Another Jetting question
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Anyone know if these slides would fill the bill?Xpongebob said:
http://www.amr-of-tucson.com/concen~1.htm
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Just a note that almost no honest vendor will sell you a past variety of Chromed brass slides d/t the Chrome flaking to be inhaled and chewed by valve seats till spit out. Broken inhaled plain ole pot metal slide pieces are a piece of cake for chamber to process merely peckering the Al combustion surfaces. As much as we love to blame the decades of owners for ham fisted handling by far most the bigger size Amal trouble comes from not changing the casting methods so as the cast cools it distorts bores and flanges. A metal casting fella explained these innate faults to us on NOC list some decade ago. I've measured this on brand new out the boxe 932's so check out your own for sense of what to doo doo. All jetting data points in manuals - assume the float fuel level pressure gradient - is set to 1.5 air screw turns out for best idle. Its not that big a deal though as plenty of great running slow to fast Cdo's have pilot screw in or out from this ideal nit picking setting. The richer down low ya can get away with by slide cut out, float level pilot screw setting and needle groove raising the more spunk hits on low throttle snap opens. Bumping spark adv just short of back fire starts or detonation on the octane rating also adds up the grins.
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Duh, I don't know Bob. I quit my world wide hunts over a decade ago after new carbs gotten from British Bikes in NZ with great exchange rates back then $160 usd for a pair shipping included. They are the ones that told me they had a good stock of chrome slide but would not sell anymore d/t the damage reports. I sat up one night bored and decided to mic the carbs for a bit of disappointment in bores, wall thickness and flange squareness. Not enough to really mess with mixture but for sure the fine fit and sealing lasting beyond 10k miles or so.
Ms Peel wore out in 7000 miles most the regular slides and bores leaving fluted surfaces that Trixie wore out the rest of the way in a few 1000 miles till could not keep at idle. Tested with grease on slides for nice idle so got the anodized slides one/half cut out smaller [bores still fluted] and so far so goodie on Trixie Combat. I have not cleaned Trixies carbs in like 8000 miles as working well so far with anodized #3 slides but have had many screws loosens or fall out leaving float bowl hanging or manifold gasket hanging to run pretty good with some throttle till trying to start or idle down, till fault found at stops or at home investigating.
Ms Peel wore out in 7000 miles most the regular slides and bores leaving fluted surfaces that Trixie wore out the rest of the way in a few 1000 miles till could not keep at idle. Tested with grease on slides for nice idle so got the anodized slides one/half cut out smaller [bores still fluted] and so far so goodie on Trixie Combat. I have not cleaned Trixies carbs in like 8000 miles as working well so far with anodized #3 slides but have had many screws loosens or fall out leaving float bowl hanging or manifold gasket hanging to run pretty good with some throttle till trying to start or idle down, till fault found at stops or at home investigating.
Thanks gents, I put that badly. I'm well familiar with cracking the throttle open too quickly which is why its hard to explain. Mine takes just the right amount of rate of throttle opening to go from dying to staying alive, not talking about cracking it open as fast as I can twist the wrist...........I know that's never going to work without an accel pump. What I can't get a hold on is the very slow opening of throttle and having the engine die. It's when the slides just start to lift, maybe only 30-40 thou, you can hear it stumble. It seems to be the transition from idle circuit to cutaway but it happens long before the cutaway is supposed to come in at 1/8 open. Only when hot so it has to be rich. I guess I'll never correct it so will go back to living with it
FWIW the idle jets are clear and about equal 1.65-1.75 turns out. Oh and when hot we are talking a 1200 idle otherwise it stalls on deceleration.
concours
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Keith1069 said:Thanks gents, I put that badly. I'm well familiar with cracking the throttle open too quickly which is why its hard to explain. Mine takes just the right amount of rate of throttle opening to go from dying to staying alive, not talking about cracking it open as fast as I can twist the wrist...........I know that's never going to work without an accel pump. What I can't get a hold on is the very slow opening of throttle and having the engine die. It's when the slides just start to lift, maybe only 30-40 thou, you can hear it stumble. It seems to be the transition from idle circuit to cutaway but it happens long before the cutaway is supposed to come in at 1/8 open. Only when hot so it has to be rich. I guess I'll never correct it so will go back to living with it
Often when an idle circuit is plugged (or partially) it can be masked by raising the idle up onto the beginning of the pilot circuit. What you describe sounds close. Re-visit the idle passages, proper tiny wire/drill bit, VERIFY flow in ALL circuits using an aerosol solvent. Bowl gaskets are fresh?
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About plug checking. Years ago I listened to a lecture about reading spark plugs by Barry Smith who raced internationally. Until then I just used to look at the plug and if it looked too white, I'd richen the jetting a bit. I never knew until then that there should be the black ring at the base of the porcelain. In later years my brother and I jetted H1 and H2 two stroke Kawasakis to run on methanol for historic speedway sidecars . We ended up in the range where the black ring just disappears . The carburation is so lean that if you lower the needles one notch, you have immediate disaster. We even counter bore the needle jet slightly, so the tip of the needle won't obstruct when the throttle is wide open. On methanol the main jet is the same size as the needle jet in our motors. In both two strokes and four strokes getting the needle and needle jet right is critical. My own 850 runs methanol, and I made my own needle jets using number drills and I use three taper Mikuni petrol needles in Mk 2 Amals. Nice and lean right up the needle is the way to go as long as the motor doesn't cough.
About rapid opening the throttle. On two strokes the large carburetor size dictates that you must feed the throttle open fairly slowly. You don't have that problem with a Norton twin. If your bike won't respond immediately, it is more likely that the jetting is lean rather than rich. If it is rich, the motor will be sluggish when you are riding the bike, but it will usually still respond. If you get a gasp when you wind the throttle on - usually means lean.
This my brother with his 750cc H2 Kawasaki speedway sidecar. - It is really too much, the 500cc H1 looks identical except for the number place colours and it will do everything needed to win every race he enters .
About rapid opening the throttle. On two strokes the large carburetor size dictates that you must feed the throttle open fairly slowly. You don't have that problem with a Norton twin. If your bike won't respond immediately, it is more likely that the jetting is lean rather than rich. If it is rich, the motor will be sluggish when you are riding the bike, but it will usually still respond. If you get a gasp when you wind the throttle on - usually means lean.
This my brother with his 750cc H2 Kawasaki speedway sidecar. - It is really too much, the 500cc H1 looks identical except for the number place colours and it will do everything needed to win every race he enters .
Well I just carried out Ludwig's slide modification except I bonded the plate in with metal based epoxy. Yes I know if the adhesive fails - I feel unlikely - the plate will be restrained by the needle. It could just conceivably jam the slide open of course but on the basis of threadlocked screws loosening - also unlikely - I went for the glue only. It makes a difference at idle and I needed to open the idle mixture screws another 1/2 turn per side. I was surprised, a little. However when the engine gets to a certain temp after 10 mins idling/blipping at 7 deg C (45F) it still wants to die. As soon as it did this I pulled the mixture screws, ran a drill thru the jets and reset. It started but was not happy until I increased the idle speed. It will be interesting to see if it changes anything on the road but it looks like its going to carry on being a pig in traffic when it gets hot. Oh well, done everything with these carbs, new bodies, chromed brass slides, thick manifold spacers, sealed joints (no air leaks). People keep telling me its time to give upon the Amals, maybe it is and I should face the fact its beyond my ability to sort them 100%.
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If the cam timing is wrong, it would have to a long way wrong to give symptoms. If it is too far advanced, the exhaust noise is usually louder , if it is retarded the bike usually won't pull well. If the ignition timing is wrong, you might have those symptoms. Ignition timing changes can give the same indications as jetting changes under some circumstances. My feeling is that your problem lies in the carbs. I'd be stripping them down, and checking the jet sizes against the standard specifications, in case a previous owner has done something silly, like boring an air jet. Years ago I had those round Amals on my Triumph. I seem to remember that there was a mid range jet behind the needle jet. Could be blocked ?
I accept that but it was the surprise that the mixture screws needed another 1/2 turn out that made me think the 'Holy Grail' of smooth and consistent idling was close to being achieved! It's absolutely perfect for 10 mins or so, until it gets to what I'm thinking (right or wrong) a critical temperature. However, the fact that it is also very hard to start when this occurs is probably another clue. By the way, float height has been set by the book.
I do not spend a lot of time in traffic and on the road it pulls well but it would be nice to solve this annoyance without constant manipulation of throttle to keep it running.
Yes I have seen that before but when I saw your plate I did not make the connection.
I did look at that. My plate is made from old 'White Goods' sheet metal and is 0,8mm, 1,1mm with adhesive.
As background information the carb bodies are from the new Amal tooling. They have No.3 chrome plated brass slides, 220 mains, 106 needle jets and 2 ring needles in top groove. Aluminum needle valves are fitted. One slide is showing a little wear at the front and they have done 8,300 miles since April '09 with a year off in 2011. Originally, the floats were sticking due to a tight fit in the new bodies. That was corrected. When the new bodies and slides were fitted the mixture was clearly rich at a steady throttle as it used to 8 stroke a little and produce black smoke. That was with the needle in the middle groove.
Appreciate your help Ludwig. Thanks.
I knew you would say that
They are at one recommendation of 2,0mm below bowl edge and it has been lower in the past but I do not remember any difference. I don't like constant messing with the needle seat so I might try the new floats with tabs. That would be perfect. I keep talking/thinking about a Dyno and it would be so informative to find out exactly what happens as it reaches what I believe (right or wrong) to be some kind of critical temp. when the idle deteriorates. I still don't believe its idle jet related but I am fitting inline filters as a precaution. Since I lined the tank with POR15 it has remained rust free but there may be other small pieces of s**t that get through and don't show up. I know, I should have them anyway. Thanks for the advice, it's always welcome.
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Perhaps a dyno might not help you get your motor to idle well ? It sounds to me as though you have partially blocked jets , or the breather to the tank is blocked. If your tuning is correct, you should need the chokes on to get the motor to stop spitting back when cold. However when it is warm it should idle perfectly with the chokes off. Correct tuning means that the carburation is as lean as possible right across all throttle openings when the motor is hot, as long as your plugs show the black ring at the base of the porcelain, right down inside where it meets the metal. An extremely cold air temperature should cause the carburation to lean out enough t o give coughing and spitting when the chokes are off. If it doesn't do that, the settings are too rich, and you are not getting maximum performance .
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The crap that plugs pilot jets is the same white stuff that collects in bowl bottoms and has very little to do with crap in the gas and everything to do with zinc oxide fromation that only acid or alkaline boil or mechanical probe can clear. That seems handled in this instant case but don't hurt to triple check.
Any engine w/o boost or a accel pump can be stalled out if throttle snapped open fast enough, except of course vacuum diaphram carbs the term sharp acceleration response don't apply too.
A good Amal can take pretty quick throttle just off idle and not stall but with a bit of finess can be feed w/o any bog per say. The hardest test of idle range tune for me is creeping up a slick slope that dead idel stalls but much over idle spins out, so loading lugging with fairly hi throttle steady as she goes. In other words no matter how slow you open throttle it should just rev up to follow smoothly.
To get a bit more umph down low, fit a #3 slide and slice a v notch out back side of spray tube if not already cut out. lowering the spray tube also adds a bit more low down snap tolerance grin.
If ya really bored to optimalize fiddle float level and timing so best idle is dang close to 1.5 air turns out. But if pilot screw is responsive then float level close enough for me now adays for nice starts and reliable idle hot of cool. My slides have open choke hole at bottom but did plug the top cable hole.
Get new anodized or the verified good new chrome or other non pot metal
surface slide soon as can as each ride prior takes that much more off the bores till fluting air paths.
Any engine w/o boost or a accel pump can be stalled out if throttle snapped open fast enough, except of course vacuum diaphram carbs the term sharp acceleration response don't apply too.
A good Amal
To get a bit more umph down low, fit a #3 slide and slice a v notch out back side of spray tube if not already cut out. lowering the spray tube also adds a bit more low down snap tolerance grin.
If ya really bored to optimalize fiddle float level and timing so best idle is dang close to 1.5 air turns out. But if pilot screw is responsive then float level close enough for me now adays for nice starts and reliable idle hot of cool. My slides have open choke hole at bottom but did plug the top cable hole.
Get new anodized or the verified good new chrome or other non pot metal
surface slide soon as can as each ride prior takes that much more off the bores till fluting air paths.
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Basically , as soon as you change Exhaust , Comp ratio , cam timing , or intake system . Checking Jetting is Mandatory .
As is maybe differant sparking plugs .
For Amals a 270 isnt unusual . In fact some find em neccesary . though I found 280s excessive .
the T100 race bike , throttle W.F.O. on a track , one kilometer and the ( canadian Champion ) plugs go AWOL . Cease to Function .
N 57 Rs were necesary for sustained full throttle use .
Haveing a kill switch , youd cut full whellie in 3rd or 4th , declutch & coast , then pull plugs and ' read ' . plenty of plug reading info on google .
http://www.4secondsflat.com/Spark_plug_reading.html
https://www.google.com.au/search?q=spar ... =firefox-a
As is maybe differant sparking plugs .
For Amals a 270 isnt unusual . In fact some find em neccesary . though I found 280s excessive .
the T100 race bike , throttle W.F.O. on a track , one kilometer and the ( canadian Champion ) plugs go AWOL . Cease to Function .
N 57 Rs were necesary for sustained full throttle use .
Haveing a kill switch , youd cut full whellie in 3rd or 4th , declutch & coast , then pull plugs and ' read ' . plenty of plug reading info on google .
http://www.4secondsflat.com/Spark_plug_reading.html
https://www.google.com.au/search?q=spar ... =firefox-a
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