T80 carb. Mystery spring position. Help needed.

Hi, i have recently obtained a shed found T80. The carb was jammed up with dried out petrol deposits. I have managed to clean it up,unfortunately i have a mystery spring which i can not see where it fits. The carb is the standard VM16SH Mikuni. According to my Haynes manual, the spring is in the vicinity of the throttle valve arm and the throttle valve assembly. The book says to carefully unhook the arm from the throttle valve, taking care to avoid losing the spring which will tend to fly out. My problem is i cannot see where it locates, there are also no visible marks to guide me. All of the exploded parts lists i have seen do not show this spring. The spring measures approximately 12mm x 6mm. I am at a loss to find out the location for it. If there is anybody who reads this that can guide me i would be very grateful. Thanks for looking.

This should help:

Hi, thanks for posting the diagram. Unfortunately this is the same one, as i already have. For some reason a lot of the carb internals are not on the drawing, one of them being my spring. Thanks for your help.

Can you post a pic of the spring and I can check with a new carb that I have?

Hi 3hundredspartans. Thanks for the offer of help. I am struggling to list photos of the carb. I will get my daughter to have a go in the morning.

Success!

Are you talking about the spring next to the metal rule?

3hundredspartans wrote:Are you talking about the spring next to the metal rule?

If its the spring near rule it could be from the idle or mixture screw (4 & 5 in diagram). There is also another similar one on the accelerator pump adjustment, not shown in the diagram, so probably that one

Hi guys, yes it is the spring next to the ruler 3hundred, It measures 12mm in length and 6mm in diameter approx. The 3 springs that you mention John are all present in my carb. I have totally stripped it down and cleaned all jets and drillings. In my Haynes manual it says to remove the throttle valve arm with the throttle valve attached, taking care to avoid losing the spring which will tend to fly out.  If you have the Haynes manual this information is on page 77 6/4. I took photographs of the carb before and during strip down but did not notice the spring position. I cannot see any wear marks, and am at a loss where it goes. If you could look inside your spare carb 3hundred, i would be very grateful.

Ok, there are only three such springs on the carb and they are:

• one for the air mixture screw (item 4 - Air screw set)
• one for the idle screw (item 5 - Throttle screw set)
• one for the throttle linkage, not sure what it is called. I did a quick search on the web and cannot find what it is labelled as. It is actually missing off the parts list.

Photo of mine here:

Hi chaps. thanks for your efforts. I have examined the carb yet again, the 3 suggested springs are all present and correct on it. There are a lot of parts not illustrated on the drawings. I have been told that those parts omitted were never available as spares and that the whole carb would need replacing if there were problems. How true this is i do not know but seems a good explanation. I am wondering if the mystery spring goes under the throttle valve over the needle although there are no obvious signs of wear. I have placed the spring on the needle in the attached pictures, your thoughts are welcome. Thanks.
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you.

No it does not fit on needle. Rather than fit it somewhere it should not go leave it out and re assemble the carb without it. The only other compression spring is a very light one under the accelerator pump plunger, but it is far too strong for that.

Hi Chaps. Any more ideas please?

prah wrote:Hi Chaps. Any more ideas please?

Code:

Stop worrying about it. As i said before assemble the carb without it, if it works OK job done, the spring was probably incorrectly fitted somewhere by a previous owner.

Hello,

here are some photos,

First there are two kinds of valve throttle and i don't know which you have

This is mine :



If you look at these valves from the top you will see the position of the spring



and the other one:



So you have to put the spring in this way :



and after the arm,



the arm holds the spring in position