[Bruce Woodrow]

Jesper,

You’ll probably find that you will need jets in the 130 – 145 range for most conditions.

Bruce

[Bruce Woodrow]

Placed my order on Feb. 25th, had two updates following further inquiries, last one on April 13th which said:

We are still waiting for our shipment. We are doing our best to satisfy the west coast once we receive.
We will contact you when ready to ship. Hopefully real soon

[Bruce Woodrow]

…and why aren’t K2010 helmets allowed?

[Bruce Woodrow]

Eric,

I agree with Mark – everything indicates that much smaller jets are required with the XS carb., compared to QS/QD. Also, you should limit the throttle travel, as beyond a certain opening no more air can get into the engine because of the exhaust restrictor – opening the throttle further just messes up the mixture preparation as the air velocity past the slide reduces.

Some MicroMax Evo Q&A from Australia:

2.1) 125 Micro MAX

Q: Which upgrades for existing engines are mandatory or recommended?

A: Mandatory upgrades are:

– 18 mm exhaust socket with gasket ring

– Perforated tube silencer with 22 mm elbow

– Squish gap

A: Recommended upgrades are:

– XS carburettor

Q: Is it necessary to install the new Dellorto Ignition System to my existing engine?

A: No, it is not necessary as the Dellorto Ignition System will provide the same engine performance as the

existing Denso Ignition System.

Q: What is the benefit of the new Dellorto Ignition System?

A: More equal engine performance, improved throttle response, easier to use, less manipulation possibilities.

Q: Is there a stop sleeve in the new XS carburettor to limit the opening of the carburettor slide?

A: No, but it is recommended to set the accelerator pedal stop to a 60-80% opening of the carburettor slide

(depending on driver’s pedal length preference).

Q: Will a different maximum opening of the carburettor slide have an impact on the maximum

performance of the engine?

A: No, but the improved ease of applying the throttle might improve lap times.

Q: Will the new 125 Micro MAX specification result in faster lap times?

A: Yes, but just slightly.

[Bruce Woodrow]

Leland,

Your original posting was two days late.

[Bruce Woodrow]

Aaron,

Once you have made sure that the power valve is moving freely, you can check that it is closing by removing the exhaust from the cylinder ‘socket’ and looking in through the exhaust port – the blade of the valve should close off quite a lot of the port and be pretty close to the piston when the power valve cover and spring are fitted.

Bruce

[Bruce Woodrow]

Joel,

Yes – it’s the stamped number near the starter gear. Maxspeed also require that you send a photo of that serial number on the crankcase.

Bruce

[Bruce Woodrow]

Aaron,

Also, assuming that you running a ‘senior’ engine – check the power valve. If the power valve is stuck open, the bottom end power will be terrible and then be OK from about 7500rpm up.

Bruce

[Bruce Woodrow]

Phil,

It’s all in here, see pages 86/87:

http://www.rotax-kart.com/upload/files/2465.pdf

Just one ground wire to connect/ disconnect.

[Bruce Woodrow]

Mark,

M6 thread jets for VHSB carbs appear to be available in sensible steps down to 44 and then jump to 30.  See here:

http://www.dellortodirect.com/Parts/PHVA-Parts/Dellorto-PHVA-6mm-Main-Jet

[Bruce Woodrow]

I haven’t seen any minimum jet size specified for Junior.

Be careful with the 112 jet as that is quite a big % reduction in flow area from the 116!

 

 

[Bruce Woodrow]

Angel,

I don’t know about the DD2, but for the 125 Max I would start at a 160 jet – assuming a barometric pressure of 1020 mBar and that you are NOT using an Evo engine (XS carb.)

[Bruce Woodrow]

Brett,

Sorry, no – those specs are for the prevo QS and QD carbs, the rules for the Evo XS carbs are:

Specific regulation for Dellorto VHSB 34 XS

Carburetor slide shows digits “45” in casting.

Jet needle must be stamped with “K57”.

Two floats marked “4,0 gr” are legal to be used only

Idle has to be stamped with “60”.

Idle emulsion tube has to be stamped with “45”

Needle jet  Stamped with ”DP267” Total length: 51,0 +/- 0,3 mm          Length of bottom section: 33,0 +/- 0,2 mm

Carburetor insert must show stamping “12,5”

 

Bruce

[Bruce Woodrow]

It is always good to have a spare starter and/or starter rebuild kit, a spare fuel pump and/or rebuild kit and a spare charged battery.

[Bruce Woodrow]

Thanks!

[Bruce Woodrow]

Well, now I am back in the USA, perhaps we’ll even get to race again.

Emerson and Weil – your turn!

(I don’t think you’ll ever hear from Jon Andrews again)

[Author]

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