Update on the baboon - she runs, but too rich.

[knewsom]

Ok, so much thanks to MRO for helpin' me out with some massive engine work - turns out that ticking was PISTON SLAP!!! aagggh! The bike is running, but running too rich (she'll cold start without the choke).

...this essentially means I need to tweak my jetting. In order to do that, I need to unscrew the jets from the emulsion tubes. Now, I don't know if anyone remembers, but my emulsion tubes are fairly well shot (and by shot, I mean one of them is badly cracked and essentially STRIPPED), and as I recall, mikesXS didn't have tubes that really FIT the 78. IF that's true, where can I find them? IF that's NOT true, then which ones are the right ones? Has anyone used them successfully?

Thanks in advance all.

[TopCatGr58]

Hey KNEWSOM,

Welcome back, sorry to hear you've been getting slapped around!

I vaguely remember MRO suggesting to someone to use the MIKESXS ones, and the ONLY ones that are the right shape are the Y-O series, for BS34 carbs, 80-84, Mikes#48-0660.

As you can see by the photo below, there are different styles, the one on the right is like MikesXS one, note it doesn't have that extra lip that sticks out above the carb throat when in position. I don't know if the 78 is like that one, or the others?

Needle Jet - Y-O
Needle Jet - Y-O - Fits: XS650G/H/SH/SJ/SK/SL (1980-84) Stock Mikuni BS34
CV Carbs.


Part #48-0660 $12.00 USD EA.

I was looking at the list of Mikuni Needle Jets on motorcyclecarbs.com, and the X-2 is just above the Y-0 in the list and both are in the RICH zone of needle jets. The hole pattern on the side may also be different than your OEM.

Having one ODD needle jet in a bank of 4 may make tuning it a little difficult. However, in 79, Yamaha started mixing up and using 2 different types in the inner pair vs. the outer pair trying to make the inner pair a little more richer to control engine heat. It would be rather expensive to get a set of 4, but getting 2 and putting them in a matched pair, either 1-4 or 2-3 depending on whether the MikesXS needle jet has more or less holes than your OEMs could allow for a more balanced tuning chance. More holes is leaner, less holes is richer.

Regrettably, the X-2 needle jets are no longer available from Yamaha/bikeBandit! Motorcyclecarbs.com lists them, but don't know IF they have them?

Hopefully someone will post that they have used the MikesXS!?
T.C.

[knewsom]

"tubular", TC!

OK, so I think I'll probably just shell out for the mike's XS ones, and put them in all four (true, two of mine are probably salvageable, but hey, might as well try to be consistent since these don't have the lip thing). Do you think the lip (or lack thereof) will be a problem? Will it even make a difference? I'm having trouble even thinking about what exactly the lip would DO.

I'm hoping that the mike's ones have more holes than mine, but from the pics, I think they're the same. I'm running rich anyhow, so I think I'll first try putting back in my stock jets on #1 and #4. If it's still rich then I'll change 2 and 3. If it ends up being too lean, heck, I guess I'll rejet again.

First things first, before I can REALLY TUNE the bike, I need to have usable emulsion tubes, so I can swap out the jets effectively.

[pggg]

Well that lip must cause turbulance in there and maybe the gas gets sucked out quicker. Or slower. Or gets atomised better or something but it ain't gonna make a shred of difference if the bike runs good.

[knewsom]

LMAO!


well, just to be safe, I think I'm going to buy several sizes of main jets so that I can finally get her runnin' right before the rally.



...but she is runnin' strong, despite the rich and semi-rough carbs and a small miss. After I get the carbs in order, if it's still got a miss, I think I'm gonna have to rig a crossover in the exhaust.

[underdog57]

Adjust needle jet ??

How about raising or lowering the the needle jet , that will adjust your midrange ....
The main jet is for top end ....


Bob

[knewsom]

I thought main jets were for an overall adjustment..? I'm sure readjusting the needles will be part of it - I forsee pulling my carbs 8 or 10 times before I get 'er totally "right".

In any case, I ordered a set of 140 mains, 142.5 mains, and new emulsion tubes from Mikes' XS.

...hopefully they'll ship using USPS instead of FedEx (the latter always takes like two bloody weeks, whereas the former is more like 3 days).

[underdog57]

carb link

check this out ...

http://www.factorypro.com/tech/carbtun.html

Bob

[knewsom]

wow, sweet link, dude! Thanks so much!

-Kris

[underdog57]

Carb tune site

The link is on this site , found it again off the tech section !!
In links , lots of great stuff in their ....

Bob

[knewsom]

OK, so I think I've got a hold on this - floats are for low range, needle for mid, and jets for high.

Top end is pretty badass on this thing, after 4500 or thereabouts it pulls like a sonofagun, but it's a little rough and sometimes stutters a bit in getting there.

My plan of action is thus: replace emulsion tubes, lower fuel level, lower midrange needle, test it.

That should correct the midrange and low end issues, but I think I need to also have a look at my idle mixture screws and make sure that they're set right (I think I may have set them too far out when I reassembled my carbs)

[knewsom]

oh yeaahhh.... the SPRINGS TOO!

Forgot one pretty crucial thing - perhaps I need to lengthen my springs by about 8mm too... Should help it take the throttle better and even things out a bit.

[knewsom]

Jetty Jetterson!

OK - so I got me new jets etc. from Mike's XS - I guess if they ship your order on Monday, it'll get to you on Friday! Sweet!

SO - took out the old emulsion tubes, put the new ones in me carbs (PITA, btw, had to use a drift and hammer them in using a THICK piece of leather to protect the shiny new tubes).

Aside from the lip difference, there are fewer holes on the new ones, leading me to believe that this will run RICHER than the last ones? (the old ones had 4 holes on each side, the new ones is three, four, three, four)

I lowered my needle two notches (was on the next to the highest setting - yikes!), I'm going to put in one size smaller jets, and lower the floats a mm.

I'm also going to make sure my springs are good and happy by checking their length, and lengthening the shorter ones to be the same length as the longer one (that is, if there's any difference).

OK - wish me luck, I'll be back with results, er, I hope.

[knewsom]

hmmm.... the floats are all right at 22.5mm, all of them are DEAD EVEN.

I'm going to forego the flat adjustment at the moment and see how she deals with all the mods other than that so far.

[knewsom]

AHHHH CRAP!

Good thing I decided to check the spring length. The first three were all 91mm long, the fourth was 101mm long, AND a different gauge wire. the springiness of the different ones is remarkably similar, but I think I now need to order a uniform set of springs. Any suggestions on where to buy good springs?

Sheesh... I wish I had caught this before.