Hard Starting Engine By station180 (Read 1,530 times)

[station180]

I have a 2013 peace sports scooter that is driving me crazy. It has been upgraded to the 100cc big bore kit. It runs great when it starts but it turn and turns forever until it does. I have had the engine apart and checked the rings and cylinder they are good look like new.Compression is also good. Replaced the coil and plug Cleaned the carb. Changed the auto enricher. Played with the valve gap currently at .005 Checked all the grounds.For some mysterious reason the scooter started great for 4 days last week then it started sputtering when you give it throttle put in another cdi and its back to running great if you can get it started. its just as hard to start using starting fluid. So i know its getting fuel and spark i cant figure out how it can run so good and yet be so hard to start. i appreciate any advice

[Alleyoop]

Valve gap on a 50cc should be .003 inchs on both or .003 inchs on the intake and .004 inchs on the exhaust.
Also have you adjusted the carbs fuel mixture and what do you have as a AIR FILTER? On the scoots for starting nice and easy the mixture has to be set pretty good, also do you have a PERFORMANCE CDI which would have the timing advanced. If so try putting on the original CDI to see if it starts easier.

Alleyoop

I SAID FUEL FILTER I MEANT AIR FILTER:

[station180]

yes I have cleaned the carb several times adjusted the valves to 3 and 4 back to 5. I am a small engine mechanic by trade but have never worked on scooters just mowers trimmers chainsaws ect. Never seen anything like this! It seems like a spark issue but when i ground the plug its getting fire. whats really confusing is if you get it started it idles smooth the power is good top end is about 45 to 50 its ujust that it might take you 20 minutes to get it started! It magically healed its self lat week for 4 days and started as soon as you hit the button but then went back to the same old thing. a guy i kno thinks its the stator going bad but would it run good after its started if it was the stator?

[station180]

Also the guy i know that works on scooters has some cdi boxes tried an orange one wouldnt start at all. A red one still hard to start and sputter and skips at about half throttle. original hard to start runs goo after starting. The air filter is one of those high performance cone looking ones. Have tried the idle mixture from ! to 3 turns in 1/4 turn incriments

[Alleyoop]

Since it has a BBK was the pilot jet changed? the carbs on the 50s are usually 18-19 mm and come with pilot jets 30-32 and mains from 69-72. Do you know what jets are in the carb?

You can test if the PILOT is to small start it up and start turning it clockwise it should kill the motor when you have 1 full turn from the closed position. If it keeps running after all the way closed the pilot is to big, IF it kills the motor when there is 2 or more turns left then the pilot is to small.
Alleyoop

[station180]

I bought this scooter about 3wks ago with this problem thinking it was just a valve adjustment issue. All the mods had already been done. I dont know about the carb but I know they upgraded it. it is a keihin. When adjusting the mixture screw I get the fastest idle at about 3/4 to 1 turn out which leads me to believe the jets might not be quite right but that wouldnt explain how it started as soon as you hit the button for 4 days?

[Alleyoop]

So they stuck a big arse pilot jet in there and your getting to much fuel for starts seeing as the enricher is also feeding it extra fuel. So open the carb bowl you can just loosen it and turn it on its side to get at the screws or if easy you can take the carb off but no need to take the throttle cable off and see what size pilot jet is in there.
Alleyoop

[station180]

Looked at that last time I had the carb apart there were no numbers on either the pilot or the main jet

[Alleyoop]

How about the carb size did you measure the carbs intake side to see what size carb it has. They may have overdone it and overcarbed the sucker with a to big of a carb then they could not get it to run good so they sold it. Happens a lot with the young and or not so mechanically inclined folks they always think dump a gallon of gas and it will tear up the asphalt(NOT).
Alleyoop

[station180]

no i havent measured the carb. What size jets should it have with the big bore kit. I will try to get some from the guy I know or maybe another carb to try.

[Alleyoop]

If it has what they call 100cc=83cc really, then main should be in the 90-95 and the pilot no bigger than #32. Stock they usually come with a #30 pilot and main 69-72. But jetting is really trail and error because it all depends on the motor and compression it is making and how much air it is sucking in. So two motors with the same BBKs will run different and make different horsepower to many variables can be different between both of the motors. So the best we can do is at least get close so as not to run them lean and damage the motors.
Alleyoop

[tvnacman]

I'm thinking its an ignition coil problem, I have trial and terror on the same symptom and the ignition coil has done the trick. Have you tried another coil? The valves on these little engines can be a bit of a challenge I would recheck them just for piece of mind.

John

[station180]

it will fire like it want to crank but cant get it going at all today. tried a different plug no luck. I guess it could be getting to weak of a spark from the coil. I dont have a spare here but i borrowed one a couple weeks ago and it didnt help so I gave it back to the guy.

[cyborg]

During the mystery 3-4days when it lit right up was it cold those days?

[Guitarman]

Good question Pete.
What was the weather like on the 3 or 4 days it started right up? Rain? Snow? Cold, hot?
Also, what kind of gas do you have in it? Fresh? Old? Ethanol mix?

Obviously the usual fixes are not working, so lets look at the unusual.
Did there happen to be a hottie in a bikini in view when it started right up?