Weber carb to rebuild? for a cat 1998 xflow 1600 supersprint

[uberfrog]

Hi all,

My caterham is equipped with two weber 40 dcoe and they need adjustement, we changed all the seals and gasket but not much improvement, the idle is at 1500 and when we tried to put it at 850 the car rattles a lot.

Would it be a good idea to have the carbs rebuild completely and if yes where should I send them.

An alternative would be to put an aftermarket fuel injection system but not sure if the performance will be as good.

Any input would be like a gift from heaven.

Thank you,

N6

[GWise]

I'm a bit confused - do you need them rebuilt completely or do you need them adjusted? I'm not sure there are many options for fuel injection on a crossflow. Most people just go to a zetec.

Where are you located?

[uberfrog]

weber

I'm a bit confused - do you need them rebuilt completely or do you need them adjusted? I'm not sure there are many options for fuel injection on a crossflow. Most people just go to a zetec.

Where are you located?

Good morning,

I am located in mountain view. As for the webers I would love to have them adjusted but where? Might be easier to have them rebuild, I don't know how bad they are so.

Best regards,

Etienne

[escondidoron]

Concur with Gwise regarding adjustment.

But just in case, to get you started, here's a good video describing DCOE assembly:

[escondidoron]

As for rebuild, as long as the throttle shaft bores are not overly worn, in my experience, a good adjustment will solve most Weber / Dellorto issues, assuming that the jetting is correct. Also, the anti-vibration isolators shouldn't be too tight or too loose. If too tight, you will get excessive fuel slosh in the float bowls leading to uneven operation and/or stalling. If too loose, you will get a vacuum leak, again leading to uneven operation and/or stalling. Balancing is accomplished easily with the use of a decent vacuum gauge / synchrometer.

Starting with the basics, here's a video describing how the DCOE idle circuit works:

[escondidoron]

Balancing is simply a matter of getting each cylinder to draw the same amount of air. The adjustment process is to set the venturis on each carb and then adjust the balance bar between the two units to equalize the carburetors.

As for balancing tools, I recommend using a 4-tube manometer or synchrometer. I have both types. For the DCOEs on my Seven I prefer the synchrometer. For the Dellortos on my Esprits I prefer the 4-tube manometer. This video shows a synchrometer in use on a twin cam (although it doesn't show how to adjust the balance:

[escondidoron]

Also, you should check the float height to ensure both carbs are set at the correct height:

[escondidoron]

Here is the general process that I follow when setting up a multi-Weber or Dellorto carburetion system:
1) Check for FULL THROTTLE OPENING:
With the engine OFF, move the accelerator pedal while you watch the throttle shafts rotate to the fully open position. Adjust the linkage, if necessary to achieve full opening. Make sure that the bellcrank under the carbs is not sticking on its shaft.

2) Check the FLOAT LEVEL:
a) Let the engine idle for two minutes. Remove the wingnut caps.
b) I use the depth gauge end of vernier caliper to measure from the top of the lower shelf to the top of the fuel surface.
Note: For my 1340cc 109e pre-crossflow engine setup the 40 DCOE float height spec = 1.14 inch (29mm+4.5mm). You should check for your installation to be sure of the correct setting.

3) Check for Air (vacuum) leaks:
Check for Intake System AIR LEAKS while engine is running Wiggle the carbs and spray something like WD40 or even water from a small spray bottle on each of the carburetor and manifold sealing surfaces up to the cylinder head and listen for a change in the engine speed. Repair the leak(s) if any are found.

4) Synchronizing:
Make sure that the throttles are synchronized. Remove the brass plug (above the off-idle holes) of each carburetor section. Shine a flashlight into each of the holes to see that the edge of each throttle plate is aligned with the same hole when the throttle is slightly open. Adjust the spring-loaded screw in the linkage between the two Webers. Make sure that the Idle Stop Screw is NOT against its stop when you are making the adjustment or you will be even more confused. Fine tune the adjustment with a synchrometer or 4-tube manometer

5) Adjust the IDLE SPEED:
Adjust the idle speed by turning the Idle Stop Screw. If the idle is set too high when the Idle Stop Screw is NOT touching its seat, the throttles are NOT returning to the closed position. Make sure that the linkage is not binding.

I hope that this helps. Good luck.

[GWise]

Lots of great info above. The problem with rebuilding them is that if they aren't adjusted correctly, rebuilding them isn't going to help.

You're in luck that you're close.

Join here:

https://groups.yahoo.com/neo/groups/sidedraft_central/info

You can do a lot of reading on this site which is quite informative. If you'd prefer a hands off approach, contact the moderator Keith Franck. He is based in the bay area and can help you tune your carbs (and install some of his hypojets) for a modest fee. He's done a few sevens and he owns an elan. You may need to buy and install an O2 sensor bung though.

[uberfrog]

Thanx Ron 4 the info for the 7

Concur with Gwise regarding adjustment.

But just in case, to get you started, here's a good video describing DCOE assembly:

Hi Ron,

I forgot to send you a pix of the seats you sold me, it looks and feel good.

As for the weber infos it's more than I could dream for and I will show your info to my mechanic so he can adjust them properly and if he can't I will have Keith from the bay area look into them.

Best,

N6

[uberfrog]

weber

Lots of great info above. The problem with rebuilding them is that if they aren't adjusted correctly, rebuilding them isn't going to help.

You're in luck that you're close.

Join here:

https://groups.yahoo.com/neo/groups/sidedraft_central/info

You can do a lot of reading on this site which is quite informative. If you'd prefer a hands off approach, contact the moderator Keith Franck. He is based in the bay area and can help you tune your carbs (and install some of his hypojets) for a modest fee. He's done a few sevens and he owns an elan. You may need to buy and install an O2 sensor bung though.

Dear GWISE,

Thank you for your tips, where can I find Keith Franck so it might be easier and save time to tune my 7 if he already done work on 7.

Best,

Etienne

[GWise]

I believe this is his email:

[email protected]

[escondidoron]

Hi Ron,

I forgot to send you a pix of the seats you sold me, it looks and feel good.

As for the weber infos it's more than I could dream for and I will show your info to my mechanic so he can adjust them properly and if he can't I will have Keith from the bay area look into them.

Best,

N6

Hi Etienne;

Glad to try to help.

I'm glad to hear that the seats are working out for you. They were just going to take up too much space in the already cramped cockpit for my 6'5" body to work for me! I'd love to see the what they look like installed. Maybe you can post a few pics here?

Regards,
Ron

[uberfrog]

I believe this is his email:

[email protected]

great thank you.

etienne

[uberfrog]

DSC_0005.jpgDSC_0008.jpgDSC_0007.jpgDSC_0011.jpg