Carb Cleaning Questions

[Smudgemo]

Today I stripped down for a rebuild an extra set of carbs that I'll be installing in my '96 1100 this winter. Everything looks to be in fine condition, and the only carnage was a stuck screw holding the plenum in place (that gave up when challenged by a left-hand drill bit.) I have a handle on cleaning hard parts, but for the air cut valve and the vacuum piston membranes, what is the appropriate way to clean them? Nothing looks damaged or torn, and I aim to keep it that way. They aren't even all that crusty, but there is a bit in the metal center of the air cuts.

Thanks for any insight.

 

[The Cheese]

I would just wipe them off with a weak dish soap solution. Or possibly a weak Simple Green aircraft cleaner solution. Biggest thing is to dry well after. The SG is what I use in an ultrasonic cleaner.

A note I'd like to make. If you're not using a JIS screwdriver on this carb set, expect more troubles. It is essential to have the proper fitting drivers, or screws strip out easy.

 

[Smudgemo]

Thanks, Michael. I've got both dishwash and SimpleGreen, and an old toothbrush, and I think I'll probably only touch the cut membranes. I went back out to the garage to look at the vacuum pistons, and they are hardly even dusty so I might do nothing with them. These carbs you sent me are in fine shape, although it looks like a mud wasp tried to get something started in the middle of the bank. It was a nice, relaxing half a day pulling these apart.

I do have JIS screwdrivers, and three sizes in fact. That one screw might have been my mistake to not take it more seriously, but no harm. Just need a replacement screw now, in case anyone has one.

And I've got a friend with a friend who has an industrial sort of ultrasonic cleaner I'm hoping to send this group to this week. None of the jets looked plugged, but I don't know in what shape the other passages are.

 

[Oldbikefixr]

And I've got a friend with a friend who has an industrial sort of ultrasonic cleaner I'm hoping to send this group to this week. None of the jets looked plugged, but I don't know in what shape the other passages are.

I use a WD-40 spray with the red plastic nozzle to check carb passages. Just insert the tube into a passage and squeeze. If liquid comes out the other end of the passage, it's fine. If it it blows back all over your hand, there's a bit of additional cleaning to do.

 

[The Cheese]

I forgot to say rinse well after washing.

Post a pic of the screw. I'll see if I have it.

Simple Green aircraft is different from regular SG. Much more gentle on stuff.

 

[ReSTored]

Aside from info here the ST-Riders site has a great post on 1100 carb refurb. You may not need all the info, but it is a great resource with lots of pictures.

Carb Removal and Rebuild ( ST1100 )

Carb Removal and Rebuild ( ST1100 ) *

Carb Removal and Rebuild ( ST1100 ) *

www.st-riders.net

 

[Smudgemo]

Certainly WD-40 would be less scary to work with than carb cleaner.

Noted on SG Lite. Here's the screws. Just one of eight 6x22 pans for the plenum to carb attachment. They are no longer available where I buy parts (hard to believe) but CSML might get an order from me at some point soon and they have something. Seems like just a basic fastener that wouldn't be difficult to source something.


I'm following along with the noted rebuild tutorial above. More complicated than the in-line four from my '76 CB, but nothing difficult.

So here's another "what would you do?" question: $14 for the float bowl gasket or $25 for the gasket kit? The float valve filters appear to be in fine shape, but I don't want to be kicking myself later for not spending the extra on new filters and the o-ring for the drain screw. I'm not breaking this down any further, so I don't need the connector o-rings.

 

[The Cheese]

I bought the cheap float bowl gaskets off ebay and had good results. I can't find the exact seller I used but the link below is similar. If it were mine I'd replace just the gaskets. What's in the "kit"?

Float needles look good? Use em. Filters look good? Use em. Clean the jets and emulsion tubes and reassemble.

Since it's still together have you removed all 4 cut off valves?

4pcs for honda ST1100 ST1100A ST 1100 P Carburetor Float Bowl Gasket O-Ring | eBay

ST1100A 1992-2001. ST1100 1991-2001. Carburetor gasket.

www.ebay.com

 

[bdalameda]

You can keep the diaphragms soft and pliable by cleaning them with dish soap and water and after drying them take some silicone grease and gently massage the grease into the diaphragm.

 

[Smudgemo]

So here's where I'm at now. The air cuts are all removed and while there is a bit of crustiness in the center, the rubbers look great.


The other side and the tool I had on hand that gave me access to the screws. Where did I ever come by this thing? I've had it forever and can't remember ever using it for anything.


Piston membranes look nearly new, too:


This is the stuff I've been using for treating rubber lately, but at this point and looking at these photos, I'm inclined to carefully brush off the metal parts of the air cuts and call it a day unless I want to condition the rubber while it's out as suggested above. Parts seem to be pliable.


I'm also on board with skipping the gasket kit and just getting bowl gaskets. It seems to be the only part I really need since everything is in such good shape. Not sure I want to get the cheap Chinese part, but mostly because of experiences others have had on the SOHC4 forum when I rebuilt my '76 CB carbs and was asking for advice. At least those are fairly easy to change out in place if anything goes wrong.

 

[Smudgemo]

New question and it's needle shims. I decided to order a set of shims as noted in the above carb rebuild guide and they are not the same size as the ones I took out. You can see that they are smaller, but they seem fit the needle better, or at least with less movement allowed by a smaller hole in the shim. This is side by side and another new one on the needle.



The "OEM" shims also don't fall out of the slide when tipped over. I had to reach in with a hooked pick to get them out, and putting back in will require something solid like a pencil to push them back in place. I guess I'm wondering why would an interference fit even be needed when the spring/cap holds it all in place?

So my question is whether the original shim fit in the slide is appropriate or should I use the new ones? I'm trying the rejet to Canada specs and figured I'd buy shims while ordering jets. The original measured .019" and the new one .020". No idea whether that makes any difference, I'm just going by the experience of others, so I'd appreciate some guidance on this before I start reassembling and screw it up.

 

[The Cheese]

Like you touched on the thickness is the important part. Not the diameter. I don't remember having to pry them out. I think maybe yours had some tolerance stack against you. I don't knkow what the one tho difference would make.

 

[Smudgemo]

I went ahead and used the replacement shims and got the parts all reassembled last night, and to my (mild) horror, only three OEM shims to be found when wrapping things up. I was sure I was careful about reassembling each carb, but nagging doubts like did I really screw in each jet properly, or did the float height really get measured properly started to creep in. Luckily I found the missing shim this morning on the floor when I took another look.

I will note for posterity, that when you assemble the needle/slide, you should look for the two tangs/tabs/whatever they are called to be flush with the bottom or the slide or the cam lock won't seat properly. You should feel and maybe hear a satisfying click as it locks in place. I had to go back in and redo the first one when I realized this. They can get out of place when removing the shim.



I have all the cooling system parts on hand to replace while I'm in there installing these, and I'm itching to see what this work has gotten me. I'm pretty sure the bike doesn't run like it should at slower idle speeds, and it seems to warm up way too slowly so maybe both will be addressed shortly.

 

[jrp]

[...]
I'm trying the rejet to Canada specs and figured I'd buy shims while ordering jets. The original measured .019" and the new one .020". No idea whether that makes any difference, I'm just going by the experience of others, so I'd appreciate some guidance on this before I start reassembling and screw it up.

Note that the Canadian bikes have a different slide part number and a different needle holder. The needle holder is much smaller in diameter as opposed to the U.S. spec holders which go all the way to inside wall of the slide. This changes the rate at which the slide moves up (and maybe down). Also, the drilled hole on the bottom of the slide is in a different place on the Canadian slides. I am only mentioning this to let you know that there is more than just jetting going on with the Canadian bikes.

The Canadian needle holder does not fit the U.S. slides. I tried:

ST1100 Needle Holder - Canada Type? | ST1100-Carb Talk

Anyone know why the needle holder is different in the Canadian market? Just curious. Snide remarks are welcomed.

www.st-owners.com

 

[Smudgemo]

I am only mentioning this to let you know that there is more than just jetting going on with the Canadian bikes.

Right. I appreciate input, but my issue is only that the physical ID/OD of the shims I got following the noted rebuild process were smaller. Everything else is OEM. The replacement shims fit the needle better as the ID was closer to the needle size, but they were not a press-fit to the slide so they could be considered more sloppy if that matters. But since they are a shim and everything is spring-loaded, does it matter? I don't know. The needle doesn't have any side to side play due to the size of the hole in the slide, so I'm struggling to think of how it matters.

I probably won't tear that far into the bike for another few weeks at the earliest, so there's time to swap these out if I should.

 

[jrp]

Right. I appreciate input, but my issue is only that the physical ID/OD of the shims I got following the noted rebuild process were smaller. Everything else is OEM. The replacement shims fit the needle better as the ID was closer to the needle size, but they were not a press-fit to the slide so they could be considered more sloppy if that matters. But since they are a shim and everything is spring-loaded, does it matter? I don't know. The needle doesn't have any side to side play due to the size of the hole in the slide, so I'm struggling to think of how it matters.

I probably won't tear that far into the bike for another few weeks at the earliest, so there's time to swap these out if I should.

I apologize if I gave the impression that you were doing something wrong with respect to the shim diameter. It doesn't have to be a press fit. It was your comment about 'Canada specs' that got my attention because I researched this previously.

I was merely commenting that the slides on the US-market bikes have a different design than the Canada-market bikes and that is for a reason. The slides in the Canada-market bikes rise faster giving quicker throttle response. The design of the needle holder for the US bikes is restrictive and results in the slide rising more slowly.

If you remember the dynojet stage 3 kits, they came with a drill bit to enlarge the hole in the slide which would cause it to rise faster. You would also have to increase the jet size and experiment with different needle heights (and possibly different needles) in order to fully take advantage of the performance potential given by a faster rising slide.

Given the difference in the slide behavior between US and Canada bikes, I don't think one can assume that if they just increase the jet size and shim the needle on a US-market ST1100 that they will get the same level of performance as a Canada-market ST1100 without modifying the slide. This stuff is all designed to work together.

I have not checked to see if the needles differ between US and Canada-market bikes.

Jeff

 

[Smudgemo]

Not at all, Jeff. I see what you're saying, and I'm just trying to walk the path of people who have figured this stuff out prior to me showing up to buy a 25 YO bike to play around with. I'm not looking to do anything special, and in reality, as long as it doesn't run worse than stock, it will be okay.

The jets and shims didn't cost all that much and it's the sort of thing I enjoy playing around with. I'm not planning to do any experimenting, I just wanted to see if anyone felt these shims were flat-out wrong to save me from pulling the plastic later and installing the originals. I appreciate your input.

 

[Dale_I]

Following.... I'm going to be starting my rebuild this winter as well.

If these are an additional set of carbs, can you harvest your screw from the set coming off your ST?

Regarding the Canadian vs US slides, If I'm understanding correctly, the slight restriction in the passage would slow the rise, which would affect the quickness of response. But, if I'm understanding this correctly, the slightly larger jet size would still be an advantage in power. It just wouldn't match the quickness to get to max hp similar to the Canadian slide. Sound reasonable?

Truly... I'm probably not a rider that would be able to tell much difference in practical application.

 

[Slydynbye]

FYI, I "upgraded" the jets on my 2000 from 38/125 to 40/128. It will start without choke and gets worse gas Mileage. Can't see any performance increase.
I will be going back to the 38 idle jets soon, might go back to 125 mains. It turns out that some of the advise from the forums is based on a different cam in early ST1100s. The 96-02 had milder cams and may not benefit from larger jets.

 

[Dale_I]

Good to know. The only reason I was going to "Canadian Spec" was because I could. I've always had enough power to do what I want. Looks like I may save the money and just go through and clean up the stock jets and put it back together.