Dhla 45s, front carb vacuum real high back carb fine. Solution ??

[Lotusfab]

Yep thats it, one more thing you can rule out.

[910Esprit]

Balance of individual throttle bodies (bleed screws) looks reasonable.   Just looks like the carb linkage is hopelessly out of adjustment.   Perhaps you could you video the linkage mechanism and the impact it has as you adjust the screw (not sure if a S1 is same as later models)   

[drdoom]

Perhaps the more direct approach in ascertaining whether the carbs are balanced is in order. I've no Dellortos handy and prior experience is with DCOEs, so are there removable plugs in the carb bodies over the progression holes? With the Webers that's a good method by which to check whether a pair are in the ballpark. Another trick, though far less handy, is to trap a thin and narrow strip of material between throttle blade and throat, thereby determining rough balance by whether both carbs will nip the test strip at the same point. Learned that one from an older motorcycle enthusiast who prescribed rolling papers ( cough, cough . .  ) though one might just as well cut strips out of aluminum beverage can.

[910Esprit]

That's a good idea - Yes, you could remove the progression hole covers and see if the butterflies are in a similar position between the 2 carbs as a rough guide.

Just a thought - Anyone know how the choke circuits work on a DHLA?   EG  if one carb was stuck open would it allow air to bypass the butterflies?

[jonwat]

On 04/06/2021 at 08:46, 910Esprit said:

Just a thought - Anyone know how the choke circuits work on a DHLA?   EG  if one carb was stuck open would it allow air to bypass the butterflies?

If the carb is stuck open then the butterflies are fully open????

DHLAs don't have chokes, they have starting devices.

All the carburettor air air flows at different throttle openings are shown as diagrams in the manual. 

Edited June 5, 2021 by jonwat

[910Esprit]

5 hours ago, jonwat said:

If the carb is stuck open then the butterflies are fully open????

The context of my post being that If the 'choke' (fuel enrichment circuit) is stuck open, does it allow air to bypass the butterfly killing the vacuum on that carb?  As I'm sure you know it is common for both venturi in each carb.

[drdoom]

The starter unit does indeed direct airflow to bypass the throttle, in doing so provides both enrichment and de-throttle in order to offset the colder, stiffer engine's reduced inclination to idle at desired revs.

Cheers

[910Esprit]

Cant we just call it a 'choke'?   If you were to order a new bowden cable that connects the lever on the centre consol to the rear carburettor. what would you call that?

Anyway, suggestion for S1guy to ensure that the choke mechanism is seated correctly in carb with reduced vacuum.  (although I cant hear it leaking in the video clip).

[jonwat]

15 hours ago, 910Esprit said:

The context of my post being that If the 'choke' (fuel enrichment circuit) is stuck open, 

Ah, I read it as it was written that the carb was stuck open.

[s1guy]

Ok guys. Popped the bolts off and checked both choke/enrichment pistons.Both working and not stuck. Throttle plates are both in the same spot when closed. Checked those by looking at the progression holes. But my timing belt def jumped 1 tooth. Belt is back on correctly and checked the belt tension. Spun it 4 times and rechecked the tension every revolution. Will check all plugs before i start it shortly to make sure i have spark on all 4. Wish me luck and thank you for all the replies. Greatly appreciated.👍👍

[semi42]

Check float heights, I had trouble setting mine up after a rebuild.

The new valves and seats I was supplied with were crap, sticking and shutting off at random settings.

I reverted back to the old ones and runs much better