Sport Bikes banner

1 - 20 of 24 Posts

·
Registered
Joined
·
45 Posts
Discussion Starter · #1 ·
In April, 10 months ago, I took my bike to a local shop. Really good reputation for the shop. But for some reason, my bike is throwing this shop for a loop. They still have it there, and it seems to be running worse than when I dropped it off. I am rather frustrated at this point, that after 10 months the bike is still there, and no better than when I had it. I'm not incapable of fixing my bike, but I just didn't want to deal with it at the time. I had recently dropped the bike(low speed, cosmetic only damage), and had road rash on my arm. I figured it was better to let someone else fix it, and get it up and running quickly. Obviously that didn't work out for me.

So what would you do at this point? They have several hours into the bike, and I know a lot more hours into it than what they are "officially" charging me for right now. I don't necessarily want to get it back to fix more problems than when I started, but there also isn't an end in sight right now. It's a YZF750, and doesn't seem to want to idle or rev up properly right now.
 

·
Mediocre Strafer
Joined
·
9,137 Posts
If it's been there for ten months they aren't working on it any more. They've given up and have shoved it in a corner.

I'd go over there, offer to pay for anything they have objectively fixed (like rashed fairings), but not pay anything for the work they haven't accomplished on the driveability. If they are legit, they will apologize profusely and give you your bike. If they push back at all, just leave without paying anything and get a lawyer. After ten months they have no excuses.

KeS
 

·
Registered
Joined
·
2,466 Posts
Been there, done that. Pick your bike up and find someone qualified to fix it.


Went through that with a local place. After a while I realized they're just another shop over charging for dyno tunes and tires. They wasted another guys time for over a year chasing down random shit and didn't fix anything. They wanted to rip my motor apart to fix an electrical problem that was causing misfires. I'm not sure why so many people love the shop. A friendly attitude and a smile only does so much, when I'm paying 100$/hr an hour I have expectations

It's sad after this place fucked me around and wasted a bunch of my money throwing parts at it, I went to a tuner a nationals racer recommended, he fixed my bike and mapped it in 5 hours.
 

·
the joke is in your hand
Joined
·
8,594 Posts
a shop that can't get a carbed bike to run.....wow
sounds like someone bought some tools from sears, likes motorcycles and so the natural next step is to open a shop...:rolleyes
 

·
Registered
Joined
·
45 Posts
Discussion Starter · #6 ·
a shop that can't get a carbed bike to run.....wow
sounds like someone bought some tools from sears, likes motorcycles and so the natural next step is to open a shop...:rolleyes
I hear what you are saying, but that's not the case. This guy is well known, and everyone else is always happy with his work. Which is normally top quality work.

I can't explain why my bike is giving him trouble. Nor can he explain it. But it is. So it seems tomorrow I'll be asking for it back.
 

·
Eskimo Bro
Joined
·
2,053 Posts
Coming from working on a few old as dirt carbed bikes. The whole carb body may need to be dipped in cleaner to get tiny passages clear. After that for me, new rubber on the insides. And after that if it still doesn't work, i'd look at electronics such as grounds and connections. Just a little friendly information man.
 

·
Registered
Joined
·
357 Posts
Why are you waiting 10 months? They should have all the parts in a couple of weeks and the repairs done shortly after. I dunno, I don't really trust the competency of some of these shops. I'm sure there are many fine technicians/mechanics around but personally I am always leery of letting some yahoo mess with the innards of my sport-bike. Most of them just want to slap it together and collect their paycheck. I have a Haynes manual and TuneEcu for tune-ups, and I took my time and even did the valve shim job myself last summer. I have the satisfaction that the job was done properly and I saved a shitload of money (and I sure as hell wasn't waiting 10 months!) I might even order the factory manual this summer.
 

·
Registered
Joined
·
1,811 Posts
My friend had a 96 YZF750. He bought it new in 1997. They finally fixed a similar problem with his 750 in 1999. The solution to fixing it was changing the emulsion tubes in the carbs. It was at three different Yamaha dealers before it was finally fixed. I remembered the issue because my FZR400 was having the same problems right after a mutual friend at Yamaha dealer #3 fixed his problem. It's a simple fix, but hard to find because the tubes get grooved internally and look great from the outside.

Anyway, it's a corky bike. They were really expensive and really unpopular. Even the ultra-rare SP's don't sell for much. If memory serves me correct, FZR1000 motors bolt right in. Do some research and if they do, cut your losses and throw an FZR motor in it, if it's not the emulsion tubes.
 

·
Registered
Joined
·
45 Posts
Discussion Starter · #10 · (Edited)
I know about the emulsion tubes, and how they wear out oblong. That has been checked, and I replaced them about 5,000 miles ago. It usually takes at least 15k before they wear out. But thank you all for the advice(and I can't tell you how long it took me to figure that out the first time).

Part of the reason I've been waiting so long, is because I didn't want to fix what he made worse. I kept hoping that he'd get it right, and at least back to where it was when I brought it in. But that doesn't seem to be the case.
 

·
Registered
Joined
·
272 Posts
There's simply no excuses. If the shop was good, it would have been fixed. With no computers involved it shouldnt be a complicated process....sometimes its time consuming, but figuring out the problem is as simple as narrowing down the possibilities.....which a good shop should certainly know how to do.
 

·
Registered
Joined
·
2,299 Posts
Emulsion tubes, mix air with the fuel before it goes into the venturi.

here is a more complete explanation.

This is a copy from a post by Tuner on the Innovate website on emulsion.

Tuner says,
"Why didn't you ask a simple question?

In the thread “750 Holley carb help” Klaus made this statement, “On carbs it's very important that the correct two-phase flow gets established during emulsion. Otherwise you will see RPM dependency of AFR.” Thank you Klaus, but forgive me if I see your remark as a profound understatement. Incorrect two-phase flow is at the root of all this aggravation. People who have drill bits but don’t know why to use them have been molesting innocent carburetors for a long time. Now some of them are in charge of the manufacture of new carbs and they think they have improved them by using larger drill bits to make the air bleed and “emulsion” orifices. I guess the guys that engineered the original carburetors on the old muscle cars were pretty stupid or they would have “improved the emulsion” 40 or 50 years ago when they had their chance. After all, they had the awesome power of the single-point ignition system at their disposal, they shouldn’t have been afraid of a little soot.

It is well documented that introducing air into the main well encourages low signal flow and can encourage or discourage high signal flow. The natural characteristic of a plain jet and nozzle (no air) is to get richer as airflow increases. The purpose of the air bleed system is to modify that behavior to accomplish a constant (or the desired) air/fuel ratio over as wide a range of airflows as possible. The particular ratios for power and cruise are realized by the selection of jet and rod or jet and auxiliary jet (power valve channel). The purpose of air bleeds is not to emulsify but to accomplish the correct fuel delivery. Emulsion is just a beneficial side effect.

What I’m going on about here is Klaus’ remark about “correct two-phase flow”. That is the description of a fluid flow that is made up of a liquid and a gas flowing together in the same conduit. As the ratio of gas to liquid increases (more gas, less liquid), at some point the gas bubbles coalesce from many small ones into a few big ones and the flow starts to “slug” and become erratic. The carburetor nozzle spits like a garden hose with air in it when there is too much “emulsion” air.


An emulsion of air and fuel has reduced density, surface tension and viscosity compared to fuel alone. This increases the flow of fuel considerably, particularly in low-pressure difference operation, at low throttle openings or lower engine speeds. Just how much of an increase (richer) is dependant upon where and how much air is introduced into the fuel flow.

Mainly, what must be understood is that because the fuel discharge nozzle connects the venturi to the main well, whatever the low pressure (vacuum) is in the venturi, it is also the pressure in the main well. The air bleed is in the carb air horn or somewhere else where it is exposed to essentially atmospheric pressure, which is higher than the venturi pressure. This pressure difference causes air from the air bleed to flow through the emulsion system into the main well and to the nozzle. The flow of air can have very high velocities, approaching sonic in some orifices. The airflow literally blows the fuel toward and through the nozzle. A larger main air bleed will admit more air to the emulsion system and that can increase or decrease fuel flow to the engine. The size, number and location of the other air holes in the emulsion system, the size of the main well flow area, the size of the nozzle and the specific pressure difference at the moment are the determining factors. The ratios of air volume to fuel volume to flow area, with the air volume's expansion with the venturi velocity induced pressure reduction being the key. The bubbles expand as the pressure drop increases with airflow. Suck on an empty balloon to experience the effect.

The fuel flow through the main jet is the result of the pressure difference between the atmospheric pressure in the float bowl and the venturi air velocity induced vacuum acting on the nozzle and the main well. The venturi vacuum in the well is reduced (the pressure is raised) by the "air leak" from the air bleed. This reduces the pressure difference that causes the flow through the main jet. If the air bleed were big enough, the pressure in the well would be the same as in the float bowl and no fuel would flow. Think about drinking through a soda straw with a hole in it above liquid level. B***** hole, less soda. Suck harder, not much more soda. Big enough hole, no soda. This is the means by which the emulsion system can "lean it out on the top end". Incidentally, the vacuum that lifts water up a soda straw is in the most sensitive operating range for emulsion systems.

It is in the lowest range of throttle opening, at the start of main system flow, that the effect of adjusting the introduced emulsion air (and it's effect in increasing the main fuel flow) is most critical. Small changes can have large and sometimes unexpected or counter-intuitive consequences. The goal is to seamlessly blend the rising main flow with the declining idle/transition system fuel delivery to accomplish smooth engine operation during opening of the throttle in all conditions, whether from curb idle or any higher engine speed. The high speed and load mixture correction is usually easily accomplished, in comparison.

The vertical location of the bleeds entering the main well influences the fuel flow in the following ways.

1: Orifices above float level or between the well and the nozzle allow bled air to raise the pressure (reduce the vacuum) in the nozzle and above the fuel in the well. That delays the initial start of fuel flow from the nozzle to a higher air flow through the venturi and is used to control the point in the early throttle opening where the main starts.

2: Orifices at float level increase low range (early throttle opening) fuel flow by carrying fuel with the airflow to the nozzle.

3: Orifices below float level increase fuel flow by the effect of lowering the level of fuel in the well to the hole(s) admitting air. This is like raising the float level a similar amount (increases the effect of gravity in the pressure difference across the main jet) and also adds to the airflow carrying fuel to the nozzle. Locating the orifices at different vertical positions influences this effect’s progression.

4: The "emulsion holes" influence is greatest at low flows and the "main air bleed" has most influence at high flows.

In the first three cases above, once fuel flow is established it is greater than it would be with fewer or smaller holes. Visualize wind blowing spray off of the top of water waves. It doesn’t take much pressure difference to cause the velocity of the airflow through the bleed orifices to have significant velocity in the orifice, even approaching sonic (1100 F.P.S.) if the orifices are small. The phenomena of critical flow is what limits the total air flow through an orifice and allows tuning by changing bleed size.

Essentially, the emulsion effect will richen the low flow and the air bleed size, main well and nozzle restrictions will control the increase or reduction of high flow. Again, the desired air/fuel ratio is the primary purpose of the bleed system. "Improved emulsion" is an oxymoron if the modification of air bleeds to "improve emulsion" results in an incorrect air/fuel ratio in some range of engine operation. Correct proportioning of all the different bleeds (and, of course, the idle, transition and power circuits) will give the correct air/fuel ratios over the total range of speeds and loads and a flat air/fuel ratio characteristic at wide open throttle.

Now, do you have any easy questions? "
Induction, carb sizes, fuel types and their effects. • Speed Talk
 

·
A guy on a scruffy bike
Joined
·
15,367 Posts
So that's very weird to me, both because I've never heard the term before, and because my understanding of the definition of "emulsion" constrains its use to liquids.

KeS
I have heard the term. Those were the first things to go on my carbs.

Technically, an emulsion is a suspension of one fluid in another with which it is immiscible. The most common types are oils-in-water with a surfactant to keep them more stable, but other types of emulsions exist.

PhilB
 

·
Mediocre Strafer
Joined
·
9,137 Posts
I have heard the term. Those were the first things to go on my carbs.

Technically, an emulsion is a suspension of one fluid in another with which it is immiscible. The most common types are oils-in-water with a surfactant to keep them more stable, but other types of emulsions exist.

PhilB
So what's the context of this use - hydraulic engineering or something, where they consider both gases and liquids "fluids"?

KeS
 

·
Registered
Joined
·
2,299 Posts
i think its most of the sciences.

any way, how i think of it and i could be totally wrong, is:
emulsion=mix where the two things remain distinguishable/do not dissolve in each other.
emulsion of solid in liquid=mud
emulsion of solid in gas= foam(hard)
emulsion of liquid in liquid= margarine
emulsion of liquid in gas= froth(but I often call it a foam to)

some how this is related to colloids, but i do not know how.

In other news, sorry about the thread jack speedwagon.
 

·
Mediocre Strafer
Joined
·
9,137 Posts
i think its most of the sciences.

any way, how i think of it and i could be totally wrong, is:
emulsion=mix where the two things remain distinguishable/do not dissolve in each other.
emulsion of solid in liquid=mud
emulsion of solid in gas= foam(hard)
emulsion of liquid in liquid= margarine
emulsion of liquid in gas= froth(but I often call it a foam to)

some how this is related to colloids, but i do not know how.

In other news, sorry about the thread jack speedwagon.
Here's what wiki says:

"An emulsion is a mixture of two or more liquids that are normally immiscible (nonmixable or unblendable). Emulsions are part of a more general class of two-phase systems of matter called colloids. Although the terms colloid and emulsion are sometimes used interchangeably, emulsion should be used when both the dispersed and the continuous phase are liquids."

That exactly matches my lifelong understanding, btw. I thought an emulsion had to be liquids.

Not really apologizing for the threadjack since speedwagon seemed to have a consensus answer. :)

KeS
 

·
A guy on a scruffy bike
Joined
·
15,367 Posts
Here's what wiki says:

"An emulsion is a mixture of two or more liquids that are normally immiscible (nonmixable or unblendable). Emulsions are part of a more general class of two-phase systems of matter called colloids. Although the terms colloid and emulsion are sometimes used interchangeably, emulsion should be used when both the dispersed and the continuous phase are liquids."

That exactly matches my lifelong understanding, btw. I thought an emulsion had to be liquids.

Not really apologizing for the threadjack since speedwagon seemed to have a consensus answer. :)

KeS
Probably, people naming carburetor parts were not strict chemists, so it may be not entirely scientifically accurate. It does convey the idea, though, that the purpose of said tubes is to suspend the gas in the air, and that is what many people call those parts, so there we are.

I have mostly worked with liquid/liquid emulsions, but I was under the impression that an emulsion did not have to be that.

PhilB
 
  • Like
Reactions: kevin_stevens
1 - 20 of 24 Posts
Top