My bike won't start. Can I get some help troubleshooting please ?

Hi all, I am in a spot of bother and was hoping that someone out there can help me. I have a 49cc air cooled cag that simply will not start. A couple of weeks ago I changed the carb to a dellorto copy. Once fitted, I fired up the bike with some start ya bastard and had it running nicely. I then went up to Lakeside for an afternoon of riding and the bike refused to start. I have tried everything I can think of to make it run. I have tried 3 spark plugs, a stardard timing key, an advanced timing key. I have tested for spark by pulling the plug out and earthing it to the frame and pulling on the starter. Spark is fine. I thought it might have been the carb, so i took the carb off and shot start ya barstard straight into the reed cage, but alas, nothing. I took the reed cage off to check that it was in the right way and it was. I have checked for an exhaust blockage, it flows fine. I have checked the earth and it to is ok. It simply will not fire. I am lost for what to try next as I have been over everything multiple times. Does anyone have any idea what it could be as I am becoming more and more frustrated.

is there compression?
if not check your pistion ring check all bolts are done up
if yes make sure the spark plug is in and boot is on propley
also clean your carbie out blow throught the jets with a compresser or what ever make sure there not blocked

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barnsey
aka bj#5

another thing disconect your kill swith completely and give it a go they tend to short out id give that ago

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barnsey
aka bj#5

As bj said the kill switch may be shorting out is the spark a nice blue spark?, also take the bowl off the carb make sure there is a good fuel supply

If you have a good spark & good fuel flow to the bowl & all else seems ok inspect the crank seals, it may have a leaky seal or even popped one out,
To test put half a coke lid of fuel straight into the top end via the plug hole & see if she kicks
if it kicks then it sounds like a crank seal or crankcase leak.

if that don't help then pull the topend off & have a quick inspection,
when a 2 stroke has fuel, spark & compression they should at least fire or kick, but of a crank seal is gone then it may be sucking in air only from the leak & the reeds may not have enough suction to open & draw in the air/fuel mix into the case

and you could also check for the rubber seal on the inside (manifold side) to see if its still there..

I once had the rubber o seal on the inside of a new del rep go through my reeds and into my case once... didnt harm the reeds but wasnt sealing i guess and probably didnt like the floaty in the cases...

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Regards,

Gray.

MortysMiniMotos

i've since noticed only the 15/15 reps have this rubber o seal and not the 14

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Regards,

Gray.

MortysMiniMotos

some do
the better 14/14s reps do have a plastic spacer & rubber oring in them so i would say some factory's may have cut corners & not used the oring that gos behind the small plastic sleeve so yes i would check that

Air.
Fuel.
Compression.
Spark.

That's about the only things it possibly CAN be on these bikes.

Air: Dirty filter? As a test, try pulling the air filter off and putting a section of pantyhose over the mouth of the carburetor with a rubber band. Any air leaks around carburetor, exhaust port, reed cage, engine case? Spray these points with carburetor cleaner - any leaks will ignite. (Don't worry, it's safe - just shoot a tiny bit on there...)

Fuel: check your fuel lines? Carburetor? Fuel valve turned on? (I know, sounds like a stupid quiestion, but htere are people who really DON'T know about this ...) Dirty fuel filter? Washed out the tank with clean gas?

Compression: Are you getting any compression? Pull your spark plug, put your thumb over the spark plug hole, and pull the starter a couple of times. The compression should blow your thumb off the hole. If not, there's a leak.

Spark: Check the spark? Since you have the plug out already, put the wire back on it, and ground it against the frame or the cylinder. Pull the pullstart - what color is the spark? Blue-white, or orange? Blue-white is good, orange is okay, not great - means you may need a new coil, or at least an adjustment. Take the pullstart off - underneath is your coil and your flywheel. Your coil should be a business cadr's thickness away from the flywheel. If not, loosen the bolts, and readjust.

That's about all I can think of rght now ... good luck.

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"The Rat":No fairings, period.Volkswagon gas filter.DuPont spraycan muffler.Altoids box air cleaner. Dremel wrench killswitch cover.Check it out here: http://www.pocket-bike-racing.com.au...html#post92825

Hey guys, thanks for all of your help. I had checked the bottom head bolts and assumed that as they were tight the top ones would be too. A silly mistake that caused my problem. the thing goes like stink now with that new dellorto on it.

whoa...

Good tips...

The compression tip is a really good idea w/ the tumb over hole

Whoa....

good tips spyguy,mac,bj........

learn alot off this thread

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#77