Technical Tuning the Weber 28IMB

[dangfiat]

Hello Experts!

Just got my '67 500F delivered (will post pics after I take them tomorrow - car was delivered at night). Super excited!!!

Anyway, it smells like it's running rich. It has the Polski 650 with a Weber 28IMB (I think - looks pretty origional). How does one go about adjusting the mixture on these little carbs? I know how to do it on an SU, but not on the Weber. Do I have to get new jets?

Other things I'm going to have to figure out (after a quick nighttime inspection). Sorry for the list (it's to help me figure out what I need to do as well)
1. Tune it up (see above)
2. The hood latch cable is broken. Have to use a flat blade screwdriver to open the hood
3. Only the right turn blinker works. Seems the left tries at times, will have to dig into it and see if it's the stalk switch or the blinker relay (does it have one? I assume)
4. Door locks don't lock. The plunger goes up and down, but it never actually locks. Gotta be a busted/miss adjusted linkage in there somewhere
5. Clutch: It seems to bite in a narrow range, is that normal for these cars? It's almost like an on/off switch. Will read Haynes to see if there's an adjustment

Finally: get smaller feet! It's pretty tight in that footwell, will take some getting used to

Thanks all, and apologies for the long list. Just super excited! Go little car go!

Daniel

 

[bugsymike]

Hello Experts!

Just got my '67 500F delivered (will post pics after I take them tomorrow - car was delivered at night). Super excited!!!

Anyway, it smells like it's running rich. It has the Polski 650 with a Weber 28IMB (I think - looks pretty origional). How does one go about adjusting the mixture on these little carbs? I know how to do it on an SU, but not on the Weber. Do I have to get new jets?

Other things I'm going to have to figure out (after a quick nighttime inspection). Sorry for the list (it's to help me figure out what I need to do as well)
1. Tune it up (see above)
2. The hood latch cable is broken. Have to use a flat blade screwdriver to open the hood
3. Only the right turn blinker works. Seems the left tries at times, will have to dig into it and see if it's the stalk switch or the blinker relay (does it have one? I assume)
4. Door locks don't lock. The plunger goes up and down, but it never actually locks. Gotta be a busted/miss adjusted linkage in there somewhere
5. Clutch: It seems to bite in a narrow range, is that normal for these cars? It's almost like an on/off switch. Will read Haynes to see if there's an adjustment

Finally: get smaller feet! It's pretty tight in that footwell, will take some getting used to

Thanks all, and apologies for the long list. Just super excited! Go little car go!

Daniel

Others here are Fiat Experts, all I can give is what I haven't quite forgotten retired after 50 years as a mechanic, so not model specific.
As you say jets on the Weber carb, unlike SU which was a case of raising the centre jet holder up or down in relation to the needle, which along with the needle and spring in the dashpot and thickness of oil above it could quickly be altered.
If only just delivered it may have spent a lot of time on choke with stop start breaks along it's path to you, so first I would start the car up and once off choke give it a run to get to normal temperature and see how it runs then. There will be a mixture screw adjustment , but it is only for whilst idling.
Re item 3. I would check for a bad earth or corrosion at the bulb holder as quite common. Sometimes a jump lead from the earth side of the battery using a screwdriver clamped in the jaws as a test probe to the earth point on the bulb holder can pin point an earthing issue.
Item 4. Door panels off and likely as you say broken linkage or clip, sometimes even adjustment/bending of the link rod .
Item 5. I am guessing a cable adjustment on that model and once correct adjustment with a little freeplay at the pedal, that is a start. Re fierceness, on/off clutch operation , whilst not as soft an action as modern type diaphragm clutches, it may get easier as given more use, assuming no oil has got on the clutch friction plate causing it to grab. It may sound a "bodge" but if you do a "lazy, bad driver" hill start a few times it can clean any light muck from clutch plate and smooth out the operation, only a couple of times, don't get in to the habit .
In the late 60s,early 70s as mechanics we would have bets on how many times an owner would stall driving off the forecourt after a new clutch had been fitted, particularly on rod linkage clutches on Austin A30s , Morris 1000s etc. It wasn't the owners fault as they had got used to it slipping for months and suddenly it was totally different.
Re foot size in footwell on pedals, on some cars it is possible to ease/bend the pedals apart slightly which can help. Always embarrassing coming to a halt pressing brake and clutch to find engine screaming as the accelerator is getting the same attention.

 

[the hobbler]

Others here are Fiat Experts, all I can give is what I haven't quite forgotten retired after 50 years as a mechanic, so not model specific.
As you say jets on the Weber carb, unlike SU which was a case of raising the centre jet holder up or down in relation to the needle, which along with the needle and spring in the dashpot and thickness of oil above it could quickly be altered.
If only just delivered it may have spent a lot of time on choke with stop start breaks along it's path to you, so first I would start the car up and once off choke give it a run to get to normal temperature and see how it runs then. There will be a mixture screw adjustment , but it is only for whilst idling.
Re item 3. I would check for a bad earth or corrosion at the bulb holder as quite common. Sometimes a jump lead from the earth side of the battery using a screwdriver clamped in the jaws as a test probe to the earth point on the bulb holder can pin point an earthing issue.
Item 4. Door panels off and likely as you say broken linkage or clip, sometimes even adjustment/bending of the link rod .
Item 5. I am guessing a cable adjustment on that model and once correct adjustment with a little freeplay at the pedal, that is a start. Re fierceness, on/off clutch operation , whilst not as soft an action as modern type diaphragm clutches, it may get easier as given more use, assuming no oil has got on the clutch friction plate causing it to grab. It may sound a "bodge" but if you do a "lazy, bad driver" hill start a few times it can clean any light muck from clutch plate and smooth out the operation, only a couple of times, don't get in to the habit .
In the late 60s,early 70s as mechanics we would have bets on how many times an owner would stall driving off the forecourt after a new clutch had been fitted, particularly on rod linkage clutches on Austin A30s , Morris 1000s etc. It wasn't the owners fault as they had got used to it slipping for months and suddenly it was totally different.
Re foot size in footwell on pedals, on some cars it is possible to ease/bend the pedals apart slightly which can help. Always embarrassing coming to a halt pressing brake and clutch to find engine screaming as the accelerator is getting the same attention.

 

[dangfiat]

Thanks all for the help, much appreciated! I'm very excited to start going on this little car!

 

[Toshi 975]

There is very little to adjust on the 28IMB carb, just the throttle stop screw to adjust tick over and the idle mixture screw. The normal starting point for this screw is 1 1/2 turns back from fully screwed in. Apart from these you need to check for wear and correct fitting with good gaskets. It has been said that it is better to rebuild an original carb than buy one of the later reproductions.