V1 with 80cc Polini, good mid-high end, terrible low.

Fox W. /

fox_w

Sep 26, 2019 06:00AM

Lazer Sport 50, Minarelli V1 with:

80cc Polini kit + VM20 carb + HPI 210 mini-rotor CDI kit and people's pipe.

NGK resistor boot

NGK B7HS (5110) plug

MLM intake & K&N RC-1070 mikuni air filter - 43mm ID

150 jet

87 octane 34:1 oil mix (yes a bit oily, thought maybe good for new engine?)

VM20 is as-is out of the box except with 150 jet (played with 135 to 170)

10 tooth front, and a 40 tooth rear

Timed with buzzetti-ignition-micrometer

Hello, my issue is that the bike doesn't have any power until you get going over around 10mph or so. Below that, it bogs, hardly wants to go at all. I've played with my needle position and jets. After you get going it has a point where it suddenly sounds like it opens up and is happy and then you can really roar to about 47mph or so. But that starting off is so weak, worse than when it was a stock 50cc for sure. Sometimes it even just doesn't want to go at all and will stall out after it gets warm. My head temp reading is typically 300 or so, moves around that.

Most people keep saying timing, but after doing the micrometer, I just feel doubtful I can get it any finer, but I'll try adjusting it if that's really the most likely issue.

Ideas and suggestions?

Thanks.

Re: V1 with 80cc Polini, good mid-high end, terrible low.

Brandon Weiss (Detective brandon to you) /

mopedallday

Sep 26, 2019 09:38AM

I think VM carbs in general come with way too big of an idle jet for most mopeds, so if you didnt change it then that's probably your issue..you're too rich off idle. You need a smaller idle jet. Symptoms support that theory too.

Also, 300 max temps is very cool, you could afford to run a little hotter, but once you get the jetting fixed I'm sure you'll go up a bit.

Re: V1 with 80cc Polini, good mid-high end, terrible low.

baird co /

bairdco

Sep 26, 2019 10:17AM

I agree with the idle jet. Do VMs have an air mixture screw? I forget. Dialing that in might help.

Also, here's a little clutch secret for you. Treatland has a performance clutch for V1's, but the pedal start is out of stock. You can buy the kick start clutch, drill out the rivets holding the KS gear on, and it works amazing for the pedal start engine.

Re: V1 with 80cc Polini, good mid-high end, terrible low.

Dmitry K. /

airend

Sep 26, 2019 01:49PM

> baird co Wrote:

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

> Also, here's a little clutch secret for you. Treatland has a performance

> clutch for V1's, but the pedal start is out of stock. You can buy the

> kick start clutch, drill out the rivets holding the KS gear on, and it

> works amazing for the pedal start engine.

Yes! Thank you, sir!

Re: V1 with 80cc Polini, good mid-high end, terrible low.

Daniel '' /

Go to branch

deesal

Sep 26, 2019 08:44PM

You set the timing with a micrometer, but what is it set to?

Re: V1 with 80cc Polini, good mid-high end, terrible low.

Fox W. /

fox_w

Sep 27, 2019 04:35AM

Great question, I was going for 2mm BTDC, and I think that's what I managed.

Re: V1 with 80cc Polini, good mid-high end, terrible low.

Fox W. /

fox_w

Sep 27, 2019 04:40AM

Gotcha. Well my Idle is size 20, I forgot to mention. I think I've also tried a 17.5. That's about as small as they go. :/ So confused what my issue is.

Re: V1 with 80cc Polini, good mid-high end, terrible low.

ken gilbert /

ride5000

Sep 27, 2019 06:39AM

> Fox W. Wrote:

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

> Gotcha. Well my Idle is size 20, I forgot to mention. I think I've

> also tried a 17.5. That's about as small as they go. :/ So

> confused what my issue is.

vm20 idle/pilot jets do come smaller... I grabbed a 10, 12.5 and a 15:

http://www.braigasen.se/jetting_parts/mikuni/pilot_mikuni/m281001_mikuni/

Re: V1 with 80cc Polini, good mid-high end, terrible low.

Daniel '' /

Go to branch

deesal

Sep 27, 2019 09:44PM

Did you read the directions? 2mm is so retarded. Try 2.5mm at the lowest, remember on an hpi and other digital ignitions; you’re setting the max advance not where it starts.

Re: V1 with 80cc Polini, good mid-high end, terrible low.

Daniel '' /

Go to branch

deesal

Sep 27, 2019 09:45PM

> baird co Wrote:

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

> I agree with the idle jet. Do VMs have an air mixture screw? I forget.

> Dialing that in might help.

>

> Also, here's a little clutch secret for you. Treatland has a performance

> clutch for V1's, but the pedal start is out of stock. You can buy the

> kick start clutch, drill out the rivets holding the KS gear on, and it

> works amazing for the pedal start engine.

Dude shut up! Blowing up the spot!!!!

Re: V1 with 80cc Polini, good mid-high end, terrible low.

Fox W. /

fox_w

Sep 29, 2019 06:37AM

Yes, they say 2mm, and that seems to be a general consensus for a starting point on these variable timing (curved) systems.. 2.5mm is an upper limit, not a lowest, according to everything I've read? (edited)

Re: V1 with 80cc Polini, good mid-high end, terrible low.

Fox W. /

fox_w

Sep 29, 2019 06:49AM

But conflicting with that I can see the hpi instructions suggest between 2 and 4mm, so I will try moving it up. I guess I was looking in the wrong places perhaps. Thank you.

Re: V1 with 80cc Polini, good mid-high end, terrible low.

Fox W. /

fox_w

Jun 15, 2020 11:04AM

Ok so I made the advance from TDC 3.5mm and it seems stronger but still only in the mid/high, the low is still all boggy and awful.. when it's like that opening the throttle wider just makes it worse. But then it has a point as it gets going where it rips.

Re: V1 with 80cc Polini, good mid-high end, terrible low.

>>>taykoff [s2m] /

taykoff

Jun 15, 2020 05:03PM

What clutch springs are you running? Stock clutch with stock springs? That could be a part of the issue...need to slip the clutch a bit longer and build up rpms for better take off...get your low end back. Stock clutches with upgraded springs perform really well...

Re: V1 with 80cc Polini, good mid-high end, terrible low.

pat splat /

ggspeed

Jun 15, 2020 09:53PM

instead of too rich it might be lean down low, choke it for a second to load it up and then gun it to test.

Re: V1 with 80cc Polini, good mid-high end, terrible low.

Satan 666 /

pepilapeau

Jun 15, 2020 10:06PM

With the bike on the stand you should be able to snap the throttle and it should come back to idle pretty fast for your pilot circuit? How many turns out are you?

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