'84 FJ1100 resto mod

[Pat Conlon]

Robert what is the Point of drilling the hole in the slide? Thanks

Some jet kits will have you drill out the hole to change the rate at which the slides react to the vacuum signal above the diaphragm.  Similar to the different slide springs some jet kits will come with.  

^^^ Yeppers  

Here's how I remember it....(longer version)

Back in the '80's the beef with Mikuni CV carbs is that they are slow to react to throttle input. You twist open the throttle, the throttle plate opens and it takes a fraction of a second for the air velocity to increase the vacuum and get the slide and needle raised. If you ever have a chance to ride a bike with flat slide or roller slide carburetors you *will* notice more immediate snap at the throttle.
The tuners said to themselves, "Hmmm, how can we make these CV street carbs snap open faster like the flat slide racing carbs?"
Enter DynoJet...they said, "We know how to get those CV carb slides to open quicker. We will use softer slide springs."
And they did.....
However, with the new soft DynoJet slide springs, now the slides were opening fast...so fast that the momentum of the slides were now causing them to raise up too far in the barrel, causing a mid range bog from the excess fuel.

So.....drilling out the vacuum port on the slides became needed to slow down the slides and get rid of the bog

Unfortunately, once you drill out the slides you can't un drill them, although I have heard of folks epoxying close the holes and re drilling the correct diameter vacuum holes. Looking at today's installation instructions for the FJ1200 stage 3 DynoJet kit, I notice that there is no longer any mention about drilling out the carb slides.
https://www.dynojet.com/amfile/file/download/file/8797674a71107a5810137671621d3b32/product/3724/

I guess they learned their lesson.

Cheers

[stou]

 The Ragged Moto calc confirmed #40 and 117.5 mains for me using the default settings (sea level, 70*F)

My point....get your jetting close and the vacuum from air velocity thru your CV carbs will raise or lower the slide and needle where it should be... with normal street riding your needle height is 80% of your tuning.

My '84 FJ (canadian) was completely stock and has #110 and #40 jets. On the Ragged calculator with pods, stock exhaust and default sea level and temp, it give me #112.5 and #41.

If I enter default '84 US FJ jetting from the Haynes book, #112.5 and #37.5 in the calculator, with pods, stock exhaust and default sea level and temp, it give me #115 and #38 or #117.5 and #39 with aftermarket silencer.

It look like there's a difference between US and canadian model, probably because of colder weather. Pat did you had #112.5 and #37.5 when stock?

[FJ_Hooligan]

What does the calculator recommend for the needle position setting?

For intake mods (like removing the airbox or low restriction filter), the needle position is far more important than the jets.  The idle jet has influence until about 1/8 - 1/4 throttle and the main jet only controls fuel delivery at WOT.  The needle position is the dominant fuel delivery circuit for throttle positions between ~1/4 and WOT. 

IOW, where we spend about 99.99% of our time riding.

[stou]

There's nothing about the needle position in the calculator. And you are right, the needle position is also very important.

[Pat Conlon]

. Pat did you had #112.5 and #37.5 when stock?

It's been a long time....I remember my pilots being 37.5 for sure....my mains I thought were 110....but looking at the 1984 LC stock jetting combo,  I see they must have been a 112.5.

Imputing that combo (37.5/112.5) as the stock jetting on the Ragged Moto calc, I get a 120 main jets and #40 pilots.(Default: below 2k', 70*F)
117.5 and #40 pilots worked fine for me when my engine was stock. (w/shimmed needles)

Listen to David....the needle position is most important....at the very least, shim your stock needles or if you have the funds ($$$ ouch) invest in some fully adjustable (multi step) Mikuni needles.

[Dieselman7.3]

Does anyone know the high incriminates of the adjustable needles? That way shimming non adjustables gives us a measurement for shims. Thanks

[Pat Conlon]

Last I checked the RPM needle shims are equal to 1/2 step increment. Great for fine tuning.

Stand by, Robert will chime in shortly....

[RPM - Robert]

Last I checked the RPM needle shims are equal to 1/2 step increment. Great for fine tuning.

Stand by, Robert will chime in shortly....

Correct, one shim that we sell equals half a notch of adjustment on the Mikuni adjustable needles. I can not answer for other shims that I have seem people use or where they even came from but some are about 3 notches on the needle, others are a complete notch so kind of a guessing game with those.

[Dieselman7.3]

Last I checked the RPM needle shims are equal to 1/2 step increment. Great for fine tuning.

Stand by, Robert will chime in shortly....

Correct, one shim that we sell equals half a notch of adjustment on the Mikuni adjustable needles. I can not answer for other shims that I have seem people use or where they even came from but some are about 3 notches on the needle, others are a complete notch so kind of a guessing game with those.

Thank you. I will be ordering a bunch of carb stuff before the snow melts so I can be already for the sunny warm days.

[stou]

I received my RPM parts yesterday. I rebuilded the front brake master cylinder, everything was good. Today I took apart the clutch master and I had a very bad surprise. The parts are differents.  

New kit on the left and bike parts on the right.


I looked a few place on the net and it's obvious that the clutch master that was on the bike was not from '84 FJ1100. So now I must find another clutch master because the other bike I have, don't have a clutch master  

So now I have a brand new FJ1100 clutch rebuild kit for sale ($40)
https://www.rpmracingca.com/proddetail.asp?prod=M%2FC%3A1100CLTCHMCKIT

[f4fwildcat]

If you uploaded a picture of the clutch master housing someone might be able to identify it. Maybe its an FJR master or an FJ1200, there should also be some type of part number on the master so that might help you identify it and see what you have.

[stou]

From what I saw on RPM website, it's not an FJ1100 or FJ1200 master. It doesn't have any brand name on it. Anyway, I ordered this kit from Amazon. The buyers comments are good and they look a lot like the one on the bike. And they are only $45 for the pair.

[Pat Conlon]

What are the m/c piston sizes?
FYI...The oem FJ is 5/8"dia. (16mm)
If you ever decide to double up on your clutch spring, you will appreciate a 15mm piston on your clutch m/c.
If you ever decide to upgrade to the Yamaha blue/silver/gold dot monoblock brake calipers, you will appreciate a front brake m/c with a 14mm dia. piston.

[stou]

I don't know the piston size, it is not indicated in the product info. My goal for now is to have a good running FJ and then I'll see if I keep the bike or not. I don't want to put to much money on it for now. If I really like the bike, then I'll probably update some parts. In the last years, I putted to much money on my '77 CB750. Complete engine rebuild with 836cc kit, USD GSX fork, new Progressive shocks and more. With the FJ, I try to get a nice running bike whitout putting to much money on it. I also have a 2016 Honda CRF1000 Africa Twin, which is my daily bike.

[stou]

A small update! Like many of you saw it in the "Float" thread http://www.fjowners.com/index.php?topic=17021.45 I had some problem with carbs leaking. But now that is fixed, I can go back to other work.

Carbs, 112.5 main jets and new Uni air filter are installed. I lubricate the throttle cable and installed a new choke cable. I installed the new clutch master and lever. It seem to work fine.

I started the bike and it run not too bad considering carbs are not synchronised and it's cold outside. The gauges are working correctly.

Next step after my 2 weeks vacation, body repair and paint.