Engine Trouble 80cc cutting out at higher rpms HELP

[scorpion1]

My bike used to go 35 on flat ground and now will only go 25, it reaches a point where it just holds back, like its cutting out. I just replaced the carb with an hp carb and no difference in the top end. It has alot more torque and smoother response at lower rpms though.

IT RAN FINE FOR MONTHS, then one day started this

It is getting plenty of fuel flow as i have changed the petcock out a while back.

Is it 4 stroking?

Do i need a new ignition coil?, plug? they are still stock

HELP!!!!

 

[FurryOnTheInside]

I would start by cleaning the air filter, or upgrading it. High rpm demands more airflow.

The plug, boot and wire can be upgraded. It could be vibration causing the boot to lose contact, but the upgrades are good to have anyway so it's a win/win.

 

[crassius]

I'd first check that head gasket is tight.

 

[scorpion1]

Thanks gents.

I just put on this carb(picture) so the filter is new. The carb didnt fix the issue which started with the cheapo carb on it.

So carb change didnt help, and filter is clean.

Does my bike have a CDI??? (its all stock) if so would the stage one performance NGK 'ready' work with it(picture also) http://www.bikeberry.com/engine-kit...formance-cdi-electron-ignition-coil-3776.html

Also, what is a boot?

ALSO ****The bike runs perfect up to 25 then starts the sputtering. It doesnt slowly get bad, just hits all at once

THANKS SO MUCH FOR OFFERING HELP!!

 

[Street Ryderz]

Thanks gents.

I just put on this carb(picture) so the filter is new. The carb didnt fix the issue which started with the cheapo carb on it.

So carb change didnt help, and filter is clean.

Does my bike have a CDI??? (its all stock) if so would the stage one performance NGK 'ready' work with it(picture also) http://www.bikeberry.com/engine-kit...formance-cdi-electron-ignition-coil-3776.html

Also, what is a boot?

ALSO ****The bike runs perfect up to 25 then starts the sputtering. It doesnt slowly get bad, just hits all at once

THANKS SO MUCH FOR OFFERING HELP!!

What exhaust are you using? And did you do a proper breakin?

 

[Frankenstein]

Almost seems like a too rich issue, maybe leaning out the carb a tiny bit would help. Possibly there was an air leak that left it exactly right for a while and somehow it resolved itself and put you into being too rich as a result.

The Dellorto clone can only be adjusted by changing the jet, so if you have some or know somebody who does try a smaller jet size. I only assume it's rich because it hits you all at once which makes sense if it starts 4 stroking at the same speed continuously like most rich conditions will. As the engine breaks in you'll need to adjust things to keep it in the happy zone. Didn't switch fuel types anytime recently did you?

 

[scorpion1]

Almost seems like a too rich issue, maybe leaning out the carb a tiny bit would help. Possibly there was an air leak that left it exactly right for a while and somehow it resolved itself and put you into being too rich as a result.

The Dellorto clone can only be adjusted by changing the jet, so if you have some or know somebody who does try a smaller jet size. I only assume it's rich because it hits you all at once which makes sense if it starts 4 stroking at the same speed continuously like most rich conditions will. As the engine breaks in you'll need to adjust things to keep it in the happy zone. Didn't switch fuel types anytime recently did you?

It has 350 miles on it. My exhaust is lengthened with the stock muffler that has been 'cleared out' a bit. I thought this new carb gave the proper amount of fuel being that it doesnt have an adjustable needle like the stock one. I dont remember changing fuel. Maybe i need some fresh since i hadnt run it in several months....?

Can i use the CDI coil i posted?

 

[FurryOnTheInside]

The boot is the thing on the end of the plug wire that fits onto the top of your spark plug. The stock one is not good (I haven't even used it though, saw it and decided to upgrade to an NGK non resistor boot right at the start).

The stock CDI should be fine for up to at least 35mph. Personally, I have retarded timing at the magnet key anyway, but that's up to you.


Having read your further information, if the carb has been sitting for several months with fuel in it then it would be a good idea to clean it out by shooting some carb cleaner through it. Buy a can online or wherever. It could be that the fuel flow is being restricted within the carb by a residue of old oil.
And yes, use freshly mixed fuel.

 

[scorpion1]

Thanks, i want a new CDI though cuz i have hit 37 a few times and the one i posted i would prefer. Will it work with my motor?

 

[FurryOnTheInside]

Thanks, i want a new CDI though cuz i have hit 37 a few times and the one i posted i would prefer. Will it work with my motor?

Idk but I'm sceptical about bikeberry products being any different to stock, lol.
37mph doesn't actually mean anything without knowing what your gearing ratio (sprocket and wheel size) is.

All I know from my experience is that filing the magnet key by 1.2mm (1mm should be fine too) to retard timing is working nicely for me.

I'm using the stock CDI and I have been trying to take it easy, only once been tempted to go to 8000rpm (which is 37.27mph on my bike) but I'm still breaking in so four stroking all the time except on steep climbs.

Filing the key is certainly the best value for money because it's free! So I recommend you try that first before spending money on a CDI.

Offset timing by magnet key

• FurryOnTheInside
• Sep 17, 2017

1.2mm offset key for a 5.4° postponed base timing (if I'm correct).