Won’t cold start/choke.

Anything related to Lambrettas... ask tech questions, post helpful info, or just read and learn.
Jasio
registered user
Posts: 9
Joined: Sat Aug 08, 2020 8:42 am
Main scooter: Lambretta TV175
Location: Devon
Contact:

Sun Aug 09, 2020 11:05 pm

Hi all.
I’ve read so many similar(ish) posts but couldn’t find exactly this. I have tried many things I’ve read on here and it’s been a great help. But I still have a problem starting the old girl from cold.

I have a S3 TV175. I’ve slowly been making it good, from a complete bag of spanners it was when I bought it. As bad as it was, after a new ignition kit, and carb, the engine has been faultless. My set up is as follows.
GP200 engine. Ancillotti 42mm clubman exhaust. Jetex 22mm. 45pilot/118main/50choke. AF RAYSPEED complete electronic ignition kit with lightened flywheel (1.4kg). Original air box and filter etc.
After a couple of years off the road due to house moves and a lot of babies, I’ve set about getting the old girl out and about again. Once I had done the usual, fuel and carb clean and new petrol. Little bit of maint, I kicked her over and after 4 years, fired up 2nd kick like always. I went for a ride and she didn’t miss a beat for 20odd miles. Then ‘BANG’ almighty backfire and I just got home with it banging and sluggish sounding awful. Assumed timing. Set about looking. All ok. Re timed anyway. Starts fine. As soon as I ride out, within 5 mins ‘BANG’ and limp home. Bogging down and awful. I can’t quite pin it down, poss Stator warming and failing, poss CDI. I don’t know. So I do a bit of research and end up talking with Anthony at Scootronics. And I purchase a new AC stator and high powered CDI. Throw it all together and.... nothing. Won’t start. Check everything. Won’t start. But getting a great spark. I bump start and she fires up. Ride out and going like a dream. A little bit boggy sounding at low revs low speed, say 1/4 throttle. But otherwise great. Cruises at 55, got 70 on a slight downhill. Sweet as a nut. Stop, and kick her over. Fires up a beauty. Next day. Will not start from cold. At all. After dissecting the forums I’m convinced it’s a choke issue. I strip and clean all carb, jets, plunger. The lot. Nothing. But if I pull the choke plunger completely out of the carb, she fires up. No probs. And ticks over. Get her warm, turn off and refit choke so I can effectively turn it off, and the scoot runs like a dream on a good ride out. As good as ever has. It cold next day. Nothing. Won’t start.

Even if I strip the choke plunger out and get the engine running, just so much as offering the plunger to the hole, and instant stall.

I’ve got the old carb and have swapped plungers, jets. Cleaned and cleaned again. Placed hand over carb when kicking over. She will not start cold unless the choke plunger is completely pulled out. I just don’t get it.

I timed initially to 17’BTDC. Now I’m at 19’BTDC.

What gets me is how great my Lammy goes and runs. I ride alone. I don’t know anyone to compare anything to, and it’s my first Lambretta.

Sorry for the long post, but wanted to get all the info in to save you guys time on the details.

Thank you.

wrecklessrobbie
registered user
Posts: 390
Joined: Thu Jan 09, 2014 7:34 pm
Main scooter: li150
Location: York
Contact:

Sun Aug 09, 2020 11:50 pm

I have a rapido 200, 26mm jettex running through the airbox. 42mm clubman built by rayspeed.
Been running it...well trying to run it.
Once i get it going it runs fine. Set at 19btdc on the timing.
It will not always start, or once i have run it for 30 miles or any distance its a gamble as to wether it will start again or not.
I have changed the cdi, plug and multimetered the stator.
I have been advised to change the carb.
I am having it dynoed and a new carb fitted at the end of august.
If you have changed the cdi and reset the timing
Providing they are not faulty and you havent had a seizure and damaged the piston rings i would look at the carb.
What size is the old carb is it a jettex. If not and its big enough perhaps you should try that.
Some people have made good improvements on the jettex by changing the atomiser. See here

http://www.ilambretta.co.uk/forum/viewt ... f=6&t=3192

Me im going to try a new carb, am pissed off of stripping the carb, adjusting the floatbowl as one minute its fine the next overflowing with petrol.
Martin at chiselspeed has suggested a 24mm polini carb. I have only found one bit of information on them. They are good but if you throttle them at starting up can cause flooding.
If you havent solved it by 25th of august i shall let you know how i get on.
At present, when i ride before i stop i turn off the petrol. Let it run the carb almost empty.
If i start it next day, airbox rubber connected to the carb, choke on no throttle whatsoever. Petrol on engage kickstart and it will go after one or two kicks..
Unless of course the float has stuck and its p1551ing petrol all over the floor.
I have also altered my airmix screw and idle screw.

User avatar
coaster
registered user
Posts: 3117
Joined: Wed Jan 07, 2009 12:35 pm
Location: London and Norfolk
Contact:

Mon Aug 10, 2020 8:13 am

Might be irrelevant but you should always hold the throttle closed when starting from cold, many people make the mistake of wringing the throttle whilst kicking which results in a weak mixture, worht a try.

Daggs
registered user
Posts: 720
Joined: Wed Jan 07, 2009 1:23 pm
Location: Addington Kent
Contact:

Mon Aug 10, 2020 8:30 am

The big problem here is you seem to be tackling too many issues at once.
Are you as sure as you can be, you now have the ignition working and set properly?
(incidentally, in twenty years restoring and riding. The only time I had a scooter back-fire on me. It was the Cdi breaking down)
You're cold start issue indicates to me, insufficient fuel at start up. Though conversely it can indicate too much air.
Check for air leaks. Is the carb on tight, is the rubber hose split. Is the compression good (therefore not a leaking head gasket)
If all is well, raise the pilot jet to 48 get the scoot started and set the air mixture screw and tick-over.
One other consideration is a very worn slide in the carb. can make starting difficult

Jasio
registered user
Posts: 9
Joined: Sat Aug 08, 2020 8:42 am
Main scooter: Lambretta TV175
Location: Devon
Contact:

Mon Aug 10, 2020 2:07 pm

Thank you all.
Daggs: I’m pretty sure the ignition is a) spot on component wise, and b) Timing is bang on 19’. I would be surprised if it’s wear in the carb. It was new a year or so before I laid the scoot up. I will look into the air possibilities. I know I have mentioned a lot of things, but at the same time, nothing has changed as to how it’s set up when it started really well.

Once I get a few miles in, perhaps if it is something like a head gasket problem, that will become visually obvious. It’s just the fact when it’s running, it’s as sweet as ever.

Coaster, old habits die hard. But I will be strict on this so it may help. From my understanding, technically it’s not a ‘choke’ in the exact sense. Please correct me if need be. But more a cold start/max fuel jet to get them going. So I will get in the habit of keeping off the throttle.

Wreckleasrobbie, definitely keep me up to date on the carb please. I’ve if’d and am’d for donkeys about upgrading the carb. Some people give the jetex a lot of stick, others say a good one is a fair option. I have been in the thought of, it works, it drives well and I’m happy with the performance. But maybe if I need to look at replacing it, I could consider a change of carb completely. Like I said, it’s difficult because I ride alone, and don’t know anyone with a Lambretta to pick their brain or compare to. So changing to a different carb, for me, will be the biggest minefield going. It would be great to hear how you get on.

Thank you so far gents. 👌🏼

Cav
registered user
Posts: 40
Joined: Mon Aug 26, 2019 12:21 pm
Main scooter: SX 225
Location: West Australia
Contact:

Wed Aug 26, 2020 8:58 am

I believe your main jet is too small. Should be running a larger main jet on a Jetex with a 42mm exhaust. I know lots of folk manage to get Jetex carbs running well, but they used to be pretty troublesome back in the day. The Scootopia replacement carbs have a good rep.

Cav
registered user
Posts: 40
Joined: Mon Aug 26, 2019 12:21 pm
Main scooter: SX 225
Location: West Australia
Contact:

Sat Aug 29, 2020 5:46 am

Try a 125 main jet if you can. Changing to a new carb is pretty easy. Most will run ok straight out of the box. Interested to see if a new carb sorts this issue.

Daggs
registered user
Posts: 720
Joined: Wed Jan 07, 2009 1:23 pm
Location: Addington Kent
Contact:

Sat Aug 29, 2020 8:28 am

Changing the main jet will have no effect on starting issues.

User avatar
HxPaul
registered user
Posts: 1097
Joined: Fri Dec 06, 2013 1:58 pm
ebay user ID: panhead_5
Main scooter: lambretta Li 150
Location: Halifax,Yorkshire
Contact:

Sat Aug 29, 2020 8:46 am

Daggs wrote:
Sat Aug 29, 2020 8:28 am
Changing the main jet will have no effect on starting issues.
It will on a jetex carb,the fuel goes through the main jet before it gets to the pilot jet.

Daggs
registered user
Posts: 720
Joined: Wed Jan 07, 2009 1:23 pm
Location: Addington Kent
Contact:

Sat Aug 29, 2020 11:03 am

Indeed it does. But if the pilot is say a 45 and the main is a 100 or 110 or 120 or anything greater than a 45. It makes no difference.

Post Reply Previous topicNext topic
  • Information
  • Who is online

    Users browsing this forum: Google [Bot] and 30 guests

cron