Forum

[JOHNNY SINGLES]

If you are going to change or alter anything on your Enfield before doing so read all there is to know about it, ie changing the points. look at diagrams of the distributer, youtube is usefull and understand how they operate and how to set them correctly, this is very important for the bike to start and run correctly especially electric start models. If you are not sure get someone to show you and explain it to you.
This is how problems acure. IS IT THE HORSE OR THE RIDER.

[Chris Tindal]

Tim my micarb used to spit back and stall regularly, particularly at junctions and trafficlights, occassionaly it would blow off altogether. No matter what I did I couldn't stop it but fitting a richer slide and really fine tuning the air screw reduced it to a bearable level. Everyone I know with a bullet has this problem to some extent. I now have a lovely monobloc and allow manifold so it can't blow off and the spitting back is much less, but not completely gone.

[Dennis C]

Hi Tim, ----- It is quite easy to check the timing so I would advise you to do it as a matter of course, ---- yes the points gap is not critical, ---- but if you think about it the points are opened by a cam the face of this cam is sloping so if the points gap is smaller than it was then the cam contacts earlier and opens the points earlier, or visa versa a few thou difference on the gap can put the timing quite a long way out.----- it is common practice on bikes fitted with a magneto to use the points gap to adjust the timing as no fine adjustment is fitted. ----- to adjust the points gap just turn the engine forward to the point where the points have opened and stopped opening any further the position is not critical as the points stay open for most of the time and only close for a short duration.

[TimG]

Johnny S - in this case I'm sure it's the rider and am not attempting to blame the horse. That said, I DO know how points are fitted and adjusted in general, but as you know things differ between individual makes of bike (and sometimes between individual bikes of the same make!). I also understand the value of research. However, in this case nothing I read or Googled helped remotely in getting me to the point where I was adjusting the gap at the right point on the cam. From this I could deduce that either (a) it's not important or (b) it's generally known but not often shared. Dennis C has given the best articulation so far, suggesting (b) obtains. There must be such an optimum point, as the factory sets the points and does it very well. However, this optimum point is neither marked on the cam (as it very thoughtfully often was on older Jap bikes with a punch mark) nor published as far as I can see. So I'll have to take the info I've got and re-try. Not very satisfactory, but you see my point (pun intended...

Cheers

TimG

[Alan R]

Hi guys------here we go then !! Just when you thought it can't get any worse--------- What are you ACTUALLY achieving when setting the points gap ?? You are setting ( or altering ) something called the "Dwell angle". Take a look at this }-----------http://moodle.student.cnwl.ac.uk/moodle ... ---------- It involves the time for the HT Coil to become saturated (by magnetic flux )and then the spark to be created ( points just opened ie ignition point) and , SIMULTANEOUSLY---for that spark to be boosted almost 1,000 fold by the interaction of the capacitor ( Known by Mechanics as the condenser---which is quite an apt name for what it achieves.).So TIM G, when you changed your points---did you change the capacitor (condenser) as well ?? Finally, just to keep things in perspective---the nominal setting for our points gap is 0.015" ie Fifteen "thou" as we say. Take a look at an Engineers 6" or 12" rule. The 1/64" markings (or half of the 1/32" ) is your 0.015". ( for the Metric amongst us 1mm = 40 thou nom. thus 1/2mm is 20thou nom. ).

[Dennis C]

Hi Alan, ---- that link isn't working for me, ------ but yes two things change when you alter the points gap, one is the dwell and the other is the timing, as you increase the gap the heel of the points is moved closer to the cam so the points open earlier and close later or visa versa with a smaller gap, that's why it is important to check the timing when fitting new points.

[TimG]

Hi Dennis C - are you saying what I think you're saying here? That if I replace the points I must look at the whole timing? YIKES if so - haven't done that. AlanR - thanks for link, unfortunately like Dennis I got a 404 when looking it up. Would appreciate a re-post if poss, as it seems v useful. Anyway, yesterday the idle got so low that, per Les H's suggestion, I adjusted it using the throttle stop screw - result, great idle, bike pulling much more strongly throughout the range, backfiring almost gone. I think I may have been on the wrong track and will transfer my attention back to the inlet tract (but will still check the dwell angle/points gap again too). Ho hum - the joys of tuning.

Cheers
TimG

[Alan R]

Hi guys---------- I went back to that site, scanned the address---clicked onto it ---and got the 404 as well. Try this then }----Put into Google:- DWELL ANGLE--------- and follow you nose.

[Mike of Woking]

It is probably the rubber sleeve that is perished. Causing air to leak into the inlet manifold and weaken the mixture at tickover. Replace them with the Amal ones that Hitchcocks can supply, or better still do away with them and get an engineering shop to turn up an ali sleeve which can be heat shrunk over the manifold and the carb. Then you will never have the problem ever again. Alternatively spend £100 and put an Amal Monobloc carb on it and the result will be the same. There are loads of guys at the Kempton Jumble selling Old Amal carbs which are complete and working for £25... Job done.

Rubber sleeves are more likely to show up the leakage at tick over than at high running speed. This is because there is only a finite amounto of air that can leak through the annulus and it will be a higher percentage of the total air flow at tick over than at normal running speed and load.

I can believe your problems are ignition related.

Regards,