The tears dried to my face aren't from wind, its joy

[freak_leg]

Elanor is finally on the road and causing trouble! I've just got a couple issues. #2 seems to be running a bit rich, during deceleration is pops out of the pipe that goes to 2 & 3. and randomly (mostly when cold) it pops out the carb and obviously stumbles because of it. Could the 2 issues be related due to the wasted spark set up and a rich condition?

[dbeardslee]

Congrats on getting her on the road. If it's stock then it's got the cross over pipe on it. A recent thread on cross overs had some very interesting info. Whatever cylinder that's firing is actually using both rear pipes. Anyway, popping on decel is usually due to a lean condition. 1/2 turn out on the mixture screws often cures that. Personally I prefer to use a colortune plug for carb adjustment. Out of sync carbs can cause popping and backfiring as well.

After rereading your post I see where you said the pipe that goes to 2&3? Stock pipes are paired 1&2, and 3&4, and then connect via the cross over. If you've got high performance aftermarket exhaust installed, that would tend to lean it out if you didn't rejet. When they're cold they run a bit lean anyway, which is why the carbs have an enricher circuit. A lean problem will tend to be the worst when cold, and will improve as the engine warms up.

[freak_leg]

Congrats on getting her on the road. If it's stock then it's got the cross over pipe on it. A recent thread on cross overs had some very interesting info. Whatever cylinder that's firing is actually using both rear pipes. Anyway, popping on decel is usually due to a lean condition. 1/2 turn out on the mixture screws often cures that. Personally I prefer to use a colortune plug for carb adjustment. Out of sync carbs can cause popping and backfiring as well.

After rereading your post I see where you said the pipe that goes to 2&3? Stock pipes are paired 1&2, and 3&4, and then connect via the cross over. If you've got high performance aftermarket exhaust installed, that would tend to lean it out if you didn't rejet. When they're cold they run a bit lean anyway, which is why the carbs have an enricher circuit. A lean problem will tend to be the worst when cold, and will improve as the engine warms up.

Sorry, I need to update that. I've got some kind of after market 4-2s that link 1-4 and 2-3 with HD mufflers. I know my jets are off a bit because under full throttle it falls on its face from 4-6k rpm. I'm living with that for now. She just got on the road I don't want to take it out of service again. but I'll try to rich up the mix a bit. see how that works, for some reason #2 has always been a bit off from the other 3.

[dbeardslee]

4-6k range is generally slide needle position, but the mains will affect the entire range. I've got a few questions - are your carbs clean? What size mains are in there now (stock should be 137.5 on the 78/79 BS34II's)? Where are your floats set? What clip position are your slide needles set on? All that stuff is going to affect performance.

[freak_leg]

4-6k range is generally slide needle position, but the mains will affect the entire range. I've got a few questions - are your carbs clean? What size mains are in there now (stock should be 137.5 on the 78/79 BS34II's)? Where are your floats set? What clip position are your slide needles set on? All that stuff is going to affect performance.

To be honest, I know the carbs are clean. I watched the PO clean them, However thats all i know about the set up, I dont know the jet size. I'd guess if not factory size it would be a size bigger. because the pipes are a bit bigger than stock.

Tell me about the slide needles... I've heard it mentioned before but before i got this bike i had never laid hands on a carb. Where are they? how do i adj them? anyone got some pictures? I'm on a steep learning curve here...

[dbeardslee]

The top of the carbs have a flat metal plate secured by 4 bolts. Under the cover you will find a spring, and a rubber diaphragm (which you want to check for holes). The diaphragm is connected to the slide assembly, and the needles come out the bottom. To get the slides out, stick your finger in the throat of the carb and just push up gently on the bottom of the slide (it's the brass looking thing you see when you look in the throat) with the covers removed. You need some long reach snap ring pliers (available at mikes xs for $10) to get the needles out (and be careful - there are small parts you don't want to lose). You'll see a clip that goes into one of five slots. Factory setting is on the middle slot. If you want to richen the midrange, you put the clip on a lower slot. If you want to lean it you put it on a higher slot. Anyway, the needles work with the main jets and the emulsion tubes. You should also be aware of the Yamaha parts fiche - it has all kinds of information along with detailed parts diagrams and can answer many assembly/disassembly questions.

And here's a link to a page on CV carb tuning that I've found very helpful. It usually takes some fiddling to get them setup correctly when you've got mods - like an aftermarket exhaust. Mixture adjustment and sync are also critical. I'd probably check the sync before I did anything.

[freak_leg]

thanks! I'll check that out after i get a few miles into her

[dbeardslee]

I think we were typing at the same time, and I made some edits to my previous post. Just wanted to make sure you saw the whole thing.

[fredintoon]

- - - Tell me about the slide needles...- - - Where are they? how do i adj them? anyone got some pictures? I'm on a steep learning curve here...

Hi Tony,
they are the tapered spikes that hang down from the carbs vacuum operated slides.
They work in conjunction with the brass tubular things that stick up in the middle of the carbs to help the various jets regulate the fuel flow between ~1/4 & 3/4 throttle.
Lifting them UP lets the carbs run richer. lowering them DOWN lets the carbs run leaner.
Fitting differently configured aftermarket slide needles can improve the midrange performance if you know what you are doing (but that's not me.)

[DGXSER]

There is a thread titled "Carb Tuning 101" you can find using the search function. It has lots of pretty pictures and even some cirlces and arrows and a paragraph on the back explaining what each one is to be used as evidence......oh...wait....sorry...not so much on the paragraph part. They do have some pointers on them though to identify parts.

[randy]

Three things you should do before taking apart the carbs again:

Synchronize

Synchronize

Synchronize

[dbeardslee]

If you want to richen the midrange, you put the clip on a lower slot. If you want to lean it you put it on a higher slot.

Lifting them UP lets the carbs run richer. lowering them DOWN lets the carbs run leaner.

Just so's we don't get him confused, we're both saying the same thing. I was talking about the clip position, and Fred was talking about the overall needle position.

[freak_leg]

Thanks guys, I got what you're saying. I'll have to dive into my service manual and study the carb section. I did a bench sync a few weeks ago as i dont have a set of vacuum gauges. It made a huge improvement. a couple butterflies were a bit off. I'll tinker with the mixture screws a little bit, i gotta get the popping to go away. Its annoying...

[DGXSER]

If you look in the tech tips there is a description of how to make a plenum of PVC pipe and use a normal vac gage to synch. I use my mity-vac to synch.

[dbeardslee]

If all you did was a bench sync, then definitely start with a proper sync. Bread ties are only meant to get them close enough for a proper sync. What you're adjusting with the sync is even draw from all four cylinders. As no two cylinders are going to draw exactly the same, you really need to put the gauges on it. You can do it with a single gauge, but it's much easier, and much faster with a four gauge set. There's an acceptable set on Ebay right now for $46. You also want to make sure you calibrate your gauges prior to syncing as they sometimes read a little bit off from one gauge to another.