Hot starting - 25m DelOrto

[Gary Harwood]

My S2 TV has developed a hot starting issue. If I try starting within 5 - 10 minutes of the engine being turned off it will start first kick as usual but it will only tick over with the throttle fully open and the fuel tap turned off (to burn off the fuel) for a couple of minutes until it bursts into life, the fuel tap can be turned on and she runs normally. A new float needle didn't resolve the issue. I can live with it but it's pretty annoying, especially after stopping to re-fuel or if I (rarely!!) stall it at junctions/lights! Any ideas?

[Storkfoot]

Check your float isn't letting in fuel too. Just had this very issue this weekend.

[Tractorman]

I have this problem also, I can fix it by removing the air hose and it will start first kick every time. I have swooped carbs with my other scooter and the problem remains. I have been told that port timing can cause this but not how to fix it.

[george747]

Hi,i would also like to no how to fix the prob as I also have the same hassle,the only change is that I have a 26mm delly,only dose in now and then????

[Scootie32]

Hi, I thought it was only me! Only difference is 30mm Dellorto .
I have replaced the float, float needle but still the same.
If I turn the fuel tap off a minute before I key off everything is fine, first kick start but like was said above
stall it and it's a pain.

[MickYork]

The choke not fully returning or seating properly could cause the symptoms described.

[george747]

Hi,i wlll check the float for petrol inside,what could be causing the the bike to idle when the throttle is being held open(reving it}.thanks

[Storkfoot]

I'm guessing the original poster has a standard engine, albeit with a 25 PHBL. I'm also reading that the scooter had been running OK beforehand. For those reasons, I doubt it's port timing related or that the carb is running too rich at a certain point in the throttle progression as it would have manifested itself earlier.

Both of these could be the legitimate reasons for poor hot starting though.

You can start the scoot by holding the throttle open to allow loads of air in to compensate for the flooding of petrol or overly rich vapour in the bellows.

[Gary Harwood]

Thanks for the comments guys. My engine is not quite standard.........it has a SR top end kit and a big bore box pipe. The scooter does indeed run fine all the time except for this recent hot starting issue, and it had done almost 5,000 miles since the engine build before the issue started. And Scootie32.........I have 3 scooters and I always turn the fuel taps off and leave the engines running for 30 seconds or so before switching off. I have no issues whatsoever with the other 2 scooters but this doesn't seem to help on the S2. Maybe I need to let the engine run even longer with the fuel tap off before switching the engine off but, as another poster states, that doesn't help re-starting after a stall.

[coaster]

As Storkfoot said, it is caused by fuel being spat back into the bellows and this happens to a greater or lesser degree to all Lambretta engines. Various factors come into play such as port timings and badly seating chokes as already mentioned. Idle jet/air screw will be a factor as will the cleanliness of the air filter. Has this problem come on since the air temperature has started to drop? If so you could try a hotter running plug?

[Storkfoot]

SR barrels wear out quite quickly so it may be a case that the bore is just worn out. I'd take the bellows off and look for oily sludge (petrol evaporates leaving oil). Then strip carb down to look at float. Then, if carb not full of petrol, take top end off and check rings and piston to bore clearance.

If your carb is set on the rich side at some point a worn barrel may make the bogging down worse. IMO

[Scootie32]

Coaster, I don't run a bellows. I did run the carb open on the advice of AF, who I bought the carb off, but still had the problem.
I now run a foam filter but still the same.
I think I may take the above advice and over winter have the barrel off and check for wear.

[MickYork]

have you tried running without the filter ?

[bigbthesoulman]

had the hot start problem for years,took it to a old school lambretta mechanic in his late 70 s,choke cable was wrong,to short to be exact,every time sat on scooter it was putting it on,sorted never had problem since,he also advised bigger pilot jet

[coaster]

.............. I did run the carb open on the advice of AF...............I think I may take the above advice and over winter have the barrel off and check for wear.

Running without a filter will definitely accelerate wear so checking the top end is a sensible thing to do