@hamlin6 i think they have 27k miles on them roughly. they recommend them for 30k miles max. so i think it's time to replace them.
actually last time one of my friends suggested to apply a light coat of engine oil to its threads. that's why the thread areas are oily. but i'm not sure why #4 thread area looks different in color.
all 4 plug gaps were at 0.8mm. usually i make them all hand tight. Iridium version is also available for this spark plug model. is it a good idea to buy a set of Iridium instead of this conventional plugs ? thank you

 

Yes. Most people stick with NGK and have great luck with them.
I would say with the mileage yours have they are ready to be retired. While they aren’t cheap they aren’t expensive in the grand scheme of things either. And they make a world of difference.

 

@hamlin6 yea i'll replace them too. thank you.

 

hi. i fitted my carb to the bike and started. it started fine and ran well. i would like to thank all of you for your help
idle was fine, revving was fine and rev dropping was also fine.

i have a small problem though. i kept it in idle for a few minutes. blipped the throttle occasionally. after several minutes the engine sound became slightly uneven and RPM needle kept fluctuating a bit. before that its sound was even and RPM needle was steady too. so from my past experience i just sprayed some water to all 4 exhaust pipes one by one. #2, #3, #4 were working 100%. but #1 was not working 100%. may be 80%.

so i'm planning to remove spark plugs and see. apart from that uneven sound it ran fine. always started at first attempt wihout any issue. but i think it's better to fix this #1 cylinder running slightly cold. could this be a vacuum leak or something ? if you have any suggestions please let me know. thank you.

 

When I first started cleaning my carburetors on my 1995 CBR1000F in 2006 or 2007, I remember that it took me 3 tries to get them cleaned correctly and installed right. I don't think that is going to be the case here based on what I've seen, but the devil is in the details for sure. Have you checked and if needed adjusted your valve clearances? That is the start of properly balanced/synchronized carburetors.

 

@IDoDirt hi. yea valve clearance was checked by a mechanic a few months ago.

prior to this cleaning it had been running fine for last couple of years. only #3 was slightly cold at idle which i noticed a few month ago. but starting, idling, running and everything was fine.
i forgot to tell that at the same time the sound became uneven RPM had increased from 1500 to 2000. it also fluctuated a bit. so i decreased RPM using my idle adjuster to 1500 and blipped the throttle. but again it stopped at 2000. so i guess it's a vacuum leak. i'm planning to remove spark plugs first and check them. after that may be spray some carb cleaner around its intake manifold just to see if it has a leak. will udpate. thx a lot

 

hi. bike started fine in the morning. even in cold start engine didn't stall but RPM was not stable. also RPM tempted to hang at 2000 RPM and then slowly dropped to 1500 RPM. it happend most of the time i blipped the throttle. there was a strong fuel smell at idle too. i checked the spark plugs and all were ok. no carbon or white color (lean) deposits. sprayed carb cleaner around #1 intake manifold. but it didn't make any difference.

i sprayed some water to exhaust pipes again and #1 was the one which was running slighty cold. i think it happens intermittently. so i'm planning to check my two ignition coils with multimeter next. will check both primary and secondary side resistance with HT lines + spark plug caps.

also when looking for a vacuum leak do we need to check intake manifolds as well as the area where air box connects with carb ?



i thought it's always a bad intake manifold which creates a vacuum leak. i will check my air box too. thank you.

 

A common location for leaks would be the rubber boots that connect the carburetors to the intakes. Old ones especially since they are usually hard and don't fit well anymore. As for having had a mechanic check the valve clearances, I'm a skeptic. I don't trust anyone to do it right, even though it's not hard to do. As an example here is for the F3. All clearances should be done when the engine has had a chance to cool at least overnight. Never on a warm engine.

On a CBR600F3, The Exhaust valve clearance specification is 0.22 ± 0.03 mm. That means that if the gap is anywhere from 0.19 to 0.25 mm then it's within spec and does not need to be adjusted. That would mean that it's good for another 16k miles. So, how do you verify it. I use the Go - No Go method. I want to make sure that a 0.26 mm gauge WILL NOT fit in the gap, and also verify that a 0.19 mm gauge will fit. I get 2 sets of feeler gauges. Now, the set doesn't have those sizes specifically. But it does have a 0.20 mm and it has a 0.06 mm. I put them together (make sure they're clean) and I have 0.26 mm. For the 0.19, I use the 0.10 and the 0.09 gauges.

So, for each clearance I rotate the cams so they're pointing away from the valve I'm checking and make my check. It's not important to know what the specific gap is. Only that it's within the range. Now, if it's not within the range, then you DO need to know exactly what the gap is. This is because you have to calculate how much it needs to be adjusted (bigger or smaller shim) to bring it into specification.

 

@IDoDirt that go-no go trick is great. i have to keep it in mind. thx a lot for your detailed explanation.
in this case i doubt it's the valves since #1 had been working fine before the disassembly. but it's better to check it myself. haven't done it before so will follow the manual as usual.
but first i'll check the ignition so i'll be able to rule out that part. will update

 

hi. yesterday i could check the ignition coils. i took these readings

* voltage at Black / White lines
* primary side resistance
* secondary side resistance ( with HT lines + plug caps )

this is the result i got



they are within the specs. so i think ignition is ok. still #1 cylinder is running slightly cold. throttle response at low RPM is ok but could feel a small lag. next i'll check the carb again. thank you.