Varitronic & Miller Booster --Do I need to rejet?

[jdevane5]

Hi All,

I have my 53 125 3 speed on the road now, its got varitronic and a Miller Booster exhaust.
I have noticed the scooter is quicker with the choke out.
I have adjusted the mixture but its still quicker with the choke out.. . Do I need to rejet?

Any advise welcome.

Would love to hear of anyone with similar set up. Thanks

[jbcollier]

Yes, you will need to fit a larger main jet. Go up until it starts to "4-strokes" wide open and then back until it just stops. Go one more step down and you should be about right with it a little on the rich side.

Love to see pictures of the "Miller Booster". Heard about them but haven't seen one yet.

[jdevane5]

Thank alot jbcollier

I think I have attached a pic, could not figure out to add a pic in the comments box...
I'm guessing to try Dellorto for main jet in different sizes,whats the standard size main jet?

Thanks

[jbcollier]

Cool, that actually looks very good.

I have a custom expansion chamber on mine. It's HUGE. But it gets the job done. My primary is much, much longer to boost at low revs. I can pull 80 kph prone up modest hills. It's bleed'n loud though and I've been thinking of trying another pipe. Siagon Scooter centre used to offer one but it was absolute crap. That's why I had a custom one made.

First, check the flow from your fuel tap. You might have to take it apart and drill out the holes if you're not getting decent flow.

Next get a series of jets larger than stock. Keep going larger until it 4 strokes at WOT. Then back down as I explained above. Do not be fooled by it running "fine". 2T engines run great when lean but they then overheat and burn pistons.

[jdevane5]

Thanks alot, will let you know how I get on.
Been onto Dellorto, selection of jets in the post.

And I would love to know how fast the scoot will go -But I will need to fit a speedo at some stage!
Relying on a speedo App for now which I have had 50mph so far on a very short run.

The Miller Booster is not too loud either.

May have to uprate the 50's brakes if I carry on making it quicker...

[jbcollier]

Yours has brakes?

Mine doesn't!

Hit 50 mph and the front brake does absolutely nothing. I have an Li front hub I've considered fitting but then you have to switch to 10" wheels and pretty soon it's not a D anymore.

[nickw]

Been onto Dellorto, selection of jets in the post.

Hi, I am hoping to add a Miller exhaust to my d. Did you get the jets from Eurocarb and any trouble with them? I have heard that due to the virus Dellorto have struggled to make their stuff and that some jets/carbs are hard to get. Would you mind sharing what ones you bought please

cheers
Nick

[jbcollier]

My last order from them was just a few months ago, no issues. They have always been great to deal with.