Pulling my Hair Out !! Help ?

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Hi Dan,
I can understand your frustration. If it would help, I have a set of 32mm Concentrics you could borrow. They came off my 850 MK11a. This was running superbly until the crankcase split. The carbs, were set up for 9:1 cr, PW3 cam. & fluted Peashooters. It would prove if the carbs were the problem or not. PM me if you need them.
Martyn.
 
OP, you understand that the "choke" you refer to on the Miks is actually an ENRICHENER, and will be completely non functional if you so much as crack open the throttle, right? Even more magnified by DUAL Miks, less air flow at kickover speeds.
 
As already said, Mike hoonies dont like low speed air flow. my vincent comet would not start easy ,once amal was re- fitted and the tickler was pressed it fired right off. ensure the slide in closed fully and dont tweek it open on kicking.
 
HI Dan, seems like you will have some good support from the Blighty team........as they both have nice tuned Commando with all the goodies!!!
 
I would switch to points ... yes; good ol" fashioned contact breaker points. :) See how it runs with those for awhile. Leave them on for the next check. Known good coils, or ... switch sides, one side to the other. You have to start eliminating "possible" problems. Intermittent coils and electronic ignitions ... can make you ... er ... "pull yer hair out" :evil: Just my 2 cents ... hope ya find it and report back.
 
pommie john No one's mentioned battery voltage yet.
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Duh the rest of us are polite enough not to embarrass anyone that didn't discover/handle that before posting in public.
 
Battery not mentioned yet.. Do you have 12.7 +vlts after standing for a week????????? If you only have 12ish vlts swap it for a new battery or at least one that has 12.7+ ....

IMO the Dyno work should have picked up any faulty "ignition" circuitry and tuned the carbs, so should all be OK...

Have you had a chance to test the charge rate of generator/alt to ensure battery feed is adequate... Many a mention of the flatish batter woes in previous threads.... Mabye that got done in Dyno test..
 
If nothing else changed, the plugs surely did the last time you ran the engine. Even idling for 10 seconds as you put the kickstand down and fiddle with your gloves before turning off the keys is enough to send a marginal set of plugs over the camel's back, so to speak...

Marginal plugs and/or marginal battery AND a Boyer = no go.
 
All of these suggestions have been applied to mine.....but I like to think my carbs and ignition are in good nick and have exactly same issue as you. You mention that 'window of opportunity' which perfectly describes exactly what it is. I know that mine is rich with worn out carbs (cos I've been told so, having no chokes!!). Idling/ticking over for 8-10 mins + when hot and the idle starts to suffer and it has to be manipulated a little to stay alive. I now have a single 5ohm Harley coil, super duper iridiums and yes slightly worn Amals with chromed no 3 brass slides, needle at lowest in a 106 jet, 220 mains. How much weaker can I go? 105 needle jet? It only needs choke under 50F for easy start. Still after 10 mins idling at Donnington during the NOC 50th I switched off and it wouldn't start, me thinking it was rich. Anyway, in desperation I tickled & flooded the carbs and it went next kick. So I figured I had fuel evaporation? Insulators are fitted to the intake adaptors. I've lived with it but its annoying because you just don't know how much to tickle v time off in that 5-10 minute window. I know its nonsense but that's how it works (or seems to) for me. If the taps are flowing ok and the bowls full why should it need enrichening when very hot. If fuel does evaporate surely incoming cooler fuel will fix that, or is a vapor lock taking place preventing fresh fuel entering the bowls?
 
Thats what i found, OLD bikes like lot's of fuel for starting, get it dripping from the bowls ! Mikuni carbs dont allow flooding via ticklers..so the correct pilot jet must be installed..and have you seen how many are available ? Like 30 odd.



Keith1069 said:
All of these suggestions have been applied to mine.....but I like to think my carbs and ignition are in good nick and have exactly same issue as you. You mention that 'window of opportunity' which perfectly describes exactly what it is. I know that mine is rich with worn out carbs (cos I've been told so, having no chokes!!). Idling/ticking over for 8-10 mins + when hot and the idle starts to suffer and it has to be manipulated a little to stay alive. I now have a single 5ohm Harley coil, super duper iridiums and yes slightly worn Amals with chromed no 3 brass slides, needle at lowest in a 106 jet, 220 mains. How much weaker can I go? 105 needle jet? It only needs choke under 50F for easy start. Still after 10 mins idling at Donnington during the NOC 50th I switched off and it wouldn't start, me thinking it was rich. Anyway, in desperation I tickled & flooded the carbs and it went next kick. So I figured I had fuel evaporation? Insulators are fitted to the intake adaptors. I've lived with it but its annoying because you just don't know how much to tickle v time off in that 5-10 minute window. I know its nonsense but that's how it works (or seems to) for me. If the taps are flowing ok and the bowls full why should it need enrichening when very hot. If fuel does evaporate surely incoming cooler fuel will fix that, or is a vapor lock taking place preventing fresh fuel entering the bowls?
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I think it is worth reminding ourselves that there are LOTS of kickstart bikes out there, with Mikuni carbs, that start very easily indeed.

I think the first thing to recognise is that they are not Amal mk1s, meaning, you cannot simply transfer a starting technique that has worked for years with old mk1's over to new Miks and expect it to work! i recently fitted Miks to my Vincent so had to go through this very re-learning curve.

Comnoz says the cold start circuit on Miks needs a closed throttle to function correctly, I didn't know this, but do know hat my Vincent likes a closed throttle and choke on when cold, so it supports Jims comment.

Also, as John says, it is important to get the pilot jet right, and this may entail buying quite a few and experimenting a lot before getting it bang on.

Finally, Miks are well known for the pilot jet getting gummed up an partially blocked. So before doing anything else, this should be checked.
 
Fast Eddie said:
I think it is worth reminding ourselves that there are LOTS of kickstart bikes out there, with Mikuni carbs, that start very easily indeed.

I think the first thing to recognise is that they are not Amal mk1s, meaning, you cannot simply transfer a starting technique that has worked for years with old mk1's over to new Miks and expect it to work! i recently fitted Miks to my Vincent so had to go through this very re-learning curve.

Comnoz says the cold start circuit on Miks needs a closed throttle to function correctly, I didn't know this, but do know hat my Vincent likes a closed throttle and choke on when cold, so it supports Jims comment.

Also, as John says, it is important to get the pilot jet right, and this may entail buying quite a few and experimenting a lot before getting it bang on.

Finally, Miks are well known for the pilot jet getting gummed up an partially blocked. So before doing anything else, this should be checked.
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I've pull started Mik equipped snowmobiles for forty years (Tillitson butterfly before that) and if you think kicking unnecessarily sucks, try a rope at 0F...


The Mik enrichener circuit relies on vacuum to draw the additional fuel in. Opening the throttle slide at ALL kills the vacuum.
The butterfly type choke plate (and the guillotine type in the Amal, to a lesser degree) still creates vacuum even if throttle is opened. Old automotive habits must be discarded when using Miks.
 
Internally corroded ignition switch causing intermittent problems? Might bypass ignition switch and other ignition wiring by temporarily fitting a wire direct from battery to Boyer input.

Glen
 
A good thing about Boyers is they are very easy to troubleshoot. If you have a short (which probably isn't your problem here), simply pull the plug lead, insert a dummy plug grounded to the head, turn on the ignition and start jiggling the harness. When the come upon the short it will fire the plug. You will hear it fire.

In your case I would suspect a bad battery. Even if it shows full charge, it might not be able to fire under load. A quick and dirty test is to put your test leads on the battery, turn the key on, and repeatedly hit the kill switch, firing the Boyer. You can watch the voltage as you do this. If it drops appreciably as you fire the plugs, you most likely have a bad cell, which would make starting very difficult.

Curious as to who built this motor, as a PW3 is something that must be respected!


Good luck.
 
As a follow-on to my previous post, and in total agreement with most who have mentioned jetting, the REASON good plugs go marginal, and marginal plugs fail, is COMPLETELY due to improper carb jetting.
 
A note on measuring voltages with the newer style digital multimeters- they don't work properly when ignition sparks are happening. The digital types I have used all are affected by the RF signals given off by the ignition and produce erratic results.
The older analog style meters seem to be unaffected by RF output.

Glen
 
My Mikuni TM Flat Slide starts first or second kick cold or hot. Choke cold with throttle open about 1/4. No choke but a little throttle when warm or hot. Took a bit to get the jetting right.
 
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