Coils and spark intensity

[Anonymous]

While trying to cast out the demon that lives in my 81 GS750, a co-woker who owns a beemer loaned me his spark checker (a spark plug with a wire soldered to it) to see if my spark is blue or orange. It's blue, but seems very weak with an occasional orange flame. How strong should this spark be with stock parts?

My Cylmers doesn't mention any test except to swap my coils with known good ones -- like that's real easy to do :? There is some mention on the Resource's pages to coil checking and their readings, but it's hard to pick out an exact routine.

Can anyone give a clear "connect volt/ohmmeter from here to here" and what the reading should be for this bike? I'm beginning to think my problems (see GS750 (trouble) posts) may be either a heat related failure or something of that nature rather than floats not floating. I'm going to sink a float this weekend and see if it comes back up after being submerged in fuel overnight.

Thanks for any help!

Roger Moore

[Anonymous]

how many coils do you have on that bike?? 1 or 2

[Anonymous]

Two. It's a 4 cyl bike. The book has a test for the signal generator, but not for the coils.

Do you, or anyone know if this is a CDI ignition or not (Capacitive Discharge)? Accell makes a coil set, but make a set for either CDI or non-CDI.

Thanks!

[Anonymous]

2 coils and 4 cylinders means that you have 2 double fire coils--all of your spark outputs cannot be testing bad. why not use one new spark plug to test ALL 4 of your spark colorings--What makes you think that this thing your friend has is good any way-also what made you think you had weak coils?? was it your fiends spark plug testing tool((is it some sort of home made gadget)) or other symptoms??
things are not clear so i suspect that you would be getting more replys to your question if you supplied much more information

[argonsagas]

Scotty's right (He usually Is) You seem to skip around quite a bit.

Don't see alcohol saturating the floats, but it may be possible.

Don't believe your problem is floats, but it could be part of it.

See no reason to play with the coils...higher voltage makes for a hotter spark, and better burn, but if you have spark across your plug then the engine will run.

Follow the suggestion,,,,use ONE plug and check the spark then move the plug to the next wire and do the same. If they all work, then spark is not your problem.

(Coil rating is between 3 and 5 ohms across the terminals)

Try the following, in order.

Check compression and ensure it is even on all cylinders.

clean all plugs and reinstall.


In a previous post you suggested you had no filter and would drain a carb into a jar. Don't bother.. just let the fuel line run into a glass jar and let it sit for a few minutes. If you see even a tiny bit of sediment then you have a problem with your tank.

It may need to be completely cleaned and re-lined, but, for now, rinse it clean and install an in-line fuel filter on the fuel line/tube.

You said you used the carb series and they matched your carbs.

OK pull the bowls and remove the pilot jet in each carb.

Make the tool as recommended (take a single bristle from a wire brush and put it in a pencil eraser) clean the jet orifice gently.

Get a spray carb cleaner or WD 40, or other similar product.
Use the extension nozzle(plastic tube)

Place the jet orifice against the nozzle and spray it for a full second to clear out all possible junk.

Blow out any other orifice/jet available.

Remove mixture screws and springs. Do NOT lose spring.
Use the nozzle and blow it clean.

Reassemble carbs. Set float as required in each bowl.

Check the choke rail and ensure each carb is set properly. Lock in the set
screw.

Back off the idle screw completely so there is free space at its end.

Check the butterfly setting. Move it back and forth and watch to see if they operate in unison, each having the identical movement. If not then adjust until each one is barely closed. Loosen all locknuts and back off the bolts until butterfly is completely closed. Adjust until you get only barest movement in each carb.


Lift the throttle arc s l o w l y with ONE finger, and watch each butterfly. It must open in unison with the others. Check again to see that each one closes in unison.

If it does not close perfectly, adjust again.

Turn down the mixture screws LIGHTLY...just until they make contact...no more.

back off each screw one full turn only.

Reinstal on bike.

Check the operation of choke parts. Clean and Adjust as necessary.

Fill the carbs with gas via the PRIme setting on the petcock.

Turh the petcock back to run.

Start and run bike.

Shut choke down in stages as the engine peaks in RPM. As it is summer in Seattle area, choke should be shut down completely within 3 to 4 minutes.

Reset idle setting after bike is warmed up.

Drive bike for at least 5 minutes then pull plugs and check for colour.

Adjust mixture according to colour needs.

Unless the seats were damaged in a previous mixture setting one full turn should be enough to get you running well. but you may have to open by another half turn or so. Make any adjustments in quarter turn increments only until you get the mixture right.

Reset idle.

Drive on..

[Anonymous]

Thanks for the replies... It must seem as though I am jumping around a bit, but I'm baffled by this. I've had these carbs off a few times now (and they're off again now) and I have pulled all the jets and they are all clear. I've blown everything out (again) and will adjust the floats thanks to the clarification given in my float post. The "tool" my co-worker had was a new plug that could be attached to a good ground as opposed to finding a place to lay the plug on the engine to get the good ground. So when I put it all together I'll do as you all suggested. To clarify exactly what's happening:

>The bike sat for a long time (almost 7 years, but with some sparatic attempts to make it run, which it sort of did).

>I rebuilt the carbs using a chemical bath. All parts in the carb were replaced except the floats, diaphram assys, and choke assys.

>The bike started OK and ran fine for two days, but I felt it needed carb synch work. Plan on doing that soon, but the butterflies do all appear to be in synch looking at them.

>Then just before arriving to work the third morning the idle dropped to zero coming to a stop. When I restarted it, it was running rough and would surge up, and then slowly drop and die if I didn't fiddle with the throttle. Acceleration was poor, but would pull out of it if I pulled hard on the throttle.

>At work I drained fuel bowls - no crud.

>Plugs were sooty black

>Nursed it home, pulled the carbs and determine float level was too high and so I lower them to what I thought was right, but have now learned may be wrong (but I went from too high to too low, but the developing syptom will ultimately be the same, as you'll see).

>I reinstall the carbs, but while checking spark (just for the heck of it) I discover a bad connection to the ignitor from the pulse generator. Fix these connections. Check resistance of Pulse Generator = 340 ohms (this was cold) and met spe
c in book.

>The bike starts and runs great. I think -- ah ha, I got it. Floats were too high and flooding.

>I ride it to work today and for 9 miles it runs great and then I develop exactly the same symptoms as before (at almost the same location).

>Draing a couple of easy to access fuel bowls -- no visible crud.

>Check the spark plugs -- black as night.

>Go for ride at lunch -- runs fine.

>Start it to go home -- runs crappy. Nurse it home (white knuckles in Friday rush hour traffic -- Seattle 8O )

>Check the Pulse Generator = 420 ohms NOW while hot. Out of spec according to the manual (and the book says replace it if it is out of spec). How critical is this reading? They list 360 ohm MAX, but I know resistance increases with temp, so is this normal?

>Pull carbs, pull the floats, sink the floats -- they appear fine -- no apparent "saturation" as my co-worker suspected. No need to spend 70 bucks for new ones.

>Check coil resistance = 4.4 ohms. Probably OK.

>I pulled all the plugs and checked each of them and got everything from 0.5 ohms to 35 ohms. Not a one was the same. I notice that they were black, but showed signs of burning cleaner in the spark path, like they may have been attempting to "clean themselves up". I got some new plugs anyway (platinum units) that all measure like (I'm thinking) 3K ohms. I may have this wrong, but they appear to be resistor plugs. It's been a long day and I did this 5 hours ago.

>Tomorrow I will check every connection and reinstall the carbs and follow your step by step guide.

Hope this helps clear up the story.

Roger

[argonsagas]

Apologies....in that long post, I forgot to mention the very first thing you should do.

Check your spark plug numbers.....you may be using too cold a plug. That will cause black deposits that eventually foul the plug..

[Anonymous]

some day something will happen that is easy to find--- someday maybe??

[Anonymous]

It['s alive! Again...

Well, I spent most of the day working on the bike. Cleaned every connector, blew out every jet, new plugs, and added a fuel filter. It started right up and ran perfect. Pull from stops was perfect. Idle perfect. Plug color perfect. Now I'll just cross my fingers and hope it lasts more than two days.

[Anonymous]

Re: It['s alive! Again...

Well, I spent most of the day working on the bike. Cleaned every connector, blew out every jet, new plugs, and added a fuel filter. It started right up and ran perfect. Pull from stops was perfect. Idle perfect. Plug color perfect. Now I'll just cross my fingers and hope it lasts more than two days.

Did you ever play James Bond??

[argonsagas]

Scotty:

I suspect he may be too Saintly for James Bond, but may be looking for 0-60 time of 007

o
O
/ I \
I
/ \

[Anonymous]

Scotty:

I suspect he may be too Saintly for James Bond, but may be looking for 0-60 time of 007

o
O
/ I \
I
/ \

ARENT WE ALL

[Anonymous]

Hey, are you guys making fun of me? 8) You better be careful or I may just lose my santification.

[Anonymous]

Hey, are you guys making fun of me? 8) You better be careful or I may just lose my santification.

ROGER YOU ARE IN THE COMPANY OF A BUNCH OF NUTS WHO LOVE TO TALK AND FIX MOTORCYLES. IF YOUR BLOOD IS AS ANGLO SAXON AS YOUR NAME THEN YOUR SENSE OF HUMOR SHOULD FIT RIGHT IN

[argonsagas]

Hey, are you guys making fun of me? 8) You better be careful or I may just lose my santification.

Lose your sanctification.....we can't have that! Everyone loses their sanity here, but not their sanctity.

Tell you what, if you can come to Toronto tomorrow afternoon, we'll put it right for you. You can be right up here with the Pope! 8)