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Post rewire combustion blues
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Tricky.Stockwell
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July 5, 2019 - 4:11 pm
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Hi all,

Have just rewired my D10 - Was running ok (if a little ragged) pre-rewire but discovered  a number of frayed wires that were shorting and thought that a bit of rewire TLC may be the best solution.

New wiring loom fitted and power to all electric components looking good - also, strong spark, new battery, etc.....

But .....

Try as I may, am failing to get combustion.

I have not touched timing (as yet) since was running pre-rewire and timing not touched in the process of the rewire.

All cables to the carburettor are operating nicely (have not touched the carb in the rewire process), air filter looks clean enough. Compression seems as normal, no sign of gasket leaks.... Fuel supply to the carburettor seems fine

Anyone have any ideas as to the possible root of my problems?

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stubaker58
Sunny Felixstowe
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July 5, 2019 - 5:12 pm
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Hi,

if you haven’t touched the timing etc and you have a strong spark then it must be fuel that’s the problem.  (Having said that a new spark plug is always worth a try with a Bantam!)

How long was the bike laid up for the rewire?  Possible that the carb is bunged up or that the petrol cap is blocked. Try with the cap removed.

alternatively is the engine flooded? Drain any excess fuel out via the small drain plug under the engine and try again.

regards

D7/14 hybrid (4 speed with D7 crank etc.) on the road, D10 Bushman awaiting rebuilding.

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Tricky.Stockwell
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July 5, 2019 - 5:24 pm
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Thanks,

The bike was only laid up for about 1 month for the rewire. 

Thanks for the guidance on the fuel feed. I have already drained from the plug under the engine. Whilst there was a small dribble of fuel, there was certainly no gush. If flooded, would I expect to see a significant amount of fuel released?

I will investigate your other suggestions and let you know if I have any success.

Since my initial message, I did get it to fire up for a few moments but it quickly died and then did not restart, so fuel feed certainly looks to be the issue.

Thanks again,

Richard

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nickjaxe
Runcorn Cheshire UK
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July 6, 2019 - 9:58 am
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Dont be afraid to tickle it well before attempting to start it...I just give one continuous press of the tickler...I let it overflow for a good 2 or 3 secs.

I usually put a rag against the carb body to catch the overflow.

On my B175 I dont use choke unless its very cold outside...it doesn't seem to like it.

Sounds like there is not much stopping it...maybe give the plug a good clean before the next attempt.

Nick.

My Bantam video              https://www.you.....jpOFmzRZRI

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Sponge
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July 8, 2019 - 9:03 pm
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Sorry to state the obvious but have you charged the battery ?  Coil ignition bantams like a well charged battery.   

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Tricky.Stockwell
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July 12, 2019 - 4:42 pm
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Thanks for the contributions - all much appreciated.

Managed to get a bit of time back on this today as no work today (hooray!)

Still no ignition but more clues as follows:

1) Removed carb and cleaned throughout (though did not remove main or pilot jet at this point). Fuel in float chamber was a little murky but no sign of sediment. Air and throttle sliders operating smoothly from handlebar controls. Air filter looks a bit gungy - will replace.

2) Ran fuel through from tank into jam pot - nice and clean so no sediment from tank I believe

3) Battery is relatively new - check charge, sitting at 6.47 volts, so looks ok.

4) Checked spark again - plug is clean and good spark when rested on cylinder head

5) Tried to kick over again - ample tickle of carb, no choke, good handful of throttle - engine did not start but smell of some combustion and a few backfires.

6) Checked for flooding - removed drain bolt - barely a dribble of fuel so pretty sure no flooding

Based upon the above, I'm think either (a) still a carb issue - and will need to remove jets or (b) timing issue (even though timing hasn't been tampered with and was starting ok prior to the rewire).

If timing issue, is it wise to get one of the timing discs that I have read about or is there some simpler method?

Any thoughts ?

Thanks

Richard

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johnsullivan
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July 12, 2019 - 6:20 pm
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try a different plug they can be a snare.I suspect though you have poor earthing somewhere.Usually it is the master earth on the tank tail bolt.

67 D10. and a D7    2007 Honda Hornet FA. Honda CD200 81 93 Yamaha TTR 250 Raid, Sinnis SC 125.   75 Montesa Cota 247 an electric scooter of Famous make.

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nickjaxe
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July 12, 2019 - 6:29 pm
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Was it running ok before the rewire and how long ago was that...kick back can be over advance ignition....but in my experience its a condition that wont stop it running.

Anybody give you a bump start or a good push start.

My Bantam video              https://www.you.....jpOFmzRZRI

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Tricky.Stockwell
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July 13, 2019 - 3:42 pm
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Just a quick update on progress.

1) Stripped carb again and checked and cleaned jets - no signs of any problems.

2) Tried bump starting bike a few times. Got initial fire but no strength and engine quickly died (regardless of throttle or choke settings).

3) Earthing all looks to be ok and spark plugs new and gaps checked (.6 mm)

Going to tackle ignition timing next just in case I have upset something

Thanks for your continued suggestions

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sunny
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July 13, 2019 - 4:27 pm
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try  moving   the  poits  plate   first   not  the   cam   

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nickjaxe
Runcorn Cheshire UK
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July 13, 2019 - 4:36 pm
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You tried another condencer...they cause odd probs...and are not good quality these days.

Have you had a go at checking the slow running circuit...they block with gunge from the nasty fuel we have these days?

See the link on how to do it...causes lot of probs if its bunged up.

** Please log in to view **

My Bantam video              https://www.you.....jpOFmzRZRI

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richard hyatt
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July 15, 2019 - 9:04 pm
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hi there,

just another thought.

if you lay the plug on the head and try to kick over , is the spark a good crisp blue??? or a weakfish orangey blue??

( I must assume the points are clean and adjusted etc) if you have a multimeter , put on ohms and go across the points when they're closed - do you get a good reading of 0 ohms (showing a good contact)

ok - treat yourself to an Ebay HT neon tester , these go in-between the plug cap and the plug. so when everything is assembled and you're kicking it , you can see if the spark is there UNDER COMPRESSION. it has been known to be "blown out" ???

some modern condensers are dubious quality for sure - try the above and see .

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Tricky.Stockwell
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July 19, 2019 - 4:10 pm
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Thanks for the new ideas. Back on this today, New condenser fitted and points adjusted. Spark good, a strong blue (and maybe a little stronger than previously) but still no combustion. Will turn attention back to the fuel system. 

Thanks

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richard hyatt
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July 20, 2019 - 8:42 am
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frustrating for sure.

ok - you have what seems to be a decent spark - blue and crisp.

if you remove the carb - can you hear / do you get  a decent "plop" sound from the inlet?? indicating that the piston is sucking on its way up??

have you tried a small amount of petrol straight down the plug hole and then start it?

i've just been re-reading your previous posts and you may have tried this already

it seems that basically , it was running fine before (albeit with frayed wires etc) and all you've done is tidy up the wires and now this.

could you try  bypassing the bike's wiring ---- go direct from the battery to the coil and then direct from the coil back to the points (don't forget the earth from battery to frame).

see what happens now - this way you have excluded all the bike.

I assume the plug is decent? I have found in the past with a reluctant engine , pull a small file across the electrode and earth and get a nice clean bright area of metal for the spark to jump (as opposed to wet and dirty electrodes)

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cocorico
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July 20, 2019 - 9:30 am
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richard hyatt said
...if you remove the carb - can you hear / do you get  a decent "plop" sound from the inlet?? indicating that the piston is sucking on its way up??
have you tried a small amount of petrol straight down the plug hole and then start it?
...could you try  bypassing the bike's wiring ---- go direct from the battery to the coil and then direct from the coil back to the points (don't forget the earth from battery to frame)...

You don't need to remove the carb, though - a palm over the intake venturi will detect suction. If the hot-wire doesn't work, check the timing again (not by adjusting the points gap). It does sound as if you have 'maintenance induced failure' though. dunno

1956 D3 awaiting a new magneto. 7 other bikes in the Barn, 6 runners and a still in progress Morini 250

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