JBM Diaphrams

[Guest]

Bought a GS 1100 shaft drive a few weeks ago. It sat a few years so the carbs are a mess. I am busy downloading the great tutorials and advice on this forum in anticipation of rebuiding them. In addition I am buying new replacement parts before I start. When I search JDM diaphrams on the site they are talked about but haven't seen a recommendation. Has anyone used them? And how did they perform?

Thanks

[quexpress]

If you are talking about JBM Industries , I have used their diaphragms on my GV1200 carbs rebuild and am very happy with the results.

[Jamesp]

Thanks I hadn't heard of just changing the diaphrams-sounded good but thought it would be good to get a first hand opionion
thanks again!!!

[quexpress]

Thanks I hadn't heard of just changing the diaphrams-sounded good but thought it would be good to get a first hand opionion
thanks again!!!

You're welcome!
Note: I didn't change just the diaphragms. Many other seals, etc. were also changed.

[Steve]

Do you NEED to change the diaphragms?

There is usually no need to change them unless they are damaged, and they are seldom damaged.

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[salty_monk]

I wouldn't say "seldom". In my experience it's about 1 in 4....

[Steve]

Can't tell you how many sets of GS carbs I have gone through in the last few years,
I have only seen one set of carbs that was getting a bit thin right at the edge, but no holes.

The only holes I have seen in diaphragms were in my son's Yamaha carbs.



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[Jamesp]

I own a GS 850 but never had caborator issues since the previous owner had them rebuilt.When I purchsed the 1100 I knew the carbs were clogged up front. So being a newbie and from past experience with outboards and cars I've been running carb cleaner through it to see if I could get it cleaned up. During the carb rebuild research I've found that the carb cleaners eat up the Diaphrams plus its been backfiring thought the cabs quite a bit. So I though it would be a good thing to have the diaphrams on hand when I took the carbs off. Should I rethink that decision?

[hjfisk]

I own a GS 850 but never had caborator issues since the previous owner had them rebuilt.When I purchsed the 1100 I knew the carbs were clogged up front. So being a newbie and from past experience with outboards and cars I've been running carb cleaner through it to see if I could get it cleaned up. During the carb rebuild research I've found that the carb cleaners eat up the Diaphrams plus its been backfiring thought the cabs quite a bit. So I though it would be a good thing to have the diaphrams on hand when I took the carbs off. Should I rethink that decision?

Yes I would rethink the Idea, until you take them apart, and clean them PROPERLY, meaning a full strip and dip with new Orings and gaskets. Odds are you wont need diaphragms. I actually have only ever replaced a couple in about 20 years, and 3 of those were because of a PO not installing them properly and pinch cutting them.

[quexpress]

Yes I would rethink the Idea, until you take them apart, and clean them PROPERLY, meaning a full strip and dip with new Orings and gaskets. Odds are you wont need diaphragms. I actually have only ever replaced a couple in about 20 years, and 3 of those were because of a PO not installing them properly and pinch cutting them.

I'm with HJFISK on this one. I also think that you should hold off until after you have seen each one.
Once you have them apart, you might be pleasantly surprised after examining the diaphragms (under a light).

[Jamesp]

Thanks much I will not order until I see what they look like. When I get into it I may have a few more questions for you. really apperciate the input.

[Steve]

... I've been running carb cleaner through it to see if I could get it cleaned up. During the carb rebuild research I've found that the carb cleaners eat up the Diaphrams plus its been backfiring thought the cabs quite a bit. So I though it would be a good thing to have the diaphrams on hand when I took the carbs off. Should I rethink that decision?

In the course of "normal" operation, carb cleaner added to the fuel tank will never touch the diaphragms.

The diaphragms are only affected by carb cleaner when it is sprayed directly on them and allowed to stay for a while.

In the case of severely clogged carbs, adding chemicals to the fuel tank will not clean them. The concentration of cleaners is not enough to unclog the carbs and will not do the job you are expecting. By the time you increase the concentration to the point where it will work, the mixture will not burn well in the combustion process. It is far better to use a tried-and-true method of soaking the carbs in a good solvent.

There is a very good chance you will NOT need new diaphragms. They are just a bit too expensive to buy on speculation and have them sitting in reserve.

.

[Jamesp]

can I keep the cabs together?

It certainly looks like a carb rebuild is in my immediate future but I have another question. All the stuff I am reading says to separate the carbs when I rebuild them. It really doesn't give a reason but it looks like you can get to all the jets o rings and such with them together plus the sync will stay where it is, and should be close enough to start with or am I off in left field again???

[Steve]

Not quite left field, but you are just past the shortstop.

One reason to separate the gang is to replace the o-rings that are on the fuel transfer tubes and the vent tubes that are between the carbs.

Not sure if you can replace the o-ring on the "choke" mechanism with the carbs together. Yeah, you could do that, but it's easier to remove the plunger and make sure it's all clean, too.

Besides, where are you going to dip an entire gang of four carbs?

And if you do dip the entire gang, you will have to replace the o-rings in the transfer tubes for sure, which will require separating the gang.

You takin' the hint?

EDIT: Where are you? (Add your location to your profile.) One of us might be close enough to help you with a carb sync.


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[Jamesp]

I think I get the hint-always looking for an easier way and kind of iffy on the carb sync thing. On this 1100 the book says carbs 2-3 are set different than 1 and 4. was going to use vacuum gauges but how do you interpret 1/2 a ball into vacuum gauge terms??