Left pot miss fire back fire

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Galactic Greyhound
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Re: Left pot miss fire back fire

Postby Galactic Greyhound » Fri Aug 25, 2017 5:50 pm

Did you clean out the Emulsion Chamber and the Emulsion Tube on the LH carb?

You need to remove the Emulsion Tube to do this so be very careful you do not damage the threads in the carb body if they are seized.

If seized, you might consider boiling up the carb body in water to free the threads and minimise the risk of damage (Jaythro has a method for this).

See the 'Carb Cutaway' diagram posted previously - the Emulsion Tube is the part the Main Jet is screwed into and which itself is screwed into threads at the bottom of the carb body Emulsion Chamber.

By removing the Emulsion Tube you can clean the Tube, the Chamber and the Air Inlet port going into the Emulsion Chamber.
This is not possible unless the Tube is removed.

First note the depth of projection of the Emulsion Tube Nozzle into the carb venturi - this Nozzle is a separate component which may or may not come away with the Emulsion Tube and can be incorrectly fitted on reassembly if care is not taken in its orientation and fitting.
Ced.

R1100RT 1996.
Sent by Boson Quantum Transmission from the Starship 'Galahad'.
http://www.researchgate.net/publication ... ing_bosons" onclick="window.open(this.href);return false; - It works!

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Jet
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Re: Left pot miss fire back fire

Postby Jet » Fri Aug 25, 2017 6:51 pm

Thanks Greyhound, I did take note of your diagram and blasted the tube, inlet bore, and everything in sight to be honest, with carb cleaner. I used the little straw that comes with and it seemed to clear, cleaner was flowing thru anyway.

After seeing that new Mikuni's are about £400 and a total rebuild and restore of my Bings is £450 I think I'll be borrowing a sonic cleaner. I had one last year and had both carbs in it. I didn't strip them completely as I've never done it before, but I did manage to replace a fair few gaskets and O rings before reassembling. I thought that would be enough! Annoying because this current problem came on all of a sudden a few miles from home, and is causing such a headache. Thanks for your advise again.
1979 R80/7 also known as "Helga"

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Re: Left pot miss fire back fire

Postby PhilO » Fri Aug 25, 2017 7:29 pm

You really must check out the compression for a burnt exhaust valve.
You could even swap the carbs from side to side to eliminate them as a trouble source.

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Jet
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Re: Left pot miss fire back fire

Postby Jet » Fri Aug 25, 2017 8:22 pm

Thanks PhilO, she has had new valves and valve guides about 4 years ago, done by the previous owner, so I kinda hoped that side of thinks would be OK. The old valves and valve guides were given to me with some other bits and bobs, so I know they were done. I have a friend with a compression tester though, I'll see if I can get hold of it.
1979 R80/7 also known as "Helga"

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Re: Left pot miss fire back fire

Postby windmill john » Fri Aug 25, 2017 9:02 pm

As philo says, just swap the carbs over as a quick test, that'll narrow your issue immediately.
http://www.kittos.co.uk
Best roads: 623 Burgos to Santander. A back road to Metz; can't remember which!
Schorsch 1978-80 R65 - bit of a Shetland pony; frisky and naughty.
Friedrich 1993 R80RT - a Percheron, but can still mix it with the rest.

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Galactic Greyhound
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Re: Left pot miss fire back fire

Postby Galactic Greyhound » Fri Aug 25, 2017 9:37 pm

As philo says, just swap the carbs over as a quick test, that'll narrow your issue immediately.

+1 That will save a lot of faffing about getting hold of a compression tester and definitely prove it into a faulty carb or not!
Ced.

R1100RT 1996.
Sent by Boson Quantum Transmission from the Starship 'Galahad'.
http://www.researchgate.net/publication ... ing_bosons" onclick="window.open(this.href);return false; - It works!

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Jet
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Re: Left pot miss fire back fire

Postby Jet » Wed Oct 25, 2017 10:20 pm

Update!

I've had the points, condenser and Bings replaced (with brand new Mikunis) Same problem above still exists, although it took 40 miles to show. I'm back where I started except a few <cough> quid lighter :(

Now wondering if the coils are knackered, HT leads are pretty old too. On the plus side I have some Bings to sell!
1979 R80/7 also known as "Helga"

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Re: Left pot miss fire back fire

Postby PhilO » Thu Oct 26, 2017 2:04 pm

After re-reading this thread I am wondering if you have a problem with one plug lead or cap since you related problems with the timing light on one side. If you are using an inductive timing light it relies on sensing an impulse in the HT lead. The original HT leads are unique to this series and have a built in resistance and use non-resisitor plugs.
A quick test could be to remove the plugs and earth them to the cylinders and spin the engine over whilst observing the quality of the spark. Do it in a darkened garage or at 3 am on a dark night. If there is a difference swap bits over side to side until you identify the errant component, i.e plug, lead and cap or coil.
Without getting both plugs to deliver equally you will be unable to set the carbs up.
Another issue could be worn piston rings and bores which permit excessive oily blow by from crank case to the left hand carb intake making the plug foul up. Later models shared the breather between both carbs and, along with longer lasting bores, this helped them to cope better with the oily fumes from the engine.
If you examine the silencer exits you may find a discernable difference in the black deposits on each side, the left hand being oiler than the right.
P.S. I'm looking for a pair of flat top carbs if your's are going begging.

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Re: Left pot miss fire back fire

Postby Jet » Thu Oct 26, 2017 2:35 pm

Cheers PhilO.

I think a friend is coming round tonight and I hope to do a spark test, it's a little outside my knowledge and experience, but not his. I'm hoping that the HT leads and or the coils are playing up as it's an easy, if pricy, fix. I'm also hoping the piston rigs are OK, I think they were done at the same time and the valves and valve guides by the previous owner. Again, compression is a little outside what I'm used to, but a friend knows about these things!
1979 R80/7 also known as "Helga"

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Re: Left pot miss fire back fire

Postby PhilO » Sun Nov 05, 2017 7:36 pm

Made any progress?

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Re: Left pot miss fire back fire

Postby Jet » Tue Nov 21, 2017 6:44 pm

Hi Phil no new progress yet. To be honest I'm pretty fed up with the old girl. May have a coupe of coils to try tonight, but even if they arrive, I'm not convinced they will fix my problem. A miss fire gradually getting worse (on the left pot) over a 25 mile ride and then refusal to start doesn't sound like coils to me.

I'll keep you posted.
1979 R80/7 also known as "Helga"

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Re: Left pot miss fire back fire

Postby PhilO » Tue Nov 21, 2017 10:35 pm

I think you are too keen to keep replacing things before you have identified the problem. You may be throwing away perfectly good components.
You need to do a compression test first then go back to square one and swap things from side to side one at a time and you will find the culprit. If both pots refuse to fire up then you are in a whole new realm of trouble shooting.
Most airheads will start on one pot so if both have died then It's either fuel or spark. You could look in the air cleaner for a mouse nest.
You will need a fully charged battery to be sure of the best possible spark. It's really an exercise in logic and deduction rather than mechanics/electrics.

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Re: Left pot miss fire back fire

Postby Jet » Tue Nov 21, 2017 11:17 pm

Thanks Phil, my friend has delivered a pair of working coils to borrow, so it makes sense to try them out. I understand what you mean about just replacing stuff, it can be very expensive, and perhaps fruitless. I'll swap out the coils and have a go at a compression test and post again next week to update.
1979 R80/7 also known as "Helga"

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Re: Left pot miss fire back fire

Postby Galactic Greyhound » Tue Nov 21, 2017 11:24 pm

Thanks Phil, my friend has delivered a pair of working coils to borrow, so it makes sense to try them out. I understand what you mean about just replacing stuff, it can be very expensive, and perhaps fruitless. I'll swap out the coils and have a go at a compression test and post again next week to update.

It's not just the coils you have to swap out - its the Plugs, Plug Caps and HT leads as well - be methodical!
Ced.

R1100RT 1996.
Sent by Boson Quantum Transmission from the Starship 'Galahad'.
http://www.researchgate.net/publication ... ing_bosons" onclick="window.open(this.href);return false; - It works!

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Re: Left pot miss fire back fire

Postby boxerman » Tue Nov 21, 2017 11:38 pm

As PhilO has said, you're just changing parts like there's no tomorrow. You need to start again with a methodical diagnosis and the first place to start is to give the bike a FULL major service - if the problem still exists after that then you need to approach the issue logically - I'll give you 1000/1 that it's not the coils...
Phil Hawksley 'The Boxer Man' - aka 'Dangermouse'
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Re: Left pot miss fire back fire

Postby windmill john » Wed Nov 22, 2017 7:55 am

Echo above.
When my old oilhead started playing up, I replaced the world, plugs, leads, Hall sensors, fuel filter, can’t remember now if I changed the coils, but I changed other stuff.
I got so despondent I sold it.
The guy who bought it reported back saying it turned out to be dirty injectors.
But, the important point I’m making here is that although the injectors had been replaced a year earlier and I did the spray test, they were not right. So even taking the injectors off when I was trouble shooting and testing the spray, the spray I saw was obviously not correct.
So as Phil says, a full service, reduce the variables, but double check everything.

When I first got Schorsch I had to do two to three carb cleans. Now you could say I was not thorough enough on the first clean, but cleaner was going through every orifice pretty well..... obviously not well enough.

Try and get past the frustration, it’ll be worth it.
http://www.kittos.co.uk
Best roads: 623 Burgos to Santander. A back road to Metz; can't remember which!
Schorsch 1978-80 R65 - bit of a Shetland pony; frisky and naughty.
Friedrich 1993 R80RT - a Percheron, but can still mix it with the rest.

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Re: Left pot miss fire back fire

Postby Eddie Barnes » Wed Nov 22, 2017 10:58 am


She's done 126000 miles so am thinking again perhaps new carbs are required, but at this point I'm wondering how I can get her to my local bike mechanic for a couple of hours tinkering.


Don't waste your money!
Mine has done twice that mileage and more - still on its original carbs.
You mention on a previous post bits of black in the float bowl - suggest you replace the fuel hoses as they are prone to perish with age. I once had experience of the bike refusing to return to idle when the throttle was closed - turned out to be carbs way out of balance. Look up somewhere on the Forum instructions on how to balance using the manometer method - cheap and very effective procedure!

Failing all else - as you are in Sussex chug along to Jim Cray in Faversham who should sort you out!

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Re: Left pot miss fire back fire

Postby Jet » Wed Nov 22, 2017 12:53 pm

Thanks again everyone. By way of explanation the whole (recent) story is that my R80 has been to a BMW bloke who set her up and got her running nicely, that included new points and condenser. New Mikuni carbs have also been fitted but so far that is the only component I have changed, yes they were pricy but a few different people questioned how effective my Bings were.

Seemed OK when I left him and rode home, it was the next day when problems started again, as I have said she started OKish, but got worse as I went along finally refusing to start after stopping some 25 miles later. When I had the tank off I noticed that the left HT lead was looser that I would have expected, the HT leads are not in great condition (as well as being 39 years old for all I know) so I have ordered the bits from Motorworks to make some more.

I'll post again after I've tried new HT leads and my friends coils, Boxerman; your words are ringing in my ears! Respect and thanks to all that have posted.
1979 R80/7 also known as "Helga"


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