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Hi Guys,

I've Just taken my 1984 Gl1200IE for a spin after fitting a new saddle. The bike seemsto start and run ok until the engine is warm then whenever the engine is under load, like going up hill, it feels like the engine misses, the more the throttle is open the worse it gets until the bike slows to a crawl, the tachometer flicks from 0 to max constantly. When the throttle is shut or eased closed the engine picks up and fires on all four cylinders this lasted for about 20 miles then everything ran as normal.

Is this a vacuum related problem or engine management? I've recently changed plugs and leads and cleaned connections to the coils.

hope you can help Im a bit stuck on this one

Johno
 

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Awfully hard to sort out long distance, these cycles are plagued with electrical failures. Also, the fuel systems (carbs?) are sufficiently old to need complete rebuild. If the spark plugs are reasonably colored (somewhere from white to mild color, not black) thus not indicating a gross fuel system problem,then id start with electrics. Cleaning connectors is utter futility.

Could be fuel starvation or weak electrics. At minimum, due to its age, Id do a complete fuel system rebuild and determine whether the charging system is failed. Provided these things havent been done already...

The tach flipping points to electrics. Fuel system shouldnt do that unless the fuel pump relay is gone off on holiday. It and the tach use pulses from the ignition coil + but I dont recall which coil its from, or whether they both use the same coil.

"Could be" ignition pulse coil but if I had a (insert your local unit of currency) for every "could be" Ive stated in my life that wasnt, Id be wealthy.

Generalities:

"Works cold not hot" = fuel too rich and fouling spark plugs when hot. Cold engine demands more fuel so carbys too rich favor cold operation. OFten detected by not needing choke to start. Electrics tend to work better when cold but the ignition electrics on the GL1200 are very reliable so that usually not the problem.

"Doesnt work hot / high speeds" Possibly electrical, ignition systems naturally get weaker as speed increases. Its an electrical physics thing.

These are just crude generalities.
 

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thanks for the pointers Dave, looks like I'm going to be busy trying to find this fault. In the meantime I'll ride the bike over the next week and see if it persists.

I've just changed the plugs and this was the first ride with them in,the old plugs were of the wrong grade (cold)and were black and slightly oily.So I'll pull the new ones at the end of the week and see where I stand.

As for the charging system I fitted a new alternater last september along with a voltmeter and new battery, voltmeter reads 13-14.5volts depending on load.

The coil feeding Tacho and fuel pump sounds promising because even though I said its miss-fireing, whilst rideing it actualy felt like running out of petrol then picked up like a turbo when throttle was shut off.

I've just flicked through one of my manuals, it shows the tachometer fed from the left coil and the fuel pump relay from the right In the meantime Ithink I'll order a couple of coils and double check the fuel pump relay

Johno
 

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If this has only happened since you changed the saddle ,,would it be possible that you have upset some wiring under the saddle?
 

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It's always the simple things we miss, but no already checked that,

cheers for the reminder!

johno
 

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JOHNO wrote:
As for the charging system I fitted a new alternater last september along with a voltmeter and new battery, voltmeter reads 13-14.5volts depending on load.
Anything under 14 indicates charging system failure, regardless of engine speed. Should be 14.3 at minimum.
 

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Another point taken, the voltmeter I have fitted is an old fashioned smiths car type connected across the accesory terminals, it may be showing a volt drop due to the age of the meter andloading of my 12cd multichanger !!!

I'll get my digital meter out and get a more accurate reading at therectifier output/batteryterminals.

if the pulse coils are about to fail what sort of symptoms will I get?
 

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Did you say that after 20 miles it ran okay? Could be bad gas or water in the gas.
 

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A good quick check on alternator voltage is to take a look at the voltmeter with the engine stopped and the start it up and see what the voltmeter shows then. You should see at least 2 volts change. Even if your meter is off a bit it should be able to show the difference in the two voltages.

:waving:
 

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Tried to ride the bike to work this morning, both front cylinders failed to fire, proved by removing plug caps so the cause is now perminent and should be easier to trace, if their is water in the fuel wouldn't it affect all four cylinders? I'll drain the carbs just to make sure.

I think by checking the voltages I'm just covering all bases,

With a digital meter engine stopped battery volts 12.9 engine running (on two cylinders)14.4 so I think that eliminates the charging system.

The resistance of the pulse coils is 1079 ohms for bothon a cold day (9C), Haynes manual states 1100-1300ohms at 20C so they look ok, however, Clymer state 295-350 ohms, which is right?

So, it still looks like the ignition coils need replacing, any more ideas anyone?
 

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I would suggest swapping the ignition coils over, then if it is the other cylinders that are not firing that may beyour answer,also check the pulse generators are working.

hope this helps as to the plugs being to cold a heat range when i bought my Aspencade it was also fitted with colderplugs as reccomended in the manual for colder climates when i changed them for the correct ones it ran like a bag of bones coughing and spluttering and backfiring on the overrun!, i put the old ones back in and it has been fine ever since dont know why but it does:clapper:
 

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Good point swapping the coils once I get them out of their nice cosy hole in the front of the frame I will swap them just to confirm it is the coils.

The plugs for an 84 should be NGK DPR8-EA-9 which is what the bike was fitted with originally, unusually due to work etc, I left the bike with somebody else for a service and they fitted DPR9-EA-9 which I believe is the standard plug for later 1200 (fuel injection?), it ran fine in the summer long distance,but wasn't running right inthe presentcold spell. So I've replaced them with the 8's

cheers

Johno
 

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Johnno the DPR9EA9 are what are now fitted in my bike i suppose it is something i will have to put up with unless someone has any ideas!. my bike is a 1986 GL1200 Aspencade model AG imported from Texas.
 

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Hi malc, this is getting interesting!

My bikeis from canada the reason your plugs are differant from mine could be due to

the differance instate of tune, do you have the emission control devices fitted?or as I said, the later 1200 were fitted with differant plugs as standardand hot weather to your bike would mean crossing a desert or something!!!!!!!!!!:cool:

johno
 

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Its got no emision control gizmo,s i have noticed that the aftermarket stainless steel exhaust system discolours very quickly especially the downpipes, but it only shows three bars on the temp gauge. and as you know there ar'nt any deserts here in the uk other than Southport beach:action:
 

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Stainless steel pipes tend to blue pretty quickly.
 

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:clapper::clapper::clapper:

I Think I've fixed it!!!!!!!!!:action:

Took the coils out and did a line check of the coil feeds, the black and white wire (common) to the right hand coil had broken down. why it only affected the bike under load who knows, probably vibration.

soldered in a new wire, and what do you know, she fired on all four and ran as sweet as a nut, as soon as all the unburnt fuel flared off!!!!!!

Thanks for all your help, I've learnt a lot more about the fuel and ignition system

:D:D:D:D:DCheers Johno
 

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Exavid the downpipes ar'nt bluing they turn a bronze colour it comes up shiny again after a lot of buffing and polishing then discolours again after a few miles, i have seen other wings with the same aftermarket exhaust system and no real discolouration? the only thing i can deduce is that my wing must be running hotter than theirs or they dont bring it out much and keep the revs down.:D

BTW They are made by Motad and the silencers are stainless steel andchrome plated afterwards, the downpipes are just stainless steel with a brushed finish.

And well done Johnno:clapper::clapper: saved you a bit of cash finding that break in the wire, bet your glad you did'nt buy a new coil.:gunhead:
 

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Your not wrong there malc at £78 + p&pfor thepair!!!!:shock:

Hey but thats what this is all about, learning from each others experience and failures.

Your exhausts are fine if they're motad like mine they bronze then go black at the hottest parts see elsewhere in the forum, there's a photo of my exhaust,

If your bike runs better with the 9's in, then thats what you should have, if your not convinced, get your carbs balanced. When I first checked my bike, some idiot had balanced the right carbs together then the left carbs together but not left with right, when I checked them with a four pot vacuum gauge the differance was enormous. Once I'd set them up the bike was more economical and a lot smoother.

yourbike running coolcould be the thermostat, has it been changed since the bike was imported?

Johno
 

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Malc Force wrote:
Its got no emision control gizmo,s i have noticed that the aftermarket stainless steel exhaust system discolours very quickly especially the downpipes, but it only shows three bars on the temp gauge. and as you know there ar'nt any deserts here in the uk other than Southport beach:action:

The temperature of the pipes and coolant are not directly related. I just worked on a 84 A with perfect reading on coolant gauge (and also checked water temp) with exhaust manifolds from 420- 600+ * F. The one that was 600+ burned black. Thats a sign of either excess fuel burnign in the manifold or burned exhaust valves. Saw burnt exhaust valves turn an automobile exhaust manifold red.

They discolor due to fire out the cylinders, and by comparing the color of the steel to a color chart, one can find the temperature - blue = about 500-550*F
 
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