Topic: my bike won't run >:-(

[dakeddie]

Last weekend my buddy and I went out of town on a bike trip.  On the way home we stopped for a break at a popular climbing spot.  We sat back and watched some climbers on a multipitch wall, but when it was time to go, I started my bike up, slapped it into first and took off only to have it die a second later.  I couldn't get it started again for awhile.  Eventually I gave it rest and tried again and it did start only to die again once i started moving.  I managed to get it home by keeping the revs at all times... above 4000rpm.

I thought the problem might have been my slow jets being clogged cause I have this rubbery coating crap in my tank that is flaking off (I guess it might be Kreme, but I don't really know what it is).   I know the slow jets have extra tiny holes so I thought maybe some of the crap got past the inline fuel filters i have.  I cleaned out all my jets and made sure my filters flowed, but the bike still only ran at high rpms and always needed a rest before being started.

Eventually, I couldn't get it to start at all and I was thoroughly convinced that the problem wasn't fuel flow, so I check my spark... I had none.  No spark on any of the cylinders.  I had this problem a few weeks ago and it ended up being the battery, which I had replaced then.  At this point it was dark, and I decided to leave it for the next day.  In the morning, I pulled the cyl #1 lead and plugged in an old plug and tried to start it with a DMM across the battery terminals.  The battery had rebounded over the night from ~11.8V to 12.5V.  I saw one or two sparks and then no more.  The battery fell to ~12V.  I figured the charging system was the problem.

Today I charged up the battery and planned to figure out what was wrong with my charging system.  While the battery was recharging, I checked the rectifier, and the field coil... both fine.  And all the bullet connectors from the alternator are in beautiful condition, btw.  When I put my recharged battery back in, I expected it to start right up, but it didn't at all, not even a single spark.  I still have no spark on any of the cylinders.

What might my problem be?  It seems unlikely that both the coils would go, or both the points.  I know things might've changed, but I checked those a few weeks ago just before I replaced the battery.  I'm stuck.

Any tips before completely rip the electricals apart?

It's a 750k3, btw.

[techy5025]

I know the ignition system is sensitive to low battery voltage. Why
don't you try jumping the bike with a car battery and see if it starts
right up. If so you can start chasing charging issues...if not ignition
or gas issues.

Jim

[750goes]

Start with one problem at  time and work that through, you are giving multiple possibilities with the information provided.

1. Check your CLEAN and FREE flow of fuel from tank through to carbs to plugs, and if it's dirty or contaminated in one area - FIX that first, then go to the next step.

post the results of your fuel investigations, and how you checked and confirmed you have good clean flowing fuel from tank to carbs.

I'm not having a shot at you, just too many possible answers from the desription you have given..

good luck, let us know

[techy5025]

Based on the fact that the bike was running OK and suddenly had a problem,
I doubt if you are having fuel problems. Sounds like something electrical...battery,
alternator, bad connection, etc.

I would check everything under the points cover also....voltage on points when
open, etc. Also make sure your kill switch is not bad. The battery voltage goes
from the key switch into your headlight, into and out of the kill switch and then
to both coils. I had a bad connection there once that killed the bike. 

Jim

[dakeddie]

Yeah... I'm convinced that the problem is not the fuel... I just thought it was initially.  Definitely my problem is that I have no spark.

After a number of tries of starting it, the battery still had 12.5V on it.  This should be enough to make a spark, right?  I've considered that the brand new battery I got is a dud.  But I assume that if it holds a voltage of say about 12.5V, it should be ok.

I initially resisted checking all the nitty gritty electrical details cause I already did that few weeks ago, but I guess I'll have to do it again.   

[techy5025]

I'll bet you have no voltage at the coils...hence not at the points.
Smells of bad connection. 

Jim

[750goes]

Ok if definitely not a fuel problem, then probably a loose connection in the ignition system, broken wire, bad switch, crappy connection, whatever etc..

Your dmm should show where the bad connection is, just check each wire for continuity and voltage for any failures..

A good site I found for looking at individual circuits that I could understand was
http://oldmanhonda.com/MC/wiring.html
select the 750 bit, then do the flash player bit, then turn everything off then turn one circuit on - coils will do.
you can also print each circuit if you like - helped me lots understanding my spaghetti wiring.
try this and let us know what happens. .

[TwoTired]

I'd be checking the point gaps and contact condition.  Bright, shiny, smooth, set gap, static time with a twelve volt light bulb.  And try it again.

Do you routinely use the stop-run-stop switch?  This blocks power to the coils and points.  A fault there and ... no spark.


You don't say your method for checking spark.
So, see if your spark plugs' center electrode insulator is carboned up.  This would essentially short the plugs out so the voltage would bleed through the carbon soot instead of jump the electrode gap.

Cheers,

[dakeddie]

To check spark, I use an old plug connected to one of the leads and hold it against the case.  There are brand new plugs in the bike.

I do use the kill switch, but it's practically brand new.  I even disassembled it a few weeks ago when trying to debug my problem... all shiney with factory grease.  But I will check it in the morning, aswell as the voltage across the points and resistance of the coils etc.

The thing is that the way the bike was behaving before it completely wouldn't start reeks of a bad battery... the way it would start, then die and not start again until it sat around for a bit.  Now I wonder if my battery that I replaced a few weeks ago was actually dead.  It definitely didn't hurt to replace it as it will only hold 11.8V, but I wonder if I actually fixed the problem or just aleviated a symptom.

Has anyone ever had a brand new battery that was bad?  Or am I just making up solutions in my mind?

If it were the points, I'd expect that there would be occasional sparks, not no sparks at all.  And wouldn't it be odd to have both points go completely bad?

If the bike has no problem turning over, is it safe to assume that the ground strap is good?

Thanks so much for all your help, btw.

[750goes]

Might be as simple as checking the bullet connections from the points lead going to the coils (near where the rear brake light switch is), they connect up with both blue and yellow wires and run to the coils.. if this has come loose or connection is bad, bike will still turnover but there would be no spark.... (I think)... .

[turtle]

Sounds like coils to me. They go kinda sudden and terminal.

[my78k]

Doubt it is the coils themselves as yeah they do go kinda sudden and terminal but not usually at the same time...

This leads me to think it's a connection.

As for checking the battery could you not just do a full charge over night...then throw the dmm on it and watch for drain. I believe it was TT who mentioned this a few days ago in a post I read but basically it was something like at full charge the battery will read in the neighbourhood of 14 volts and then will drain on its own to around 13.6 or so while it finds its own equilibrium (double check the figures with twotired or look thru the older posts). After that the charge should stay right around there if the battery is good. Could always use an ammeter I guess to be certain but I doubt it being a dead battery.

Dennis

[jdpas29]

if you're charging your battery overnight, make sure you're using the 12V -  2 amp setting.

[TwoTired]

If the electric start cranks the motor vigorously, the battery has proven it can deliver 150 amps, at least for a short duration.  A fully charged new battery ought to do this for about 90 seconds (carefull not to overheat your starter motor, use 30 second engagement periods with cool down time in between).

There are some people that confuse cranking the motor, with engine catching and running, so you should probably clarify which symptom you mean when you say it won't start.

Fully charged batteries can attain a 14.5 volt surcharge level without damage.  When removed from the charger, they will discharge quickly  at first and then eventually find equilibrium at about 12.6 - 12.8 volts and still have full rated power.  They will self discharge after that at a 1% perday rate.

You may wish to measure your voltage at the coils or across the points during electric start.  Stick a matchbook cover in the point contacts as an insulator.  If the voltage falls below 9 V or so, then measure the volts across the battery terminals during electric start.  The differential is your wiring, connector, switch, and coil losses. 

It would be very odd if both coils failed simultaneously of natural causes.  But, a couple of well placed hatchet blows should do it.

Look inside the points cover for water. Water turns to steam when heated and then condensenses on the points,  Open points with a water bridge between them will prevent spark.
If you find water in there, make yourself a new cover gasket from hardware store neoprene.  I do this to all my SOHC4's now.  The stock cork ones are, at best, one time use only.

Cheers,

[dakeddie]

Good news!  I found the problem.  It was a broken wire from the kill switch to the coil... the Bl/Wt wire.  It had gotten pinched at the steering head.  I soldered in a new peice and kaboom, the bike runs better than in has in months.

I think that yes, the problem I had a few weeks ago was not entirely the battery.

Thanks again for all the help.

[my78k]

I generally refrain form using terms like "Kaboom" when discussing electricals!!! Ofcourse once or twice it has been a very accurate description unfortunately...  

[Orcinus]

Hmmm, my thoughts exactly....