LCGB Forums

Hi All,
I have fitted a 22 mm jetex carb and inlet manifold to my GP 150, it is now a pig to start, it takes forever to start and when it does it will not take above half to three quarter throttle, it just dies, I am getting really pissed off now, the float is working and there seems to be plenty petrol in the car, anybody help with this one.
Cheers
Stag

Hi

Take the float bowl off and check that all the jets are screwed in tight. Whilst you have the float bowl off check and note all the jet sizes.

Other than that check the choke plunger is seated correctly when thechoke is in the off position.

My new Jetex had a pilot jet that was not drilled out. I fitted a second hand delly pilot jet. The floats jam as well and the floats need drilling out where the spindle goes through. I have spare jets for these in my garage if you get stuck. Make sure you have a 150 slide.

Regards Colin

kennystag wrote:Hi All,
I have fitted a 22 mm jetex carb and inlet manifold to my GP 150, it is now a pig to start, it takes forever to start and when it does it will not take above half to three quarter throttle, it just dies, I am getting really pissed off now, the float is working and there seems to be plenty petrol in the car, anybody help with this one.
Cheers
Stag

what Atomiser , Pilot and main jet have you fitted ?

Don't be too quick to blame the carb just yet.

If you are using the original atomiser and jets which have no markings then remove them and put the correct Dellorto parts in their place. You are wasting your time using jets and atomisers that have no markings stamped on them . With unmarked components you cannot know for sure what size the jet orifices are unless you use a jet sizing tool

A standard GP150 should have a 5899-4 Atomiser fitted which has a 1.75mm bore
Your pilot jet should be a 45 (.45mm bore )
the Main jet should be 118 (1.88mm bore)
The slide should be a 7895-2 which has a scoop out the back and a cut out to one side.

This should be your starting point.
First you need to make sure that there is a sufficient gap under the slide for a reasonable tickover idle speed by adjusting the throttle adjust screw. Adjust your idle air mixture screw to about 1x turn out initially (ignore the label on the carb )
Make sure when starting that you do not apply any throttle whatsoever until it starts. Otherwise you defeat the choke and over-gas the engine.



Provided that you have no air leaks on the inlet and the choke is operating correctly that should at least get you started .
You soon end up with quite a little collection of jets when tuning

hey stag..... how did you get on ?

It would be nice if you could post back with a response or solution which might help other owners that arrive at this thread.

Hi Johnny Mate,
I honestly thought that I had replied, still working on It, if you look at my other request for information help I always say your help will be appreciated and thanks, so a big thanks to you Johnny mate for taking the time to send me all the info that I find very helpful, also thanks to others who took the time to respond to my help. To give you a update, I am fitting electronic ignition and when I get that sorted out I am going back to sort out the carb and will keep all posted.
Cheers
Stag

have you checked the airways aren't blocked in the filter box / air scoop?
is it an old filter?
could the standard exhaust be blocked or coked up?

Hi hullygully and all,
New Stainless Tuned Performance Exhaust fitted, filter is ok, no blockage, flywheel and stator are of the bike, waiting on electronic ignition coming, as there was problem with the stator, will be fitting when ever it arrives, then back to the carb. I will keep all informed of progress. Would also like to thank captain pugwash and grandpa for all there help.
Cheers
Stag

well keep in touch staggy cos we are all here to help one another
If you were any nearer me I'd offer to come round and help.
Sorting out the problems with these old scoots can be part of the fun of ownership but it can also become frustrating if solutions arn't found within a reasonable time frame.

Cheers Johnny boy matey,
I have been working on cars, buses, and trucks all my life but working on Lammys are temperamental, confusing, frustrating little b,,,, they beet al logic but I love them for all there faults. My first lammy LD was 40 years ago, strip down model, lol, I had to bump start her as there was no kirk start, I could not use her in the dark as there was no lights, they where the days.
Cheers
Stag

lights ! .......... I used to tie a torch on the back covered with my girlfriends red lipstick and follow cars using their headlights .
Pretty scary on dark country roads when the car in front suddenly turned off a side road
happy days

You're probably best binning the jetex and buying the Scootopia 22mm delly copy, Jetex's are a bit hit and miss. Paul