Hesitation just beyond idle

[Tor-King]

Hello!

I just finished removing my carbs for cleaning as there is quite a hesitation between 1000 (idle) and about 2000 RPM.  Beyond 2000 or so, it seems to be running fine.  It also idles fine.  What should I look at in terms of cleaning?  Should the carbs have a thorough cleaning or can I just focus my attention to a particular area.  Some guidance is necessary as this will be my first attempt.

Also, when I removed the airbox, I was unsure if the crankcase breather hose was attached or not.  Can damage result if it was disconnected for some time? Overall, it was fairly clean in the area under the airbox...if that means anything?

Thanks for your time,
Dean

[andyb]

Does it hesitate when you're going from just off idle to opening the gas semi-hard?  Or is it just when going from walking pace and gently rolling into it?

Pilot mixture screws may improve the latter.  Fuel height is probably more the trouble on the former; in either case assuming things are synched, clean, and otherwise in the ballpark.  Dirty pilots would do that as well (always have a clean pilot circuit before twiddling the mix screws).

[yamaha fj rider]

How many turns out are your air screws? What size are your pilot jets? When did you last sync your carbs? 

Kurt   

[Dan Filetti]

If you have them off, clean them entirely.  Break the racks apart and give them a good cleaning as per the most excellent carb cleaning instructions, from Raforth publishing.

That's my $0.02

Dan

[Tor-King]

Here is a little more information...

The bike starts great and will idle fine.  When I start throttling up, it dies.  It is difficult to bring up the engine speed but if I work the throttle and get it above 2000 rpm or so it runs great.  The bike ran super before I put it away for winter.  I did use fuel stabilizer but maybe not enough.  It was re jetted for a Vance and Hines 4-1 pipe many years ago and was synched about 2 years ago. 

Thanks,
Dean

[racerrad8]

Here is a little more information...

The bike starts great and will idle fine.  When I start throttling up, it dies.  It is difficult to bring up the engine speed but if I work the throttle and get it above 2000 rpm or so it runs great.  The bike ran super before I put it away for winter.  I did use fuel stabilizer but maybe not enough.  It was re jetted for a Vance and Hines 4-1 pipe many years ago and was synched about 2 years ago. 

Thanks,
Dean

The pilot jets are plugged up...

Randy - RPM

[Tor-King]

Thank you Randy, you rock! 
Any suggestions as to the type of cleaner to use? Any pointers and things to watch/look out for?  I just don't want to get over my head and tear everything apart when I do not need to.   Although I am fairly mechanically inclined and always do my own simple maintenance, this is my first attempt at completing such a task.  I will also be using the instructions as suggested by Dan Filetti.

Thanks,
Dean

[racerrad8]

Thank you Randy, you rock! 
Any suggestions as to the type of cleaner to use?

Ultrasonic...

Or just replace them, they are only $3.69 each.

But if you are going in to disassemble for a thorough cleaning, then you should get the S/S screw & o-ring kit as well.

Randy - RPM

[Firehawk068]

But if you are going in to disassemble for a thorough cleaning, then you should get the S/S screw & o-ring kit as well.

Randy - RPM

Damn you Randy!
You're making the list of stuff I need to get from you Bigger!     

[Tor-King]

Hi again.
Before I remove the bowls from the carbs, what can I expect for sizing of the pilot and main jets?  Will they be clearly labelled as for sizing? Also, approximately how many turns on the pilot mixture screws?  This will give me a baseline at where to start.  The bike has a Vance and Hines 4-1 and a K&N filter in the original air box.
Thanks,
Dean

[andyb]

The setting of the mix screws will depend on the pilots that you find.  2.5-4 turns is the normalish range (outside of that means you need a different jet).  For a baseline, before removing the old ones, screw them in and see how far out they are currently.

Pilots and mains will be clearly marked, but it's sometimes very difficult to read on dirty jets.  Expect numbers in the range of 37.5-40-42.5 for the pilots and 110-132 for the mains.

And yes, with the rest of what you described, the pilots and mix screws, as well as the passages between the two, are probably plugged pretty badly.

[Tor-King]

Ok...here is what I found so far...
I took off all the bowls and they were VERY clean.  I then removed each pilot jet-- discovered they were 37.5.  None of them were blocked and you could easily see light through each one.

Question 1:  Could it be the circuit that is blocked?
Question 2: With the current setup 4-1 Vance and Hines and K&N filter, should the pilot jet be changed to a 40 or leave it?  Is it usually only the main jet that is changed?

Sorry with all the questions, but I am doing a whole bunch of learning along the way!  I really appreciate all the professionalism on this forum.

Dean

[andyb]

Did it run properly with the current exhaust/filter setup and these jets previously?  Usually a set of 40's makes things run better.

Pull the mixture screws and check the ensure that they communicate well with the bowl area.  Seems like people often forget to clean that passage.

[Tor-King]

Did it run properly with the current exhaust/filter setup and these jets previously?  Usually a set of 40's makes things run better.

Pull the mixture screws and check the ensure that they communicate well with the bowl area.  Seems like people often forget to clean that passage.

Thank you Andy!
It did appear to run well, but if I can recall there appeared to be a little, barely noticeable miss, like a burble sound from the exhaust at idle.  I checked the mixture screws and they are turned out exactly 3 turns.
Question 1: Would you recommend going with a set of 40's?  If I do install them, what would you say I should start with in terms of the mixture screws (how many turns)?
Question 2: When I clean this circuit, should I remove the idle mixture screw, pilot air jet and pilot jet?  To clean, can I spray some cleaner into the idle mixture screw hole and use compressed air to blow it through, or would it be better to blow air from the pilot jet hole or does it matter?

Thank you again, you have all been great help.  I will keep you posted of results!

Dean

[Yamifj1200]

Ok, get yourself at least a couple of cans of Berrymans (sp) carb cleaner to start with. It is what David R recomends and it works great. Its also a good idea to read through David R. carb cleaning procedure several times to have an idea what is involved in the job.

http://www.fjowners.com/index.php?topic=655.0

Yes you need to removed the mixture screws and pilot jets to clean those passages. Many owners here have opted for #40 pilot jets, as have I.
Use the brake cleaner through every passage in each carb to make sure there is no obstuction in every passage. There is also a very small jets in the bottom of each carb bowl that need to be clean.

Read though David R's proceedure and follow it to the letter and your carbs will be good to go..


Eric M