Power loss After Changing CDI By crst (Read 3,635 times)

[crst]

This is a Roketa MC19-150 scooter with a 157QMJ 150cc engine.
I replaced the CDI unit to obtain more power for climbing hills and for riding with a passenger.
The first test ride after changing the unit I could only go 38mph.
I put the old CDI back in it (that was getting me 60-65mph) now
it is only giving me 38mph max speed as well.
Both CDI units are A/C (the two pin plug has two wires).

Twice after changing back to the old CDI while driving a full throttle suddenly it started giving me more power back up to 55 and then dropped back down after only a few minutes. It has not
cleared up again since then.
Only 700 miles on this scooter.
Removed and checked the fuel screen from the fuel tank and diagram pump. Screen is clean and tested the diagram pump with vacuum,works fine, filter is clean hoses are all perfect condition and clamped tight.
Intake filter is clean all hoses are good and clamped tight. Checked all wiring connections for all components.
Battery is full charged and generator is working good.
Removed and tested the fuel inricher from the carb, tested good.
But I did find only 2 volts feeding the inricher, should be 12V if I am not mistaken. So I disconnected it and feed it 12 volts then took it for another test ride, no help still only 38mph.
Starts perfectly hot or cold. Runs smooth all the way from idle to full throttle. It's like from half throttle to max there is no change in rpms or the way it sounds.
Thank you in advance for any help with this.

[Alleyoop]

A CDI is not going to give you more power unless it is adjustable to change the timeing.
I would at this time change the Coil and try your Old CDI again. To get better climbling uphills you should change to lighter weights in your Variator. That will keep your rpms higher and the belt lower in the Clutch Pulley when the Load is on.
Alleyoop

[crst]

Thank you Alleyoop
I will look into the lighter weights for the Variator, and remove the spark plug and check for a hot blue spark.
Perhap I should just move the power wire for the choke to a wire that is hot when the ignition is on.
Yesterday I ordered a new coil & spark plug.

[crst]

Sorry about that. I will check the connections again.

[crst]

Today I am going to check out the quality of spark with the old
stock CDI.
I agree the purple performance CDI that I put on it started the problem only minutes later & after only a few miles had knocked it down from 60-65mph to 38mph max. almost as though I had put a rev limiter on it instead of a CDI.

[crst]

I checked the spark today, has a blue spark. Very tiny.
It has a NGK plug # C7HSH with a gap of .20
Is this the correct gap?

[oldchopperguy]

I had a similar problem, and first changed the coil. That helped a lot... Evidentally, the original coil was going bad as Bashan said. I then put in a no-limit CDI and everything worked fine. These scooters have individual personalities, and what worked on mine might, or might not work for you.

I do believe both the factory coils, AND CDI's are pretty poor, and tend to slowly go bad, which slowly drives you NUTS! I used a Japanese Bando orange coil (about $20 on eBay) and a "New Racing" (red version) CDI (I just HATE that stupid name, but it works great... LOL!) also about $20 on eBay.

I also had to do the typical re-jet on the carb, raise the needle a LOT, and replace the stock airbox/filter with a Uni "sock" filter to get bog-free acceleration and smooth top end. Mine (the ol' hoss in my avatar) never would run right with the factory "tuba" airbox and intake.

Only problem I've encountered is a need to REALLY watch the tach, as the motor will turn a quick and honest 10,000 rpm if you don't watch it. Not so good on rods, mains, valves and my old heart... LOL!

Keep fiddling with the CDI, coil, carb and air filter and you'll get it perfect!

Ride safe,

Leo in Texas

[Alleyoop]

Bashen,
Well I have a Performance PURPLE CDI and a Orange Performance Coil from Buggyspartsnw since last year and doesn't seem to be a problem. I know I am still chaseing the 600 or more RPM loss but I lost those before I bought the Performance stuff. As a matter of fact I bought them thinking the OEM Coil and or CDI were causing the problem but NOT

Right now my Trike is running beautiful but only gets up to around 6800 rpms and that is all she wrote.
Alleyoop

[crst]

Problem found. Hey Hey!!
After testing all of the electronics Thanks to all the great test procedures I found posted on this site, I started with the mechanical side today.
Started with the valves, the exhaust valve was tight. I adjusted it to .004, intake valve was fine.
The I moved to the carburetor. I removed it and started breaking it down, The first piece I removed was the top cover for the diagram and BINGO! there it was a 1/4" split in the rubber.
I put a dab of rtv silicone on it, let it dry and put it back on and wala RPMs, power & speed are back. Now I am going to order a new one for it.
Great learning curve for me. It all turned out to be a coincidence
after changing the CDI and road testing that the diagram split.
Well I did not know anything about these scooter before this and now I know it pretty well thanks to all of you and this Forum
Thank You All.

[Alleyoop]

Ok guys, how about my power loss I have tried everything in the book I THINK:) I put in a new carb, put in the OEM Variator with 10 gram weights which it came with I am out of ideas.

The Engine runs fine when I open it up it almost all the way it revs up to 6 grand and it starts to pull and gets up to speed really nice. At 6 grand when up to speed it is hitting running 50mph then I twist a little more and it climbs another 500 rpms then I twist the throttle all the way open about 1/4-1/2 inch twist and nothing it just keeps running at around 6500 rpms.

There is no hesitations, sputters, bogging, NADA like the last part of the throttle is dead.
Any IDEERS, with the setup it should be running in the 7000 rpms range. Heck when I put in the orginal 10 gram weights with the orignal variator it should of ran in the 8000 rpm range.
Alleyoop