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Discussion Starter · #1 · (Edited)
Yeah, took the old girl out for a good thrashing today (rode her 80 miles at 3 to 5,000 rpm's before mishap, wound her out to about 5,000 rpms about a dozen times) and she was running really well (octane booster really helps these old triumphs) (but used about a pint of oil) then I noticed a spot in the throttle that seemed pretty stiff, like if I twisted it to that point (about 3 K rpms in 3rd gear) there was resistance then she felt free past that point. Well, eventually the throttle stuck in fully open position, had to use brakes to slow, when I would pull in clutch to downshift, it would rev right back up again towards 5-6 K rpm. So I turned off ignition when in 2nd gear on the parkway offramp leading into the Bronx and shifted to neutral and then coasted to the shoulder. Cable seemed free enough down into the carb. Upon inspection cable would move in and out of carb top piece as well. Think maybe the throttle slide is stuck. So after about a half hour of fruitless fiddling started pushing the old girl home, would have been about 10 miles and straight through Harlem, up hills etc., but there was no way I was leaving my old Tiger behind. After a couple of miles, I'm pushing her through the Bronx (wearing my Lewis Leathers Bronx jacket which is fitting enough) and fellow named Rich with some grocery bags asks what's wrong, I explain throttle cable is stuck, requires I think dismantle and repair carb, or at least free up internal throttle slide mechanism which has a spring that should be taking the slack out of the cable but isn't working. Rich says I can help you out calls his friend Pat with a pickup truck. Pat arrives with his 1974 Chevy 4x4 pickup, and is literally the world's nicest guy, won't take any money other than let me buy him some gas (I offered him $50 but he wouldn't take it, said it wouldn't be a good deed if he did). There are definately good folks in the Kingsbridge section of the Bronx. We pushed the old girl up into his truck and now she's safe and sound in her garage spot. So .. about the stuck throttle, what do you guys think is the problem?
 

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worst case: carb body warped from heat. best case: slide gunked up with carbon.

I'll bet it's fine once you knock the slide back loose and let it cool off - until it happens the next time. When it's idling, is there a little slack at the bottom of the throttle where it idles poorly, then - when the slack gets taken up - idles better?

If that's the case, then the body/slide is worn out of limits.

Maybe just needs a cleaning after the winter.
 

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Discussion Starter · #3 ·
Thanks for the reply, Psasak. You have confirmed my suspicion that throttle slide is stuck. Now I just need to free it up so that the bike can be ridden to my mechanics shop, then I'll have him dismantle the carb and decide if I need a whole new carb or to re-sleeve it or somehow fix this problem.

Do I need to remove the carb from the bike to free up the throttle slide? I have tried tapping on the side of the carb to free it last night after mishap, but that didn't work. Is there another way of freeing the throttle slide without having to take the carb off the bike?
 

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If the carb is old , l assume its an Amal, and the slide and body look worn do what l did and replace with a new one. Like my tiger you only have one and smoothing ect is only putting off the inevitable. l ordered my ones with chromed slides and have not had trouble in ten years. Mine jambed in town at a crossroads, you don't want that twice!
 

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Discussion Starter · #5 ·
Hey Keyman, thanks for the advice, I will lean towards getting a new carb with a chrome slide.

My only issue now is to get the bike to the shop, which is about 5 miles away. So I just want to get the slide freed up in the carb to ride the bike that short distance. I'm going to take off the air filter, disconnect the fuel lines from the tank, remove 2 bolts attaching carb to intake pull carb off manifold and lower it to unscrew top plate of carb then I should be able to pull out throttle slide and cable and free it up. I'll try to keep rpms low on the trip to the shop, because the point where the throttle starts to stick is 3,000 rpm's.

Is there's an easier way to free up the slide, or is the way I described above the best and surest method?
 

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Discussion Starter · #6 ·
well, not wanting to take the carb off the manifold unless i had to, and also not wanting to even partially disassemble because of potential reassembly problems i found some good exploded diagrams of the aml concentric in the online guide listed here:

http://www.oldbritts.com/amal_tun.html

and it looks like if i'm guessing correctly i can stick a long stiff wire such as a straightened out paper clip into the hole in the top of the carb where the throttle cable enters and by pushing on the wire can free up the throttle slide and the spring should push it back down to the closed throttle position. i will give myself a good pat on the shoulder if this works as in general when i take spring loaded complicated things apart like a carb i have a tough time putting them back together!! Cheers all and enjoy the riding, i just wish i could be out there flogging the hell out of my old girl, to teach her a lesson for stranding me on the side of the road. i'm looking into my crystal ball right now and i think i see a new amal carb with a chrome slide!!
 

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Just freeing the slide up without resolving the issue is just asking for more trouble on the way to the shop. Take the carb off and do it proper, or take the carb to the shop, or take the bike if you arn't comfortable taking it off and replacing it.
 

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Free it up to ride it SLOWLY to the mechanic, fine.

Get it fixed properly.

You lucked out in two ways: You didn't get injured or killed from an out-of-control ride, and you didn't blow your engine from severe over-revving. Hopefully, you didn't over-stress the engine enough to result in any maladies like excessive smoking or low compression.
 

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Discussion Starter · #9 ·
Yes, I'm glad it worked out ok. didn't happen in busy city traffic, but instead in 70 mph moving highway traffic that wasn't too congested. i think i handled it pretty well because i let the engine rev at about 4000 rpm's but kept the brakes on and downshifted to 3rd then 2nd then cut ignition and shifted to neutral and coasted to shoulder. Didn't ride the bike like that for more than 1/4 mile. i think the motor's fine, i'll keep my oily fingers crossed. i was willing to push that bike home for 10 miles, but luckily someone helped me out with their pickup truck.

so, update on the situation. tryed freeing throttle slide with straightened out paper clip, nothing, still slack in throttle cable. so i removed carb, not that difficult, felt good getting to know the bike's inner workings. Looked in air intake of carb and throttle slide was all the way down, where it would be at idle. slide seemed ok in terms of moving up and down through the carb's body. Yet there's still a good 3/8 inch of slack in throttle cable. In other words I can twist the throttle about a 1/4 turn to take up that slack before the slide even starts moving up from it's lowest position. Is there supposed to be a flange where the cable enters the twist throttle pulley area (i don't recall seeing anything like that)? maybe it broke off!! or maybe my cable partly broke and stretched.

Is there any way the bike would act like the throttle is stuck wide open when instead it's like the throttle cable is stretched and there's slack in the cable? very weird.

Took off the gas tank to inspect the cable for breaks, looked ok.

This bike does piss me off because it runs great now, but it can't just run fine for 80 miles and take me home without something or other going wrong. Also used about a 1/2 quart of oil in 80 miles of brisk riding. I'll tell you what,as much as i rag on my Scrambler, it's not looking so bad right now.

i love the bike though, so i will stick with it regardless, only reason i'm riding it so hard is to seat the rings since it was rebuilt not that long ago.

i guess i will have to make arrangements to borrow or rent a pickup or van and get it to my guy's shop because i don't feel comfortable riding it through Manhattan in this shape.
 

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my two cents:

if she freed up during the unbolt you might have a warped mounting flange on the carb. comes from someone tightening one of the nuts and leaving the other loose. happens fairly often.

check the flange on a piece of glass, you can sand them flat again on most amals.

I think you're missing a spacer on the throttle that's the last thing on the cable before it goes into the twist grip? or the carb cable adjuster maybe? if the adjuster on the carb gets too loose the little spacer falls off when you roll back the throttle and the slide sticks a bit.

sort of a twofer eh?
 

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Discussion Starter · #11 ·
hey Sunshine Jim, you mention a spacer where the cable enters the twist grip? there is definately no such spacer there now. that's what i was referring to when i mentioned no flange where the cable enters the twist grip. there's a fair size hole in the twist grip housing and then the cable just goes right into that hole with a lot of extra room and it hangs there loosely.

is it possible that as the spacer was in the process of falling out it caused the throttle cable or throttle slide to stick. then once it fell out the throttle slide went back down into fully closed position as it is now.

the throttle slide didn't close as i was removing the carb, it was there all along once i got the bike to the curb, that's probably why i was able to stick that paper clip wire way down into the carb and it wouldn't push down the throttle slider, because it already was down at the idling position.

now i am hoping all i need to do is replace this spacer where the cable enters the twist grip, then there won't be any slack in the cable. if that's the case i'll be able to ride to my mechanics shop (slowly) and have him give it a thorough going over. but hopefully the carb, throttle slide, etc is not to blame and it's just this missing spacer that's the culprit for the whole mishap. That might make sense because the bike has just about every thing on it new, wouldn't make sense that the carb was over looked and left as a worn out item.

Thanks a lot, Sunshine Jim, you've given me some light at the end of the tunnel, so to speak. So what exactly does this little spacer thing a magig look like?
 

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When your slide stuck and you rolled off the throttle, it allowed the cable to go slack. The ferrule (the part you seem to be missing) probably fell out of the housing and off the cable at that time. If your carb is held on to the manifold by two bolts or studs and nuts (as most of them are), over tightening the nuts can cause the body of the carb to warp enough to cause the slide to stick. When you loosened the nuts, the carb body probably resumed its normal shape and freed the slide. How does the slide feel now?
 

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Discussion Starter · #13 ·
hey Jimmy, i'm sure that the amount of slack in the cable now is exactly the same amount when i carefully checked it right after i pulled the bike over after the throttle was stuck open. there's about 1/4 to 3/8 inch slack in the cable. i assumed that (the slack in the cable) was because the throttle slide was stuck at the top of the slide, but instead it's because i was missing the spacer (ferrule), which must have fallen out. the throttle slide definately didn't snap down when i removed the carb from the manifold it was already in the low idle position, this i know for a fact.

the throttle slide now feels like it slides ok, not out of round, but it's a snug fit. i'm thinking the cable possibly had too much slack. i'm guessing the spacer fell out in such a way that it caused either the cable or slide to stick but when the spacer finally fell out or possibly when i cut the ignition, this caused a vacuum effect and sucked the throttle slide down then. who knows what happened, maybe it was the throttle slide locking up first and then the ferrule falling out that caused the problem, i will have my mechanic thoroughly check the carb throttle slide and cables once i get it to his shop.

the throttle slide slides in the carb housing smoothly but it's pretty tight (no slop at all), but possibly the lack of the ferrule causes the cable action to feel stiff when i twist the slack out of it and open the throttle, but i can definately open the throttle now with the cable (after the slack is twisted out of it), and the throttle does snap back shut as soon as i let go of the twist grip.

well, this whole thing is a learning experience for me, and if i can accomplish fixing this myself i'll be pretty happy about that, so thanks everyone for sharing your insight in to what's wrong and how to fix it. cheers, now i'm gonna head to bed, it's after midnight here in the big apple (man i'm gettin' old!!)
 

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twist grip gizmo fab

lets make one eh?

get some 3/8 aluminum rod, a few inches long,and bring it over my house.

i'll drill a hole down the center of it lengthwise (with my incredibly ancient yet amazingly accurate atlas lathe) slightly bigger than the throttle cable,

then we turn one end down for a 1/4 inch to a diameter that makes it a tight slide fit in the twist grip body so it won't fall out so easy next time. so you now have a rod with a cable sized hole in the center lengthwise necked down to the throttle grip hole size for about a quarter inch.

next cut the rod off to a total length of a 1/2 inch and drill a hole on the opposite end to the necked down end, the fat 3/8 end so to speak, with a 1/4 inch drill or slightly smaller, deep enough to stick the whole thottle cable ferrule 'cap' or 'tip' down (1/4 inch or so deep. measure the ferrule on that end of the throttle cable and make the hole a nice fit in diameter, probably a skosh smaller than 1/4 if you have a good drill selection)

then saw a slot a TEENY bit wider than the cable itself LENGTHWISE on this little gizmo with a hacksaw or a dremel cut off wheel deep enough to meet the center hole smoothly. (you want to be able to slip it on the cable using the slot so it slides smoothly into the center of the gizmo.

smooth the cuts, polish and engrave with rosebuds and a good period quote from Edward Turner and Voila, bob's yer uncle!
 

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Discussion Starter · #16 ·
well, i was about to go to sleep then i realized i have this book with exploded diagrams of everything, the old "replacement parts catalog". sure enough found an exploded diagram of the handlebars and control levers also of the control cables. the ferrules on my cables are fine, they are, as Sunshine Jim pointed out the metal end caps over the plasticy cable bodies, also the throttle cable adjuster is fine and the nipples at both ends of the cables are fine. It's the part called the "cable stop", part # 16/011, that Jim described how a replacement could be fabricated, that's the little bugger that's missing. Hopefully I can find a replacement. Now definately gonna take a nice long snooze, man I'm beat.
 

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Additionally, if it was working fine but then bound up once the bike got hot, you're probably dealing with some heat issues. Maybe the bike is running a little lean ... maybe you don't have a heat insulator between the carb and intake ...
 

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Discussion Starter · #19 ·
thanks for all the tips and troubleshooting help.

the bike was running very well, idling ok, pulling like a freight train once above 3k rpms, no reason to think it was running lean, (but how can i check if it was too lean?) the bike did use some oil, (about a 1/2 quart in 80 miles) but i was riding it pretty hard and i think the oil was a smidgen low to begin with, so i think that probably resulted in overall higher than normal engine temp. it's got me considering again equipping it with an oil cooler, because i'm starting to think it's good for the bike to run it hard, but i don't want it to run overly hot in hard riding circumstances. plus riding it in nyc you know in city summer traffic, the oil is definiately gonna get pretty hot. the heat insulator is there between carb and manifold. btw, tightened up bolts attaching carb to manifold "2 fingers tight" is that about right?, definately didn't want to overtighten them. also i noticed while riding a little oil was dripping out of the fork at the top where it mates with the cap nut on the right side, what is that from?

let's say that high temp caused slide to stick in throttle, then cable stop falling out/getting jammed between cable ferrule and throttle housing, caused throttle to stay stuck wide open until it finished falling out. let's say carb has miniscule damage to bore or slide usch as a little burr or scratch or very slight warpage, i'm just guessing. is it worthwile to try to smooth out bore with honing, etc., or replace slide with chrome one if the problem is the slide? Or, since a new carb is fairly inexpensive, does it make more sense to just buy a whole new amal carb with chrome slide and not waste any time trying to figure out what's wrong with the old one, because even after repair it's still not going to be as good as a new one?

i have a cable stop replacement, gonna install later today, hopefully bike runs well enough to get it to shop.
 
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