Strange fuel or ignition problem

[JetdocX]

Glad you got that figured.  I guess a Steamer will run on one.  Live and learn.  Now go ride the piss out of it before winter returns to your homeland!

[Mustang]

Harre

if you want to shim the needles on Keihin carbs , it's cheap and easy
go mto the hardware store and get some flat washers that are about 8mm in diameter with a 3 mm hole in them and start with one washer under each needle to raise them up .

Tiggers with Keihin carbs run really well in colder climates with
105 main jets and the stock pilots
shim the needles so they are about .75 mm (.030 inch)higher than stock
and the pilot screws set at 2 to 2 1/4 turns out .
And one side of the airbox has the cap on the snorkel .

Starting is much easier (especially when below 15 or so degrees C)
and you will only need to be on choke for a few minutes .

It will be crisper and that god awful bog in the power at 4k will be gone

[harre]

Interesting. Your recommended setup has bigger main jets and thicker washers than Nightrunners setup, but he also changed the pilot jets. What about fuel consumption?

[nightrunner]

I recall my gas mileage went up a few MPG, and the mid-range 'stumble' went away.   And starting is easy.  After 3 turns out the screws are at the end of their range so the stock setting is getting close to that.  Also, the pilot has a big impact on low RPM roll-on power.   You may have already seen this but this is a really good write-up on how M/C carbs work and how to re-jet.  Note the chart showing that the pilot jet is "active" over the entire trottle range.  The main jet plays no role until just under 1/2 throttle opening!

Edit. corrected link: http://hondanighthawks.net/carb14.htm

In my opinions, most of the M/C jetting wisdom comes from racing and they don't care much about the low end of the range.  If I were only allowed one change in a carb I would change the pilot before the main.   Just my 0.02

[nightrunner]

And I set it up so I can run with the right side air cap on normally, and take it off for more air at hgh altitude.

Edit:  The jetting I did was for stock exhaust and air filter.  Mustang may(?) be running a K&N and/or aftermarket cans.  Just a thought.   Optimal jetting is very sensitive to intake and exhaust mods.

[jsingraham]

Ummm, Nightrunner, is that really the link you meant to post?

[nightrunner]

Ummm, Nightrunner, is that really the link you meant to post?

D'OH!  Fixed.  Thanks.  I have no idea how I managed to screw that up.

[Mustang]

And I set it up so I can run with the right side air cap on normally, and take it off for more air at hgh altitude.

Edit:  The jetting I did was for stock exhaust and air filter.  Mustang may(?) be running a K&N and/or aftermarket cans.  Just a thought.   Optimal jetting is very sensitive to intake and exhaust mods.

Every bike is an individual , you have to find what works for that bike ..........and where you live has a big impact on what works for carb tuning . ie at sea level you can run giant mains and get away with it . I live and ride most of the time at sea level to 1000 ft . and the ambient temperature hardly ever gets to the mid 80's F

my other 98 jetted the same as my favorite doesn't want the choke at all while cranking but as soon as it blubbers it wants all the choke you can give it .

My favorite steamer starts with choke on and just a stab at the button , no cranking req'd .

Harre said his bike ran better when he went back to two turns on the pilot so he is right on the money with the pilot jets . The 105 mains will get rid of that awful bog in the power at 4000 to 5000 rpm when you have a healthy handful of throttle .

While I agree that the mains are mostly noticeable to change on the upper rpms , it will also affect the transition from the pilot circuit to the mid range to a lesser extent .
If you whack the throttle to the stop when you are rolling at 3000 rpm in 3rd or 4th gear and the engine stumbles and won't pick up rpm until you shut the throttle a bit ....You need bigger main jets .
on the other hand if you are trying to cruise at a steady rpm and the engine wants to "hunt" all the time rpm fluctuating without throttle movement your mains are too big .

There is no "recipe" that can be applied to all bikes as they are all unique individuals . and to truly benefit from carb tuning you need a dyno and lots of wrench time to make changes and see what gives the best results on the dyno .

[harre]

I have a new K&N air filter installed and I will ride the bike mostly at sea level, or at the most, 1000 m above sea level. Original cans. I want a quicker throttle response on low revs as well as getting rid of the 4000 rpm bog. The Mustang #105 route requires fewer changes , so I'm leaning towards that option, however that may not give me the desired effect on low revs, so maybe I'll have to change the pilot jets and needle washers as well. I'm dazed an confused right now. Maybe I'm better off just riding. :?

[nightrunner]

Riding will definitely bring you peace and tanquility so that's the way to go.

I agree with most of Mustang's comments; expecially that each bike needs to be custom tuned.   If all carbs of the same model were exactly identical, then there would be no need for the sync adjustment because they would all be the same all the time.  

There's more than one way to get most things done so whatever works for you.  When I was learning about jetting I searched the web and that Carb Theory 101 is one of the things I found.  It made a lot of sense.   Since the pilot is the only controlling factor for starting and low throttle position, it made sense to sort that first and work my way up.  Look at that figure in the link.  At 1/2 to full WOT, there are four factors affecting performance.  I'd rather tweak one adjustment at a time than deal with four overlapping ones.  Of course its not likely that street riders are ever going to mess with the shape of the slide so its really only three.   However if you are changing a main jet to affect starting, then what are you going to change for optimum performance at 3/4 throttle?   And don't forget that for acceleration, you can also drill the hole in the slide a bit larger.  Many of the jet kits tell you to do this.  It is the vacuum of the air flowing through the carb that lifts the slide and draws the needle up and out of the main jet.  A larger hole in the slide lets the slide rise a bit faster (but it does not rise any higher).    So if there is hesitation when you whack the throttle, you may need a larger air hole in the slide as opposed to a larger main jet.    

I do think we can all agree that Tigers are damn lean out of the box.  With a K&N its going to be even harder to start, and you'll have more air flowing at high RPM too.   But if she starts easy now, then leave the pilots and go with Mustang's jets.  Use his advice for whether the jets are too big or small.  As for the shims I used brass so they wont rust.  Bought a little box of them from McMaster Carr.  I would mail you a few but I'm out of town for a while and there's no point in waiting that long.  Steel or aluminum washers should work fine too.  I would doubt you could tell a difference between 0.025 and 0.030 shims so just get the right ID and OD.  Keep us posted on how it works.

[harre]

Thanks for the advice Nightrunner. Bike is easy to start cold, needs just a little choke the first minute or so. I'll start with Mustangs settings and see how it works. I also appreciate your offer about shims. Feels good to know that I can solve that issue if I cant' find them here. I would prefer brass shims for longevity. Today is the big day. Going to do a vehicle safety inspection. In Sweden we have to do this every second year (cars yearly). They check if there is something wrong the vehicle, like steering, brakes, tyres, horns, wheel bearings, lights, emissions and so on. Of course you should check this yourself, but it does not cost much, so I try see it as a service provided by the government.