XT600E with MIKUNI single carb doable!
 

Hi all. A few of you might've read that I'm fitting a Mikuni BST40 carb on my 1990 XT600E..

Here is the deal.
IT is doable, BUT.. (HOLD your breath)

Parts needed:

1. Mikuni BST40 carburetor
2. Grizzly 600 2-1intake manifold. part number: 4WV-13586-00-00 (superseeded by 4WV-13586-01-00
3. TWO O-rings part number: 93210-36769-00 OR you can use your stock XT's stock manifolds O-rings that fit nicely.
4. Grizzly 660 JOINT, CARBURETOR part number: 5KM-13596-00-00
5. Two clamps to lock and hold the rubber boot in place.

Now you can stop holding your breath. lol

Rear shock has to be moved a little back about 40-50mm, a mount has to be made.
For the carb to fit in its place you have to CUT some metal on where I'll be pointing on the pictures give or take a little metal lol

Tomorrow a friend welder is comming here to do the work and advise me on what has to be and can be done and what has to be "reinforced"..

Vando :innocent:

I've been waiting for you to do this!!!

Full details please!!!!!!!!!!

Tom:thumbup1:

Lol :) hey

Notice at the shock location... it is exactly 55mm (center to center screws) towards the back of the frame on the small gap where the top of the air box holds onto the frame (two holes on a strip of metal that is welded onto both sides of the frame).

The shock, with my YZ250 front forks, is spot on with me on the bike lol! the seat height increases a bit matching the 5cm increase on the front and I like it lol

The kickstand will have to be increased by about 15cm guesstimate..I didn't actually measure it... or get a MX one with similar needed length that can be fitted..

Stock air box: I got to check if there is enough clearance for the rear shock but for now I can only say that it has to go back about 5cm from the top mounting holes...because of this the right seat plastic panel looses it's mounting hole..

Since I want to make a fiberglass airbox-battery-CDI (or TCI?) holder and a LowerMudguard-taillight/license plate holder I'm not really worried about the stock airbox..

The "worst" part of all this I guess will probably be finding the correct carb settings..


Vando :innocent:

pictures pictures pictures
 

Found a simple, easy to do, short-term solution for the carb-to-airbox air duct.

As the name says, It is a very flexible Air Duct in aluminum type of foil but is not the most apropriate because it isn't smooth on the inside of this tube, it is "wrinkled" which will probably cause some air turbulence from the airbox to the carb.

I will try to either fit some high quality aluminum duct tape on the inside of the air duct OR will be making something somewhat more difficult but also interesting thing which is.........liquid resin or epoxy glue on the inside just enough to make it SMOOOOOTH


BTW, for the most curious, I will have the rear shock fitted and welded into the new position later tonight I hope!


Vando :innocent:

Also, this is a thread on another forum that I sometimes post some things...

This one link is for the new shock mount position
XT600 faux-rally(e) (disturbing content) - Page 16 - ADVrider

I hope it is not against to forum rules posting this link here, if any of the admins nag about it I'll delete it or something..


Vando :D

Hi all

well...today the rear shock got its new mount!

thing is... I am not that satisfied with it because it was welded a bit further back and the bike STILL with the engine off i too f:censored:g high...

I'm gonna put the engine on the frame right after I finish this reply sooo yeah.. wish me luck!

Vando :rolleyes2:

Vando, very interesting.

What is the purpose of this mod? Why/how is this carb better than the stock one?

New technology versus old technology :) and more power lol

plus...I needed to gain 2inches on the rear of my bike because I fitted some front forks off a 2002 YZ250 which gave me 2 inches height on the front...

Vando :smartass:

humm... I thing I've just :censored:t he cap of the carb... it had a vent on top side which most BST40's do not have.

Since that vent had already been closed-covered it from the top and inside AND since the Grizzly carb doesn't have it, I went and cut the top vent! :oops2:
Now I got a 6.5mm hole on the top of the carb cap which I have to "close" it :rofl:

Any ideas on how to fix this besides getting a new cap? it's about 45USD plus shipping :confused1:


Vando :stormy:

The carb slide mod was often done in conjunction with a Dyno Jet kit.

Can you not use some metal putty stuff to plug the hole?

If I was upgrading the carb I'd defo go for a plain "flatslide" carb - not CV, as a f/slide is easier to tune.

Good luck anyhow!

yes I know about the carb mod... I've read quite a few regarding jetting and tuning...that's why I need to check all the jetting..

as for that metal putty...It might just work!!

As a last resort... new cap, no bugger..

don't know how thick is the metal you have the hole in, maybe you can use a screw to close it...

It's not a metal cap... it's some type of plastic coumpound that isn't really a plastic?!

Pics:

Well.. I think I've fixed it! lol

I've put a stainless steel screw that was just slightly larger than the hole and gave it a couple of turns in so it was surface with the interior.
After that I cut the rest of the screw.


Vando ;)

Just whack a bit of loctite or silicon on it.... shouldn't get too hot !

I will put some haraldite or loctite to cover the screw on top of the cap...
I must add that it looks pretty nice... looks like it was "welded" in lol


Vando :D

Job done lad !

Hi there... new updates:

1. awaiting the conic air filter (hope it arrives this week) Motorcycle K&N Style 60 mm Chrome Cone Power Air Filter:eBay Motors (item 250494158034 end time Oct-06-09 01:16:49 PDT)
2. Buy one of these to replace that funny tube I bought to fit as carb-to-airbo inlet: 60mm 2 3/8" Silver 2 Py High Temp Air Feed Ducting 1M on eBay (end time 05-Oct-09 10:16:48 BST)
3. buy one of these so I can fit the air filter I bought nice and easy: 60mm 2 3/8" Aluminium Alloy Beaded Hose Joiner Silicone on eBay (end time 06-Oct-09 15:29:21 BST)

these last 2 items are about 40€ worth...

Vando :innocent:

Bought those two items... air filter hasn't arrived yet...


Vando :smartass:

All parts have arrived... work is rainchecked till Christmas holidays as I'm back at college!


I'm considering on buying a grizzly 600 carburetor kit(needles and the weird not O-RING) it's about 30USD delivered so.. why not!? ;)


Vando:smartass:

Hi Vando

New here and VERY curious about your thoughts and transformations on the single carb on XT 600, as I'm about to do it on my own 1993 XT600. I got the manifold and a Keihin FCR 39 carbie. I'm determined on doing this just for the challenge. What vas your experience with the damper and behavior?

Best Regards

Jakob

Hi Jakob... Been away from the HUBB for a while now.

In order for you to get this to work you will have to change the rear shock mount position so you can SAFELY accomodate the rear shock and avoid it hitting the carburetor!

You might know already that you will need to either modify or remove the stock airbox in order to work with the single carburetor.

I've got a brand new 2-into-1 carburetor intake that you will need to make the exchange. If you want it, send me a PM!

On the pictures I showed, I actually effectively repaired the carburetor cap with JB-weld! I also used JB-weld to repair both my engine casings and it has been holding for over 3k km without any leaks or cracks whatsoever.


Vando beer

Hi Vando

Long Time and old thread. Just want to Say That I finally succeded and my XT is now equpped with a FCR 39 carb. This is in general what I did:

- removed old carb setup and airbox
- grinded out part of the frame as you did on your picture.
- relocated the rear shockmount approx. 6 cm back.
-altered the lower shockmount/linkarm to accomodate a ktm lc4 rear shock.
- fabricated a 2 in 1 manifold for the carb which is 4 cm shorter than the grizzly. Otherwise the carb would hit the starter.

Bottomline - the shit is working perfectly. Suspension is working and so is the fcr.

Pics:
Attachment 13398
Attachment 13399
Attachment 13400
Attachment 13401

Best Regards

Jakob


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So much want right now... Damn you, wallet!

But my question would be: isn't Keihin FCR 35 dual carb setup (like the ones "Performance for raptor 660") better or the same like 39 single?
I don't know if they would fit an XT or not, but I think they should.

Cutting frame and changing place for shock? No this is to much, if bike is that bad in the beginning i recomend buying a KTM 75Hp, you will never get enough hp from the XT...

Why you need it to be 25+ years old? The price here on the models around 2000 is so low that you can compare with old XT.

Actually it was just to Challenge myself as og it could be done. The lower rpm torgue has definately improved, but i'm not sure I have gained any hp.
Also i'm not sure I Can Call it a Yamaha anymore so now i'm calling it YamaKTM. Reason is this:

- Carb (fcr39) from a ktm exc 450
- rear shock from a ktm lc4
- rear wheel from a ktm lc4
- front fork is a 48mm WP USD from a ktm lc4
- front wheel with 300mm disc and Brembo caliper also from ktm lc4.

Also for me I like the simplicity of one carb in terms tuning and adjusting :)


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I've just got a dellorto phm 38mm with the cables and the throttle just so I can convert mine too... I have ordered a grizzly manifold from eBay and I'm anxiously waiting for the part to come to Greece so I can do that too... I'm not gonna cut the frame though... I'm gonna put a high flow tube with a conic air filter that's gonna go around the rear suspension... will that work?

I think your manifold and the Carb is too small... will check it further(I think I did the same mistake) but it has to do with cccm (cubic cm per min) and the flow of the intake into the engine... will check the cccm from the guy who made me my handmade exhaust... he was at school with me and I remember he had a book with all that equations about flow etc

Problem with the grizzly manifold is That in conjunction with the fcr, there is not enough space above the e-starter yet at the frame even when it's been trimmed. That's why I hat to make my own. Works like a charm. If you are using a BST or a PHM carb there might be enough space, but I can't see how you Will be able to accomodate the air inlet tube without moving the rear schock Mount backwards.


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http://imagizer.imageshack.us/v2/150...539/d8b605.jpg

just measured the measurements with a ruler... unfortunatelly i don't have a caliper so i can properly measure it accuratelly... everything was measured with a ruler lol.... if any one has some additional info i will gladly redesign the whole thing... next week i will even upload it in a solidworks format as a 3d part...
vando and u were an ispiration... thanks guys...