mikuni jets vs. keihin jets
gcash
What are the differences (if any) between Mikuni small-round-slotted jets
and the equivalent Keihin jets? How do you tell if they're one or the
other by looking at them?
I'm asking because the local bike shops seem to be out of the Keihin jet
sizes I need, and all I see available mail-order is Mikuni. Plus I got my
jets from the Yamaha shop, and it occurs to me they might be Mikunis.
P.S. the local Honda shops don't have any Honda jets, but the Suzuki and
Yamaha dealers do. Ugh. One Honda shop is so disorganized they didn't
even know what sizes they had in stock, they were all thrown together in a
box. Double ugh. I got some jets from the Honda shop that look like
they're the right thread, they just don't screw in. I have a bolt that
screws in fine, and the jets seem to match that thread. Triple ugh. I
should've brought the emulsion tube with me.
-gc
Ray Curry
The two have different profiles as you go through the bore, real Mikuni
jets are the hex shaped ones. The round ones were historically from Weber
and Solex carbs and the fuel flowed in the opposite direction. The result
is that the flow rates vary at a different rate with the rise in vacuum
from low RPM to high RPM. I would not swap them unless your prepare to
analyze and adjust the needle taper and the mainjet tube. You can
sometimes find Solex versions at Volkswagon beetle parts places but the
car carbs use a different range of numbers so a small dealer might not
have the range your intested in.
Kaybearjr
>and the equivalent Keihin jets?
Looking at the Sudco International Catalog, it seems that:
Mikunis have increments of 2.5. The range
is 50 to 200.
Keihin 99101-393-xxx jets have increments of 2.0. They are used on all Honda
VB, VD, and VE series, all Kawasaki CV and CVK series, some Honda PD and PE
series, and 600 and 1000 Hurricanes.
The range is 90 to 200.
In other words, if you had a Mikuni 100, the next size in Mikuni would be
102.5, but if it was a Keihin it would be a 102.
# * 0 * #
^
Hoyt McKagen
> and the equivalent Keihin jets? How do you tell if they're one or the
> other by looking at them?
The number systems are different and you can tell only by comparison
chart if it exists, measurement, or comparing flow rate.
>
> box. Double ugh. I got some jets from the Honda shop that look like
> they're the right thread, they just don't screw in.
They're not same thread and it will ruin jet and/or spraybay if you do
screw them in.
Regards,
Hoyt McKagen
Belfab CNC - http://www.freeyellow.com/members/belfab/belfab.html
Best MC Repair - http://www.freeyellow.com/members/batwings/best.html
Camping/Caving - http://www.freeyellow.com/members/batwings/caving.html
Animals have fleas and ticks but I have minions
gcash
Does a Keihin 100 == a Mikuni 100?? I hear Mikunis have unique venturi
bores, with a larger flow rate.
If I'm holding a jet in my hand, how do I tell what it is? I guess I look
for the Keihin bent-star logo?
What is the square-in-the-corner-of-a-square mark mean?
-gc
Rex Weaver
Rex the Wrench
Thumpers Rool!!!
gcash wrote:
>
>>snip<<
Kaybearjr
If I said yes, I would be guessing.
>What is the square-in-the-corner-of-a-square mark mean?
I have seen that in Mikuni carb parts.
Hoyt McKagen
> Does a Keihin 100 == a Mikuni 100??
No, Keihin are bigger for same number.
> I hear Mikunis have unique venturi
> bores, with a larger flow rate.
It's a lie. When Kbear said so and got echoed by the unwashed, I cut and
polished a Mik jet. It has the normal straight bore thru and nothing
fancy about it. It has a tapered counterbore each end and each end
apparently identical, so it isn't a 'reverse venturi' either.
I could have told you from simply being machinist, that the mfgrs do not
want to spend extra $$ making jets with occult contours because it
increases their scrap rate and costs customer more and at same time it
lowers profit margin.
I thought at first Kbear was really cool, but have seen too much stuff
out of lips since that isn't so. Kbear, can you tell us why denser air
will make a motor go rich, as in your air-filter hypothesis? I thought
not!
> What is the square-in-the-corner-of-a-square mark mean?
That's Mikuni, no?
--
Kaybearjr
I'm still cool, so I put a sweater on..
>Kbear, can you tell us why denser air
>will make a motor go rich, as in your air-filter hypothesis?
I never said that removing the air filter made the "motor go rich." I said that
it made the pilot fuel circuit richer.
But this is usually masked by over-all leaness.
The motor idles just fine, and then surges and pings when the rider tries to
accelerate.
If you look at the construction of a carburetor, you will see that the pilot
gas system is close to the venturi, and the outlet is just downstream of the
closed butterfly, where vacuum is highest.
If air density is low, the engine cannot produce as high a vacuum, and
therefore, less fuel flows out of the pilot fuel system.
Remove the air filter, and air density increases, and there is a greater
pressure differential across the
venturi, resulting in more fuel flowing through the pilot fuel system...
>It's a lie. When Kbear said so and got echoed by the unwashed,
Hey, I don't need to be blessed by Hoyt the Baptist at the river, yanno..
I will have you know that I bathe annually, whether I need it or not, and am
not reponsible for the personal hygiene of my fans pursuing me about the
internet...
Jesse Sands
>I will have you know that I bathe annually, whether I need it or not, and am
>not reponsible for the personal hygiene of my fans pursuing me about the
>internet...
But Maestro, how are we then to know what temperature the water should
be? ;-)
Jesse
Kaybearjr
>be? ;-)
A certain enlightened Zen master had the habit of pointing a finger up in the
air when speaking to his disciples.
A little boy began to follow the Zen master about the village, pointing his
finger in the air, mocking the master.
The Zen master produced a sharp knife, and cut the boy's finger off.
The boy became enlightened at that moment. Why did this occur?
;-)
Hoyt McKagen
> I never said that removing the air filter made the "motor go rich." I said that
> it made the pilot fuel circuit richer.
With thata in mind, how does increased density of the incoming air make
the PJ circuit go rich?
> If you look at the construction of a carburetor, you will see that the pilot
> gas system is close to the venturi, and the outlet is just downstream of the
> closed butterfly, where vacuum is highest.
True mmm ignoring one important feature ... the PJ circuit also exits
ahead of the rear edge of slide, in fact the main effect of PJ is there.
PJ even lines directly up with the hole just ahead of slide and you can
see it from the slide bore, if you look thru that hole.
> If air density is low, the engine cannot produce as high a vacuum, and
> therefore, less fuel flows out of the pilot fuel system.
You have cause and effect reversed: air density and vacuum depend on
motor action; density and vacuum are both co-dependant on velocity in the
intake tract and that is function of throttle opening and displacement
per rev.
> Remove the air filter, and air density increases, and there is a greater
> pressure differential across the
> venturi, resulting in more fuel flowing through the pilot fuel system.
I might question this but it doesn't seem relevant. Fact is any time you
increase air density you have made your mixture leaner. That is because
jets don't resond to density, only to velocity.