Hesitation when throttling in neutral (With Video)

I have been reading through the threads here, downloaded the Amal bulletins, set the floats, dropped the right side needle and put new plugs in. Originally I could screw the air adjustment screw in on the right side and it would do nothing to the engine so that is when I read everything I could. Now I have everything adjusted and getting good power but I get some hesitation when in idle and snap the throttle. Am I rich or lean? I have made small adjustments but not exactly sure if I am doing any good. Going to check the plugs when the bike cools down but was wondering if anyone could throw me a quick bone. Only reason I started a new thread is I did not want to hijack someone else s.

Thanks

Re: Hesitation when throttling in neutral

Sorry, no easy answers only questions: Are both idle air screws adjusted about the same number of turns off the seat ? Do they both affect the idle ? If you add a touch of choke, does the situation improve or get worse (improves = lean, worse = rich)? Are the plugs the same color ? Are your slides in sync ? Is your rubber balance tube leaking ?

Greg

Re: Hesitation when throttling in neutral

If you come off idle slow, does the RPM dip? That could mean either your slides are worn or the carbs are not exactly balanced with the stops at idle. That's what mine does and I haven't figured which it may be. I just took up the slop with the cable adjuster, but I know that's not a fix, just a band aid until I can get to it after riding season.

If your mixture screw is not working, you either have a clogged idle jet, or things are not set up correctly. Have you been through the JBA adjustments? The mixture screw should run best at close to 1 1/2 turn out, you might want to check the float level which can be done with the float bowls off the bike and some tubing. check for air leaks too, get new o-rings and make sure the balance tube is good. Leaky taps and leaky float needle valves don't help either.

Other think could be the AAU, or do you have EI? A worn AAU will display these faults too because the timing near idle is not consistent, weak springs or worn shaft.

Dave
69S

Re: Hesitation when throttling in neutral

Sorry I did not go further. Both screws are about the same, started with 1 1/2 turns out and went from there, turning either one affects idle. Slides in sync with some slack, before new plugs both were black equally but right side was not changing with turn of adjustment screw. New plugs in and will check when cool. Rubber balance tube is new and no leaks, check tightness of manifolds, flatness of bowls against carbs, adjusted floats per technical I found here. Filter screens clear, tank is clean with non ethanol fuel. Chokes are in sync and needed some on cold start, will idle up with chokes on and cold engine. Have power arc ignition which was installed per instructions and works great! Good acceleration through gears, seems to idle equally by sound of exhaust but I do not have another Commando to listen to and compare. Did I miss anything? Idles about 1300-1400 and seems smooth for what I know of . Bike is really smooth about 2500 rpm and up. I also put a guitar string through all the passages in the amals.

Re: Hesitation when throttling in neutral

Hey warpedscout, yes all of the above.
A hesitation (flat spot) usually means a leanness.
If Amal carbs aren't in really good condition they are almost impossible to get right, because the slides bounce around with
a mind of their own. Apart from obvious wear marks, look at the slide where the Idle screw sits. The surounding area can be worn out of shape.
An easy test is to just slightly take up the slack in the throttle cable, with out lifting the slide.
If your slide or body is worn, the tightening of the cable will pull on the slide enough to tighten up the fit, and
you will probably see a drop in revs due to less air getting past the slide.
Snapping the throttle at a stand still is very different to when riding. Try it out on the road.
If your getting a spit back through the carbs as you slightly blip the throttle on down shifting, it is probably worn carbs.
All the best.
AC.

Re: Hesitation when throttling in neutral

warpedscout said:

I have been reading through the threads here, downloaded the Amal bulletins, set the floats, dropped the right side needle and put new plugs in.

Click to expand...

Just out of curiosity, did you drop the needle on the right side so it would match the one on the left?
What method did you use to set the floats?

warpedscout said:

Originally I could screw the air adjustment screw in on the right side and it would do nothing to the engine so that is when I read everything I could.

Click to expand...

Did you need to clean the pilot jets using a technique like the one Bushman describes on his site? Do you now get a change in the rpm's when you open or close the air adjustment screws?

warpedscout said:

Now I have everything adjusted and getting good power but I get some hesitation when in idle and snap the throttle.

Click to expand...

I'll bet you can get any bike to hesitate when you snap the throttle open fast enough. A common cause is that the carbs are out of sync.

Re: Hesitation when throttling in neutral

I get some hesitation when in idle and snap the throttle

Click to expand...

If you "snap" the throttle very fast, the engine is bound to have a little flat spot for a very short time.

Remember these Carbs do not have accelerator pumps, so to me, all you are doing is applying the throttle quicker than the fuel flow can increase, hence the reason later carbs models have an accelerator pump.

The instant you snap open the throttle, the air, being the less dense fluid, starts to increase flow quicker than the more dense fluid, the petrol.

This is one of the weaknesses of the design, but really does not effect our use of the bike as we are not running the 1/4 mile.

Normal throttle use is fine ?.

Re: Hesitation when throttling in neutral

Well I screwed that up! Went out last night and checked my plugs and they were tan for the first time I have ever seen in that bike. Josh, I did not thnk about the hesitation being normal since there is not a accelerator pump so that is probably what is going on. I had gone back out and made a few adjustments and totally threw everything out of whack. I reset back to 1 1/2 turns out and will be working on the bike tonight to get back to where I was!

The method I used to set the floats was make a scribe mark 2mm below the top of the bowl. I adjusted by Bushmans manual on adjusting Amals. I dropped the needle on the right side just to see if that was my problem since I was not getting any adjustment with the air mixture screw. I feel my problem was floats not correct and too rich on the left side. I will be putting the needle back to the middle mark and rechecking the floats, mainly to make sure there is no fuel seeping out of the bowl to body gasket which I seem to have that problem on the left side some still.

Thinking back I did notice some scoring on the right side slide but both the bodies of the carbs were smooth and from eyeing were in round. Where is a good distributor for Amal slides? It may not hurt to go ahead and replace them sometime soon.

I may be overthninking this but, as stated previously, I do not have a go by as to what the bike should sound or feel like when both carbs are synced. Before I started fiddling and got everything out of whack last night the bike seemed to do really great as far as smooth idle and smoothness during acceleration. The bike seemed to have plenty of power and was ticking along very well.

I hate to say it but I never was a carb guy, always liked fuel injection but it never hurts to learn new things and Amals are not that complicated! The bike has just over 10,000 miles and probably would not hurt to replace the jets, needles and slides anyhow. Just cannot throw a whole lot of money on it right now due to a custody battle over my son.

I will be working on the bike tonight anyway, I have a leaking gearbox since I took the outer cover off a few weeks ago and made a gasket for it. Weeping some and seems the bottom screw does not want to stay tight. Going to put some loctite on it (non permanent) to try and rectify that. ALso going to put the back air filter panel back on to hold my ignition switch. I put on a K&N filter and left the filter panel off for clearance but really need a sturdy location for my switch since all I am using right now are zip ties to hold it on!!

Thanks for all the replies!!

Re: Hesitation when throttling in neutral

I don't know why, but the factory setup for the floats on mine is way too lean. I had to use the settings like my old plastic floats, then everything worked fine. Did you check for leaky needle valves in the floats? I had a problem on one of mine and it made a big difference. I've got 13,500 on my carbs, and am about to get them sleeved to end that issue. I probably should have replaced the jets and needles, but they seem to be working fine. Buying parts directly from Amal is about as good as you are going to do. They also have the anodized slides, British Cycle carries the chrome plated brass slides for $66 ea. But I think a whole new rebore and sleeve job would be better for me. I don't know if new slides alone will fix my problem.

Dave
69S

Re: Hesitation when throttling in neutral

The more I think about it I really want the PWKs from JPS, end the frustration on the carb issue, plenty of other issues just being a Norton, LOL!! :!:

Re: Hesitation when throttling in neutral

warpedscout said:

Now I have everything adjusted and getting good power but I get some hesitation when in idle and snap the throttle. Am I rich or lean?Thanks

Click to expand...

Lean. Mine does exactly the same thing when the idle screws are set "correctly".

Try screwing the idle mixture screws in a little at a time and see if it clears up. About 1/4 turn works for me. This is the final adjustment that I do on my carbs, 1-1/2 turns be damned.

Re: Hesitation when throttling in neutral

Well, I figured out what went wrong last night. I ..uh...I uh ran out of fuel. :shock: .

So I reset everything and she started on the first kick. Let her warm up and adjusted the idle, revved her a few times and saw some black smoke out the left side so I leaned the left side some. Now just tinkering with the settings to get a good even idle and decent idle rpm's.

After I got to where I thought was good I put the air filter on and adjusted some more. Daddy is happy now!!

Also got some non permanent loctite for the gearbox screws, they will not stay in and keep vibrating loose so I did that before I cranked her up and made sure they were tight!

Want to put the back plate on for the air filter so I can have my ignition switch in a decent location. Will have to put a longer oil hose after it cools off.

Will be playing more with the bike after I get the plate on later and maybe get to drive her to work tomorrow.

Thanks guys!!

Re: Hesitation when throttling in neutral

If you want your idle to be awesome, get a pair of vac gauges and a gunson colour tune, it is really really easy to do and is quite rewarding.

Re: Hesitation when throttling in neutral

Got to tinkering some more tonight to fett out the carbs some more. Was running under 1000 rpm's today when hot so I needed to mess with it anyway. Checked the plugs and one was a little darker than tan and the left was very light tan so I adjusted accordingly then fired her up. Messed with the slide screws until I got a good steady idle and am currently sitting around 1200 rpm. Will get with some local bikers and see about a set of vaccum gauges to check how close carbs are. As for a color tune the more I read it is only good for setting idle spark color and somewhat novelty, but could be wrong?! Maybe if someone I meet has one I may try it, although a little hesitant with my EI! Hey, I'm a lernin!

Re: Hesitation when throttling in neutral

Well, I spent the last half of the day pulling the carbs off and going through them according to Bushmans' link on Amals. I cleaned out the tiny air hole with a small guitar string and verified this with may times on each carb, took the metering jet apart and cleaned it. Looked closely at the needle and it has a good taper mark on the end and no apparent wear I could see and reset my needles back to the center mark. Verified my floats were set right and the bowls were as flat as I could get them on the body with no light coming through. I put a new set of ticklers that do not spill fuel all over my fingers now. I put the carbs on the bike and put a little semi permanent loctite on the manifold to head allen bolts and got them tight, even took a little sandpaper to the mating surfaces to make sure it was good and clean.

I then got about setting the slides according to the site. opened the throttle to WOT and adjusted the slides till I could no longer see them then adjusted to where I could barely see them at the top of the carb opening. Then I let them down to adjust the slides with the adjuster screws. The right side adjusted but the left side would not even feel the screw all the way in. I got it to where I could get the adjuster to touch the slide and proceeded with the 3/8 drill bit test. The slides were in sync so I cranked the bike up. Up to 3000 rpm steady and could not adjust down so I shut it down. Adjusted the slides lower with the top carb adjusting screws and went back through the adjustment process and once again, 3000 rpm and could not adjust lower. I kept adjusting the slides down and ended up with the top adjusters all the way down on the top of the carbs. Adjusted the slide adjuster screw, did the drill bit test and cranked her up, sat at about 2000 rpm and adjusted down until she was warm (I had a fan on the bike). Once warm adjusted the slides to about 1200-1300 rpm and proceeded with the air mixture screws until I had a good steady idle about 1100, smoothest I have ever felt her. Was going out to test ride and started to idle real low so I readjusted the slides and air screws until I got her back to where I wanted. Took a ride and felt really good, no hesitation when in idle and snapping the throttle, I applied very little pressure on the throttle and the rpm's did not drop, they went up so the slides must still be in good running condition even though I did see some wear on both of them . I did check play on the slides when putting them in and they did not rattle around any I could feel while putting back together.

I am learning and thankfully it seemed to do some good. I got all the numbers off the carb, jets and slides for later when I need to order parts. Going out in a little while to check spark plugs to see what color they are and adjust some. I will need to readjust anyways since I did the test run with no filter on!

As long as I can keep them running good I will continue to use Amals but I feel one day I will be ordering some PWKs from JPN once I get the funds, would like to take some work off my hands, LOL!!

Thanks guys!

I took this crappy video just to see if this is what the bike should sound like. You can hear some pattering in the exhaust but this is at idle.

[video]http://www.youtube.com/watch?v=OqAW_z4VdQ4[/video]

Just want to see where I stand with my latest adjustments!

Duh, no longer sorry for my opinion but anything over 1000 to me is beginning of mid range rpm not idle. Fudging air screws is one way to get decent idle but the rest of the circuits are all based on float level setting that gives the best idle and off idle response with screws set 1.5 turns out. When right 11-1200 rpm should take a rather fast throttle snap w/o much if any hesitation. Road going idle needs to be about 1000 to keep charger up especially with head light on. Once tuned up idle speed should only be controlled by the idle slide screws.

OK Hotbot, What should be my idle rpm? From what I have read it needed to be around 1000 due to making sure oil gets circulated. I need some good base points to get this thing feted out and running correctly. Thanks

Depending on how long and often you have to idle - about 1000 rpm is what I aim for d/t oil flow and slow pistons blow by but mainly to keep ahead of charging and out the blue stalling in traffic. When my C'do are feeling their oats I set ~900 rpm, but know I can't full snap throttle w/o bog out, so just don't do that but slightly ease on throttle to let clutch out or ease on til 1200-1500 then shouldn't bog but leap w/o hesitation. I get a lot of pleasure out of slow idle engines, hit and miss the best, but old tractors and cycles too. My Trixie Combat on points came set at 400 rpm after first start on bringing home from New Orleans. I moved it to 600 for a while then the slotted piston broke d/t rubbing on Al gasket taboo combo I'd no way to know lurking til then. With a big ole battery you can get away with long slow idle that hardly warms engine in direct sunlight summer still air. I know it ain't the best habit but rationalize it with such low loads on engine it don't need much lube to prevent fast wear out. Type of cam makes a difference to but all my Nortons have been Combats or the dragster P!! that was set to 600 rpm kettle drum in chest idle on open pipes.

I was warned off lightening prior Ms Peels flywheel 4.5 lb and 1/2" smaller OD, but she idled 400 fine and talk about throttle response off idle! I had to ease her throttle on not because of bog outs but leap out from under or spin outs. Still even so if below 1000 rpm I could snap throttle fast enough to get bog or stalls.
Don't know if the fancy accelerator pump carbs over come this or not right off dead idle.