ESE's works engine tuner

[TZ350]

Blue line = PJ. Red line = No PJ. Green line Ignitec switches a solenoid to swap between PJ and No PJ. The solenoid admits air into the PJ suction line.


So the concept works. How about that....

[jonny quest]

Has anyone cut down the stock pickup pad on flywheel, and tig welded on a new one in a different location?

[Mollihead]

I need to fill B-ports that were cast with too big a hook - it blows the mixture straight out of the exhaust port. Somebody posted here about an epoxy that they successfully used to fill the B-port passage by positioning the cylinder at a required angle and then poured the epoxy into the port. I tried searching for it but the search function does not agree with me. Does anyone have a recommendation?

I used JB Weld several times without any problems.
Heat up the cylinder to around 50 degree C.
Mix JB Weld in a tin can and warm it with a heat gun.
It becomes very liquid and you can apply it in the port and let everything cool down in the angle you wish to have.

[diesel pig]

Blue line = PJ. Red line = No PJ. Green line Ignitec switches a solenoid to swap between PJ and No PJ. The solenoid admits air into the PJ suction line.


So the concept works. How about that....

I just remembered that is how Suzuki did PJ switching on and off with there RGV250's. No help to you TZ350, I know but that sort of PJ set up has a track record.

[Condyn]

VANNIK, please update regarding the B port hook modifications. I am curious where you intend to set your target point for the rear wall. I am currently modifying a cylinder for MORE hook, as well as narrowing the C port to match Frits recommendations. The thought of too much hook has crossed my mind, and my friend cautioned me to be very careful in this area. When you say it is blowing straight out the exhaust, where is the rear wall currently targeting, and where are you intending to target it?

[Vannik]

VANNIK, please update regarding the B port hook modifications.

The designer misunderstood completely and ended up with a cylinder that blows the mixture straight out the exhaust port. Other than a lot of grinding, the epoxy in the B-port needs to be filled as shown in attached picture. It had no hook.

[Condyn]

Thank you VANNIK, Indeed the entire rear wall was slanted. As for the trailing edge of the A-port, do you intend to change this as well? I am only being curious.

( unless you consider where you live as " The World " ) like Mericans do, is beyond my limited intellect.

As an American, I can confirm this comment to be accurate for 99 percenters.

[Vannik]

Thank you VANNIK, Indeed the entire rear wall was slanted. As for the trailing edge of the A-port, do you intend to change this as well? I am only being curious.

I intend to change both trailing and leading edges.

[Mollihead]

Blue line = PJ. Red line = No PJ. Green line Ignitec switches a solenoid to swap between PJ and No PJ. The solenoid admits air into the PJ suction line.


So the concept works. How about that....

I always wonder what’s the sense of this powerjet implementation coming with PWK carbs without a solenoid switching it off after peak?
How can it be useful?

[F5 Dave]

Has anyone cut down the stock pickup pad on flywheel, and tig welded on a new one in a different location?

Why would you bother? Just get a tool maker to broach a new keyway and epoxy the old one. Done this twice.
Welding flywheel could cause strife anyway.

[wobbly]

Jonny Quest - yes , but a slight variation. It is all to easy to ruin the rotor magnets by overheating them if tig welding a lobe on the outside.
I machined off the original lobe and made a very small cut on the flywheel OD up to where the lobe outer side was.
Then I made a thin full circle ring with the new lobes on it.
Freeze the rotor and warm up the ring - an easy press fit with no heat.

[TZ350]

I just remembered that is how Suzuki did PJ switching on and off with there RGV250's. No help to you TZ350, I know but that sort of PJ set up has a track record.

Didn't know that Suzuki had done it that way. Good news though, now I know I am on the right track.

I always wonder what’s the sense of this powerjet implementation coming with PWK carbs without a solenoid switching it off after peak?
How can it be useful?

I never rely understood the power jet thing. They seemed a bit of a gimmick. Some of our engines like to have the power jet connected, others did't.

The hot mod on a TZ was these power jets. But they always seemed flawed to me. If you need more fuel, then fit a bigger main jet or lift the needle.



Now that I know how to turn the power jet off for extra top end and over run. With the addition of an air solenoid, the old TZ style Mikuni power jet could be made to do something useful now.

[Noxin]

Has anyone cut down the stock pickup pad on flywheel, and tig welded on a new one in a different location?

Yes, I added a pickup pad on a RG125 flywheel that I mounted on a 2-cyl GT250X7 and used it with a Ignitech unit.
I just made a big blob with the MIG-welder. Then I machined it to correct size.
Worked very well.

[wobbly]

TeeZee - Quote - " I never rely understood the power jet thing ", " If you need more fuel , just make the main bigger " - well guess what , that makes the mid range rich as hell, no matter what needle/tube is used
and the fuel curve goes horribly rich past peak power.
Yamaha used the " ordinary " PJ on early TZ Yamaha engines and it made a huge difference to the on track performance and tuning.
Then later they added the solenoid control , this overcomes a carburetors natural tendency to go richer and richer past peak power, as the rpm and mass airflow continue to increase, but power is reducing
thus less fuel is needed not more.
This works incredibly well , more especially using PWM control to gradually ramp in the fuel cut rate.

[husaberg]

TeeZee - Quote - " I never rely understood the power jet thing ", " If you need more fuel , just make the main bigger " - well guess what , that makes the mid range rich as hell, no matter what needle/tube is used
and the fuel curve goes horribly rich past peak power.
Yamaha used the " ordinary " PJ on early TZ Yamaha engines and it made a huge difference to the on track performance and tuning.

You stole my thunder.
although I was just going to say different fuel circuit effect different areas, with the overlapping area they effect being huge. Power jets gave a way of tuning one specific area.
I was also going to mention different fuels leaded vs unleaded like different mixtures past peak power.

Carbs are an analogue instrument highly developed.
there are or were fiddle screw adjustable power jets and adjustable powerjet kits.


Bell wrote up I thought quite well why they were useful on the early TZ etc

The Mikuni Powerjet carburettor is still rather new to road racing motorcycles
(although Yamaha have been using them since 1976), being originally designed for
snowmobile racing engines. These carburettors have, in addition to the normal 97
metering systems, another separate system with its own power jet and delivery tube,

hence the name Powerjet. The delivery tube hangs in the air intake, in front of the
throttle slide, and is connected through a metering orifice to the float bowl. Up to
almost full throttle, the Powerjet carb operates just like any other Mikuni but, as full
throttle is approached, the air moving past the tip of the Powerjet delivery tube creates
a depression great enough to allow atmospheric pressure to push fuel through the
power metering jet and up the delivery tube into the airstream.
The Powerjet therefore has the effect of enriching the mixture at full, and close to
full throttle, and then only when air velocity is high enough to create a vacuum of
sufficient intensity to discharge fuel. It is, in effect, a load sensitive enrichment system
which allows for more accurate (i.e., leaner) fuel metering at part-throttle operation.
This ensures clean acceleration and smooth running out of turns, yet gives proper full
throttle mixture richness for high power and effective engine cooling. The effect is an
improvement in part-throttle performance and reduced fuel consumption.
Additionally, some two-strokes have a tendency to lean out as they pass beyond full
power rpm with conventional carburettors, but the Powerjet Mikuni is able to cure
this. Normally, when a Powerjet carburettor is used, the main jet size will be around
70-100 smaller, depending on the size of the power jet fitted to the carburettor.
(TABLES 5.2a & 5.2b).