Idle jet - that didn't go as planned.

[CRXSi90]

I was digging into the carbs to clean them up, and stripped one of the idle jets. I was using a screwdriver which fit well, but it still stripped anyway. Still managed to get it out and I'm sure I could get it back in, but I should probably not half-ass it and should replace it so there aren't problems the next time the carbs have to come apart.

It's a 6-hole 42.5 jet from carb #3, 4G0-14142-42-A0. $5.49 from the dealer. Oh well, probably one of the cheaper screw ups which can be made.

Let's see what other damage I can do this afternoon. So far, it looks like the vacuum slide covers are going to put up a fight. I'm going to give the phillips heads a whack and see if that frees them up. I might look into replacing them with socket head cap screws when they go back together.

[motoman]

I was digging into the carbs to clean them up, and stripped one of the idle jets. I was using a screwdriver which fit well, but it still stripped anyway. Still managed to get it out and I'm sure I could get it back in, but I should probably not half-ass it and should replace it so there aren't problems the next time the carbs have to come apart.

It's a 6-hole 42.5 jet from carb #3, 4G0-14142-42-A0. $5.49 from the dealer. Oh well, probably one of the cheaper screw ups which can be made.

Let's see what other damage I can do this afternoon. So far, it looks like the vacuum slide covers are going to put up a fight. I'm going to give the phillips heads a whack and see if that frees them up. I might look into replacing them with socket head cap screws when they go back together.

Good choice replacing that pilot jet. Your local Ace or Tru-Valu specialty trays have some nice looking stainless steel button head metric allen bolts for those diaphram caps.

[CRXSi90]

update

Well, after fighting with the carbs for a couple hours, I got a first pass of cleaning done, and got the vacuum slide covers off. The covers required quite a bit of persuasion. I see that at least one of the vacuum diaphragms has a pin hole where it must have been rubbing against itself. I recall reading that any kind of repair won't hold up, but my options are either do nothing or attempt some kind of repair, since I can't swing new diaphragms right now.

Carb #2 was very gummed up both on the emulsion tube (?) And the pressed in brass jet on the outlet side of the carb. It all seemed to clean up okay. I'm going to review the carb cleaning tech tip and see if I missed anything. I didn't pull the float valves, but I can't imagine that there's any huge problems there. The viton tips look pretty good.

It seemed like the center two carbs were a lot worse than the outside two. I can't come up with any explanation as to why that would be.

I noticed something interesting - the vacuum slide covers on the outside carbs (1&4) are chrome, but the center ones seem to be galvanized or something.

[DGXSER]

Well, after fighting with the carbs for a couple hours, I got a first pass of cleaning done, and got the vacuum slide covers off. The covers required quite a bit of persuasion.

I would get some socket head cap screws/ metric, stainless steel to replace the diaphragm and carb bowl screws.

I see that at least one of the vacuum diaphragms has a pin hole where it must have been rubbing against itself. I recall reading that any kind of repair won't hold up, but my options are either do nothing or attempt some kind of repair, since I can't swing new diaphragms right now.

I have used RTV to seal up such pin holes before. Worked fine for a year or so, till I bought a new slide from , though they seem to be out of stock on it.

Carb #2 was very gummed up both on the emulsion tube (?) And the pressed in brass jet on the outlet side of the carb. It all seemed to clean up okay. I'm going to review the carb cleaning tech tip and see if I missed anything. I didn't pull the float valves, but I can't imagine that there's any huge problems there. The viton tips look pretty good.

You may not need to pull the float needle valve seat, but you do want ot clena them up wiht carb cleaner and a q-tip.

I noticed something interesting - the vacuum slide covers on the outside carbs (1&4) are chrome, but the center ones seem to be galvanized or something.

This is the stock setup for the 80-81 models I believe both Standard and Specials, I know it is for Specials.

[donebysunday]

Just a little tiny dot of super glue on the hole in the diaphragm will last. I say a little dot or dab, a big run or large spot will cause the diaphragm to not move as needed. The diaphragms develope holes because of rubbing on the inside of the carb, the carb surface is rough and actually the super glue is more resistant to the friction but it would not hurt to polish the carbs where the diaphagms rub against them.
You can also use a dremel tool or such like and a thin cutting wheel to put a new screw driver slot into that jet as long as you don't have to cut into the metering hole.

[CRXSi90]

Thanks, I'll try a teeny bit of super glue or RTV on the diaphragms. I did a bit of reading, and it sounds like others have had success with gorilla glue also.

One thing I forgot in the cleaning was the screws on top of the carb - I believe idle mixture screws. There was a bunch of dirt caked in the hole (no plug), but I got that cleaned out and made sure they would turn freely. I ran them in (gently), and it seemed like they were about 1.5 turns out. I'll check the positions again before I take them apart to do some cleaning.

[WMarshy]

Just a little tiny dot of super glue on the hole in the diaphragm will last. I say a little dot or dab, a big run or large spot will cause the diaphragm to not move as needed. The diaphragms develope holes because of rubbing on the inside of the carb, the carb surface is rough and actually the super glue is more resistant to the friction but it would not hurt to polish the carbs where the diaphagms rub against them...

Superglue is not the recommended solution to this as it dries hard and does not flex. If used you run the risk of creating a new hole at the edge of where the glue was applied. Yes, in very small amounts it would probably work fine but the risk remains. Besides, I think everyone at one point meant to apply just a pin drop and got half the bottle.

The #1 recommended repair is to use plasti-dip. http://www.plastidip.com/
Members have used this with great success. You can probably find some reviews in the product section of the forum... Not sure what it costs but might be cheaper in short term if the superglue wrecks them in a week or two and you cant ride because of it... others have used silicone/rtv material.

[CRXSi90]

Looks like PlastiDip is <$7 at Menards, a regional home improvement store. It make sense that something flexible is desirable. Based on the solvents in the MSDS (Naptha, Hexane, Toluene, MEK), I would expect it to be somewhat resistant to gasoline, not that there should be a whole lot of gasoline up there anyway.

[motoman]

Looks like PlastiDip is <$7 at Menards, a regional home improvement store. It make sense that something flexible is desirable. Based on the solvents in the MSDS (Naptha, Hexane, Toluene, MEK), I would expect it to be somewhat resistant to gasoline, not that there should be a whole lot of gasoline up there anyway.

Unfortunately, I can say from experience that Plasti-Dip WILL end up everywhere in there but where you originally put it. Experimenting, I ended up using a drop of expensive two-part tube of automotive plastic bumper repair on each of the eight wear points on each diaphram that I had. That was four years ago, and looks like the stuff also made for good wear 'bumpers' on those spots also.

[GLoweVA]

I got a set of 4 replacement diaphrams from ebay for about $60.
I've had them on my SG for about 3 months now and I'm glad a changed them all out. All 4 slides work in concert now and I'm happy.
I had thought about fixing/patching the pin hole leaks, but every time I thought about the what ifs and having to go back into the carbs, well, my time is a little more valuable to me than that.

[CRXSi90]

....my time is a little more valuable to me than that.

I definitely hear ya there. Looks like the least expensive set on eBay is going for ~$100 right now, but I'll keep an eye out. http://bit.ly/12ui0V8 Looks like replacements can be had from JBM Industries for ~$85 for a set of 4.

I'll keep an eye on eBay and see if I can score a deal, otherwise I'll check into the 2-part urethane.

[CRXSi90]

6 hole jet

Just looking to order the jet. It looks like it can be gotten direct from Yamaha:

4G0-14142-42-A0 JET, PILOT ( 42.5) $5.49

....but I was wondering if this is the same thing......

KBS3096425 DESCRIPTION: MIKUNI GENUINE OEM PILOT JETS, SIZE: 42.5, QTY: Each - OEM Pilot Jets $2.95

The image shows that it has 6 pilot holes. Can anyone advise if the "Mikuni GENUINE OEM" jet is correct?

[motoman]

Just looking to order the jet. It looks like it can be gotten direct from Yamaha:

4G0-14142-42-A0 JET, PILOT ( 42.5) $5.49

....but I was wondering if this is the same thing......

KBS3096425 DESCRIPTION: MIKUNI GENUINE OEM PILOT JETS, SIZE: 42.5, QTY: Each - OEM Pilot Jets $2.95

The image shows that it has 6 pilot holes. Can anyone advise if the "Mikuni GENUINE OEM" jet is correct?

'Genuine' makes it correct.....

[GLoweVA]

Just looking to order the jet. It looks like it can be gotten direct from Yamaha:

4G0-14142-42-A0 JET, PILOT ( 42.5) $5.49

....but I was wondering if this is the same thing......

KBS3096425 DESCRIPTION: MIKUNI GENUINE OEM PILOT JETS, SIZE: 42.5, QTY: Each - OEM Pilot Jets $2.95

The image shows that it has 6 pilot holes. Can anyone advise if the "Mikuni GENUINE OEM" jet is correct?

I will advise you that you most like will get a genuine mikuni part, but it will have NO holes. They used to come with 6 holes, but now adays Mother Yammy has sent out these now. I 've order that particular part number twice now from 2 different places and the jet I got had no holes. That doesn't mean it won't work. I've got 2 of them in my SG and they work great. Some here swear that the 6 holed ones are what must be used, I beg to differ.
The air gets mixed in with the gas AFTER the metering orfice. Both my G and SG carbs ar built this way. I haven't had a chance to check out the '79 carbs that TC let me borrow to check this out on yet.

In other words, don't be suprised if the jet that shows up doesn't have 6 holes. It should still work.

[CRXSi90]

Thank you for the heads up about that. I would have worried if I received those. I just looked, and on my particular carbs, it doesn't appear that the holes would serve any purpose since there is no passage "outside" the jet.

I can fathom a design where the fuel outside the jet gets diverted to the enrichment circuit or something like that.