Wondering about the carb diaphragms......

[syscrusher]

So I replaced all four carb diaphragms a couple days ago with the Sirius "SD-1". I used my thumbnail to shove the inner "rim" between the two plastic disks on the slide. When I placed the sliders back into the carb bodies and tried to seat the outer "rim" into the groove on the carb bodies it was difficult because the diaphragm was, as the English say, "proud" of the carb body by about 1/4". I had to tuck each down and hold them in place with my fingers spread while I then captured them with the "lid". By gently sliding the lid around slightly I could reach a point where the lid would finalize the placement of that outer rim and I would get a quiet metal-to-metal clapping of the lid onto the top of the carb body, very tedious.

 

It runs well now but it could be my imagination that hard acceleration seems not as hard as I remembered. While the bike was in my garage I had been riding another bike that is quicker and don't know if I'm expecting it to at least perform like that now.

 

The real question is whether the surplus material that I found difficult to tuck in could also be preventing my needle from raising as high as it should? Should I have used some sort of tool to shove more of the center "rim" between the two plastic disks, thereby reducing the amount of surplus material? What have others experience been with this?

 

I still lose cruise control going uphill, etc. What should I look at next to get my cruise control working perfectly?

Edited July 22, 2014 by syscrusher
needed correcting

[MiCarl]

The diaphragm lip pretty much only fits the carb body with the slide in the up position. This is true of the factory diaphragm too. The motion you describe with the lid is something we have to do with almost every carburetor that comes through the shop.

 

It may be that without the diaphragm leaks it is running a bit rich. That would cause performance to drop off. After I replaced my diaphragms my MPG went to crap, and I eventually put in the skydoc needle shim kit to get back to reasonable fuel consumption.

[Marcarl]

With the diaphragm seated properly on the slide there should be no gathering of material around the outside of the slide. To work the material into proper position use a credit card or something similar. Once you have the diaphragm installed properly you can usually get them to seat well onto the carb by reaching inside the carb and holding the slide to the outside as you install the cap. I have done as you described and later found that the diaphragm had not seated as well as I thought, and so ruined the seal of the rubber in the process. Tricky business this.

This thread describes what I mean.

http://www.venturerider.org/forum/showthread.php?t=19271

[syscrusher]

I don't know if I have the stones just now to re-open these and check them, but I might.

I didn't think of inverting the diaphragm, but that would probably have made it easier for sure. I may want to try a credit card for driving the center rim in as far as possible and I may try raising the needle if it bothers me further. I wonder if I can get fuel/air ratios tested for a reasonable price at the local bike shop.

 

It runs smooth but loses cruise sometimes. When I cold start it always has a period where it doesn't like the choke anymore but won't keep running on it's own either.

[Condor]

Here's another 'trick' to get the diaphragms to stay in the groove. It's easy on a 1stGen. Not so on a 2nd. What's happening is the spring starts pushing the slide before the cap gets close to the housing and pulls the lip out of the groove. So.... remove the air filter and you can see the slides in the venturies. Take a long screwdriver and gently hold the slide so it doesn't move. Place the cap on the body. Remove the screwdriver. Piece of cake....

[hell yea]

yes fited new from Yamaha diaphragms and slieds fuel economy gone to **** and it wont pull anywhere near as hard and if i execrate real hard it backfires on desell

[hell yea]

a set of 1300 springs fixt it yeha shes flying agane everdentaley the 1200 slides were lighter and the springs shorter go figer took sum working out that one :cool10: