Shims and muzzy install with pics and a question. (Updated)

[rider123]

Well the temp went up to 16 degrees Celcius. So I decided to go and shim the needles and install the Muzzy. Installing the pipe was super easy, but boy did that stock exhaust weight alot, easily double what the muzzy weighs. No offense to the people who love their bike stock, but the stock pipe is a total POS! It's heavy as hell and if you look inside the diameter is about the same on my '84 GS750. Anyway I degress, I popped it on with no changes to the A/f mixture plugs at first. So I rode it to work and wow there is definately an increase in power, definately lean down low though. I left in the snokle in for now just to see what I can do untill I decide whether or not to pull it. It was popping a bit on de-acceleration and was flat off idle. So on my way home I turned it out half a turn over stock. It was obviously a little rich as when I did a plug check when I got home the plugs were a little dirty so tonight I turned it in about 1/8th of a turn and will see what goes on in the next few days. It was also mushy down low when hot being so rich.

Here are some pics and notes for other guys that want to try this mod. Takes about an hour in total.


Ok I tried #8 washers they were way too big!!! Take a look, also #6's were way too big. I highly suggest the radio shack or hobby store shims otherwise they dont seat properly. As you can see in this fuzzy pic(sorry) the #8 washer is way over the diameter of the nylon donut.



I used the smallest shim in this "source"(radio shack buyers in Canada)shim pack the smallest on the left which is abuot 6mm. It is a PERFECT fit between the nylon donut and the needle clip.



Also I found the 2 overflow tubes under the tank were almost impossible to take off myself. So what I did was take off the fuel line, vaccuum line and fuel guage sender and propped the tank sideways along the airbox and it worked great it was solidly perched there and worked fine, saves you a bit of work if you want to try it this way. Notice that I stuck a rag in front of the carbs to catch the teeny weeny "O-Ring of death". It saved me alot of pain when I almost lost onof those little O-ring's so I highly suggest you put something in front of there.



Here is a pic of the finished product. Damn I have to hold my hand steady with this digital camera!!  



THese are my settings as of now, it's supposed to get really crappy in Toronto where I live so I don't know if these will be final but it's probably fairly close.


1mm shim (.040)
Snorkle in for now <--- I'll experiment when it gets warmer out. Anyone know if this should be in or out?

mixture screws

Cylinder #1 1/8th under 3 turns
Cylinder #2 2.75
Cylinder #3 hair under 2.75
Cylinder #4 1/8th under 3 turns

As far as the pipe it's not that obnoxious at all and has a nice grumbly tone. It sounds MEAN!

Anyone know about the skorkle? In or out?

[bstard]

Hi
Why do you have the mixture screws set differently.
I mean why are they all not at the same settings.
You have the outside carb,s set different to the inside ones.
Whats the reasoning behind that ?
Richard

[Red01]

Because the center two cylinders run hotter that the outer two.

[kedeg_97B12]

Because the center two cylinders run hotter that the outer two.

Shouldn't they be farther out then? Richer usually runs cooler.

[rider123]

When I do a plug check some cylinders are running different from others. If I don't equalize them the idle is "lopey" and uneven. Once fine tuned, the idle is nice and flat and all cylinders are at the same mixture with no stumbling. Say you give it throttle and the super rich cylinder is firing at the same time you take off it's going to hesitate. If you take off when the perfect cylinder fires it won't.


For example if I set every one of my carbs to 2.5 for stock configuration:


(this is a hypothetical example)
cylinder 1 is perfect
cylinder 2 is slightly lean
cylinder 3 is super rich
cylinder 4 is slightly rich


If you run you're bike this way it will be all wonky. You have to equalize the mixtures so that the cylinders get the same amount of fuel. As far as the snorkle goes I'm thinking I should pull it out. It seems like for me to run correctly I have to almost set the A/F screws just slightly richer than stock to get it to idle nicely but then it's too lean off idle. If I richen the screws than idle is too rich. Maybe taking out the snorkle will give enough air in there so I can richen up the pilots to get rid of the hesitation off idle without it being too rich. Anyone have any definitive answer on the snorkle?

[Red01]

Because the center two cylinders run hotter that the outer two.

Shouldn't they be farther out then? Richer usually runs cooler.

  You're right! But he expained his reason above.

[rider123]

Well I pulled out the snorkle and it ran better almost right away. THis is sitting in the parking lot of course but what was happening was that as soon as it was warmed up it would just be sort of air starved and run rich even if the pilots were set right. I think it needs that little bit of extra air. THis of course is with the airbox UNMODIFIED. I think what is happening is that while I opened up the end with a slip on, if you keep the airbox with the snorkle in it it's not getting the airflow it needs. While taking out the snorkle only slightly opens it up but it spreads the air evenly amoung all the cylinders better which probably helps. I'll know for sure if the weather gets better, but it already seems to work better down low. I can probably now tune out the low hesitation now(if it's not gone already) that it's getting the proper amount of air in there.

However if you change the airbox by drilling holes and such it would probably disrupt the airflow enough that you need to put the snorkle back in to create the low speed velocity that is needed. Even with the snorkle taken out the air is still going through one hole so it's speeding it up still. Once you spread the air over many holes this effect is gone so you probably have to pop the snorkle back in there to compensate slightly.

I'll know for sure in the coming days or weeks but it looks really crappy for the next bunch of days here in Toronto.


Just as an observation looking at the snorkle and the stock exhaust. This bike is heavily restricted! Like crazy restricted, my 1984 GS750EF has 3 times the snorkle size. While old it was considered a "sport" bike(full fairing). Also the exhaust is about double the size of the stock B12. That's on a bike with just over half the displacement. SCARY!!! NO wonder the B12 runs better with a little more air.

[rider123]

Here is an airflow chart for the 2" mods and stock airflow from "Krazy Ed". Thanks Ed you're just "krazy"!

It's a well known fact that the Bandit 1200 is starved for air by the teensy-weensy airbox opening (originally designed for the Bandit 600).  I decided to see just how bad the situation really was...

2" Hole -> 2 inch diameter = 50.8mm = radius of 25.4mm
Snorkel -> 1.5 inch diameter = 38.1mm diameter = 19mm radius
Stock Carb -> 36mm diameter = 18mm radius

(you can already see by this that the 1.5" opening in the snorkel is about equal to the opening of *ONE* carburetor)

single 2" hole area = 3.1416 * (25.4mm * 25.4mm) = 3.1416 * 645.16 = 2026.83mm sq.
Single 36mm carb area = 3.1416 * (18mm * 18mm) = 1017.88mm sq.
1.5" snorkel area = 3.1416 * (19mm * 19mm) = 1134.12mm sq.
36mm area * 4 carbs = 4071.51mm sq
2" hole area * 2 holes = 4053.66

So, the carbs can utilize up to 4072 sq mm of area (at full open).  Leaving the snorkel in place (with no other holes in the airbox) gives you only 1134 sq mm of area (less than 28% of what the carbs can utilize when fully open). Using the dual 2" holes gives you 4054 sq mm of area (99.6% of what the carbs can use).

As you can see even me taking out the snorkle is only opening up the airbox enough to utilize half of the potential total air volumn of all 4 carbs. This box is restricted!! However since I haven't put in new mains only shimmed the needle it should even itself out.

[rider123]

For those still tuning in I'm running rich from the low mid-range up and am compensating with the pilots so it's a little wonky. It may be that 1mm(.040) is too much even with the snorkle out, the stock needle design is a very flat taper so I don't think it gives way to heavy duty lifting without comprimising the driveability. I think it should probably be around .5mm or (.020). The only thing else I can think of is that the diameter of the washer is still too big and the needle isn't seating. But I'm %90 sure that it is seating properly, I can pull the right most carb off without taking the tank off so I'll check soon as I can. Iit's gotten too cold to ride now in Toronto anyway and report back. So far here are my solutions:

A. Go back to stock untill I get a jet kit. This sucks as I'd rather not take two steps back to go 1 forward and I spent time making my new muzzy seal perfectly in the stock headpipe.

B. If the shim diameter is too wide and not seating properly(I highly doubt it) I could shave the diameter down to fit.

C. I could forgo the shims for now and put the needle back to stock with the snorkle in there so I can drive around at least. THis sucks too because what's the point?

D. Somewhere in the universe these shims must exist in Toronto. I've been trying alot of hardware stores but have had no luck as of yet. I'll try Home Depot or some other super hardware store on the weekend to see if I can find these suckers. Unfortunatly for us in Canada, Radio Shack has been bought out so I can't get the "official" Radio shack shims anymore, DaveG another forum member here is going to the States to pick up a pack or two of these so I may be ok.

E. Take the shim on top of the circlip and put it on the bottom. I'm not sure if this will screw up the seating of the needle but I doubt it. THis is the last resort.

At least I have an idea of what I need. According to this chart:

http://www.engineersedge.com/plain_washers.htm

I need #2 "narrow" (.025 thickness) and may pick up #2 "Regular" (.032 thickness) as well. # 4 may work too. At least I can print this sucker out and take it with me to Home Depot or Rona's or any other "Super Hardware" store. If I can't find any I guess I could try and call Dale and see if I can buy some shims from him. I'll probably just need 1 shim on each, maybe I'll post in the wanted ads. Does anyone have any extra shims they could mail me in case? I'll pay triple what the shims cost just for the zero agrivation.

[DaveG]

ok i'll pick up two packs of radio shacks

The #2 narrow may have too small an id but could drill it out with a 1/8 bit if needed.


we know the rs ones work so hopefully i can get them this week if not the 24th for sure.


I work at Winston Churchill and Dundas so maybe could deliver half way some lunchtime.

[rider123]

I'll trade you some hooch for those shims Dave!   I could try Brofasco if Home Depot doesn't work out.

[chupacabra]

I have some, but I'm in San Diego!

[rider123]

Well I'll pay for you to mail me if you can. PM sent.

Now that I'm thinking about it the #4 shims I used out of the "source" pack must be slightly too large and hanging up in the slide. I think that's the reason it's so rich. It's only 1 mm(.040) and I have the snorkle off and it's still rich. I haven't been riding due to weather, when I get a chance I'll pop off number 4 carb cap as it can be taken off without having to pull the tank and see what is going on in there. Even if it's only lifting only an extra couple of mm's(hard to detect) it still is alot on the needles. If that is the case for fun untill I get the correct shims I may shave down the "source" shims outside diameter to match the circlip on the needle and then mark the needle and measure whether or not it's actually seating properly and only lifting the needle a mm from stock. ahhh.....the joys of shimming!!  

[rider123]

Well I pulled a carb and I was right and wrong. At first I thought that the needle was seated properly...it wasn't. Even that tiny .2 of a millimeter diameter caused the needle to rise an extra 1-1.5 mm for a total of 2-2.5mm! Whats that? 8 shims worth?!! Argghhh! No wonder I was rich. I don't think the needle even seated in the emulsion tube at idle! Ok so I filed the shim down to less then the diameter of the circlip(shim is plastic for now, "source" shim) and it's lifting the proper 1mm compared to stock. I marked the needle seated at stock at 6mm then put the filed shim and it went up to 5 mm instead of just under 4mm without the filing. So at least my theory was correct that the needles had to be stuck in there somehow. Anyway I'll give it a shot tomorrow even though it's going to be super cold to see if it works.

[rider123]

Well I finally got a chance to ride it today with the corrected shims. Wow! At 3 and half grand the front wheel wants to come up! I think I broke it!    I have the mixture screws turned out just under half a turn over stock and it's still a little lean on the pilots. I'm going to try and post a comprehensive evaluation if possible when I'm done to help out  some other guys here and hopefully save them some time and pitfalls.

Shims: 1mm or (.040) I'm using the "source" 1mm shim. Shaved outer diameter to correct size.

Snorkle: Out for now. I get a bit of popping around 2 and half thousand on de-accelreration, and down so I'm thinking the pilots are still a little lean in this crucial transition area from the mains to the pilots. They could probably use an 1/8th to a 1/4 turn out. Alternatively I could pop the snorkle back in but if I can get it to run with the snorkle out so it breaths much better that would be my first choice.

Mixture screws: little less than 1/2 a turn from stock. Probably could use an extra 1/8th or 1/4 turn out. If I was doing this again. I would immediately turn the mixture screws out half a turn and fine tune from there. It would have saved some time.

When I get it perfect I'll let you guys exactly know whats going on so it can save your time. Thanks for all your help and the shims!! I have a shitload of shims now if anyone needs them just PM me your address and I'll stick them in the mail.


IMPORTANT! If you are buying shims DO NOT get #8's as is commonly said here. You need #4's! #8's as you can see in the picture is WAY too big. When you shim the carbs mark the needle and measure how much it lifts when you shim it. If it is more than what you are shimming it's getting stuck in the slide and you have to file it down untill it's the same diameter or less than the circlip.