It started! well...sort of..

jimmytwin · Dec 1, 2011

Finally! I worked out that id timed the electronic ignition (pazon) wrong :roll: A quick reset of that, a bloody good kick made it fire up...but only on one cylinder. The oil returns great which is good. The RH exhaust pipe blats out a healthy noise, where as the LH one doesnt. Ive got compression 45psi LH 50psi RH, ive disconnected the plugcap and run it whilst holding the ht lead on the plug top then pulled it away, no change. Changed the plugs over RH to LH,still only RH cylinder firing so the plugs good. Valve clearances are good. Carbs flooding ok. im outa ideas bar taking off the head and having a look....
in summary

spark on both cyl
fuel to both cyl
compression on both cyl
tested ignition
fuel evident on plug-LH was a little wet actually..?

..Any ideas?

grandpaul · Dec 1, 2011

Likely the Left side carb has the low speed passages blocked.

jimmytwin · Dec 1, 2011

Thanks for your speedy reply, i'll go pull it apart again and see if ther eis any crud in it. I was considering new carbs as there flood a little-old floats and slightly worn slides. I would of thought that the LH pipe would have chimed when it was revved up tho..?

jimmytwin · Dec 1, 2011

Cleaned LH carb, all passaged clear. If i disconnect RH ht lead it fires on LH cylinder,not as loud as the RH pipe but when I put the RH ht lead back on, it revs up then dies...

pete.v · Dec 1, 2011

Sometime the clip come off the needle and drop down. 45psi and and 50psi? Pretty low even though relatively equal.

Make sure the carb/cables are sync'ed (equaled) up before starting.

westernjesus · Dec 1, 2011

First, compression is really, really low. But I suppose well enough to run. In your explanation above you didn't indicate that you confirmed that the left jug is even receiving sufficient spark. The plug may be fine since it works on the right jug, but that doesn't mean juice is even getting to the left. I'd start by poor mans spark check and pull the plugs and leave them on the leads, hold the against the cylinder and kick it over. Compare spark. Maybe left is weaker or nonexistent. Then can start moving backwards using the right side jug as your testing ground. Since plugs ok, now lets swap spark plug wires. If wires good, now lets swap coils. Once defect found, your running jug will change to the left and right will be dead.
Carb could be the problem, but since you said the plug was wet with gas, I don't think you are getting any spark.
You have to look into the compression problem though.

bill · Dec 1, 2011

+1 on the low compression unless it was a typo. I would put 90 as the lowest it should run on. what are you using for coils??? if it is a dual lead type in could be going south if not swap sides with the coils and other parts one at a time to see what part it follows.

pete.v · Dec 1, 2011

jimmytwin said:
Cleaned LH carb, all passaged clear. If i disconnect RH ht lead it fires on LH cylinder,not as loud as the RH pipe but when I put the RH ht lead back on, it revs up then dies...

This tells me that it is a carb adjustment issue.

You need to adjust the slided by first lower the stop screww out so the slides rest on the bottom of the carb.

Turn your throttle to see which slide moves first and by how much before the other slide moves. I am sure your right side will probably move first.

Anyhow, turn the cable adjusters on top of the carb to get as aqual as possible.

Some people put a drill of the same size in each throat under the slide lip and then can see which side moves first by the movement of the drill. I just put my fingers in there and feel it.

Once you get that right, bring the throttle stop screws in to touch and then give them equal turns so the slides will be roughly the same off the bottom.

This should give you a good starting point in which to adjust after starting.

jimmytwin · Dec 1, 2011

I thought the comp mite be a bit low but the guage may be wrong as it takes a really good swing
On the kickstart to turn the motor over. Carbs slides are balanced, using twin 6volt coils.
Probably something stupidly minor. Will swap coils and ht leads over tomorow and see if it changes.
To be honest im more glad to see it sort of run after around 30years of sitting idle.
Thank you all for your replies,ill report back in the morning..

Jim.

grandpaul · Dec 1, 2011

To get a proper compression reading, you need both plugs out and kick it really firmly several times in succession with throttle held wide open.

I'm betting compression reading will go higher...

AussieCombat · Dec 1, 2011

Hey Jimmy,
Yes compression testing takes two good men, and as Paul said,.. throttle wide open and
several good kicks.
If your comp doesn't come up, then you may have a valve timing issue.
However, lets assume all is right in there, is your battery in good shape, ?
If you have Electronic ign, then a good battery is neccessary.
Some thing may be draining your power.
Lights on, Indicators on,......?
AC.
Peter, have you been drinking.? or is it me that should go and have one.
AC.

pete.v · Dec 1, 2011

AussieCombat said:
Hey Jimmy,
Yes compression testing takes two good men, and as Paul said,.. throttle wide open and
several good kicks.
If your comp doesn't come up, then you may have a valve timing issue.
However, lets assume all is right in there, is your battery in good shape, ?
If you have Electronic ign, then a good battery is neccessary.
Some thing may be draining your power.
Lights on, Indicators on,......?
AC.
Peter, have you been drinking.? or is it me that should go and have one.
AC.

I don't know. Maybe i am grasping t straws but he said he had spark on both sides. He said that when the right lead was removed, the left cylinder took over the duties as if the carb were grossly out of balance.

I am also thinking that since this bike is being re assembled ( isn't this the "72 Commande Resto"?), and the cylinder pressure is so low,that it just might be the cam timing (valve timing as you state).

Murray B · Dec 1, 2011

Amal has posted an interesting looking tuning guide at http://www.amalcarb.co.uk/documentdownload.aspx?documentid=43

Hope it helps.

jimmytwin · Dec 2, 2011

Afternoon all and thank you for the replies. I started with the ignition, ht lead on LH cyl was weak so ive replaced that.. Good bluish spark that will jump roughly a half inch gap. Compression re test revealed approx 120psi per cyl so its gota be fuel? Swapped coils over aswel, stillo only RH clyinder firing. Might be new carbs for xmas.... :lol:

Guido · Dec 2, 2011

pvisseriii said:
jimmytwin said:

Cleaned LH carb, all passaged clear. If i disconnect RH ht lead it fires on LH cylinder,not as loud as the RH pipe but when I put the RH ht lead back on, it revs up then dies...

Click to expand...

This tells me that it is a carb adjustment issue.

Go thru the carb sync process first that pvisseriii layed out. It fixed mine. I've got dual Webers on my VW which need the same sync adjustments or it will seem like one side is dead.
Plus it is important that you have a good battery with electronic ignitions.
Do all that and then see what happens before going out and buying new carbs.

Matt Spencer · Dec 2, 2011

If buying carbs , you may as well buy three sets , if its Mk 1s . Unless you can find the magnesium bodied ones .

Mk IIs however , it may well run properly .

Used to wonder how many engines were ruined by knackered Concentrics . A pair of monoblocks wouldnt be retrograde .

It started! well...sort of..

Similar threads