Shakedown run jetting issues.

TheRadBaron · March 07, 2011, 04:33:04 PM

The emulsion tubes all looked good. The hole was nice and round with no visible wear. Strange considering the condition of the needles, but I guess brass is a lot more corrosion resistant that aluminum, after all.
The more I think about it, the more I suspect that I might not have the stock slide springs in my carbs. I've read about some heavier springs that came with certain Dynojet kits for the 4-1 exhaust. The needles that were in the bike when I got it were much shorter than the Mikuni needles I got from Randy. Here's a picture of what I mean.

It was suggested that these were old DJ needles, and I think that the main jets were DJ as well. I bought the bike from a friend and he said that it ran really well until one of the needles became so corroded that it was hanging up in the emulsion tube. I'm thinking that maybe these carbs have the heavier DJ springs installed to match the short needle. That (might) explain why my idle circuit seems good, my main circuit seems good, but it absolutely sucks in the midrange, even with the needles all the way rich. Does this make any sense?
So now I need some known stock Yamaha springs to use for tuning purposes. Does anyone have a used set for sale? Or even a set that they would let me borrow so I could determine if that was the problem or not before I buy new ones? I'd pay for shipping, of course. Yamaha wants $15 per spring. I bet Randy could get them for cheaper, but I'd rather get some used ones for cheaper still. Thanks.

RichBaker · March 07, 2011, 07:23:48 PM

My '90, the stock slide springs looked like smaller-diameter Slinky, the DJ springs were much shorter and have wider spacing between coils. They were much lighter, weight-wise, and stiffer than the stock springs.

TheRadBaron · March 10, 2011, 06:05:59 PM

Damn. Well I think I figured out what's wrong with my set up. The good news is that now I know what to fix... the bad news is that one of the POs drilled out the holes in the bottom of the carb slides ($). I don't know how big they should be, but the holes are 4mm in diameter now. Man, I thought that I was almost done buying parts for this thing. Oh well, it's only money and I'm sure that it'll be worth every penny when the bike is running right.

Flying Scotsman · March 10, 2011, 06:22:04 PM

I get 3.95 mm or.155 "

SlowOldGuy · March 10, 2011, 06:26:06 PM

The 2nd generation DJ kit for the '85 included a drill bit for drilling the slides. Not a significant amount. I have drilled slides on my '85 and no problems.

DavidR.

TheRadBaron · March 10, 2011, 06:36:15 PM

Hmmm. Mine are 4.15 so they are only about .20 mm bigger than they should be. Maybe that's not the problem after all. If it doesn't make a noticeable difference, than I wonder why did DJ would have you do it?
David, do you still have the DJ kit installed, or do you have the DJ drilled slides in carbs with Mikuni needles, etc?

Flying Scotsman · March 10, 2011, 06:37:40 PM

Yes mine is drilled as well.How far from Rolling meadows are you I might be able to help.I had to fix a couple of things with my carbs,diaphram and float hieghts.I have some extra parts too so that might help.

Flying Scotsman · March 10, 2011, 06:42:23 PM

1985 pdf

http://www.dynojet.com/pdf/4109.pdf

Flying Scotsman · March 10, 2011, 06:49:14 PM

#19 drill = .166"

TheRadBaron · March 10, 2011, 06:54:49 PM

Quote from: Flying Scotsman on March 10, 2011, 06:37:40 PM
Yes mine is drilled as well.How far from Rolling meadows are you I might be able to help.I had to fix a couple of things with my carbs,diaphram and float hieghts.I have some extra parts too so that might help.

I'm near Champaign, so it's a bit of a trip but not too bad. If I don't get it sorted out soon I'll get ahold of you. Thanks.

TheRadBaron · March 10, 2011, 07:11:56 PM

Here's another weird thing. I just went to the Dynojet website and they list a kit for the '84 FJ1100 and another kit for the '85. However, it includes different needles than the '85 kit as PDF'd above. The drill bit included in the '84 kit is a #28 (.1405") instead of the #19 (.166") included with the '85 kit. I'm not sure what's different between the '84 and '85 models that would cause the different needles and drills, but mine's an '84. Since the '84 instructions tell you to enlarge the holes with the .14" drill, they must have started out somewhat smaller than that. Mine are now .164" in diameter. So the holes in my slides are at least .025" bigger than stock, probably more.
This seems like enough of a difference in size to cause it to run differently, though I'm no expert. Has anyone had any luck repairing drilled slides? I'm considering pressing an aluminum dowl into the holes and redrilling it to stock size. Either that or get the DJ needles to match the #19 holes that I have.

Flying Scotsman · March 10, 2011, 07:26:15 PM

1984 had different slides I think.I think they had flat bottom slides.85 and later had a radius cut out on the slide bottom.

Flying Scotsman · March 10, 2011, 07:38:38 PM

Either the 84 or the 85 set up should work if you have flat bottom slides then the 84 set up would be the way to go.I have some extra slides you could try,undrilled but there for a 85 or later.(for later when I get a hole in one).Why are you convinced its the slides ?.You can blow in the intake and raise the slide.Then see if it holds pressure.

racerrad8 · March 10, 2011, 07:58:35 PM

Quote from: Flying Scotsman on March 10, 2011, 07:38:38 PM
Either the 84 or the 85 set up should work if you have flat bottom slides then the 84 set up would be the way to go.I have some extra slides you could try,undrilled but there for a 85 or later.(for later when I get a hole in one).Why are you convinced its the slides ?.You can blow in the intake and raise the slide.Then see if it holds pressure.

The slides are not interchangeable. The 84 is specific to the flat slide as the emulsion tube is flat as well.

The 85+ use the radius slide and the shrouded emulsion tube.

Randy - RPM

TheRadBaron · March 10, 2011, 08:04:51 PM

Well, I'm not totally convinced that it's the slides. I still have a few variables to work out. The float height is too high for one, and I'm not sure that the slide springs are stock either. At this point I'm just trying to get everything in the carbs in a "known" condition so I know what I'm working with. This bike has a shady maintenance history, so some things might just be plain wrong. As far as the slides go, I've got flat-bottomed '84 sides for sure, but they seem to be drilled with the #19 bit which should be for the '85 slides.
My slides weren't looking so hot anyway, so I think that I'll suck it up and buy some new '85+ spec slides and the corresponding emulsion tubes (assuming I can find the slides for a non-insane price. If not, I'll find decent used ones). My tubes weren't bad, but this way everything will be nice and new and I won't have to worry about a raggedy diaphragm getting a hole in it at any time. Once the new slides and stock carb springs are in and I've fixed the float levels, I should actually be able to make some tuning progress.

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Shakedown run jetting issues.

SlowOldGuy