Question about '87 GSXR .

[pehayes]

Guzzisteve, can you please hang that cargo dolly somewhere else?
 

Patrick Hayes
Fremont CA

[JohninVT]

'87 Yamaha TW200's are infamous for an intermittent CDI.  The bike will run fine until everything gets hot and then it'll misfire, pop and eventually refuse to run.  Wait an hour and it will fire right up and run great until it gets hot and the cycle will repeat itself.  A GSX-R CDI unit is about a hundred bucks.  It is not beyond the realm of possibility that both of your 30 year old CDI's are bad.     

[guzzisteve]

Guzzisteve, can you please hang that cargo dolly somewhere else?
 

Patrick Hayes
Fremont CA

Had my fare share of playing 'OCC'

[Turin]

Some pics would be nice. I like Vintage sportbikes. Red and black or blue and white?

[KiwiKev]

Some pics would be nice. I like Vintage sportbikes. Red and black or blue and white?

And a couple of the beautiful girlfriend please :-)

[flangeman_70]

I have read the posts multiple times but I can't be clear on this:-

The first CDI starts the bike and once warm it starts misbehaving, correct?
I assume the second CDI won't start the bike cold but works perfectly when warm, correct?

Does the bike have a dual speed fuel pump? It was common on later model bikes with carbs but 87 seems a little early. This is driven by the CDI output and once X revs is reached voltage to the pump is increased by a the relay.

Check and clean connectors to battery, crank pick-up, CDI (grounding is critical), Fuel pump and all related fuses. Check the voltage at the fuel pump connectors. Check the carb fuel bowl vents are not blocked.

Report back.

Good luck!

Adam

[bigpants]

hey flangeman (never thought id say that).
So whats been happening is i go out to start the bike and it starts but misses and pops etc .
I then change cdi and it runs fine all day.
Next day i have to repeat the process.
Theres no cdi works better hot or cold , its just whichever one is fitted that day has to be changed.
Well thats how it was , yesterday it packed up all together and wouldnt start on either cdi. I checked and had no spark. I happened to have one of the origional 10 year old plugs to hand so tried it and got a good spark. Changed all four of the new plugs for the old ones and it fired up ! Just done 10 lovely miles on it and didnt miss a beat. So whats going on there ? The plugs i took out looked fine and theyre new , why would they stop working and how would changing a cdi make any difference ? And will it require a cdi change tomorrow morning ?

[bigpants]

Oh and no fuel pump or anything like that , just old tech.

[Chuck in Indiana]

Have you checked the boots and wires with an ohmmeter? It sounds to me like there is something that is overloading the CDI. FWIW, I have an aviation spark plug tester that I have modified to test automotive plugs. I have found new ones that tested bad. When they do, they exactly mimic a coil going bad on a twin cylinder lawnmower engine. Don't ask me how I know this..  (misfiring until it quits as it gets warm)
At any rate, I'd put new plugs in it and make sure I didn't have any high resistance boots or wires to start with.

[bigpants]

Well I've just been out again on the old plugs and it ran sweet. I also noticed that the ht leads from the new coils are not a good fit on the plug caps , could be losing some power there.

[Chuck in Indiana]

Well I've just been out again on the old plugs and it ran sweet. I also noticed that the ht leads from the new coils are not a good fit on the plug caps , could be losing some power there.

[/b]

And.. heating up the CDI because it's having a hard time with that gap. Have you ohmed the wires/caps yet? It's not rocket science.

[Kiwi_Roy]

With your ohmmeter measure from each plug cap to ground, they should be all identical. I'm wondering if you have those nasty carbon resistor leads.
A Guzzi typically measured 8k, your rice burner will be different but all the same.
Just one thing, if you have double ended coils with a wasted spark you may have to measure between a pair of plug caps instead of to ground, in this case each pair will be the same.

[bigpants]

Not had a chance to do my duty with the meter yet as breakdowns this morning on the way to work and again on the way back have depleted my resolve . Ruminating with a beer now but on the job tomorrow. I sprung a pin hole leak in the tank today and had ride the 30miles home one handed in the dark with petrol wicking all up my sleeve. Glad to be home.

[rodekyll]

You can fix a pinhole temporarily by rubbing a bar of soap (I used Ivory) on it.  It holds for an hour or so -- long enough to get somewhere safe before it burns down.

[bigpants]

Really , soap ! I had to settle for no more nails as it was the nearest to a glue that I could get. It held for about 1min so I gave up and used the finger.

[bigpants]

Ok I've been out with multimeter and I'm afraid I have nothing to report except my incompetence.  I cannot get any repeatable or stable results. The meter fluctuates between 30M ohm and 5M and keeps dropping and rising. I tried without a plug cap and got the same results. I'll have a coffee then go try to improve my set up.

[bigpants]

Ok I think the fluctuating results were because all I was measuring was my own resistance ! So making sure I wasn't touching anything I did get very repeatable results. O.L on the meter which I presume means overload and isn't right.

[Kiwi_Roy]

OL = open circuit I think, at least on my meters
Maybe you have the carbon core resistor leads if so find some copper core stuff

Does the cable unscrew from the coil?
If not try unscrewing it at the plug end and either shorten it by 1/2" or take a sewing pin and jamb it up the wire to make the circuit

The plug cap might measure 5k from the cable connection to the cap, that would be normal for a resistor cap but you shouldn't have resistor cap & resistor leads.

As I said before if you have double ended coils like a lot of 4 cylinder rice burners you probably wont get a circuit to ground but should get a circuit from 1 cap to the other.
I'm only guessing when I say 8,000 Ohms just look for the same value in the other coil.
I found this schematic, it confirms the double ended coils are not grounded, they spark through both plugs in series. But it also confirms you should get a circuit between plug caps.
http://www.classiccycles.org/media//DIR_1653304/DIR_1762756/1b0aa491b60a7ac3ffff8496ffffe415.pdf

[bigpants]

Thanks again Roy , you're gradually working through my entire collection of dilapidated bikes. The coils are copper core. I'm pretty sure a defective lead on my meter is at fault , I'll need a meter to check my meter , I forsee an infinite series of meters. I do have good news though - we can put this thread to bed , she's fixed. I'm sure no one will be surprised to discover the problem was just a corroded wire deep down in the chassis. I was trying to get the rear brake light working and had to stick a finger into no man's land behind the frame , the engine cut out. Restarted and repeated and same result. It was a power feed to the fuse box. The terminal always read battery voltage but if I touched the hidden wire the engine cut out. Stripped it out , cut in a new section and bike fired up , Rev counter stable and hasn't missed a beat since even through a pea souper this morning. I've learnt a few things this time such as always check your meter , I've got 20M ohm resistance and 13v ain't always 13v. Thanks for all the help and advice everyone. I promise not to start working on my scooter for at least a month.