Idle speed adjustment screw

Ok, I need a sanity check. I'm trying to resolve an idleing issue on an 81 maxim 550. I downloaded a service manual and in the carb description it shows a throttle stop screw (idle adjustment??). Anyway, I realize the manual may be for the seca and there may be some differences. But long story short, this screw is either MIA or invisible. I've looked for it several times and I can not find it.

Can someone with a Maxim verify that the screw should be there, and if not is there a master idle adjustment? Or do you have to do each carb individually?

 

Grab a flashlight.
Shine it right between the middle two fuel bowls.
There should be a Idle Adjustment Rod with a Knurl to Adjust the Idle.
If its missing; there will be an empty Grommet in a bracket.

Its tough trying to keep the Bike running WELL if you are missing that Rod.
In a pinch ...
You can use the Throttle Cable Tension Adjuster.

If the Cable is Tight; loosen it some to lower the Idle.
If you are stalling-out; adjust the Barrel to raise the rpm's until you can get a Idle Rod if yours is missing.

 

http://www.bikebandit.com/1981-yamaha-x ... s/s/mg7946

This helps me find all sorts of things.... Many that I had no clue that I was looking for!

 

Ok, I've had 3 different people looking at this with a flashlight and with the fuel tank off. If you're looking straight down on the carbs I'm assuming it shouldn't be hard to miss? I'm going to assume it's missing.

I looked at the bike bandit link, I'll have to replace it, but 40 bucks is crazy for a screw. Any idea how hard it would be to throw something um... non oem in there to make it work?

 

Check out his post
http://www.xjbikes.com/Forums/viewtopic ... carbs.html

In the first carb pic

That hole in between the center two carbs at float bowl level is where the idle adjust screw should be.

Throw a Wanted post in the Sell, Trade, Swap, Wanted section. I would lay odds that someone here has one available. Make sure you get the spring with it.

Thats how i replaced mine that i lost.

Ghost

 

If you're looking straight down from above you won't see it at all.

It's (supposed to be) underneath the rack, in the center; accessible from the right. Looks like a miniature faucet knob.

 

Fair enough. But I've basically stuck my hand between carbs 2 and 3 and can't feel anything remotely resembling a knob or sticking out like it should. I haven't had a chance to check since I posted this last night, but I almost think the rail that should be on the bottom of the carbs that holds the screw Assy is missing as well.

Once I figure out what all is missing I'm going to post on the buy, sell trade section. But there's not much point of getting the screw if there's nothing to screw it into.

 

I can snap a couple pics of my spare 550 rack when I get home tonight so you can see exactly what's supposed to be where.

 

That would be much appreciated. Ive been scratching my head on this for a week now.

 

Well here's a fun twist. It looks like the rail that connects to the bottom of the carbs and holds the idle screw assy is missing. So it's actually worse then I thought. I can see where it should be, but there's nothing screwed into the bottoms of the carbs. I'd say there's a good chance that this is the source of my idle problems.

Any assistance on what these parts are actually called so I can ask for them on the sell, buy, trade forum?

 

According to Yamaha's online parts fiche, what we refer to as the idle adjusting screw is called a "Throttle screw set" (31A-14103-00-00), and there's a "bush" (bushing, 4GO-14998-00-00), a Throttle Stop Spring (143-14133-00-00) plus the requisite mounting screws which can be had locally. Oddly, the bracket into which the idle adjuster actually goes, nor the L-bracket it mounts to that the screws go through, have part numbers of their own.

I'd call the whole assembly the Lower Carb Mounting Bracket.

 

Thanks for the help. Of course the challenge now is finding the mounting bracket since it doesn't have a part number. I found a few throttle screw set assy's on ebay, but alas no bar.

Here's a fun thought. What do you think the chances are that this all can be installed with the carbs on the bike?

 

Given the cramped quarters, and the fact that there are no less than eight screws holding the thing onto the carbs (two per carb), in my opinion...

...slim to none. And Slim done left town.

In theory, one could just get the adjuster screw and its bracket, grab some angle iron locally and drill/tap the appropriate holes to make your own. In theory, that is.

In theory, there's no difference between theory and practice. In practice, however...

 

that's what I was afraid you'd say. I feel this project getting more expensive then I'd hoped. If I pull the carbs off, I might as well change the boots that attach them to the engine then.

 

Before you start Fabricating and Pulling-off Intake Manifolds; take a look at what is says on the back of the sign you need to read, ... first.

[ ⬅ She-It Creek ➨ ]

Don't do anything that will make a BAD Situation ... Worse.

Buy a set of "Parts Carbs" off Ebay.
Take what you need off them.
Save what you don't need for a week or two; 'til a Newbee comes-in and asks what to do now that he has done broken-off a Float Hinge Pillar.

Use the Rail and Rod set-up.

Before you embark on removing Intake Manifolds, ... for any reason.
BEWARE ++++

Those Allen Cap Screws used to Mount the Manifolds are --> SOFT Steel.
If they are SEIZED, ... they will TWIST and Break-off.
They act like they are being extracted, ... until they break.

From where you are right now, ... don't make a false move without being fully aware of the consequences.

If the remainder of this Season depends on a Rail, Rod and some Screws.
Just do that much.

Take the Boat-ride after you ride the bike for awhile.

 

I bet chacal has what you need. I was missing stuff from my carbs that made me think I was swimmin in that same creek. chacal had what I needed (couple of things) he said he has lots of carb sets and parts. may be faster than fishing around till what you need pops up. the situation sucks-been there.

 

Rick,

I appreciate the point you're trying to make, but I think I may be the victim of not knowing the proper terminology. If I end up having to take the carbs off anyway to install the bracket and associated adjustment screw parts. Wouldn't it be easy to change the rubber (I think??) boots that attached to them and the cylinder. basically the forward boot or I think I may have seen them called holders on ebay.

I ask because the ones on my bike are showing surface cracks and I'm concerned that eventually they'll need replaced regardless to prevent leaks.

In anycase I'm very open to suggestion on this as I'm in more then just a wee bit over my head. I haven't played with a piston engine in years. Used to fix jets.

 

I am with RickCo on the intake boots. DO NOT MESS WITH THEM unless you absolutely have to. Visible light through cracks. Half torn off etc...

The problem is that those allen head bolts rust, and seize inside the intake boots. It takes very little effort to snap them off. Then you could be stuck with having to drill, and retap those mounting holes. which requires engine removal

You can get through the rest of the riding season by filling the cracks with RTV sealant, and covering the boots with a bike inner tube. Put those mounting bolts on a religious diet of penetrating oil (Kroil, PBblaster) for the remainder of the riding season.

While you have the carbs off, Do yourself a favor, Give them a good cleaning.
The save yourself the headache of having to pull the rack off a second or third time. Clean them again.

Read the following two topics
IN THE CHURCH OF CLEAN
Clean Your Own Carb's - The Whole 9 Yards - by: Rick Massey

schmuckaholic has also made available a pdf file giving a photo walkthrough on tearing down the carbs completely.

Keep the questions comming. You will be back on the road before you know it.

Ghost

 

While you are going through the carbs. You can get any parts you may need from our resident parts expert Chacal @ The XJ 4ever button at the top of every page.

Just PM him with your bike info. VIN, What you are working on.
He will make sure you get the right parts, and more info than you may think you want to know.

Ghost

 

I've been messaging Chacal, and I think I've got my parts list. However, while I was getting ready to order and was reading his part list there was a note about the screws that hold the rack bracket on to the carbs that now has me concerned. I can't go and physically check in any way until this evening, but what do you think the chances are that the reason the bracket is missing is because at some point someone stripped the holes in the carbs?

I hate to go and order this stuff to find out they can't even be attached. Anyone mess with these rack brackets at all, and have a feel for how likely that is?

 

OK, a little late, but as promised; some pics: (Apologies for the fuzziness, I didn't feel like fighting with the camera.)

The little bugger in its natural habitat; you can see it there just past the #2 float bowl:




Looking from the bottom of the rack:




Looking in from the rear; in this pic you can see the whole adjusting screw (although the fuel supply fitting sort of gets in the way




Hope this helps, and helps you further identify exactly what's missing. For what it's worth; the closeups are of my "parts" rack; I paid less than $20 for it off eBay.

 

Thanks for the pics. They pretty much confirm my findings. Everything attached to the lower rack bracket including the bracket itself is missing. I haven't had much luck finding a set of carbs on eBay, and I still haven't figured out if the carb screw holes are stripped out. Any chance you could take a look at a screw from both the top and bottom rack brackets and see if they're the same size? That way I could just remove one of my top screws and test it in the holes on the bottom

 

Actually, I'm pretty sure they're different. IIRC, the uppers are the same as the carb "hat" screws, while the lower rail screws are some big beefy things.

What I'll do (again, when I get home) is figure out what size and thread pitch they are; and see if there's a compatible-sized screw somewhere on the bike you could use to check them with if you don't have a metric tap and die set.

Unless somebody can beat me to it.

 

Hey-- check this thread-- a member with a bunch of 550 Seca parts he's getting rid of, including a RACK O'CARBS... http://xjbikes.com/Forums/viewtopic/p=2 ... tml#288545

 

even if your srew holes are stripped you can retap them, and Im pretty sure chacal has the tap, its pretty easy. I just last week had to retap my idle mixture screw hole and it was pretty easy. just use the right cutting oil and be careful. worked out great and my carbs are in BETTER shape due to claen threads and new parts. getting a whole new set isnt a bad idea but the set you have can come back good as new. and fitz is correct the holes for the top rack are like m4 I think and the bottomn are larger. Larger even than the bowl screw. Again chacal will know

 

Well I've ordered all the parts from Chacal. Thank you everyone for the assistance. Hopefully the install goes relatively well. Perhaps there's one last question I could use an answer for. How does the idle adjusment screw hook up to the carb on the adjustment side of things. I can figure out how the rack bracket and everything hooks up, but with out the parts in front of me I'm having a hard time visualizeing how it actually adjusts the idle.

Thanks again

 

Look at the bottom picture that Fitz has posted......the idle speed adjustment bolt/screw doesn't really "attach" to anything on its working end; the blunt tip of the bolt merely pushes open against the flat throttle shaft bracket "arm" and thus forces all of the butterflies open a small amount.

 

Lol thanks again Chacal. Who needs a mechanic when I've got you around. Everyone has been more helpful then I could have expected. I was pretty sure I was screwed just a few days ago. Now I'm pretty sure I may just get to ride the bike without it stalling every time I pull in the clutch and let it idle.

 

You've only just begun the road to recovery. When you are truly SOL you will have just as many willing to tell you so. Information flows like fine wine around here.

Here is another bit of helpful info for you.
Before you go puting gas to those nice spiffy carbs. Take a look inside your fuel tank. If you see any discoloration, or rust buildup you need to get that tank cleaned out. Add an inline fuel filter, and check the petcock for proper operation.

Get it all taken care of now while you have it apart and you'll enjoy the bike more knowing that it is in top operating condition.

Ghost

 

As promised:

The LOWER RAIL SCREWS are M6 X 1.0; which happens to be about the most common size small bolt on the bike.

All of the cover screws, valve cover bolts, the little clamping bolts for the shift lever and brake lever, the bolts that hold your master cylinder to its clamp, clutch perch clamp bolt--- all M6 X 1.0.

And again, Len is right. The bracket that's attached to the lower rail is the only support for the screw, but it has another tab toward the front, so it supports the screw in two places. In the lower pic, the part that the spring on the screw is pressing against is that tab.

 

bigfitz,

Thanks again for the help, the pictures you added are what made it easy for me to tell what all was missing.

Speaking of missing..... When I took the bracket and such out to the bike earlier to come up with an install game plan, I noticed something new.

It looks like I've got a bolt missing on the crankcase. If you're looking at the ignition cover plate, it's the first flange bolt to the right on the crankcase. Don't know how I haven't noticed that before, but since we're playing the how screwed am I game.... How screwed am I? will the case be leaking oil? Which I haven't noticed yet. And what are the chances that this hole is stripped out?

I open the debate up for opinions. And perhaps I should have titled this thread "This bike runs despite the PO"

 

Alright, I just thought I'd give an update to all the folks who helped with this project. I installed the rack bracket and idle screw assy tonight. I did have to remove the carbs, which was... interesting. But it's all back together and she's purring like a fricking kitten.

Thanks again to everyone on this. I am still concerned about the missing screw on the crankcase though, and would love some advice on how big of an issue it is and what the best approach to fixing it would be? Can I get away with just ordering the screw and putting it in?

 

Identify what screw it is.
Look-up its size in the back of a Factory Book.
Determine what you need.
Go buy one at ACE Hdwe.

Or, ... IF the missing fastener is securing a Cover of Case.

Pop for a Stainless Kit.
See Len.

Also ck Ebay.

 

Which bolt is missing?




THIS one? (The only bolt in this pic besides the cover screws.)

 

Yes. The bolt in the middle of the second picture with the bolt head pointing up. That'd be the missing bolt.

 

Oh my, you'd better get a new one asap, pretty sure that holds the crankcase halves together

 

That's exactly what it is. It's a crankcase shell bolt; DO NOT just go buy something at the hardware store.

It's an M6 X 1.0; not sure how long but they're like a Grade 9 automotive bolt IIRC, with the flared head. Yamaha still sells them or get one from chacal; but get the right bolt. Torque spec is 8.5 ft/lbs; not super tight.

 

Alrighty, looks like I'll be making another order with Chacal. I realized when I bought the bike that it was 30 years old and would have some issues, but some of these random missing parts are blowing my mind. I don't even want to know how long the PO was riding it without the idle adjustment.

 

The "Flared-Head" does not make that Fastener ... Unique.
It's just a Manufacturing time saver.

The flare on the fastener just makes it a "Speed fastener."

The assembler saves having to place a washer onto the Bolt.
And, ... the Bolt Head doesn't slip deep into the Socket ... allowing it to be touched and fitted without the Tool pinching the assemblers fingers.

 

True. Except it's a crankcase shell bolt; if replacing it with a standard Grade-8 automotive bolt, you WOULD need to add a washer, which would likely overhang the edge of the casting at the outside.

I stand behind my recommendation to use the correct bolt.

 

We both probably have precisely what he needs in a drawer or a box that we haven't touched in months.

 

Alrighty, looks like I'll be making another order with Chacal. I realized when I bought the bike that it was 30 years old and would have some issues, but some of these random missing parts are blowing my mind. I don't even want to know how long the PO was riding it without the idle adjustment.

 

I hope that sucker isn't broken off in there.

 

you and me both wizard. We'll see how that goes.

 

you and me both wizard. We'll see how that goes.