I think r1000 is right on on his advice to look at the carbs. Also what year cbr1kf do you have?
only early models come factory with electric pump and inline filter

Keep us posted

Dub

 

It´s a 1997... gravity fed...

 

Hi!
I drained the tank completly today and filled new gas and some carb/injector cleaner. Didn´t drain the carbs though, figured i could run it out and new petrol would reach the carbs pretty fast. I noticed no change on how it runs. Applied choke as R1000 said, and yes, it does run significant better with some choke! Didn´t have time to raise the needles today, but will do it next time I´m free. R1000: doesn´t this contradict your claim that my new exhaust would restrict the engine? The fact that it seems to need more fuel now must mean that more air is flowing thru? Or am I thinking backwards?

 

Good news for you, the engine will make more power when fixed. There is of course a small risk that the choke engagement indicates a clogged carb, but it would be very nice if it just depends on a better exhaust flow. If I remember right I said that dual slip-ons is better than a single slip-on with a plugged rear outlet on the stock downpipes. Your new system may flow better in midrange than the stock system, but it would flow even better with two free flowing slip-ons since there is a very restrictive T-joint to the middle pipes. It is strange that the stock downpipes works as well as they do, but the difference with a new 4-2-1 system is still huge. One aftermarketmuffler would definitely be better than the two stock pontones if the T-joint was eliminated. And maybe, the stock mufflers are so restrictive that a single new muffler as in your current configuration is better at all rpm's, that would be real nice.

The downpipes on the Blackbird are similar to the Hurricane but slightly better since one outlet is almost straight and only one is a directed 90 degrees at the exit. When I changed the complete system on the Bird it becomes much stronger over the whole band except below 4 krpm. With the new system it was very easy to lift the front wheel, and not so easy with the stock system where it only lifted at he end of gear one. After additional work with the head, new cams and raised compression, the bike raises very quickly to 11 'o clock (as much as I dare..). The Hurricane also responded very well to a full system, not as agile as the Birdbut enough to walk away from new sportbikes on high speed twisty roads. There is a lot to gain when the flow increases; hopefully you have done such a step by the new slipon.

 

Yes, I was thinking about clogged carbs too... Will make a much longer spin during easter holiday, to give the carb cleaner time to do it´s work. If no change, I will lift the lids on the carbs and raise the needles. About that, will I need to balance the carbs afterwards? It got balanced last august during the service. Looking in the service manual, it´s seems alot easier to raise the needles then to adjust the pilot screws, and I suppose the needles are affecting that RPM-range (4000-6000) more than the pilot screws?

Some pictures: from the first ride of the season and from when draining the tank, notice the high tech rigging technique, especially the Donald Duck-bucket and the welding pliar

[IMG]local://upfiles/6357/CFB62F940AC64B5595F663E145C62A8F.jpg[/IMG]

[IMG]local://upfiles/6357/EF1B1D6FB5AA4B2596817F3011EE56D2.jpg[/IMG]

 

You shouldn’t need to balance the carbs if you just raise the needles. There are some good stuff on carb tuninghere: http://www.factorypro.com/tech_tunin...m_engines.html

I seems that the pilot screw is effective up to about 4000 rpm at light loads, but start to adjust the needle height since that is easier. They also point out how important the float level is, which reminds me of when I bought my CBR 1000 F that runned like ****. On two carbs the little spring loaded pin on the float valve was stuck. A small amount of white corrosion caused that, which resulted in about 5 mm to low float level. In case you have to open and clean the carbs, it is at least quite easy. They should be OK though since you drained the carb during storage.