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**Nastydude** · 07-20-2004, 08:44 AM

I'm not exactly a mechanic but from my understanding the diaphragms are quite expensive. I have had the diaphragms off on my bike a couple of times in the last few days. nothing to it as long as your careful. just remove the four screws on the cap but hold on to the cap while you remove the last screw as there is a large spring which could fly. then remove the cap, lift out the spring and gently loosen the diaphram from the seat around the out side edge and once it is free i stuck my finger in the carb throat and pushed the plunger and needle assembly out (once again gently). thats it

I wouldn't think that a torn diaphragm would affect idle but that it would affect everything above idle. especially mid to full. I am not a mechanic and have never had your problem maybe some one else could give you a better heads up as to the effects of a torn diaphragm

**ratbyk** · 07-20-2004, 08:59 AM

Diaphragm

Matt, if the vacuum line you are referring to is the one from the ignition vacuum advance there is no replacement part. You have to replace the entire vacuum advance cannister.
Usual cause for this to fail is when someone hooks that vacuum line up to a vacuum source other than the small nipple on #2 carburetor. This is the nipple that sticks up from #2 carb just as it joins into the intake manifold rubber runner.
Test the vacuum cannister by simply drawing on the vacuum line with mouth created vacuum and observe the arm on the vacuum advance unit.The arm should move and the diaphragm should not loose its vacuum. If it holds you do not need to replace it.
Ken/Sooke

**ultra6xlt** · 07-20-2004, 09:35 AM

Thank you both for the replies. I wasn't sure if I can post a pic for you to see what I am talking about, so I posted it on a website. Here is the link to the area that I am talking about: http://www.users.qwest.net/~christensonmatth/

I know that there are diaphragms inside the carbs. I am not sure what you call this diaphragm. Everywhere I have looked, it has been called the "Diaphragm Assembly". I have highlighted the areas that I am talking about replacing/fixing. Please let me know if the link works for you, and you can view the images. Thanks again! I hope that I can get this figured out soon, and get it back on the road. It is too hot to be riding inside a car. Take Care!

- Matt

**ratbyk** · 07-20-2004, 09:49 AM

Diaphragm

Sorry Matt. My previous post was for the ignition advance diaphragm. The one you have illustrated is for the octopus on a special. I'm not familiar with this unit. I own a standard. I'm quite sure someone familiar with this unit will chime in.
Ken/Sooke

**Jeremy_Sells** · 07-20-2004, 10:19 AM

What I found is that the diaphrams from a vacuum operated "Standard" petcock is the same as the diaphram in the "Special" diaphram that you highlighted in your previous post. I discovered this by trial and error and found that they are the same part and are completely interchangeable. Mine failed and contributed to a bad idle for nealy 2 years... Very frustrating!! Try disconnecting the vacuum hose from the manifold and sucking on it to see if it seems airtight. If you can draw endless amount of air, the diaphram is bad. Simply get a petcock repair kit like this one and you're good to go:

https://www.partsnmoreonline.com/PNM...PAIR%20KIT.htm

Take care and good luck

**Nastydude** · 07-20-2004, 11:25 AM

it could be the inside of your vacuume hose also that is shedding this rubber the proceedure to remove this diaphragm is basically the same remove the four screws hold on to the cover as you undo the fourth as the spring is quite small and could be difficult to find if it flies. slowly lift the cover lift the spring and look at your diaphragm if there isn't a hole i would suggest changing your vacuume lines.

**ultra6xlt** · 07-20-2004, 11:30 AM

Thanks Jeremy! If the diaphragm is bad, I just need to buy that petcock repair kit? Is it pretty simple to install? Do I use all of the parts that come with it? I haven't taken the diaphragm assembly apart yet, and I cannot find an exploded view of the assemply. Are there any recommendations that you have with the install? Were your previous symptoms rough idling and rough running until around 3k RPM? Mine runs rough through 3k RPM, and then takes off when the bike gets past 3k RPM. I checked the pickup coil, and everything was fine. The clogged vacuum line and bits of rubber made me think it was this part. I will test the diaphragm tonight, and look to order the part you recommended if it is bad. I will let you all know how it goes. Thanks!

- Matt

**Jeremy_Sells** · 07-20-2004, 12:01 PM

If you can draw continuous vacuum through the diaphram, then it is probably bad. If you are using that kit, all you will need is the square diaphram piece. Just remove the 4 screws that hold the cover to the diaphram in place and do the swap. There is a spring in there that has to go back in and take your time to clean any corrosion or debris while you're in there. After it is all back together, check again to make sure that everything is airtight. The symptoms on my bike with a bad diaphram were inconsistent idle speed and a general roughness at idle, everything else was alright, somewhat. After the fix, it was like a new bike.

Have fun,

**skids** · 07-20-2004, 12:38 PM

I have to chime in. If your bike runs well above 3Krpm, but crummy below that, the petcock diaphragm is not the issue. The octopus (special) or petcock diaphragm is simply an automatic fuel valve gizmo. You are getting fuel at higher demands, so I suspect the problem is carb related. Pilot jets is where I would look into fixing. If it runs rough, like two cylinders, it could be the pick-up coil wires. You might try letting it run rough for a while, hit the ignition stop switch and immediately pull in the clutch to come to a stop, and check to see if the plug electrodes are wet. If your pick-ups are not letting spark to the plugs, or if the pilot jets are too large, plugs will be wet. If they are dry, there could be a problem with too small of pilot jets or some other lean problem.

Originally posted by ultra6xlt
Thanks Jeremy! If the diaphragm is bad, I just need to buy that petcock repair kit? Is it pretty simple to install? Do I use all of the parts that come with it? I haven't taken the diaphragm assembly apart yet, and I cannot find an exploded view of the assemply. Are there any recommendations that you have with the install? Were your previous symptoms rough idling and rough running until around 3k RPM? Mine runs rough through 3k RPM, and then takes off when the bike gets past 3k RPM. I checked the pickup coil, and everything was fine. The clogged vacuum line and bits of rubber made me think it was this part. I will test the diaphragm tonight, and look to order the part you recommended if it is bad. I will let you all know how it goes. Thanks!

- Matt

**ultra6xlt** · 07-21-2004, 07:40 PM

The Solution

Gentlemen,

Thank you all for the help. I have it running like a champ again. Here is what I fixed:

1. The gas lines have always appeard a little kinked, so I put in new lines with a Y and L connector to keep them flowing.

2. The vacuum line (coming off the diaphragm assembly) that goes into carb #2 did not seem that it was tight enough, so I replaced it.

3. My ignition coil wires always were a little sketchy. They had cracks in the casing, and I cut some off the terminal end due to corrision. I replaced the ignition coils with a set that had better wires.

I started it up, and it is running better than ever. I am not sure what that rubbery deposit was in the vacuum lines, but it appears the diaphragm is working just fine. Thank you all again for the help! You cannot replace experience with a book. It is time to get out there and ride now. Take care!

- Matt

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Diaphragm Assembly Replacement/Repair

Diaphragm Assembly Replacement/Repair

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