Mikuni Carbs? who can enlighten me?

[SixString]

I have a 1999 Pitbull. The engine code is Z1134, so I'm guessing it's a 107ci. Someone has put a Mikuni carb and intake on her. The Mikuni needs rebuilt. I have 4 questions.
1) Is the Mikuni better than the S&S that was original to the bike?
2) Should I rebuild the Mikuni? (I will have to also replace the intake gaskets at the jugs)
3) Should I replace the Mikuni with a S&S carb and intake? ($500 for the kit)
4) What S&S carb should I use with the 107ci? (Super E, G, etc)
Your opinions would be greatly appreciated. Thanks!

 

[bigdogtech01]

Mikuni is superior to the S&S. It requires a little more tuning than S&S, but by far a better performing carburetor. I would rebuild what you have.
What is it doing or not doing that makes you feel it needs to be rebuilt?
Intake seals are easy and only $10.

 

[john sachs]

Mikuni is superior to the S&S. It requires a little more tuning than S&S, but by far a better performing carburetor. I would rebuild what you have.
What is it doing or not doing that makes you feel it needs to be rebuilt?
Intake seals are easy and only $10.

I agree ........:2thumbs:
John

 

[Letbigdogintocanada]

Mikuni is superior to the S&S. It requires a little more tuning than S&S, but by far a better performing carburetor. I would rebuild what you have.
What is it doing or not doing that makes you feel it needs to be rebuilt?
Intake seals are easy and only $10.

Andrew is right,mikunis are a much better carbs for your daily riding,s&s work great at full throtlle,I believe 42 or 44mm work best on the 107,s,so if I was u ,I just rebuild the mikuni.

 

[SixString]

Thank you Andrew and John. I have three issues with the carb:

1). When the engine is not running and the petcock is in the on position, gas
streams out of the overflow tube.
2). There is a leak where the intake manifold connects to the front jug.
3). The bike idles well, and accelerates smoothly. However, when trying to hold * a steady speed, say at 40mph, the engine runs poorly.

 

[SixString]

Thanks, JR. Please explain the 42 or 44mm for the 107ci. I'm new to custom bikes. Lol.

 

[SixString]

Also, if it has any bearing on our conversation, I am going for dependability, not necessarily speed. Thanks again guys. Your opinions and experience are greatly appreciated!

 

[bigdogtech01]

Most likely just needs a float needle. The needle is probably worn out and is causing your overflow issue. I would check the float height as well when you have it apart. Someone before you might have played with it. The fuel we have now a days at the pump sucks as well and can cause a lot of problems if it sits in your carburetor for a period of time.
The issue you are having at constant cruise speed is most likely caused by the intake leak.
It sounds like its all easy fixes. Just take the entire carburetor off the motor along with the intake manifold so you can clean and inspect everything.
I believe you can buy a complete Mikuni rebuild kit that will come with everything needed for less than $80.

 

[SixString]

That's what I'll do. Take off the tank, remove the breather, carb and intake. Clean and inspect everything. Buy new intake gaskets and a rebuild kit. This will also give me a chance to replace all the oil tank lines and give the area between the jugs a good clean and polish. (might as well) Of course, you know I'll be hitting you guys up for advice when I can't get everything back together. Hahaha. But hey, I need to learn to wrench my own bike. And you guys are really cool for helping novices like me do the work myself. Its a matter of pride!

 

[john sachs]

HSR Mikuni carbs come in 42 mm. 45 mm. & 48 mm. Not 44 mm.
I find the best place to get Mikuni parts is Fox Distributing in St. Charles , Il. 630 513-9700. :2thumbs:
Get the parts you need, and also have them send you a tuners manual for your carb. Overhaul can be a little tricky in the slide area.
John

 

[SixString]

Thanks John for the info on where to get the parts and directions on rebuilding the carb. Is there anything I need to know on replacing the intake gaskets? Or is as simple as removing the bolts, replacing the gaskets, and putting it back together. I'm probably going to need a torque wrench...

 

[X-ray Doc]

I think the 1999 had a 96" motor as stock, if it is a 107" it should have SA stamped
on the engine case near the serial number (SA=special application). If you changed
the intake manifold it would be shorter in lengh than a 107. I would not change it
the Mikuni is better IMO.

 

[SixString]

Been reading up on the repairs. When trying to determine the size (42mm 45mm) I'm guessing that refers to the diameter of the slide... right? I'm pretty sure its not the 48mm monster, it only being a 107 with no internal mods that I know of. There are no markings on the carb that I can see without removing it. Guess I'll remove everything and see what I got. Wish me luck

 

[SixString]

I think the 1999 had a 96" motor as stock, if it is a 107" it should have SA stamped
on the engine case near the serial number (SA=special application). If you changed
the intake manifold it would be shorter in lengh than a 107. I would not change it
the Mikuni is better IMO.

Wow, Gene. I really need to look into this. I was under the impression it is a 107ci. I'm guessing the Z in the code refers to the year (1999), so how does one determine the cubic inch of a given engine? All I found was, of course, "S&S Super Stock" and the engine number, *Z1134*

 

[john sachs]

Wow, Gene. I really need to look into this. I was under the impression it is a 107ci. I'm guessing the Z in the code refers to the year (1999), so how does one determine the cubic inch of a given engine? All I found was, of course, "S&S Super Stock" and the engine number, *Z1134*

Call S&S, give them the motor #, and they'll let you know what's up.
Mikuni size is stamped on the back of the carb. You have to look real hard, but it's there.
John

 

[Jersey Big Mike]

you've got dirt in the carb.

Run the bilke then turn the petcock off and tap the top of the carb to try and knock the dirt loose -- has happened to mine a couple of times.

Rebuild if needed is a piece of cake.

 

[X-ray Doc]

As John said call S&S and give them your serial number, 1-608-627-8324 and they
should be able to tell you what size the motor is, then cylinders are taller on a 96"
as the stroke is 4 5/8" vs the 107 of 4 1/4".
As stated earlier, rebuild the carb, the gas has most likely swelled the float needle
o-ring making it stick.

 

[SixString]

Well, I called S&S... didn't like the answer. My engine was built for Big Dog in Dec of 98. Apparently it is not the 107ci I was told it was when I bought the bike. It is an "88ci Custom with a 4.25 stroke, and shipped with the Super E carb".:bang:

 

[X-ray Doc]

That's a bummer man! Most likely the carb is a 42mm for the 88"

 

[SixString]

It's all good, though. I love the bike. So what if it's only an 88ci engine... I'm still gonna fix her up!