Triumphrat

GleaminTwin

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?

psasak

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.

__________________
2005 Bonneville: 18 tooth sprocket, 135 Mains, 40 Pilots, 1 shim/Thruxton needles, no AI, K&N filters, Emgo Slip-Ons.
My Photo Album
2005 Bonneville 1968 BSA A65L
1972 Triumph TR6R

GleaminTwin

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?

thekeyman

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!

GleaminTwin

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?

GleaminTwin

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!!

Jim Chamberlin

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.

GrandPaulZ

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.

__________________
GrandPaulZ
Author of "Old Bikes"
Born Again Bikes
My Photo album

GleaminTwin

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.

Sunshine Jim

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?