Why does my carb slide stick?

viclioce · Post by **viclioce** » Thu Dec 31, 2015 11:58 am

OK. Several of you have heard me talk in the past about my carb slide sticking. I still can't figure out why.

I have checked the following:

Slide comes out clean, no gunk or sticky fuel on the slide or inside the carb. My fuel mix is 1:32, and using Motul T2 710 synthetic. No castor oils and haven't for a good while.

I have sanded it and the carb throat smooth with 800 grit this time instead of 2000 grit. Smeared a light coating of two stroke oil on the slide before inserting. I even checked the pin inside the carb throat and lightly filed it's sides to make sure it wasn't hanging up in the slide groove.

Pin is smooth, slide is smooth & carb throat is smooth. Yet it still hangs up. The carb throat is all clean inside and so is the slide.

I've checked the return spring and it still has plenty of bounce. Also checked my cable. It seems fine and is also new. I don't think it's being pinched under the tank. I can twist the throttle and pull the slide up. Sometimes when I release the throttle the slide returns and sometimes it doesn't. The inconsistency is what's really confusing me.

I'm open to suggestions. ; D Victor

thrownchain · Post by **thrownchain** » Thu Dec 31, 2015 12:10 pm

Take the tank off and do the same test, if it still sticks, then it's cable or slide. Make sure throttle barrel is moving smoothly, All bends in the cable should be as flowing as possible. Have you a run little lube thru the cable ? Is the slide "loose " in the carb body ? may be tilting slightly and sticking at that point?

viclioce · Post by **viclioce** » Thu Dec 31, 2015 1:02 pm

No. The slide is tight in the carb body. Sometimes I can't even push it down into the carb without force, while other times it is smooth as silk. I have yet to find sand, dirt or other grit on the slide or the carb throat. This is why I can't figure it out. And the carb was damned near frozen when I first got the bike. Application of 2000 grit made it function again but sooner or later it gets stuck and the cable returns but the slide doesn't. I'm damn near ready to get a new intake manifold (round) and a new carb to mount on it. It just gets scary to be riding down the road or dirt and have the carb freeze wide open and having to ride it to a stop with my thumb on the kill switch. At least I've mastered THAT technique! ; D Victor

ossa95d · Post by **ossa95d** » Thu Dec 31, 2015 1:07 pm

Vic,
While you have the tank off open the throttle by pulling on the cable directly above the carb. You should be able to tell very quickly if the throttle slide is sticking by itself or if the cable is involved. I would stop sanding the slide. A worn slide will make the bike difficult to start and difficult to jet at low throttle openings due to an unmetered lean condition. A very worn slide can stick due to the reason that Dan mentioned. Sanding will not improve either situation. Good luck and Happy New Year!

ossa95d · Post by **ossa95d** » Thu Dec 31, 2015 1:09 pm

It looks like you posted while I was typing mine. It definately sounds like your slide and/or carb body is the culprit. I don't have any other ideas without seeing it.

viclioce · Post by **viclioce** » Thu Dec 31, 2015 1:15 pm

It almost feels like the slide gets off balance and locks up. It's hard to tell. I don't know what the PO did to this carb. But I know I shouldn't have to use a screw driver to push the slide down into the carb. It seems to stick mainly after having the throttle wide open for an extended hold. When the slide is all the way down, at low rpm, it seems to move more smoothly. But if I should happen to push the throttle wide open she is more likely to stick. It's almost like either the bottom of the slide or the top of the carb body is out of round but it doesn't appear out of round by visual examination. When it sticks you can close the throttle and the cable will travel down out of the slide and you can see the cable through the venturi.

Bullfrog · Post by **Bullfrog** » Thu Dec 31, 2015 1:19 pm

Vic:

I sent a response which seems to have flown off into the ethers. (or it will show up at the same time as this one)

I am WAYEEEEE curious about the situation you report with your carb! So curious in fact that I would like to offer a free "warranty review". Would you mind sending the complete carb to me for review? I'll try to turn it around over-night.

Ed

viclioce · Post by **viclioce** » Thu Dec 31, 2015 1:21 pm

I think it's just time to get another carb. IF I can find a flange mount carb for a good price, I'll try that. If I can't, the. I will have to upgrade the carb. I may as well go with the 28mm carb and intake manifold if I can get one reasonably because this bike has a Model 95 top end on it. And I will eventually convert it to Reed valve. ; D Victor

taber hodaka · Post by **taber hodaka** » Thu Dec 31, 2015 2:09 pm

You could try a new different slide, if you have to push it down with force you are almost looking at the problem. I would not even try to start it with such a problem. Sounds like a potential risk to others.
Clarence

racerclam · Post by **racerclam** » Thu Dec 31, 2015 2:12 pm

Seen this before , use a magic marker or dykem or what ever you can cover the whole surface of the slide with , not paint though has to be real thin , then push the slide through its bore once and then look at the slide to see where the dye scraped off and you will find the high spot in the carb body then relieve that spot. Carbs can get knocked around over the years.

Rich

viclioce · Post by **viclioce** » Thu Dec 31, 2015 2:15 pm

Ed. I appreciate the offer! Need your shipping address!

I don't know why it would do this. But it's been perplexing! There are times where it will go for days on end without sticking. Then all of a sudden, WHAM! The bike took a good while to get running great (as per my article in the Resonator Revisited), and even though this is a 24mm from a Model 93 Super Rat, it just seems to have this "flaw," not that being from a Super Rat is a flaw.

Tell me sir, where I should send it? It also fits, shall we say "snugly," on my Model 94 intake manifold. Let's see, it's a Model 03 chassis with a Model 94 bottom end (based on serial number), a Model 95 top end, minus the piston/ring, with a Model 94 intake manifold and a Model 93 24mm carb..... Yeah I''ve stated this before

Let me know where to send it! ; D Victor

thrownchain · Post by **thrownchain** » Thu Dec 31, 2015 2:28 pm

If you have to force the slide down, you have your problem send it to Ed, he'll give it the once over and hopefully have a solution, but I'd say replace the carb.

viclioce · Post by **viclioce** » Thu Dec 31, 2015 2:32 pm

Clarence, et al. I have two other slides in my carb box. I will try it when I pull the carb off to send it to Ed. I suspect there may be a ding or some sort of out of round near the top of the bore but I suspect the dye or marker test would only confirm it. And I don't know what I would do to remedy the problem. I'll see what information Ed deciphers from it and go from there. The cap/top can also be difficult to unscrew at times. So I'm guessing it may be the slide tube itself may have been knocked out of round.

It's funny. I can massage the slide into the carb and then it doesn't stick until I grab a big handful of throttle. When I let go, the throttle doesn't, and I have to use the kill switch and either pull the carb open or push the bike home. I don't want my Grandson to be riding the bike and have it happen to him. And I so want this bike to have "proven reliability," which it still does not have because of this singular problem.

I also wonder what if there is a possibility that the Model 94 intake manifold puts stress on the slide tube when tightened down. Probably not, because it sticks even when the carb is off the bike. But could there be the possibility that the Model 94 intake manifold has warped the carb slide tube? I don't have any micrometers so I can't measure for inaccuracies in diameter. ; D Victor

Bullfrog · Post by **Bullfrog** » Thu Dec 31, 2015 3:10 pm

Check your private messages.

Interesting mystery!

Ed

thrownchain · Post by **thrownchain** » Thu Dec 31, 2015 4:15 pm

Slide sticks on top, and the cap ring doesn't want to thread on....carb body at the top has been squeezed at some point, only have to be off. 001 to cause an issue.

viclioce · Post by **viclioce** » Thu Dec 31, 2015 5:23 pm

Got it Ed. I'll mail it to you on Saturday via Priority Mail. I'll also include some $$$ for return postage. ; D Victor

Bullfrog · Post by **Bullfrog** » Thu Dec 31, 2015 5:38 pm

no need to send $$. I'm willing to contribute a bit to the cause . . . because I'm so curious about the situation.

Ed

junker2k · Post by **junker2k** » Fri Jan 01, 2016 5:35 pm

I know you are sending the carb to Ed, but did you try taking the cable lose from the throttle and just pulling the cable to see if it sticks.
I will wait for Ed to take a look.
Jack K

viclioce · Post by **viclioce** » Sat Jan 02, 2016 9:05 am

Jack. It's definitely the carb. I pulled it back off and removed the 2.5 slide which is in it. I inserted both a 1.5 and a 1.0 slide and they both stuck the same way. I'm hoping there is something Ed can do to it to correct the problem but I fear the top of the carb may be far enough out of round that all I can do is take it apart and get another carb to build a replacement.

I'm going to Colorado to pick up an Ace 100 on Thursday. I'm hoping the guy I'm buying the Ace from might have extra Carb's and other parts I might be able to get from him and build a replacement with what I have. If not, I may go the eBay route or post here for the possibility of buying a used one to keep costs down.

But my grandson and I both want to use this bike and fixing or replacing the carb is the only thing left to do to give it "proven reliability." I haven't gone forward with replacing the wiring harness because I want this addressed first. ; D Victor

Zyx · Post by **Zyx** » Sat Jan 02, 2016 9:23 am

Vic addressed the question of the cable being the problem when he says that when the slide is stuck, the cable end can be seen dropping free of the slide when the throttle is closed. The problem is probably something simple. It could be as simple as missing the rubber gasket/washer at the top of the barrel letting the slide travel too high causing a bind. Could be lots of little things not easy to see. But if the cable drops free when the slide is stuck, it isn't the cable.

Seems to me if the carb body was bent out of round enough to stick the slide, it would be tough to get the slide in and out of the barrel every time. The problem will present itself on inspection.

viclioce · Post by **viclioce** » Sat Jan 02, 2016 11:53 am

The rubber gasket for the top IS in the top cap. So that's not the issue unless it's worn so badly that being there doesn't make a difference. However, any of the slides bind even when the cap is off so that probably rules that possibility out. And there's still the issue of the top cap not threading on and off easily. So I suspect the top of the carb is out of round.

I put the carb in the mail to Ed today, so he should have it by mid-week. If he determines He can fix it then I'm home free. If he tells me it's not repairable, then I'm gong to buy a 28mm carb and I will replace the 24 mm intake manifold with a 28mm manifold. I will then change out the piston to use a normal CW piston and make it a compete piston port top end. Later down the road I can then consider upgrading it to reed valve with the proper porting to be done then to make it work. That will mean machining the cylinder and buying the reed valve and intake manifold and replacing the piston again. I'll also bore the cylinder then to .020 over and use the corresponding piston and ring(s) to go with it.

Presently, I just want it to get it to "proven reliability." That's a term Danny Cooke lent me! ; D Victor

viclioce · Post by **viclioce** » Tue Jan 05, 2016 2:32 pm

Ed. Did the carb show up yet? If not today probably tomorrow... Just checking in! ; D Victor

Bullfrog · Post by **Bullfrog** » Tue Jan 05, 2016 6:58 pm

Just got home from our Christmas/New Year trip and picked up our mail from the neighbor . . . and the carb box was on top of the pile . . . will open it tomorrow.

Ed

viclioce · Post by **viclioce** » Wed Jan 06, 2016 11:39 am

Oh cool! Glad to know it got there. I hate dealing with lost mail insurance! Let me know what you figure out! ; D Victor

Bullfrog · Post by **Bullfrog** » Wed Jan 06, 2016 3:20 pm

I had forgotten that we were talking about a 24mm carb as opposed to a 28mm unit, so that was a surprise (but with no effect on the search for the sticking slide).

Initial exam shows a carb in pretty decent shape. Sure there are some small issues which are easily fixable - such as a deformed needle clip (already fixed) and warped flange mount (correctable by lapping) . . . but generally a good looking used carb. NO evidence of knocks which might have deformed the slide bore. But wait . . .

Does the photo look deformed? Does it look like the carb throat is oval? Um, that is because it IS oval - and it shouldn't be.

I've not found evidence (yet) on what might have squeezed the sides of the carb body enough to make the carb throat 1.14mm narrower than it is tall (25.2mm tall by 24.06mm wide). The force required to deform the rather "heavy" flange area of the carb had to be considerable.

Probably as a result of the deformation of the flange area (but mayhaps from something else), the slide bore is almost 0.002" wider than it is in the fore-and-aft direction. I'm still trying theorize/visualize how the deformations might have been related - the carb throat got squeezed narrower (side-to-side) but the carb slide bore got wider (side-to-side) (near where the cap screws on). I haven't yet checked diameters nearer the bottom of the slide bore.

I have not been able to replicate a "full stick" of the slide - but it is most certainly snug. And when installed on my Combat Wombat, which has not been ridden/started/moved since October of 2014(possible "draggy" cable), it took about 5 seconds for the slide to drop when released from full throttle. I reckon that is close enough to being stuck open to count!

If it is OK, I'd like to peer at the carb and mull on it for a couple more days. Would it be OK to ship it back on Monday or Tuesday (Jan. 11 or 12)?

End of preliminary report

Ed

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