Honda Dio AF27 problems / help

[ratcat98]

Honda Dio AF27
Current mods
1500 rpm koso clutch springs (contra and small)
New oem type belt (old one started to tear)
Lightened rollers, (2x 8g, 4x 4g)
V8 pipe,
Upjet, current 80 main jet (stock 75)

Relevant replacements
Throttle cable

Main issues:

1. Throttle stays on, as in the engine revs high, even when cable is fully recessed, revs right up to full throttle unless I brake. (This has been happening for a while, may not be related to other issues)

2. Shuts off occasionally if I come to a stop, or when I go up a hill then let off the throttle on a slight flat
-on downhill, engine doesn’t idle / can’t hear it when let off throttle until I pull throttle then it will bog then accelerate
-Weird boggy noises throughout it running
-When it dies, I try kickstarting it numerous times and have to wait a minute or two before I can start it, first kick
(These are probably all connected issues, they have been happening since I put the bigger exhaust on, I took the new exhaust for a run and the moped died at every set of lights and I couldn’t kick start it for ages. Once I pushed it home, I put the stock exhaust back on hoping everything would be safe and sound, nothing changed, the issues persisted. )

Electrical issues ——

Low lights
Batatery has voltage 12/13V off of moped
Sometimes the dash lights up and can indicate very dim, when I turn the key but sometimes it doesn’t unless I turn the engine over.

[90GTVert]

1. Check the throttle cable and slide in the carb. If the slide isn't in right or if the cable has any issues, this can happen. You can take the air filter off and look in the carb to verify that the slide closes most of the way. If not, again the slide could be wrong and you should check the idle speed screw to make sure it isn't too far in and the throttle cable adjustment and make sure nothing is wrong with the throttle assembly. If the throttle appears to be closing, then maybe you have an air leak. The best way to check for that is with a pressurized leak test. More info here : 49ccscoot.proboards.com/thread/506/make-2t-leak-tester-ways Other possibility is that it's very lean at some throttle position and that can make it rev up some, especially if paired with a high idle speed setting.


2. Have you tried other jets or just the 80? You may want to check fuel flow to make sure it's not running out. If it stops and then you have to wait to restart, that's very often either a soft seize, where the engine gets hot and the piston expands more than the cylinder so it seizes, or it is running low or out of fuel. Typically fuel flow is an issue at wide open throttle, but when one of mine was stock it would shut off if I used much throttle at all sometimes and I'd have to give it 30 seconds at least before it would restart. The vacuum petcock was the issue. I don't use vacuum shutoffs on any of my scoots now. I prefer manual as there's less potential for failure. Just takes the effort to shut it off when parked and turn it on when ready to start.


Electrical - Check your grounds first. I always like to tie the battery negative, frame and engine together at one point with a fairly large cable... at least 12AWG.

[ratcat98]

Thanks for the reply, I have upjetted from 80 to 85 and now currently at 82, no improvement. I have checked throttle cable head to toe, slide is fine.
The engine is now seizing after I have it running, where 1, if I kickstart it on a stand and put it down, when the wheel stops spinning, the scoot will die, and when I put it down, it takes some grunt to move it and then the engine starts, mega confused. The engines getting oil, I’ve changed jets, maybe try 78?. Air flow is not an issue. I have to have the idle screw all the way in to start the engine, hence why it over revs I guess, not really a big issue, when I turn idle screw down / out I think that issue stops. Not so worried about electrical anymore, they work fine when engine is turned over. I’ve had a decent look into the fuel lines and I haven’t touched anything previously, the carb is getting enough fuel. I’m stumped.

[kosmos]

usually you have an airbox mod of some type to go along with a bigger exhaust. Did you replace the air filter?
try up jetting to 85-90 thats usually in the ball park.
get a cht gauge to see if its running too hot. when you start modding the motor, grab one to make sure you arent seizing it.

..for the full throttle on start issue. Weird. the brakes have nothing to do with the carburetor. totally lost on that one. just dont start it with it on the street or you'll go wheeling off into someones bumper

[mopedmofun]

If you are reving to the moon i think it’s an air leak.