DavidD wrote on 12/31/69 at 16:00:11:



Dave,

Sorry, I struck out altogether here. Can't find the picture of the two screws side by side; which I had posted in another thread here, but appear to have deleted from my website AND computer!

So... I broke down and went out to the garage to dig through the 'leftover' parts boxes. I know I saved the one  screw I ordered from them in the bag it came in; which would show the real Suzuki part number. But danged if I can find it anywhere!

Even found a couple of shipping "bill of materials" from Ron Ayer's, neither of course included the screw/jet in question. Finally logged on to their site and searched my past orders and found their part #: 13279-47070 but it did not look like the one that came from my Mikuni:



That is a picture of the Ron Ayer's page for our LS-650PH model's version of the Mikuni (BG40 isn't it?) At the bottom is the silhouette of the actual screw I pulled out of my 87. It looks just like the screw in the picture to me, but the one they sent me from that part number did not. A warning here: you've already noticed that each dealer uses a slightly different parts numbering system, and not the factory numbers. Real convenient for cross referencing huh?

While pulling my screw out, I discovered that it was only set at 1/2 - 3/4 turn out instead of the 2 turns I thought I'd left it at. And as I mentioned before, there was no spring under my screw from the factory. Unless the old man who had the bike before me replaced the screw without a spring; as I know that he had recently cleaned the tank and carb before I bought the 87, but I assumed he hadn't been into the idle screw circuit. I guess you can by the plug to replace over the screw so it doesn't show you've been in there tinkering.

Oh, best I could see down in the hole with my magnifying glass, if there is a small o-ring and washer covering it down in there, I couldn't see it. I'm not inclined to go digging around down in there either, since the setup I've got works well.

Anyways... just as you, I'd like to get this issue resolved once and for all: Which screw and associated assembly of parts are the correct ones for our 87 models?

If I get time tomorrow, I may dig back into my parts boxes and see if I can find that elusive screw... but for now this is all I have...

The bottom one looks like the "better" one to use.  It appears to have more adjustability since the entire end is tapered.

For the record: I ordered a new idle mixture screw from Crotch Rocket, and it matches the one that was in the bike - it's brass and has the stepped-down area on the end.

Part # for the Idle Mixture Screw for an '87 : 13269-37400

Crotch Rocket's site says it "replaces" part # 13269-37410, and calls it various names - "screw pilot" on the site, "screw air" on the packing list - neither of which sound like much fun...  

Will be installing it this weekend to see what difference it makes.  I took apart the carb last weekend and I swear it's clean now.  I swear it.  I took out all of the jets I could find, except that little tiny one under the choke diaphram (or whatever the diaphram is that's "behind" the choke) - it wouldn't budge and I couldn't find it on any of the fiches, so I decided it would have to do since bunging it would mean a replacement carb...

I just installed the new screw and put the carb back on the bike.  I'VE GOT IDLE AGAIN!!!  Musta just been a clogged passageway in the carb somewheres.

But I still don't get much difference from adjusting the screw.  From all-the-way-in to 3 turns out, the idle sounds pretty much the same. It does sound a little better once I get it down to less than one turn out.  I'm guessing the lack of tweakability is from the big 55 pilot jet I've still got in it.  I'm gonna pull the carb and put the 47.5 jet back in to see if that makes a difference.

Then I've got to figure out why the front brakes are dragging.

Then I've got to figure out where the oil is leaking from the crankcase.

Then I've got to figure out why I'm getting so much black smoke out the exhaust.

Then why there's an oil leak near the exhaust manifold.  And what's making the thunk-thunk-thunk noise from the drive sprocket area.  And how I'm going to fix the crows-nest of wires under the gas tank. Perhaps even get the decomp solenoid working again.  And then maybe one day I'll tackle the switch pods - right now the "horn" button now starts the engine...hehe.  Somebody made some interesting wiring adaptations in the back hills of Kentucky...

Yep. winter is gonna be busy... glad my Nighthawk is still in good shape.

Thanks guys, for all of your help and suggestions.  Maybe one day this bike will be road worthy again.

I put the stock 47.5 jet in yesterday, but haven't had time to fine-tune the adjustment screw.  But it was OK enough to test ride at about 1 1/2 turns out.  But I've run into a bigger problem.

If I'm going along at about 1/2 throttle and open the throttle all the way, the engine speeds up by a few hundred RPM but then starts sputtering like it's gonna stall.  Any suggestions?  My first guess was maybe the needle jet, since it was in really bad shape when I first started working on the carb, and I thought I had done a good job of cleaning its holes pretty well, but maybe I hadn't done it as well as I thought.  I haven't modded the jet needle washer, but that's not to say the PO didn't.  Or I wondered if maybe the slide diaphram had a leak or something and wasn't pulling the slide high enough.  I dunno, I'm sorta just guessing at this point.

Any suggestions are much appreciated.
Thanks,
Dave