Tuning and Jetting My 1982 450

[pete]

Hey Jeff, I don't have good ones either... I use a pair of long nose pliers you can see here:



But they tend to slip out of the circles on the circlip when trying to lift it, so what I've done is gotten a piece of wire and bent a hook in one end so that as I squeeze the circlip, I can hook the wire under it and lift it up.

As for the springs and vacuum hole, yep that's right

My suggestion would definitely be to get your jetting right first though so you know how it should run, then do one modification at a time.

[jeffasaurus2]

I finally resorted to a pair of long needle nose pliers from a hardware store bargain bin. Just ground the tips down a tad with the Dremel, work pretty good!

I've got my jetting pretty dang close, definitely not spot on, but close. Luckily I've got a complete extra rack of carbs, so plenty of parts to do experiments on.

I went to drill the slides and shorten the springs yesterday and found out that the new set of carbs I purchased a while back had already been shimmed (or 'un-shimmed') to run richer. I've got a mixed set of diaphragm/slide assemblies, (one old-one new), in my on-bike carbs now, so one's stock, ones rich...goes to show you shouldn't believe PO's! I've now got the shims set equally, one shim richer than stock, and plan to drop them in tomorrow!

[pete]

Excellent, you should be all set!

[MOC]

Pete,

Ive been inspired by this thread to start fiddling with my bike and i made some discoveries. You mentioned before that cutting the springs has made a difference, and i'm getting close to doing the same.

Background:
Pods
Stock exhaust
Rejetted the mains to 130
shimmed the needles up ALL the way.
Pilots turned out 2.5 turns.
Floats set to 24 mm

The bike was running pretty well from idle through 1/4, and pulling strong from 3/4 - 100%. the mid range was iffy when the bike was cold, but got better as things warmed up. I assumed this was a lean condition given that air gets less dense as it warms up. This is why my initial reaction was to raise the needles. After thinking about it for a few days, I have reevaluated a bit.

Clues to consider:

1 - the bike was starting right up without choke when it was stone cold
2 - my fuel mileage was around 50 mpg, much lower than i expected.
3 - the exhaust smelled rich on startup, and if i choked it it would die, warm or cold.

Action steps today:
1 - lower the floats from 24 - 26 mm in keeping with the recommendations
2 - shim the needles down 1 shim's worth on both sides
3 - replace the spark plugs so i can get a good read on the plug chops

Results:
1 - bike is much more happy at idle, and choke no longer kills it, but instead helps with cold starts.
2 - bike feels strong from idle through about 1/2 throttle, but then gets boggy
3 - bike pulls like a mule past 3/4 throttle
4 - occasional spitting/popping from the intake during stop and go traffic.

Im assuming that lowering the needle a tad was helpful in the mid range, but the plug chops didn't seem to indicate much. I did these chops after a 1/4 mile run at 1/2 throttle and 6k rpms in 4th where the bogging has persisted. These are brand new plugs gapped to spec:

Left side:


Right Side:


Neither were wet with fuel, or black with carbon, or white with ash. The left side electrode seemed a bit blue, but i chocked that up to being brand new.

With all this said, it seems as if the bike is dialed in fine until you get to about 6k rpm, at any throttle position between 1/3 and 2/3. It will accelerate fine, in any gear, all the way up to about 6k, and then kind of bog. The only way to get through it is to blip the throttle up to 3/4 or 100% to get it fully onto the main jet, and then it pulls great.

Thoughts?

[pete]

I'm crap at reading plugs

If it pulls hard in WOT, that typically would say your main is good.

From what you say though, I'd be shimming your needles a bit richer again.

Most likely you're going to have to end up with some sort of compromise while still using the stock needles as from what I can see of available alternatives, the stock ones are designed to be quite lean.

[MOC]

Yeah, I took it for a long ride today and it seems soft in the mid range again. I may give the folks at jetsrus a call and ask for input. That, or turn some grooves into my stock needles on a lathe.

[pete]

Well... according to the shims I bought on eBay, the needle grooves are 0.04" apart, and the shims I bought have 0.01", 0.02", and 0.03" sizes in there.

I believe Mikuni shims are 0.02", so two of those would be one notch, and four two notches which in theory would be the equivalent of my 4C3 needle's richest setting.

How many shims do you have on the needle?

[MOC]

well until saturday there were none (richest setting). i added 1, and the problem got fractionally worse. i would assume this means i need to raise the needle beyond the limit of the clip and groove currently available to me.

[PPPPPP42]

OK its looking like we really need to identify a currently available needle for the US folks to swap in that is in the correct range and has the notches.

Could someone explain what the second diagram down is trying to tell me about where to measure the needle:

http://mikunioz.com/needles_numerical_list.htm

Are those arrows with numbers 10-70 10mm increments to measure?
What the heck is the a and b measurement? Overall length and length to start of the taper?

If all of that is correct the 4C2 needle (mine is labeled with mikuni stamp and 4C2) is an odd job, it would be about:
A: 48.2mm
B: 20.5mm (or so)
D1 and D2 (before the taper) are 3mm which is above any series 4 needle on the smaller chart of measurements.
D3 2.88mm
D4 2.74
End of needle is about 2.65

EDIT: confirmed that in Mikuni needle measuring A is overall length, B is the length from the top of the needle to the start of the taper (on a single taper needle) and the D measurements are in 10mm increments (D-1 = 10mm from top of needle)
Also finished measuring my needle though its far from exact.
Comparing my numbers to petes (next page) and taking into account measuring errors (these things are impossible to measure accurately) I think the 2 needles may actually be the same but the US ones are non adjustable (only one clip position).

[jeffasaurus2]

Quick question.

If I give the bike the beans and then let off I can hear some slight popping on decel. I had thought this was due to running lean but am not certain.

Is this a symptom of rich or lean?

[pete]

That's the best I could measure mine.

Note that most Mikuni replacements are actually longer, so I couldn't get a D5 measurement.

This is probably not 100% accurate.

For you US guys, if there are no shims, I suspect that this will be the middle setting on the needle, so if that's correct you should be able to add 4 shims to get to the richest setting.

Jeff, pops on decel can be either but are more likely lean (like mine). I dialed most of it out with the mixture screws which is why I'm 3 3/4 turns out now, but really I need a richer needle.

[MOC]

For you US guys, if there are no shims, I suspect that this will be the middle setting on the needle, so if that's correct you should be able to add 4 shims to get to the richest setting.

It doesn't work like that on my carbs. They are laid out as follows:

Top to Bottom -

Retaining stem (Plastic thing)
Shims/nylon spacer
Needle clip and needle
spring
slide body

refer to the hastily sketched drawing below:



adding shims beneath the needle clip does nothing to raise the needle because the clip has nowhere it can travel upwards. Its pressed firmly into the base of the retaining stem and nylon spacer. The only option for richening the mix is to remove the nylon spacer. I have done this, and currently the clip is the only thing pressed up against the retaining stem. The only way to keep going is to either modify the stem (yuck) or buy another needle (yuck).

This is why I was so eager to see how the spring/venturi modifications you've made on the slide panned out. Shortening the spring will effectively reduce the amount of vacuum necessary to lift the needle, and increasing the venturi hole size will increase the speed that the slide rises in response to throttle movement.

sigh. I would kill for a pair of euro spec needles. Either way, keep up the good work. This is awesomely detailed progress on your tuning experiments and I appreciate the effort you're putting in.

[PPPPPP42]

MOC you seem to be correct, I just looked at the carb I took apart again and for some reason it had never occurred to me before now to look and figure out exactly where any shims would go.
The only way to adjust it would be to remove the thick nylon spacer and replace it with a thinner one or a stack of washer shims. So you would essentially be unshimming rather than shimming to raise the needle.
I should mention that mine has a washer between the spring and clip that isn't in your diagram there though I assume its just to keep the spring from tangling up in the clip and not an actual shim.

What the heck does the non US model have for hardware surrounding the needle? Its like 2 totally different carb designs here.

BTW sorry for hijacking this thread into a general 450 tuning thread pete.

[MOC]

.BTW sorry for hijacking this thread into a general 450 tuning thread pete.

Yeah.. Sorry!

[PPPPPP42]

Edited my previous post (page 4) with the rest of the measurements.
Curious to see if there is a difference in hardware of non US needle setup or just different needle.
Its looking like if you want to change a needle you normally need to change to a different jet to match it.

Skipping between pages in this thread keeps crashing firefox (annoying).
Somehow lost my carb needle and found it across my room in my slipper which I haven't worn in weeks after searching for 10 minutes (no joke, no freaking clue how, and very annoying).

Also these are the pliers I use to take the snap ring out, the tips are small enough to fit in the holes and make it super easy to snatch out and put back in:

http://toolsandmore.us/needlenosepliers1.aspx

Got it from a local store at some point in the past for jobs like this.

Nother edit: the plastic bit of crap above the clip in my carb is 2.2mm thick, the needle positions I read on another site are about 1mm thick, the shims people use are .5mm thick, so 2 shims=1 clip position adjustment.
SO, if you remove the plastic thingy you moved the needle 2.2 clip positions richer, you could add 2 shims to lean it out one position if that is too much. This seems to be the limit of the adjustment for this design unless I am missing something obvious. Really curious about non US stuff now. Oh and that extra washer I had between my spring and clip that wasn't in your diagram is exactly .5mm thick so its either a shim, or the same as, though positioned where it was makes no sense.
EDITED the EDIT (getting ridiculous) just saw that petes measurements on the needle notches are not the same as what I read on another site, could you please verify needle notch spacing measurements pete so I can straigten out my shim calculations?