Hesitation question for a DMSA Carb

[Seattlefiat]

Hello Gentlemen,

I’m new to the site and I’ve very much enjoyed reading the vast amount of info that this site can provide from you all.

I have a 1974 Spider with a DMSA running on a 1800 engine. The car really hasn’t been driven for about 20 years however the fuel system has been cleaned and sealed and the dual points have been replaced with a Crane Fireball 700. I was having a major hesitation when you jump on the gas and it was running very rich. The car can actually stall if you don’t feather the gas. I took off the DMSA Carb and did a total clean/rebuild on it. It helped on the running rich issue but not on the hesitation. I’m thinking it must have something to do with the accelerator pump but I went all through it and cleaned everything and replace the diaphragm and the washers to the pump nozzle. When I manually give the carb gas, I can see some gas being sprayed down the carb but I don’t know if it’s enough. I read somewhere that the DMSA has a ball check valve in the accelerator circuit, I didn’t see any ball when I did my rebuild. Is this why my accelerator pump not working every well? Also, I never changed my coil when I went to the Crane Fireball Electronic ignition, could it be my spark isn’t strong enough.

Any thoughts?

Thanks

[BEEK]

the check ball is inside the brass piece that holds down the squirter jet. when removed, you can just shake it and hear the ball ratteling. if you hear that all is good there. did you soak the carb in proper carb cleaner, usually over night? if not you still may have a varnish buildup inside some of the minute passages

[Seattlefiat]

Thanks for the reply, I don't remember hearing the rattle but I'll check. You're talking about the brass screw that holds down the nozzle correct. Also, there looks to be a brass needle that screws down the carb body into the accelerator diaphragm area. Anyone know what that is for?

I did soak the carb over night in a gal of carb cleaner but I didn't soak the small parts, I just sprayed them with carb cleaner, most the time you could see if there needed to be additional cleaning or not.

Thanks

[Seattlefiat]

Well, I took the top off my DMSA carb and the brass screw (Valve) that holds down the nozzle has a hole that goes streight thru it. I understand this is where ball check valve is supposed to be. Now my question is, where do I get the valve or bb with the lead plug to fix it.

Any thoughts?

Thank you again, I think I've have found the problem now it's just fixing it.

[majicwrench]

The check ball sits underneath that screw, down inside carb. Usually if you tip carb upside down ball will fall right out and roll where you will never see it again. Dont understand "lead plug"
Check ball comes in carb kit.

[BEEK]

sorry to disagree with you. you are incorrect. the check ball is in the brass hold down piece and the lead plug is in the top of that.



the brass piece on the bottom goes thru the squirter, it contains the check ball. the lead plug is in the top

[Seattlefiat]

I have to agree with Beek. I have two DMSA carbs, this is why I know that the ball sits in the brass screw because my other carb is that way. I'm try to get both DMSA carbs up and running and would like to source the screw or the ball and lead plug.

Thanks your guys, love this site...

Steve

[majicwrench]

Ooooops, me must be thinking something else, crawling away now.....
Keith

[Seattlefiat]

It's all good Keith, thanks for your reply anyway. I had no clue...

Steve

[BEEK]

again , nothing hurtful intended

[Seattlefiat]

Just to give you guys an update. Replaced the brass screw in the DMSA Carb with one that has the valve (BB) in it, the engine now purrs and has no hesitation when you step on it... Thanks for the advise.... The 1974 is running again after more then 15 years... How cool is that...

[majicwrench]

Glad its purring!!! And no worries bout correcting me, I was wrong, and have no issues with being straightened out, I aint perfect (close tho....)
Keith

[BEEK]

Glad its purring!!! And no worries bout correcting me, I was wrong, and have no issues with being straightened out, I aint perfect (close tho....)
Keith

I was wrong once. It was when i thought I had made a mistake, and i didnt

[squealingtires]

Do all 34 DMSA carbs have the check-ball in the brass screw? I'm in the process of rebuilding my carb and noticed that there is in fact a lead plug however through visual inspection there is no ball to be found inside the screw. All of the manuals I have found describe the check-valve inside the screw so I'm wondering if I need to find one. I do have the check ball on the inlet side of the accelerator pump diaphragm (in the the carb body) which I can hear ratting around.