Carburetor diaphragm good or bad? 82 Heritage Special

[Borracho]

I need some help determining if one of my carburetor diaphragms is still good to go or trash. I'm thinking the latter but maybe not. I pulled off the cap and noticed that the diaphragm was not inserted correctly the last time I took the carbs apart. As a result one of the edges was flattened by the cover as shown in the pics below. I know, total noob blunder. But hey, one learns from his mistakes. If it is trash, has anyone had luck with the replacements sold by jbmindustries.com? Beats the hell out of paying $100 for the whole slide assembly from mikesxs.net. Just not sure how well they would work or how easy the install is.

By the way, what caused me to initially take apart and investigate the carb was an excess of oil I found inside the air box and carbs. I recently had the oil changed and from everything I read on this topic is that there was probably too much oil added which in turn caused an overflow from the breather valve into the air box which eventually made it to the carbs. If someone has a different opinion as to where the oil may have come from, I'd like to hear it. I'll take all the help I can get. I've been unable to get this bike to run properly for over 4 months now and I'm missing all the best riding weather here in Austin, TX. As soon as I take the bike off choke she dies. This is the most recent problem I encountered and wonder if it has anything to do with the diaphragm issue.

 

[richardthemotorcycle1]

Hi borracho, welcome to the forum. If the carburetor diaphragms are torn or not sealing probably, they won't work probably, may have to replace them.

 

[Borracho]

Hi borracho, welcome to the forum. If the carburetor diaphragms are torn or not sealing probably, they won't work probably, may have to replace them.

Thanks Richard. I had a feeling the diaphragm may be bad. Any ideas on where the oil may have come from? Could it be just overflow?

 

[5twins]

Yes, if you put too much oil in the engine, the extra will blow out the breather. In fact Yamaha recommended only filling these bikes midway between the high and low mark, not all the way up to that top line on the dip stick.

 

[DogBunny]

Quick answer: I think your diaphragm is good. If you want the long answer, call me. I will PM you my phone number.

I live in Austin, and carbs are my thing. I have built lots of XS650 carb sets for forum members and for Austinites. If you need help with your carbs, or if you want to buy a good used diaphragm if yours really is bad, then call me.

As for the oil, yes I think it came from the crankcase breather, and filling to the top of the dipstick will increase the amount of blow-by that comes out of the crankcase breather.

 

[Borracho]

Thank you all for the helpful suggestions. DogBunny, I saw your response concerning the diaphragm after responding to your PM. I'll have to have you take a closer look to see if it's salvageable. I'll give you a call and set something up for the near future.

 

[gggGary]

The quick diaphragm test is to assemble, cover the half moon port at the top of the intake with your finger, raise the slide and let it drop. It should descend rather slowly. Compare, the two carbs should be similar and by removing your finger from the port, there should be a noticeable difference in how fast it drops.

IIRC the diaphragms are said to start raising at about 4000 RPM so they shouldn't be the reason for remove the choke and dies.

Are the rubber caps on the pilot jets? Have you removed and cleaned the idle needles?

 

[Borracho]

The quick diaphragm test is to assemble, cover the half moon port at the top of the intake with your finger, raise the slide and let it drop. It should descend rather slowly. Compare, the two carbs should be similar and by removing your finger from the port, there should be a noticeable difference in how fast it drops.

IIRC the diaphragms are said to start raising at about 4000 RPM so they shouldn't be the reason for remove the choke and dies.

Are the rubber caps on the pilot jets? Have you removed and cleaned the idle needles?

Thanks for the tip Gary!

 

[Borracho]

I wanted to send a big THANK YOU to forum member DogBunny. He took the time out of his day to help a fellow Austin rider sort out some carb issues. Not only that but he also shared some great tips and mechanics of these particular carbs. I am pleased to report that my Heritage Special runs good and strong (so far). DogBunny, I will contact you via phone and update you on the status as soon as I put some more miles on her. Thank you again!

 

[richardthemotorcycle1]

Glad to hear its running good.