MB5 70cc Jetting

any advice on where to start jetting?

Using the Dos Cycles 70cc cylinder (not very agressive) and a VM20.

tks.

Re: MB5 70cc Jetting

I would say 120-160 start high work down needle clip in the second notch from the bottom. Use a temp gauge it will help. Vm20 is very sensitive to temperature change so u can have the jetting dialed in today and it will be off tomorrow.

Re: MB5 70cc Jetting

Dirty30 Dillon /

> Tomos A35 Wrote:

> -------------------------------------------------------

> I would say 120-160 start high work down needle clip in the second notch

> from the bottom. Use a temp gauge it will help. Vm20 is very sensitive

> to temperature change so u can have the jetting dialed in today and it

> will be off tomorrow.

This sensitivity doesn't happen when you run a real airbox

Re: MB5 70cc Jetting

i'll start there, thanks!

Re: MB5 70cc Jetting

> Dirty30 Dillon Wrote:

> -------------------------------------------------------

> > Tomos A35 Wrote:

>

> > -------------------------------------------------------

>

> > I would say 120-160 start high work down needle clip in the second

> notch

>

> > from the bottom. Use a temp gauge it will help. Vm20 is very sensitive

>

> > to temperature change so u can have the jetting dialed in today and it

>

> > will be off tomorrow.

>

> This sensitivity doesn't happen when you run a real airbox

Temperatures changes every day enough said. Why would u run a vm20 through a air box instead of a air filter made to fit on it?

Re: MB5 70cc Jetting

Dirty30 Dillon /

> Tomos A35 Wrote:

> -------------------------------------------------------

> > Dirty30 Dillon Wrote:

>

> > -------------------------------------------------------

>

> > > Tomos A35 Wrote:

>

> >

>

> > > -------------------------------------------------------

>

> >

>

> > > I would say 120-160 start high work down needle clip in the second

>

> > notch

>

> >

>

> > > from the bottom. Use a temp gauge it will help. Vm20 is very

> sensitive

>

> >

>

> > > to temperature change so u can have the jetting dialed in today and

> it

>

> >

>

> > > will be off tomorrow.

>

> >

>

> > This sensitivity doesn't happen when you run a real airbox

>

> Temperatures changes every day enough said. Why would u run a vm20

> through a air box instead of a air filter made to fit on it?

Because most high-strung shifter bikes (and most, if not all mopeds) run 10x better with an actual airbox. Large bore carbs love pulling from a large available well of still air.

An airbox also helps mitigate ambient air temperature changes as the enclosed space being so close to the motor is consistently warmed by engine operation.

These are facts. There is no Uni or Metal Mesh filter that will outperform a properly sized and constructed airbox.

Re: MB5 70cc Jetting

> Dirty30 Dillon Wrote:

> -------------------------------------------------------

> > Tomos A35 Wrote:

>

> > -------------------------------------------------------

>

> > > Dirty30 Dillon Wrote:

>

> >

>

> > > -------------------------------------------------------

>

> >

>

> > > > Tomos A35 Wrote:

>

> >

>

> > >

>

> >

>

> > > > -------------------------------------------------------

>

> >

>

> > >

>

> >

>

> > > > I would say 120-160 start high work down needle clip in the second

>

> >

>

> > > notch

>

> >

>

> > >

>

> >

>

> > > > from the bottom. Use a temp gauge it will help. Vm20 is very

>

> > sensitive

>

> >

>

> > >

>

> >

>

> > > > to temperature change so u can have the jetting dialed in today

> and

>

> > it

>

> >

>

> > >

>

> >

>

> > > > will be off tomorrow.

>

> >

>

> > >

>

> >

>

> > > This sensitivity doesn't happen when you run a real airbox

>

> >

>

> > Temperatures changes every day enough said. Why would u run a vm20

>

> > through a air box instead of a air filter made to fit on it?

>

> Because most high-strung shifter bikes (and most, if not all mopeds) run

> 10x better with an actual airbox. Large bore carbs love pulling from a

> large available well of still air.

>

> An airbox also helps mitigate ambient air temperature changes as the

> enclosed space being so close to the motor is consistently warmed by

> engine operation.

>

> These are facts. There is no Uni or Metal Mesh filter that will

> outperform a properly sized and constructed airbox.

There's pros and cons to that. More weight a new home for critters if the bike lives out side. Not all bikes have room for a well constructed air box. Air is all around us doesn't matter if it's being sucked through a box or a filter on the carb. Air doesn't stay still as it's being drawn through a box or the carb. It might help temps but not by much it would be more work to clean it 2.

Re: MB5 70cc Jetting

Dirty30 Dillon /

> Tomos A35 Wrote:

> -------------------------------------------------------

> There's pros and cons to that. More weight

Added weight? a plastic airbox weighs less than 2 lbs. On a 120 lb. MB5, that hardly matters.

> a new home for critters if the bike lives out side.

Not a real con by any means. Critters can also crawl into your ears when you sleep, but I don't think you're plugging your ears every night.

> Not all bikes have room for a well constructed air box.

True, but most do and the MB5 comes stock with a fitted airbox.

> Air is all around us doesn't matter if it's being sucked

> through a box or a filter on the carb.

This is false. Rudimentary Fluid Dynamics pretty much dissolves that argument.

> Air doesn't stay still as it's

> being drawn through a box or the carb. It might help temps but not by

> much it would be more work to clean it 2.

Air doesn't stay still but having no pressure variations from passing air creating a low pressure zone in front of the venturi helps the carb more accurately meter fuel across rpm and vehicle speed.

Most of your cons deal with just having to clean or construct the airbox, not with the fact that it will 100% increase performance in this application. I have tuned multiple carbs across the MB5/NS50/MBX series of bikes, EVERY one saw a massive benefit from running either a modified stock, or properly setup aftermarket airbox.

To the OP. If you want the VM20 to run well, modify the stock airbox for the VM20, or build another one.

Re: MB5 70cc Jetting

It's a moped not the space shuttle.

Re: MB5 70cc Jetting

Dirty30 Dillon /

> Tomos A35 Wrote:

> -------------------------------------------------------

> It's a moped not the space shuttle.

It's not even a moped.

Re: MB5 70cc Jetting

And the space shuttle doesnt even have an IC engine so it has no use for an airbox anyways.

Re: MB5 70cc Jetting

> Cameron Cate Wrote:

> -------------------------------------------------------

> And the space shuttle doesnt even have an IC engine so it has no use for

> an airbox anyways.

Ha . The whole shuttle is an air box .

How do you think those guys breath ? LOL

« Go to Topics — end of thread

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account