it won't go anymore!

[dunworking]

Help! My Sprint will run fine for a short period, about 300 metres, then suffer from what seems fuel starvation (if I pull the choke out it momentarily improves the situation) all power is eventually lost until all I can do is trickle along on tick over until it dies completely . If I wait a couple of minutes the engine will fire up and the whole procedure starts over again.

I’ve changed the inline fuel filter, cleaned out the petrol tap (and tank), cleaned the jets and checked plug and points all to no avail - Anyone got any ideas?

I should add that this suddenly started last week whilst out for a ride, I had been out for about 45 minutes and was happily scootering along at 45-50mph when it died on me.

cheers
Sean

[Ilan]

well maybe its an electrical problem after all ...

ride the sprint without the side panel
when the engine stops, immediately try to see if theres a spark
pull out the cable (from the plug side ofcourse) bring it close to a metal body part and kick the starter a few times, watching for a spark

you should do this immediately when the engine stalls

[dunworking]

Just tried and have a strong spark. I'm going to get the carb off and strip it on the bench just in case I've missed something simple. Thanks for the advice.

[bryno]

Does sound just like crap in the carb jets to me or maybe a restriction in the needle valve reducing the fuel flow, could be it runs until the float bowl is empty, then starts again when the bowl fills ??, I know you have cleaned it out, but certainly worth doing again..

Something on the ignition side would most likely cause a misfire, so fuel related IMO..

[skrappey]

Could be as simple as a blocked breather hole on the filler cap. Try riding without filler cap on and see if it stalls. Try simplest thing first.

[dunworking]

You know what, I ve recently fitted a new chrome filler cap and now I think about it thats roughly when the trouble started - know what I'll be doing in the morning!!
cheers skrappy (and bryno for earlier advice)

[skrappey]

Please tell us if it sorts itself out.
So I can gloat a bit.

[dunworking]

Tried this evening, sorry to report no gloating for you today. Im sure its something to do with fuel flow though, as once it starts to die theres nothing that will help until it stops (will just about tickover and twisting throttle makes it worse) i have to wait a few minutes and its up and away for a hundred yards or so. I can just about limp home on more or less closed throttle and occasional use of choke (made it to 10mph this evening). Carb off again tomorrow. Also does anyone know how I can check to see if flow from tank is good enough?

[bryno]

Hmm, you can time the flow rate i.e. remove tank, and measure how long it takes to run 1ltr through.

I did this on mine once, can't recall where I found out what the flow rate should be though, think it was in the haynes, whihc probably won't help you much..

[nroberts13]

Have you checked to see if the carb is leaking fuel? This has happened to me..

[skrappey]

It's obvious the fuel isn't entering the float chamber fast enough, clean filters and check supply pipe, both at carb and at base of tank. You'll know if it's at tank because of the smell of petrol and puddle in your drive. If you need to take tank out, check the tap, it could be only turning half way if it's a T5, which has an all or nothing tap, no reserve setting. It could only be half open. Sounds a bloody annoying one this, keeep on and you'll find the problem eventually.
Wish you luck.

[phinw]

HI dunworking,

My LML Star is suffering precisely the same problem. I came across your post in search of answers. So far, I have cleaned the fuel cap vent, installed new jets, new fuel tap and fuel line but no success. It's been suggested to me that either the carb float or needle is damaged and/or fuel filter is full of gunk so I’m rebuilding the carb this weekend. I’d love to hear if/how you resolve this!

[dunworking]

It's still not going despite having tank out again, re-cleaning everything, replacing all gaskets and seals. Even had the housing off to replace that gasket. However I have noticed that the throttle slide cap has a lot of micro-fractures and I’m wondering whether this is causing the problem (i.e. when it starts to warm up the fractures open up and completely ruin the mixture). I'm having a last go this week changing the cap and more cleaning and checking. Then if it doesn't work I will drag it down to Medway Scooters and have them sort it out (otherwise I'll end up hitting it with a hammer) What’s really p***ing me off (sorry Spence) is that its probably something really simple! And skrappey your probably right, it is more than likely lack of fuel to the carb, it doesn’t seem to be flowing fast enough but I just cant see why! Fuel tap isn't blocked; it has a new filter and a new inline filter. Flow is the same whether in "on" and "r" position. Perhaps I'll order a new tap and see if it makes a difference.

The only saving grace is that the weather has been so bad I haven't missed a great deal of riding

[dunworking]

;D Whey hey!!!! I'm up and running again. I replaced the fractured throttle slide cap and bingo – no more stopping after a few hundred yards. It’s a bit “flat” during the first part of acceleration through each gear now but I'm sure that’s probably just a bit of tweaking with the mixture.

Thanks for everyones help

[bryno]

Blimey, well done for spotting the fracture, would never have guessed that!

[dunworking]

I only noticed them because as i removed the retaining screws part of the lug cam away . I then noticed what looked like tiny scratches over the cap, which on closer inspection turned out to be fractures, some going the whole way through some not. If the lug hadn't broken I'd still be looking for the problem !

[skrappey]

Another possible cause recognised and fixed, only 1,999 to go.