MK2 cuts out and refuses to start. HELP???

[Sean91]

I could use a bit of help from you crm guys!!! Since owning this bike ive had problems with the engine cutting out and refusing to start, ive paid two different mechanics to sort it out but its only ever ran temporarily before the fault quickly returns, however owning this 2 stroke has tought me a few things about bikes...

Lately even though its been off the road for 3 weeks its been starting first kick and running fine, as soon as i got it on the road today though its a different matter. It still has a really good power delivery, it has so much grunt for a 250! But it does idle quite high and the revs do increase without touching the throttle. I rode 5 miles today, turned the bike off for half an hour to see a friend, when i got back on the bike it started 2nd kick but died 30 seconds later and now it refuses to start once again. At first there were no signs of life, no neutral light flashing on the dash or lights flickering like it usuall does but then i started to get both when i try to kickstart it. We tried to bump start it but with no luck, i then pushed it to a local mechanic but he had no joy and no space to book it in which leads me Back to square one.

Im still not very experienced with bikes but it sounds to me like its sucking too much air in, hence the revs and seeing that the carb has been serviced twice now it cant be that. The bike also doesnt start even when im getting lights so it cant be the killswitch, i dont think? Im thinking its a worn gasket on the crankcase or something like that which is letting air in.

Any further help would be appreciated

[jompy]

you got me !
as mines been stood for a while the generator quite often has no residual power in it so when you kick it you get no nutral light or headlights lighting up with each kick for the first few kicks , the revs rising does sound like it could be air getting in , you culd have a perished inlet rubber one of the tricks is while the bikes running spray ( and someones going to have to confirm this although it was mentioned in a thread recently ) something like WD40 around the carb & inlet rubber so if theres an air leak it'll suck in the vapor & the revs should rise ( some one will correct me ).
my CRM used to cut our & i found that it seemed to be the ht lead had a break in it & it would sometimes cut out & be a pain to start , coincidentally my KTM Duke II started cutting out when it was warm about 6 miles up the road at a set of trafic lights that took ages to change , that turned out to be corrosion at the end of the ht lead where the plug cap screwed on .
sorry i can't be more help but at least you know your not being ignored , now where are all the people that know what the hell they're talking about

[fallenmikethebike]

To much air will cause the high, and rising revs. The oil spraying trick on the rubber manifold temporarily fills the porous areas and the revs should fall. There's no gasket [ paper] for the crank halves, but generally some sealant would be used.
It also sounds like an intermittent electrical gremlin, the wiring looms are now some 20 years old, and the primary culprit for a fault. Is the plug wetting up when the bike won't start? Buy a handful of cheap BR8ES plugs and next time it won't start swap one of those into the bike, checking for a spark on the new plug.
Mike

[Sean91]

I dont think so, there have been times when the engine is cold that ive heated the spark plug up with a lighter and thats been enough to start the bike. I dont know if thats relevant

What sort of wiring fault are we talking about?

Cheers

[rich1960]

I reckon you have more than one fault, one us electrical and one fuel/mechanical.

Re the electrical fault, my mk2 was doing the sambas yours...dead with no flicker when kicking, turned out to be the wires going in to the ignition barel, the connector block that the wire from the ignition barel was faulty, so I cut it off on both sides and used bullet connectors on all the wires....no further problems, and, I wired the bullets so that if there ever was a problem, I could bridge the wires iliminating the ignition barel...but I never needed to. Also, for what it's worth, I made a new earth wire, cleaned the frame back to metal and bolted it back.

You need to fix one problem at a time and then assure yourself it's right, trying to fix more than one problem plays with your mind.

Good luck, it will be worth it when you get it right.

Rich

[fallenmikethebike]

Some of the starting problem might be familiarisation with your bike and it's specific starting routine, you'll find what works eventually. Make sure the throttle body is bottoming out. and the cables aren't frayed .
The weak mixture will eventually lead to a run away R.P.M., and catastrophic engine failure.
Mike

[pudzie83]

the cutting out is definitely to do with electrics and im with rich its near the ignition barrel. along time ago my barrel was faulty i replaced it with a 1.99 B&Q (hidden) switch never had a issue since and as mikes mentioned check for any air leaks around the carb and your mixture is right

black plug=to rich (plugs will die excess oil out of end can)
white plug=to lean (NOT GOOD)
golden brown=perfect (happy two toker)

Is your throttle cable routed correctly as well?