Anyone tried to put XJR carbs on an XS11?

[Geezer]

A cheaper way to do it is to find a US serviceman stationed in Germany and work a deal to buy it over there then ship it home by military transport.

The down side is you have to find someone scheduled to come home soon or you may end up paying somebody to ride your bike...

Geezer

[Michael Oppelt]

XJR Carburator

Hi,

I've just read the questions about the XJR carburator. I drive a 1979 Martini since many years and have some experience with:

1. dirty original carburator (which made it very difficult to drive in the alps - less oxygen nearly stopped the engine)

2. ultrasonic cleaned and optimized original carburator: Ran very well, took a lot less gaz.

3. 10 days ago we put a XJR 1200 carburator on the bike and it's running totally different now. To make this carburator fit you need to do some small things like: "drilling a hole into a 6 mm screw, drill a hole for the screw into the carburator, fix the screw there and then use this for the ignition-adjustment-hose".

I hope (but am not quiet sure) that my english is good enough to explain - for all other questions (like translation of german poetry) just mail me directly. And there are some more small things to do.

The main thing I want to say is: Yes, the XS runs a lot better (a lot more horsepower although it was not weak before) with a XJR1200 carburator. I read some information about the XJR 1300 carburator where people wrote, that this one doesn't fit as well - are there two versions of the 1300? Anyway - there is one "bigger" 1300-version (outside size and inside) which does not fit as well as the 1200 (No own experience but that's why I bought a 1200 carburator). I am not at the end of the optimizing - procedure (still running bad below 3000 rpm) but - really - wow - it's such a strong, modern and aggressiv engine now.

Contact me directly if you need more infos


Michael

[MAXIMAN]

Michael

Your English is fine. And keep us up to date on the carbs. A very interesting topic indeed.

[Michael Oppelt]

XJR carb

Ok, now I have some new experience to share.

1. experience:
even after 5 hours in an ultrasonic-bath a carburetor still may have something blocked (dirty) inside .... This was a new experience for me. So, we found the blocked hole. And then ... wow ...

2. experience:
Take a XS1100 - 2H9 (1979) and a XJR 1200 carburetor and do the things mentioned before in this thread. Use the original main jets of the XS1100. You don't have to change any other jets. With a 2 in 4 exhaust your XS should run just perfect. Different sound, different power (really strong) and what I like best: Running very smoothly starting at 1500 rpm. The engine is very close to real XJR1200 engine now.

The best thing I ever did to my XS.

Greetings from South Germany

Michael

[mro]

2. experience:

Hi Michael,

Have been wondering how things had turned out.

If you ever get the chance to run the bike on a dyno please post the results here.

May start a rush to get XJR carb's.


mro
btw

Bandit can't reply right now until he cleans of the "drool" on his keyboard.

[Michael Oppelt]

I have more Information about the XJR - 1200 carburator in the XS11 now. We found out, that there are two types of needles: The original one with 5 notches (do you say notches?) and another one with 3 notches which is sold for tuning reasons here in Germany by a company named "Topham".

My description was about the Topham - needle. The Original one gives a lot less fuel (is a lot thicker than the Topham-Needle).
The needle-jets (the big jets where the needles sit in) are the same.

With the original XS1100 mainjet (132,5) and with the original XJR1200 5-notch-needle the XS seems to have a bit too little fuel (white spark-plug). So check this, if you use this type of needle and want to do full speed.

The Topham-needle gives more fuel and runs well (as I described earlier). But also the original 5-notch needle seems to run well if you use a "fat" needle - position.

Thats all for the moment - I will do more testing.

[MAXIMAN]

I'm sure you know the XJR1200 engine is the same as the FJ1200 sold stateside. The cars are pretty much the same too.

Last summer when I rebuilt Zilla's powerplant we installed a set of FJ1200 carbs. They seem to work fine but I am certain we did not gain as much with them as we had hoped.

With the big bore kit, web cam, ported intake on the head and radius'd intake valves, with 4-1 header....the FJ 36 mm Mikunis are jetted 115 main and 40 pilots.

The fact of the matter is even this 1196 big bore doesn't really need carbs that big. Oh I'm sure it didn't hurt anything but the 34mm Mikunis that are stock will flow enough air for a hopped up over bored Eleven.

As a matter of fact I suspect the 36m carbs might hurt low end and mid-range torque because torque is a function of airflow velocity through the chamber. The larger diameter carbs creates less annular velocity. Of course this is all theory and the only way I could prove it to myself is pull the 36's and replace with 34's...and in the words of The Duke........"I AIN'T DOIN' THAT!"

[trbig]

the only way I could prove it to myself is pull the 36's and replace with 34's

Just ride down to Texas this weekend and we'll pull mine off and throw them on yours... I even have the same size mains! lol.


Tod

[MAXIMAN]

#1 I can't be there. I have other plans

#2 I have a set of 34's on the shelf.

#3 If I did this it would be at Stillwater Kawasaki -Polaris...on the dyno to ssee the diff.

Sorry I can't be there this weekend. I wanted to come but had toher plans

[pggg]

Guys, forget flow charts, velocity rates, volumes, measurements, 'facts', mathematical formulas, figures, theories etc.. etc.. the performance kick from a set of re-jetted CVK 36mm Keihins over the original BS34's - is real. Well, it is on my bike anyway The guys runnin' GSXR slingshot carbs on their XS's will tell ya the same too...

[MAXIMAN]

Strange...

I didn't see any flow charts, velocity rates, volumes, measurements, 'facts', mathematical formulas, figures, theories etc.. etc.. in this thread.

[Michael Oppelt]

Hey Maximan.

In Germany, the FJ1200 is an old bike. In the 90's it was replaced by the XJR1200. So, maybe in the States Yamaha uses other names for the bikes and models. Anyway, we all know, that XS1100, FJ1100/1200 and XJR1200/1300 are similar concerning engine and carburator.

My experience is, that the tuning-effect of using a XJR1200 carburator on an XS1100 is high. A lot higher than I expected it to be. Without doing anything else. I did not use a dyno to proove it and I will not do it in the future (because I can't see a bike and a clutch beeing tortured ...)

But it feels like 120 PS (don't say that's not possible, I just sayed: "It FEELS like ..."). If I would have to guess I would say: At least 15 horsepower more than before. Another difference is, that the engine runs differently - it is a lot more spontaneous - like a racing-boat compared to a steamer.

Thanks for your input. It's good to give and receive valuable technical information. A lot more valuable than to just exchange opinions.

Michael

[MAXIMAN]

Hey Micheal...in the US the FJ1200 is an old bike too...they quit making it in the mid 90's. The XJR1300 maybe a newer model but it's that same old technology with fuel injection. As a amtter of act the technology is so old Yamaha will discontinue the XJR because it can not meet the new Euro Emissions Standards.

Having said all that...I've already installed "XJR1200" Carbs on my Eleven. Last summer...we added 36mm Mikunis and a lot more...big bore kit...cams...ported head blah blah.

I gained a whopping 32% (23 hp) taking the bike from 72 hp at the rear wheel to 95 at the rear wheel. But know where near 120...and certainly not just from the addition of 2mm larger carbs.

Here's the thread on that topic:


Godzilla - Rebuilding the Beast

Your mileage may vary from mine...but it won't by 50 hp.