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MKIII 850 commando starting problem

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MKIII 850 commando starting problem

Posted by michael_wallace at February 15. 2017

New fuel,Choke on (single Amal MkII con), started first time and ran great. New battery fitted ign. on then the phone rang. I left the ign. on for at least 15 mins when I returned there was a hot plastic smell. Tried to start to no avail, occasionally firing and now wont start. I have decent sparks (maybe not good enough). So I'm now thinking new plugs and coils. They've not done much mileage but are years old. The plugs quickly get wet so fuel there.

Any suggestions welcome.....not get the Honda out.

Mike

Re: MKIII 850 commando starting problem

Posted by christopher_winsby at February 15. 2017

Previously michael_wallace wrote:

New fuel,Choke on (single Amal MkII con), started first time and ran great. New battery fitted ign. on then the phone rang. I left the ign. on for at least 15 mins when I returned there was a hot plastic smell. Tried to start to no avail, occasionally firing and now wont start. I have decent sparks (maybe not good enough). So I'm now thinking new plugs and coils. They've not done much mileage but are years old. The plugs quickly get wet so fuel there.

Any suggestions welcome.....not get the Honda out.

Mike

Check all electrics. Where did the smell come from? Have you still got the 2MC capacitor? if  original probably due for removal or replacement. Coils can short to case and to frame if not insulated.

I would remove tank and check under for melting and shorts. All depends when last checked out?

Re: MKIII 850 commando starting problem

Posted by john_holmes at February 15. 2017

If you have fuel and sparks then try new plugs, modern fuel fouls plugs really quickly.

 

Whats your ignition,  all the electronic ignitions turn themselves off after a few secs to protect themselves and the coils, with points one coil would have got very hot and maybe damaged, but as you have sparks they should be ok.

Re: MKIII 850 commando starting problem

Posted by Martyn Watson at February 16. 2017

Previously john_holmes wrote:

If you have fuel and sparks then try new plugs, modern fuel fouls plugs really quickly.

 

Whats your ignition,  all the electronic ignitions turn themselves off after a few secs to protect themselves and the coils, with points one coil would have got very hot and maybe damaged, but as you have sparks they should be ok.

Like john says, with a contact breaker system when the ignition is left on and one set of points is closed the coil is continuously energised and will over heat. Also the condensor will be connected across the battery and could fail internally and cause a short.

Spark quality is more important than just a spark.

Re: MKIII 850 commando starting problem

Posted by Alan Sessions at February 16. 2017

I kept burning out my mk3 warning light control unit - it gives the smell you describe. If it is shorted inside, you will have a problem - disconnect & isolate all wires to it & you may be able to start. My original fault was done to a couple of duff cells in the battery - I had zeners, rectifier,coils etc checked & they were all OK.

Re: MKIII 850 commando starting problem

Posted by donald_tovey at February 17. 2017

Previously michael_wallace wrote:

New fuel,Choke on (single Amal MkII con), started first time and ran great. New battery fitted ign. on then the phone rang. I left the ign. on for at least 15 mins when I returned there was a hot plastic smell. Tried to start to no avail, occasionally firing and now wont start. I have decent sparks (maybe not good enough). So I'm now thinking new plugs and coils. They've not done much mileage but are years old. The plugs quickly get wet so fuel there.

Any suggestions welcome.....not get the Honda out.

Mike

I did the same thing. It burnt the coils out. I left mine on overnight. A new set of coils sorted my bike out. I run a Boyer system on mine without a power box. It's a question of replacing one item at a time if you don't have the correct tools and the knowledge to use them.

Best of luck, but in sure you will get it going eventually.

Re: MKIII 850 commando starting problem

Posted by christopher_winsby at February 18. 2017

Previously christopher_winsby wrote:

Previously michael_wallace wrote:

New fuel,Choke on (single Amal MkII con), started first time and ran great. New battery fitted ign. on then the phone rang. I left the ign. on for at least 15 mins when I returned there was a hot plastic smell. Tried to start to no avail, occasionally firing and now wont start. I have decent sparks (maybe not good enough). So I'm now thinking new plugs and coils. They've not done much mileage but are years old. The plugs quickly get wet so fuel there.

Any suggestions welcome.....not get the Honda out.

Mike

Check all electrics. Where did the smell come from? Have you still got the 2MC capacitor? if  original probably due for removal or replacement. Coils can short to case and to frame if not insulated.

I would remove tank and check under for melting and shorts. All depends when last checked out?

If you have not gt one, get your self a cheap multimeter. You can then carry out a lot of basic tests.

Re: MKIII 850 commando starting problem

Posted by michael_wallace at February 24. 2017

Thanks Gents,

I forgot to say I have a new assimilator and fitted with Boyer. So I`ll take the tank off again, check wiring and replace the coils and plugs. Decent multimeter I have already. Spark quality is a valid point.

see you on the road.

Re: MKIII 850 commando starting problem

Posted by michael_wallace at March 08. 2017

OK took delivery of and fitted 2 new coils and plugs, tank off to inspect wiring. LH capacitor under steering head wire broken but as I understand should not be a problem (new battery) also a spade connector from LH coil could have been broken inside insulation, all repaired, bingo! Started easily the coils or coil wire seem to have been the problem.

It is a battle though to get to the engine warm phase and the on or off choke of the MK2 Amal con. doesn't help. The revs sometimes race and may cut out immediately starting easily again. I think the next step is timing (not easy if I can't get something akin to an idle) and carb settings. I have had the carb off , new float needle and resealed.

Any tips where to buy a timing gun or otherwise to Amal setting?

Re: MKIII 850 commando starting problem

Posted by christopher_winsby at March 08. 2017

Previously michael_wallace wrote:

OK took delivery of and fitted 2 new coils and plugs, tank off to inspect wiring. LH capacitor under steering head wire broken but as I understand should not be a problem (new battery) also a spade connector from LH coil could have been broken inside insulation, all repaired, bingo! Started easily the coils or coil wire seem to have been the problem.

It is a battle though to get to the engine warm phase and the on or off choke of the MK2 Amal con. doesn't help. The revs sometimes race and may cut out immediately starting easily again. I think the next step is timing (not easy if I can't get something akin to an idle) and carb settings. I have had the carb off , new float needle and resealed.

Any tips where to buy a timing gun or otherwise to Amal setting?

I would check the carb float level, manifold sealing, condition of rubber mount, choke operation, condition of choke. Are you sure it is clean? I stripped my carbs six times due to pilot jet blockage. I have just soaked them for 3 months in carb cleaner and given them an hour each in the ultrasonic cleaner. What looked like clean carbs have turned the cleaning fluid black.

Check also you have play in the cables.

Google Amal carbs there are lots of good sites with advise.

Check out Marks posting-  Amal concentric MK2 on commando. it comes up on google, to save time searching.

Re: MKIII 850 commando starting problem

Posted by mike_sullivan at March 09. 2017

I picked up a Gunson strobe from Halfords years ago, works perfectly well. When you perform this task, take the bike off the centre stand & get someone to sit on it when revving to 5k (this stops the bike 'walking' around the garage).

this one £35 from MachineMart (other sources & prices available)...

https://www.machinemart.co.uk/p/gunson-g4113-timestrobe-xenon-timing-light/?da=1&TC=GS-010814113&gclid=COfj2ffmydICFci1wAodOn8Htg

Can't help you with the Carbs, I'm on Mk I's

Mike,

Mk III Commando

Re: MKIII 850 commando starting problem

Posted by michael_wallace at April 30. 2017

I've woken this query up again before I commit Hari Kari! Did all the above things and bought a timing gun.

Whilst waiting for delivery I started (easily) and attempted to ride off. The engine would not take any load at all. The plugs are immediately sooted up (choke on). Then back in the garage attempted to check timing. The MKII amal started flooding, running out of the air intake. With all the time I've spent on servicing the carb I'm inclined to send it back to Amal for a check or buy a new one, stay up float maybe.

Process of elimination then I could perhaps check the timing.

Any words would be appreciated gents.

Mike

Re: MKIII 850 commando starting problem

Posted by christopher_winsby at April 30. 2017

Previously michael_wallace wrote:

I've woken this query up again before I commit Hari Kari! Did all the above things and bought a timing gun.

Whilst waiting for delivery I started (easily) and attempted to ride off. The engine would not take any load at all. The plugs are immediately sooted up (choke on). Then back in the garage attempted to check timing. The MKII amal started flooding, running out of the air intake. With all the time I've spent on servicing the carb I'm inclined to send it back to Amal for a check or buy a new one, stay up float maybe.

Process of elimination then I could perhaps check the timing.

Any words would be appreciated gents.

Mike

Check what float needle valve you have. I found that stay up floats still needed the brass  rubber tipped valves ( on the MK 1). With the lighter valves the vibration on the engine causes them to leak. It would seem they only do one valve for the MK 2 for petrol. The stay up float is easier to adjust.

You need someone to help with the timing. One person to sit to bike with it off the stand, the other to do the timing.

Also have you checked the choke condition and operation making sure it seals when OFF .

Re: MKIII 850 commando starting problem

Posted by michael_wallace at May 02. 2017

I think I need to order a stay up float then there is not much more I can do with this carb. I never get so far as to be able let the choke off, backfiring etc. I' m curious Chris, why should I only check the timing with the bike off the stand? Is this someway significant?

Re: MKIII 850 commando starting problem

Posted by john_holmes at May 03. 2017

The stand is mounted directly to the engine plates so vibrates with the engine, so with the engine revving and the stand down the bike wanders. So stand up or stand down but on a rubber mat when strobing.

Re: MKIII 850 commando starting problem

Posted by christopher_winsby at May 03. 2017

Previously michael_wallace wrote:

I think I need to order a stay up float then there is not much more I can do with this carb. I never get so far as to be able let the choke off, backfiring etc. I' m curious Chris, why should I only check the timing with the bike off the stand? Is this someway significant?

The extra vibration can cause the carb to flood. On the stand the Isolastics  are not allowed to do their job properly.

John is also right, I move mine around the garage this way. Timing it it would try to leave the garage.

Re: MKIII 850 commando starting problem

Posted by dave_taylor at May 03. 2017

Previously michael_wallace wrote:

I've woken this query up again before I commit Hari Kari! Did all the above things and bought a timing gun.

Whilst waiting for delivery I started (easily) and attempted to ride off. The engine would not take any load at all. The plugs are immediately sooted up (choke on). Then back in the garage attempted to check timing. The MKII amal started flooding, running out of the air intake. With all the time I've spent on servicing the carb I'm inclined to send it back to Amal for a check or buy a new one, stay up float maybe.

Process of elimination then I could perhaps check the timing.

Any words would be appreciated gents.

Mike

Mike,

The plastic float hinge can catch the two gasket lugs causing flooding. The new stay up float clears these gasket lugs by miles, I reckon it's a good buy.

Popping and banking can be caused by a weak spark or fouled plugs.

 

Dave

Re: MKIII 850 commando starting problem

Posted by michael_wallace at May 25. 2017

well I think the stayup float with correct carb. fuel level setting was the answer all along. Bike now starts and settles to a good tickover with choke off very quickly, and I haven't even checked the timing yet. I never would have thought that the float bowl level would be so critical. thanks for all your help gents.

Mike

Re: MKIII 850 commando starting problem

Posted by Neil Wyatt at May 25. 2017

Michael, very critical when depending on one carb. Without raising the fuel level you will forever be running out of fuel. It took several tweeks on mine before I got it right though that was on a Mk1 Amal. (The danger is creating flooding on the other hand)

Enjoy lower maintenance and 65 mpg economy.

If you are using the RGM type manifold then ensure you have lock tighted the two inside allen screws. If one comes out there is only one place it it going!

Re: MKIII 850 commando starting problem

Posted by keith_owen at May 26. 2017

Neil,

Can you provide some further insight as to how you went about tweaking the float to get it right? I am keen to know more.

 

Keith

Re: MKIII 850 commando starting problem

Posted by Neil Wyatt at May 26. 2017

Keith, very simple really, although a fiddle. With the ethanol resistant stay up float you basically bend the tangs to the desired position but every bike is different so best to raise the level a tiny amount until you have the desired performance.

When testing your new settings make sure the engine is fully warmed up and try in different situations such as acceleration / closing the throttle, checking for response (Clean pull or hesitation) & the acid test of stalling in stop start traffic.

I could have explained that better but if you type 'the new Amal stay up float' into a search engine you will find the Amal guidelines I used. They don't recommend messing with the needle and I had no need to.

I'd have given a direct link if the site software would allow me to.

Have fun.

 

Re: MKIII 850 commando starting problem

Posted by keith_owen at May 26. 2017

Hi,

I think I'm going to have to buy myself a bag of patience...........when I tried before (on my Ariel)  it seemed very hit or miss and it took any number of attempts to get the level within the spec given by Burlens. And at that I made a jig so that I could mount the bowl off the carb and remove the float easily for tweaking!

How have you found the single Mk 1 carb to perform? I have bought the bits ready, since I'm rebuilding my bike (the carbs on it were shot) and hope that there isn't too much loss of performance?

 

Keith

Re: MKIII 850 commando starting problem

Posted by Neil Wyatt at May 26. 2017

Keith, It took about 7 attempts to get my stay up float to optimum performance and with the change back to 20/50 oil will start first kick. A bag of patience is exactly what you need at this stage.

It was Les Emmery who advised me to buy the Mk 1 set up. And now it is well set up I'm not regretting it. (68 mpg) I hardly notice the performance change. I suspect the twin carb set up performance is all at the top end. The price for that was a mere 45 mpg.

Commando expert, John Dunn who runs a Mk3 on my set up gave me another bit of sound advice, much appreciated and that was to change the main jet from 270 to 260, that was a big improvement.

Thanks for letting us know how you are getting on.

BTW, Editor Mark W ran an article on setting float height a few months ago. Too late for me!

Re: MKIII 850 commando starting problem

Posted by keith_owen at May 30. 2017

Hi Neil,

bank holiday got in the way of things a bit and I didn't read the forum.

Thanks for your feedback It is always good to hear from others of their experiences. On the question of the cutaway I assume you are using a 3 1/2 cutaway? and the needle, is it in the top notch?

Keith

 

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