Opened up the engine, looky what I found

jaybob · Post by **jaybob** » Fri Apr 10, 2009 8:51 am

Chris

The jets I got were used Genuine Mikuni jets.
I have been waiting for someone to chime in with an honest opinion on what would seem to be waaay too large of jets.

I would agree with you on everything being too fat except for a few supporting indications.

1. The current plug read, with 117.5s the bike currently was not waay to rich. I never fouled a plug and the bike ran great and started easy before with the 117.5 and 112.5 main jets.

2. It would appear some amatuer port work may have been done. I can see evidence of grinding in the intake tract and in the transfer ports.

So I really was not sure what to do so I posted the pics in the beginning of this thread. All I can do is try a few things until I find out some sort of indication that I am going in the right direction.

Buffalo-guy · Post by **Buffalo-guy** » Fri Apr 10, 2009 11:10 am

My two bits worth.
By the looks of your plugs, I would have to say that your center cylinder
is running the best with the 112.5 jet, which brings up my next point.
The buffalos require the smaller center jet due to the non-symetric
combustion chambers. The 380 and 550 have fully symetric chambers,
and should run one size on all three. Needle position plays just as big a role,
as that is where we ride most of the time anyway. If the big jets run well,
and show well on the plugs, then they are the right ones. Seat of the pants
tells a lot more than a book. I agree with Rick on the change to synthetic
oil. I've been running Amsoil HP injector oil for years to great satisfaction.
NGK B8EV's work awesome in my bikes. They just don't seem to give up.
I haven't met a Jap bike yet that hasn't benefitted from running ignition
power to the coils directly from the battery through a relay switch triggered
by any 12 volt source that comes alive with the ignition switch. The voltage
to the coils is improved noticeably by eliminating the resistance through the
wiring harness. As for Ians concern about radio interferance, I don't think
your Boyer electronis are complex enough to be bothered, and as for a GPS, it may react, but I found that an AMA paper map does not.
That pretty much covers it.
Fred

jaybob · Post by **jaybob** » Fri Apr 10, 2009 4:10 pm

Fred and Chris thanks. I really appreciate the input. I'm faar from being an expert and can use all of the advice I can get.

I now have a full complement from 112.5-125 and if I can get myself a little more organized and get it put together the rest of the way I'll get to run the darn thing.

tz375 · Post by **tz375** » Fri Apr 10, 2009 6:07 pm

Jason,

To pickup on what Chris and Fred have already said, the pertinent points here are that we can't read the plugs because we have no idea how you ran teh bike to create that color.

For example if it was run mainly on the needle jet, the main has some influence, but not much. Most of us run our bikes on the needle jet and rarely on the main, so if we are a couple of sizes too large, we will usually not know.

As far as we know, the center is jetted differently because it has a split exhaust which behaves differently than the two large pipes. Change to chambers and all three should be jetted the same.

With the changes made to your 550, one would expect to need and increase of 2 or three sizes - but what that means isn't always universally understood. For some of us a change of 10 is a jet size and for others it's 5 and 2.5 represents half a size.

Starting with the stock #97.5, go up two #5 sizes gives you 107.5, so a set of 112.5 would be a good place to start.

But the main jet only works 100% at WOT, at 1/4 to 3/4 it's more about the needle and needle jet, and the stock needle position is in the 4th clip, so I would raise the needle/drop the clip to #5.

The right sequence for tuning is slow jets and air screw first, then main jet at large throttle openings and then work the midrange.

I suspect that your current setting is slightly rich at the very top end and that the needle is the restriction.

Chris has a clean running (and great looking) 550, and that's a great place to start, but yours may need something different.

The main jet has to be tested at 3/4 to 100% open throttle under load, so pick the location carefully.

Do a plug chop and inspect the mixture ring for err mixture, and the electrodes for signs of overheating.

When you are happy with the top end try moving the needle up or down to fine tune the midrange/mid throttle.

If it's fine at the bottom and top but still lean in the middle, we might get away with a larger main jet to add fuel all the way through. If not I can see what alternate needles are available. Mid range is where bikes run and it's where most of them fail, so it's worth getting right.

I doubt you will have to change needle jets, but that's always possible. On the Aprilia AF1 (250 race smoker), more than 2 small sizes up on the mains and it was time for different needle jets (nozzles). We had boxes of needles and nozzles for those things.

That's where the action is, but hopefully you'll get away with less drastic changes.

jaybob · Post by **jaybob** » Sat Apr 11, 2009 7:20 am

Richard and all. Thanks for the hand holding. I know some of this stuff is basic to some of you but I appreciates the time it takes to slow down and help me out.

Also I found that my jet needles are pretty worn with some flat spots on them. I'll be ordering up some new needles. Hoe in the heck do I get the needles out of the slides? ON the individual carbs it is easy but I have'nt figured out this rack set up yet.

Jason

tz375 · Post by **tz375** » Sat Apr 11, 2009 8:21 am

Jason, if the needles are worn, then the needle jets will also be worn.

Do you have a copy of the Suzuki carburettor manual? It's here:

http://www.3cyl.com/~tripleed/suzigtcarb/

The Sudco Mikuni manual is a good read too. Here's one:

http://www.mikuni.com/pdf/vmmanual.pdf

Stripping those carbs is quite easy. To get the slides out, you remove the carbs from the rack without disturbing the linkages etc if at all possible. The slide is pulled up by a rod which is retained with a screw (2?) to the slide. Remove the slide and pop the needles out.

Coyote · Post by **Coyote** » Sat Apr 11, 2009 4:49 pm

Yep. You have to remove the lifter rod from the slide as it retains the needle as well. These type carbs are a big pain in the butt to change needle positions. It's practically an all afternoon job, even after you've done it several times. There are no shortcuts.
The CV carbs on the buffalo have a plastic ring that retains the slide. No screws and no linkage. You can do those in about 30 minutes.

jaybob · Post by **jaybob** » Mon Apr 13, 2009 2:48 pm

Thanks Chris I like some things about the rack but maybe I think maybe the bad points may outweigh the good.

Side note:

I checked the compression with the new head today. I got 150, 152, and 155 psi.

Looks like with some quality gasoline and plenty of it I should be good to go.

H2RICK · Post by **H2RICK** » Mon Apr 13, 2009 4:49 pm

Jaybob, I've been away for a week and just checked this thread and noticed.....HORROR.....that you're "storing" your jets on pices of WIRE !!!
Numbah 10 BAD idea !!!! You are taking a big chance of damaging the metering holes in the jets by doing that. ANY wire you use for this purpose will be HARDER than the brass that the jets are made of. Stick each size of jet to a piece of duct tape and then put the tape and jets in a pill bottle using one bottle for each jet size. Keeps 'em clean AND won't damage either the metering hole or the threads. A word to the wise.....

jaybob · Post by **jaybob** » Mon Apr 13, 2009 5:29 pm

Rick

Thanks for the tip. They were stored in plastic trays at the shop I got them from and they had them set out for me on wire when I got there. Don't worry they are safe and sound at home now.