Carburetor diaphragms on 86 Venture

[Burninator]

What happens when the diaphragms go ont the 1300 motor? Does it limit the amount of fuel that can be delivered to the cylinders? If so that may account for my very low top speetd.

 

Is it difficult to access the diaphragms to check or replace them?

[CrazyHorse]

I think it would since if your diaphram leaked from holes or tears it would not be able to fully pull the needle out thus not delivering more fuel. They are easy to change four screws on the side silver covers of each carb. Try looking at the sliders (part of the diaphram setup) through the top of the airbox with the motor running and see if each one is moving in a pattern with the others. Rev it a little a see what they do. Take them out and use a flashlight and see if you see light through the rubber of the diaphram (ie meaning holes etc.) flatoutmotrcycles.com usually has the best prices for diaphrams about 55 bucks each.

[Gearhead]

I just replaced them on my 87 - about 60 bucks apiece. I think that they are pretty much all shot on these 20 year old bikes, unless they've been replaced.

 

Yes, they won't rise up all the way and will block fuel flow and possibly airflow as well. Poor top-end power is a classic sign of bad diaphragms. Although mine ran pretty well, 3 out of 4 were badly cracked (the 4th had been replaced at some point). With the new ones my top end did improve; I was also hoping for a fuel mileage improvement which I did not get (I figured the bad ones would affect the mixture adversely).

 

They are one of the few easy things to get to. Remove the side covers and you can access the back two carbs; remove the lower fairing (easy) for the front two. The slide covers will be staring out at you. The only remaining challenge is a tamper-resistant torx screw, one on each cover. I used vice grips, then put in all new hex head screws.

 

Jeremy

[Gearhead]

BTW, my four slides all appeared to move together with engine running, but 3 of 4 were badly torn.

 

Jeremy

[CrazyHorse]

I bought the torx tamper resistant torx drivers at auto zone for 10 bucks I think.

[Big Daddy]

What happens when the diaphragms go ont the 1300 motor? Does it limit the amount of fuel that can be delivered to the cylinders? If so that may account for my very low top speetd.

 

Is it difficult to access the diaphragms to check or replace them?

 

Is that you Christian? Ha! I caught you! So it sounds like the peanut gallery agrees with me eh?

[Guest Popeye]

My carbs clogged recently due to tank rust. A full redo job.

 

However, the diaphragms all had holes in them, but I never noticed any performance issues, except 32 mpg.

 

With carbs redone, diaphragms, plugs, & tires, I now get ~42mpg.

No real way to pin it on diaphragms though.

[Dano]

Ok guys, how do you get the lip to stay in the groove while you're trying to get the cover on? Do you use a little form-a-gasket or what?

[GeorgeS]

Hmmm, I did not have a problem with that.

 

With the new ones, I mean.

 

Don't forget the little O-rings on the port under the diaphram cover.

[Dano]

George, not that I can tell, it just won't lay in the groove. I have the slides all the way in, but being new, it just wants to pop (flex) back out. I just wasn't sure if there was a trick to it.

Thanks, Dan

[Gearhead]

I've always found that if I form the diaphragms into the right shape they will stay in. Fold the rubber over toward the slide end, then gently bottom them out in the carb bore - worked for me.

 

Jeremy

[Squeeze]

Hi,

 

those Diaphragm can soak some Gas and will grow dued to that.

 

Once they are on Air for some Days they shrink back to normal Size.

 

Jeremie's Strategy for putting them in is what i do also.

[Dano]

Thanks squeeze and gearhead, will try it tonight after the garage cools down. 98+ (F) here today.

Dan