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March 07, 2021, 01:53:58 AM

Changing the tuning on Weber 32/36

This is a discussion for the topic Changing the tuning on Weber 32/36 on the board Beach Buggy Engine and Exhaust Help.

Author Topic: Changing the tuning on Weber 32/36  (Read 2009 times)

this user is offline ajp

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on: September 03, 2018, 10:46:16 AM
Hi all,

So we’ve now had the buggy from Snoopy for a month, during which we’ve really enjoyed 850 miles of smiles…I love it, missus loves it, kids look for excuses to go out in it! We have the bug(gy)!! :D

As is my way, and it seems that of buggy owners generally, I am starting to fiddle with it, and for me, that way lies danger… ;D

Carb advice please…

1300TP with Weber Progressive 32/36

Has a noticeable stumble when accelerating from standstill. Can live with it, but not ideal.

Went to Peter’s excellent manxmaniac site and compared jets etc with his weber specs. Found I have –

Primary – idle 50, air corrector 160, F66 emulsion, main jet 137
Secondary – idle 60, air corrector 165, F50 emulsion, main jet 140

These would seem pretty much out the box sizes for a 1600? Idles are swapped around, but I’ve read that’s a good thing(?) Air correctors are also swapped?

So, using Peter’s numbers for a 1300 I purchased new jets and set it up as –

Primary – idle 50, air corrector 165, F66 emulsion, main jet 130
Secondary – idle 60, air corrector 160, F50 emulsion, main jet 135

When removing the idle jets I noticed they had no o-rings, so bought and fitted 1 of those to each jet. Started up the buggy and it ran really poorly. Hard to start, didn’t want to idle, puff of exhaust smoke.

Had coffee, pondered. Figured primary idle jet. Removed o-ring again and re-started the engine. No problems running fine, steady idle.

So, what next?

I want to keep driving and not cause myself an issue trying to improve a functioning buggy!

From the parts diagram, I am assuming there should be o-rings fitted to my idle jets. Presumably as there have not been, the idle jets would have an air leak that has been adjusted out with the mixture screw?

Any input before I move too far away from where I started with no easy route back is much appreciated.
Ta,
Andy


this user is offline ajp

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Reply #1 on: September 03, 2018, 12:45:01 PM
OK. So fatally the sun is shining and I have the day off...so messed with stuff again. Writing out the help request earlier kinda cleared things in my mind so...

...I followed the weber tuning guide and checked the basic idle/lean best idle settings.

Engine warmed up, choke disengaged, with the 50 primary idle jet, o-ring fitted sealing the jet, i have the mixture screw one (barely) turn out to get best running. The idle speed screw is down 1 full turn against the stop to get a base idle.

The engine has a steady idle. There is a little smoke from the exhaust - not much, but then the engine is largely unknown.

Presumably, given that the mixture screw is only one turn out this would suggest that the primary jet is still not quite right -  Guide says "go down on the primary idle jet" ;D That means smaller number yup?

Test drive this arvo to see how she goes methinks ;-)up


this user is offline Merscury

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Reply #2 on: September 03, 2018, 01:04:36 PM
Hi Andy, There were no o rings on either primary or secondary idle jets on my 32/36 and that was new out of the box
Have fun. Be lucky


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Reply #3 on: September 03, 2018, 01:13:10 PM
Thanks Merscury - that'd be typical...create a new problem by fixing one that wasn't there in the first place!! ;D


this user is offline Paul1953

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Reply #4 on: September 03, 2018, 02:30:49 PM
Thanks Merscury - that'd be typical...create a new problem by fixing one that wasn't there in the first place!! ;D

This is how it goes.... Don`t give up trying to improve your buggy... ;-)up ;-)up


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Reply #5 on: September 03, 2018, 04:25:11 PM
Thanks for the encouragement Paul - no danger of stopping anytime soon ;-)up

Test drive was fun in the sun, nearly forgot why I was doing it & just had a 20 mile blat around the local villages.

So the stumble has changed. Before it was a sharp drop then rise in power when pulling away at low-ish revs, like pulling away from a junction. Now it's a less sudden, but more pronounced flat spot at slightly higher revs - say roll on at 25mph in 3rd - steadily press yer foot, little response for a few mo's and then out the otherside, all is good. Mid-range and higher end (hohum, it is a 1300) has improved noticeably - much more pull in 3rd and top with yer foot to the floor so presumably the 36mm side of the carb is nearer where it wants to be? ;-)up

So, any ideas how to improve the lower rev response - play with jets or have I entered the twilight zone of intake heat? :D

'Tis all good fun!


this user is offline Zip Buggy

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Reply #6 on: September 03, 2018, 05:28:46 PM
Thanks for the encouragement Paul - no danger of stopping anytime soon ;-)up

Test drive was fun in the sun, nearly forgot why I was doing it & just had a 20 mile blat around the local villages.

So the stumble has changed. Before it was a sharp drop then rise in power when pulling away at low-ish revs, like pulling away from a junction. Now it's a less sudden, but more pronounced flat spot at slightly higher revs - say roll on at 25mph in 3rd - steadily press yer foot, little response for a few mo's and then out the otherside, all is good. Mid-range and higher end (hohum, it is a 1300) has improved noticeably - much more pull in 3rd and top with yer foot to the floor so presumably the 36mm side of the carb is nearer where it wants to be? ;-)up

So, any ideas how to improve the lower rev response - play with jets or have I entered the twilight zone of intake heat? :D

'Tis all good fun!

Do you have a 009 distributor or one with a vac advance?
Who needs prozac when you can drive a buggy?


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Reply #7 on: September 03, 2018, 06:06:36 PM
Vac advance ;-)up ;-)up


this user is offline Zip Buggy

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Reply #8 on: September 03, 2018, 06:44:14 PM
Vac advance ;-)up ;-)up
Hmm. Have you checked if the vac advance is working ok? If you pull the vac tube from the manifold and remove the dizzy cap, when you suck the pipe it should move the plate in the dizzy - probably ok from the symptoms you describe but worth a quick check.
Who needs prozac when you can drive a buggy?


this user is offline ajp

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Reply #9 on: September 03, 2018, 07:51:46 PM
Thanks ZB, have checked and that's all fine.

I suspect we are in to the subtle realms of fine tuning. Snoopy did a splendid job refurbing the buggy before I bought if and it was running fine - could hit 70mph and cruise all day at 55-60...but I thought there was a niggly little stumble I might investigate!

...and everyday's a school day and I like fiddling so :D

It all started cos the circlip on the choke arm went MIA on me last week which caused us to limp home at half speed and I lifted the carb top off to take a look!! ;D


this user is offline snoopy

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Reply #10 on: September 03, 2018, 08:04:40 PM
 about the carb I spotted one the other week on a beetle fitted 180 degrees to the one on the GP so you could get at the mixture screw and speed screw easily to set it up, never had a chance for a close look but the accelerator cable was still pulling where it is on the GP so extra linkage must be available for a conversion although the rest I have seen are fitted like the GP.
Is the accelerator pump jet squirting a steady flow as you open the throttle, if not dirty jet or diaphragm has failed.
The Manifold pre heater tubes are still getting hot as apparently theses carbs like them hot or they suffer running issues
You will need to wind the speed screw out about 1/2 turn to get the air flow correct and then set the mixture screw if it is only 1 turn out the idle jet is too large.
As a thought could you bolt it on 180 degrees out for setting up then take it off and fit it properly.


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Reply #11 on: September 03, 2018, 09:06:29 PM
Thanks Keith, will go over everything as suggested. Good idea that 180 mounting. I used one of those changeable screwdriver bits and a spanner, big fiddly, but doable.

Out of interest, went out again this evening to run a quick errand (any excuse!) and no stumble or flat spot to speak off on the way out only the slightest hint. Stopped for 10 mins then headed back, only a couple of miles each way, and the flat spot was back with a vengeance...could be a bit of muck swilling around perhaps?

I'll take a look sometime tomorrow ;-)up


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Reply #12 on: September 03, 2018, 09:42:04 PM
could well be a bit of dirt I did strip and clean it as I knew nothing about it only the last tax expired Aug 94 but that engine may not have been in it then. Another strip and blow through may get rid of something that had moved with 1000 miles use.


this user is offline Merscury

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Reply #13 on: September 04, 2018, 10:21:30 AM
Hi Andy, shame I don't live a bit closer as I run a 32/36 and am now a dab hand at cleaning and setting them up. I have a 1641 engine and Bosch 009 distributor (no vac advance) and contrary to what most people say about this combination I have got it to run perfectly with no flat spots and on a long motorway run at 65mph it returns 43mpg. Around town or spirited driving on lanes this drops down to about 30 to 35 mpg.                                                                                                                                                           
 On the 1641 I have a .50 primary idle jet and also a .50 in the secondary idle so in your 1300 I'd guess .50 in the primary is just a touch to big, although by having the mixture screw turned in 1/2 a turn further than the instructions say you will be compensating for that to certain extent.                                                             

I'm not sure snoopys idea of turning the carb round 180 degrees will be a good idea because if your inlet manifold is like mine, the central cast section has 2 separate bores of different diameters and there is a chance this may affect the set up. For cleaning I would suggest removing the carb completely plus once clean and the correct primary idle jet is fitted then the mixture screw and fast idle screw are accessible enough to do the set up.                                                                 

I would read up on how the primary idle works as it feeds fuel into the carb throat in 2 different places, 1st the primary idle port and 2nd the transition port. These can be seen looking down the primary throat,,  the idle port is just below the throttle flap, the transition port is just above that and should be just above the throttle flap, both these ports are fed by the primary idle jet.                     
screen shot in windows                                                 

For cleaning I use a solvent carb cleaning aerosol spray and have found the transition port also has to be cleaned from inside the throat of the carb as you can't get to it properly by just removing the mixture screw.  Top tip, once you have cleaned it all, clean it all again because you don't want have to remove the carb again just because your not sure you've done it well enough.       


When doing the set up make sure the engine is HOT and choke disengaged and follow the instructions to the letter, it is important that before you set the mixture screw that the fast idle screw is backed off to the point where the engine is barely able to keep running it is only then you should adjust the mixture screw. Once the the mixture is set only then can you adjust the fast idle screw to give you 850 to 900 rpm at tickover.  Once set up it is important that at tickover the transition port is still just above or level with the throttle flap, definitley not below the throttle flap.   

http://www.carburetion.com/Weber/adjust.htm

Have fun. Be lucky


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Reply #14 on: September 04, 2018, 01:08:12 PM
Thanks Merscury, that's great info and really useful...even if I did read it after coming back in from cleaning all the jets with the carb on the engine, out in the street, without looking at transition ports & throttle flaps ;D

Did re-set the float height to 35mm as per the book as it was at 39/40mm - suspect I had caught/moved it previously.

Mind you, I too am getting a dab hand at pulling the top off & whipping the jets out - practise makes perfect!!

Cheers for all the help peeps.