Ducati Motorcycles

Ducati Accessories

Ducati Clothing

Kawasaki Motorcycles

Kawasaki Accessories

Kawasaki Clothing

Used Motorcycles

Motorcycle Clothing

Motorcycle Boots

Motorcycle Helmets

Motorcycle Gloves

Motorcycle Accessories

Motorcycle Security

Motorcycle Exhausts

Motorcycle Tyres

Workshop & MOTs

Dyno Tuning

Frame Straightening

Stock Clearance

Gift Vouchers & Ideas

About Us





Seastar Superbikes UK
Dynojetting A detailed look...

... and carburettors

What is a Dynojet kit>?

Dynojetting is a system of carburettor adjustment. This adjustment may be acheived by changing the idle mixture, needles (generally a radically different shape), varying slide lift speed, either bychanging the spring length, changing the spring strength, the size of the releif hole in the carburettor slide. and finally by varing the main jet size.

Why Dynojet

All of the above are addressed with a Dynojet fitment.The aim with a dynojet kit is to improve the factory carburation.
For example, an early Blackbird suffered a problem at constant throttle (cruise), and with fast acceleration from constant throttle.
Part of the fitting of the kit is to enlarge slide lift holes, which stop the slides fluttering at cruise. - Problem solved. Honda revised production after 18 months to include this design change.
Generally however, a kit would only be contemplated after the fitment of Air Filter, Exhaust can/ Exhaust System or if a cylinderhead had been gas-flowed. Smooth power and engine longevity is really the essence of Dyno tuning.

What results can be expected

Generally an increase in top end horsepower will be seen, however this is not always the case. If the flow through the fuelling system is already increased with a free-flowing exhuast can, then the majority of power increase will have been had.
The purpose of Dynojetting in this instance is to correct the fuelling in mid-range and the throttle response. The most noticable improvement for the majority of cases is during "fast acceleration". It is interesting to note that it is possible to increase the mpg returned by a motorcycle by adding more fuel!

Why should it be set up on a Dyno

It should be noted that not all bikes show a great response to dynojetting. For instance a Yamaha R6 even with a race can does not need to have it's fuelling adjusted. (Fitting a full exhaust system can change that!)
Dynojets come with a basic fitting manual and some recommended settings, but it is rare that these settings are final, and have been known to be out by a country mile.
A rolling road dynomometer allows us to compare run after run against the original power characteristics of the bike. The next level of monitoring is that of Fuel/Air mix, to do this efficiently this must be done "real time" and Seastar have invested in just that facility. We may examine in detail the efficiency of the combustion at whatever revs and throttle opening.

Gas/Air monitoring

The Gas/Air monitor, used on all Dyno runs measures the ratio of unburned fuel to air. This is not only a constant monitor, but thanks to the lack of delay in the processing this data the information is available to plot the fuelling curve over the top of power or torque curves, and so indicate a direct relationship between the two. It is this information that allows us to achieve and demonstrate beyond doubt that we have acheived the best fuel setup.
Power Runs - Only 30-00 +VAT
Our aim is to give you the best advice possible

Technical Detail

Needle Jet(Emulsion Tube) & needle Jet Caps
Dynojet have shroud or cap style nozzles for adjusting the upper or lower top end. They also have an effect, rather like fuel injection by breaking up the fuel as it enters the air-stream.
Fuel Needle
This is where most of the R&D time is spent to ensure that the needle shape has little or no effect in below 3000 rpm, gives the correct amount of fuel through the mid range and has little or no effect on the main jet. This separation if the circuits from each other allows reliable setup for mid-range and driveability.
Main Jet
Dynojet main jet serves two functions, Static fuelling and Dynamic fuelling. Static Fuelling refers to the fuel received in the upper gears, where the tachometer moves slowly. Dynamic fuelling refers to the fuel received during the mid-range. The design of the Dynojet allows it a larger performance envelope, for example mimicking the characteristic of a 125 jet for top end and that of a 135 jet for mid-range. This is accomplished with one 130 Dynojet.
Main air jet
This allows air into the emulsion tube thus mixing the air with the fuel. The main air jet may be reduced or even blocked to achieve the flattest fuel deliveru curve possible.
Pilot circuit.
Pilot jets are not changed during Dynojetting, however Idle and Off Idle may be adjusted with the Mixture screws and or float height adjustment. The Pilot or idle circuit controls fuelling to about 4000 rpm.

Click here for further detail on Fuel Injection Manipulation


« Back  

How and why we have invested over £60,000 in Dyno facilities

Why Dynojet ?
What results ?
Why on a Dyno ?
Gas/Air Monitoring ?
Technically Speaking ?


Seastar has 2 Dynojet rolling roads. A Dyno 200 & a Dyno 250.
We are an accredited Powercommander / Tuning Link Dyno Centre.
Dyno 200 (Mobile dyno) This is able to measure power, torque and Gas/Air ratios against RPM.
Dyno 250 As per the dyno 200, but has on board an inertia brake that allows us to put a load against the drive of the rear wheel.


K&N Power Filters

Available for the most bike models and are Lifetime replacement filters (with believe it or not a million mile guarantee - having said that we don't know anyone that has managed to make any bike last that long.)

The idea behind the use of a K&N is to improve the rate of gas flow through the engine.

From stock, generally the most restrictive part of a motorcycle with regard to gas flow is the Exhaust Can. Fit a Race Can or in many cases even better a Full System and the gases are immediately allowed to escape more easily.
The next most restrictive point is the Air Filter. Once an Exhaust and K&N is fitted, it is simply down to the flow of the Cylinder Head, and short of having that gas flowed you have just about reached the limits.
Although K&N filters are generally in the region of 2 to 3 times the price of an OEM filter, it is the last one you will buy.
In addition to this, the proud owners of the more recent RAMAIR bikes who's steeds will swallow anything to the size of a small elephant through the intake scoops will be pleased to hear that the filters can be washed, re-oiled and re-used. (A useful tip for RamAir bikes - Clean the filter every 1500 miles.)


Home | FAQs | About Us | Meet the Team | Special Offers | Workshop | Tuning | Email Us | Site Map
All content © 2013 Seastar Superbikes. Website created by PCIOT. (Company Registration No.1238789)
The Seastar Co. Ltd t/a Seastar Superbikes, The Garage, Ipswich Road, Newton Flotman, Norfolk. NR15 1PN - Tel:- 01508 471919