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Hi Chaps,
I have a Jet 200 that came with an open mouth 26mm Dellorto phbh with AF Rayspeed clubman.It will only start if I cover the venturi to act like a choke.I have now fitted a standard air filter and bellows to tool box.The jets are needle X7 pilot 50 tube V266 and choke or starter jet 70.If I turn the choke on when its running it bogs down slightly.I have sprayed easy start around joints when running but no effect.When it wont start the plug is not really wet as if it is not sucking enough fuel.Once running it revs ok .It is on a sorn so dont Know how it runs on the road.Looking on this site most suggest a 50 starter jet
Is a 50 starter jet bigger or smaller than a 70?
Does it make a difference that carb is tilted see pics?
I have not played around with float heights yet
Fresh fuel and carb cleaned twice especially the channel in float bowl that feeds starter jet.Jets blown out with compressor.Compression seems good.If I cover the venturi will start second kick.
If I cover the venturi completely when running it will stall.
Any ideas appreciated.
Thanks Grandpa.

I had a carb once that wasn't drilled for the choke jet in the bowl but you say yours is ok so you could always try a larger choke jet from Eurocarb, normally a 70 is sufficient but try an 80. Another thing I've found is to not let the plunger go fully open, this seems to restrict the amount of air through the channel but still lets the motor pull fuel through.If the motor doesn't stall with the choke on when warm it would suggest the jet is too small.Another thing is if it's an old motor is to check the motor will cut out when you block the tailpipe as it may be drawing air in , weakening the mixture and whether the rings are worn .

Adding that hose & filter should have made it more likely to start by emulating your hand in choking it...

The choke jet should preferably be of the type that has an 'o' ring fitted on it. (The bowl needs to have a recess to suit the 'o' ring as well as drilling to allow fuel to the choke jet) These can even be retro-fitted to VHB's (with the correct bowl) & are, essentially, a two stage choke jet, delivering a slug of neat fuel for enrichment when the engine is first turned over, then acting as a normal mixture enrichment (choke) whilst cold running.

The image here shows the 'o' ring groove but no 'o' ring fitted:



For clarification, I presume that you have a choke jet of 70 & a pilot of 50? If so & the choke jet is of the type detailed above, you shouldn't be too far away with what you have....

Compression test ? Rings might be worn.

Hi Chaps
Thank you for your prompt replies.I may have made some progress.This morning I checked compression as suggested by Chris in Margate which was 80psi just kicking it over,with some oil down plug hole it went up to 83psi.
WT1 I am concerned at the angle of carb hence picture so I lifted the scoot and put a 5" block under right hand stand leg to lean scoot and make carb more level...thereby allowing more fuel for the starter jet...........and it started from cold second kick! .It may be a fluke so I will let it cool down whilst I download the Dellorto manual and find out about float height and how to adjust it.
I have only experience with Jetex.Is this common to have carb at this angle?
It has an inlet manifold with MBD (mark Broadhurst?) could this be the wrong manifold for this carb?
Thanks for your help
Grandpa

The carb angle is fine, they're supposed to work up to 45 degrees. Float height is 24 mm give or take .5 mm with the bell mouth flat on a table and the needle just touching the float jet

Wack wrote:The carb angle is fine, they're supposed to work up to 45 degrees. Float height is 24 mm give or take .5 mm with the bell mouth flat on a table and the needle just touching the float jet

I can't add to what Wack has said other than some tuners consider some downdraft to be advantageous.

However, when checking the choke, there are many parts to it. The jet itself, the operating (cable) mechanism, the 'o' ring & the bowl with it's passageways all contribute to the function.

80 psi is low.
Mine is 105 psi on an engine that is 10,000 miles old. and I have also checked the tester on other known running engines and they have ranged from 105 -115.
I did this so I could reference out to known engines and I know on my tester 115 psi is good. Other testers may read higher or lower; what do you expect for £12.99 !!

So I am suggesting, use that compression tester on another good known engine to see if there is a difference before you start stripping down.

Hi Chaps
Update: now sorted.
I observed that If I held the float bowl at roughly the same angle as that when carb fitted and I put a small amount of fuel in the float bowl whilst it would enter the feeder channel for the starter jet it would not reach the starter jet well moulded into the float bowl plastic unless I held the float bowl more horizontal.If I held the float bowl at the angle when fitted and then turned the bowl a few degrees anti clockwise fuel would enter the feeder channel AND fill the moulded starter jet well..I left the float height at 23mm,refitted the carb and it starts every time on the first kick as there is now fuel in the starter jet well.I.E the carb now leans anti clockwise see pics.
Thank you all for your input.
Grandpa

The bottom left hand corner of float bowl now has more fuel than when carb was more vertical.
Ps.
This does mean that if I park it facing uphill on a steep hill it may not start.........but........" I dont really need a Lambretta as I have a bus pass"

Glad that you sorted it & thank you for your feedback.

I think people may easily overlook the part that the float bowl itself has to play in the function of the choke device. I've personally found them with sediment in the passageway, as it is the lowest point in the bowl until you make the carb downdraft...

Thanks Grandad for showing the pictures, my carb tilts the other way, and I wonder if this has anything to do with my issues? (My bowl set at roughly 5pm where yours is now at 6pm.)