GY6 150cc Scooter Cutting out above 48MPH By jetpilot1 (Read 1,384 times)

[jetpilot1]

Well my scooter was running OK but the plug said LEAN. I up'ed the main jet and the plug now has a little color, but TOP SPEED was still about 52 MPH (hoping it would help). It is like the ignition is cutting off. It continues to accelerate to 48 mph. Any TIPS to trouble shoot. I had the plug back out and checked the gap an color.



The scooter starts easy, idles nice. has good low speed acceleration, but right at 48 mph like clock work it misses.



I have done some work that was unrelated to fixing this issue, but just FYI:



Removed the emission system

Removed the vacuum fuel petcock and put a manual one on

The problem was before doing this work and the scooters runs the same or better (at low speed). 

[tvnacman]

what size was the main jet and what size did you replace it with?

John

[dav3]

I am having the same exact problem- idles fine,runs great until it hits 37 and then it starts bogging ,sputtering,runs like crap.
 I have not done any recent carb work to it

[cyborg]

Take out the air filter and take it for a short run see what happens,,,could be as easy as a dirty filter

[dav3]

i had a loose wire on the cdi- fixed the problem

[lostforawhile]

Dec 2, 2017 20:19:02 GMT -6 jetpilot1 said:

Well my scooter was running OK but the plug said LEAN. I up'ed the main jet and the plug now has a little color, but TOP SPEED was still about 52 MPH (hoping it would help). It is like the ignition is cutting off. It continues to accelerate to 42 mph. Any TIPS to trouble shoot. I had the plug back out and checked the gap an color.



The scooter starts easy, idles nice. has good low speed acceleration, but right at 37 mph like clock work it misses.



I have done some work that was unrelated to fixing this issue, but just FYI:



Removed the emission system

Removed the vacuum fuel petcock and put a manual one on

The problem was before doing this work and the scooters runs the same or better (at low speed). 

are you looking at kph or mph, most speedos have the numbers reversed, mph is on the bottom, no stock 49cc will hit 50 plus without a lot of work, the best ones hit 45,plus the speedos are usually off

[lostforawhile]

Dec 4, 2017 7:57:39 GMT -6 cyborg said:

Take out the air filter and take it for a short run see what happens,,,could be as easy as a dirty filter

they will usually run worse without it. The cvk carbs need the vaccume generated by the filter for the needle diaphram to work right

[jetpilot1]

Thanks for the replies. I have to check the jets, but it was LEAN LEAN LEAN when I got it (but did not cut out). I went to the larger jets and it ran pretty much the same but plug has color.  The problem did not exist for some time after the new jets.The problem came after the jet change.

The scooter is running GREAT start, idle, low speed acceleration except for this 48 MPH cutout. Before I'd get to 52 or 53 mph and it just ran out of steam, no cutting out.

I did have an electrical issue that may or may not be related. When I turned the handle bars one way the bike would not crank or start. Some times riding it died. I fixed it. It was piss poor wire routing under the fairing, that cause it to pull the wire harness tight and pull on the connectors when turning handle bars one way. I fixed it, but I need to go check these connections. It is possible I have partial wire issue, where it is not fully open or broken but partial. This partial connection may not give enough juice to the CDI/COIL?

NEW PROBLEM. I tried the replace the CDI to eliminate the CDI as an issue.  It is a 150CC GY6. So I got an aftermarket CDI and it fried (orange one you see on eBay for $8). The first one I ordered was AC CDI... It fried in seconds. I was ignorant of the different types. I determined I have a DC system. I ordered a different more expensive DC CDI, CASOLI "CF250" ($18). It also fried. What am I doing wrong. May be my scooter has different wiring. I saw one youtube video where you have to pull one wire out of the connector on the bike side?

[jetpilot1]

Thanks for all the GREAT replies...:lmao:



Well after lots of trouble shooting I found it was my main jet was too big. The scooter was running way lean and went up two sizes from what I thought was in there (which had no markings). I should have measured the orifice with a drill bit and compared to the jet kit I bought. Well the original was likely 110. Two sizes up from 110, is 1st is 115 and 2nd is 120.



Well I took the 120 out and put in 110... after verifying the original was 108.



Now before you say OF COURSE... Right after the jet change it RAN FINE with the 120. The high speed miss came later. I may have also had a spark plug issue. It was clear the plug was getting fouled. However unrelated and may be bad luck the plug may have developed a defect (meaning a crack in porcelain not visible or internal conductor break). I measured the plug and go zero continuity.



New 110 jet installed (one size up from original) and replaced plug and it runs perfect.

[czmdiver]

Jul 13, 2018 21:28:05 GMT -6 jetpilot1 said:

Thanks for all the GREAT replies...:lmao:



Well after lots of trouble shooting I found it was my main jet was too big. The scooter was running way lean and went up two sizes from what I thought was in there (which had no markings). I should have measured the orifice with a drill bit and compared to the jet kit I bought. Well the original was likely 110. Two sizes up from 110, is 1st is 115 and 2nd is 120.



Well I took the 120 out and put in 110... after verifying the original was 108.



Now before you say OF COURSE... Right after the jet change it RAN FINE with the 120. The high speed miss came later. I may have also had a spark plug issue. It was clear the plug was getting fouled. However unrelated and may be bad luck the plug may have developed a defect (meaning a crack in porcelain not visible or internal conductor break). I measured the plug and go zero continuity.



New 110 jet installed (one size up from original) and replaced plug and it runs perfect.

You may want to try other Vendor for Jets. They do go in increments of One as in the next size up from a 110 is a 111 then a 112 and so on, many Scooter vendors only carry popular sizes not all the in-betweens.
Going from a 110 to a 115 is a big jump and even bigger jump the 120