bike strands me after 10 minutes of riding

BTW i'm still not convinced the problem is all solved. The other thing on my mind is the capacitor, could that be going bad and cause a problem like this if/when it gets warm or bounced around on the road? I didn't replace it, and i'm wondering if me sitting still in the garage, with the side cover off and a fan blowing on the bike might be enough to not expose the problem if the cap could be problematic

ntst8 said:

...I think it has been posted before but it would be interesting to know whether the viton tip is ethanol resistant, or whether earlier ones were of a lower grade than later ones?
I see that some grades of viton are not recommended for ethanol fuel and some are fine...

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Just to answer my own question i sent an email to Amal and had a very quick response. "For serveral years" all genuine Amal float needles have been fitted with ethanol resistant Viton, the inference being that older ones may not be and who knows on the repro ones. Mine is an older carb so that may explain my issues.

Those battery voltages under load while running at idle are fine.

Glen

oh boy, i think you guys will figure it out this time, and i will sound DUMB, but this is the first motorcycle i've ever worked on so here goes. Decided to try another test ride, started up, let it idle for 5-10 minutes to get warm so maybe the problem would happen closer to home. everything seemed fine. Took the bike off the center stand and touched the throttle and boom there was the problem! stalled out, couldn't get it to start again. Put it back on the center stand, started first kick, and ran fine. took it off the center stand, touched the throttle, and it stalled again. The problem goes away when the bike is on the center stand. Could the primary chain be too loose and causing this to happen!? wouldn't the chain stretch a little once it warms up? Like i said i never worked on a motorcycle before, so this is one of those things i don't have a feel for.

Sounds very frustrating. :twisted: I would run a ground wire DIRECTLY to the cylinder head, FROM your battery. And also, run a wire DIRECTLY from the ignition side of your switch to the coil. If still a problem, I would leave these two connected, and try switching to OEM mechanical points and see what it does then. If still a problem, I would wire the battery DIRECTLY to your coil (with a fuse of course) ... thus "hot-wiring" it; and have a quick disconnect within easy reach to shut it off. Just my 2 cents ...

That's what we've been saying all along, hot wire the thing and see if the problem goes away. I bet he's got a bad ground connection somewhere from the sound of it. Or get yourself someone that can help with the electrical/wiring problem. It can be really confusing and frustrating if you don't work in that area.

I had to wire the auxiliary pump for the irrigation system we had put in the other week, the guys couldn't figure out a simple 24v relay, so they just disconnected the hot wire and left it like that. The first time they left the white and black wire connected on the panel breaker together because it was shorted at the motor. I sure called them on that one, but I ended up having to do it myself anyhow. Doesn't anyone know how to do anything any more? Ugh. 11 grand too, I'm glad it was the other half's money, but it still smarts, I think she got burned. Don't get me started on this one. OH, I already have.

Dave
69S

"Could the primary chain be too loose and causing this to happen!?"

No. But as far as what is happening re the center stand...gotta admit, that's pretty darned weird. Maybe the change in altitude is the problem!

"Could the primary chain be too loose and causing this to happen!?"

Click to expand...

very doubtful

but, just to put your mind at ease

why don't you remove the middle cap in the primary cover(do not start engine) and stick a finger under the chain and see if you can gently push it upwards at least 3/8 to say no more than 1/2 of an inch till it stops.

Is is ok, within those arbitrary bounds, too tight this is bad, too loose, report back?


Ok, now this centerstand it runs and immediately off centerstand is an interesting problem indeed!

I can't offer anything on that right now.

BUT, I think most everyone is limiting THE problem as to having an ultimate electrical solution.

I thank DogT and others are giving good advice that your bike is not adequately "grounded".

A loose ground can be an intermittent ground and could account for those perplexing shut offs.

As your battery appears to carry correct voltage, it may as simple as too few or poor ground wires.

Your bike is POSITIVE battery terminal "ground", not negative.

I hook a nice thicker wired to my positive battery terminal and then connect it to a point on the FRAME.

In my case I run this ground right down to one of the oil filter securing bolts, first making sure that those bolts are making contact with the black paint ground off nicely around the holes they go into.

At least this then issues your battery has a good ground.

Now, it is also important to have the motor itself also grounded, and so I then secure another length of thicker wire to the left side back engine to frame plate bolt and then run it down to that same oil filter securing bolt.

These are easy and just well considered things that should be done anyway, but they may miraculously also solve your entire problem in a couple minutes work!

By the way, don't give up and curse the bike, it IS a 40 year old British bike and yes one does have to get real intimate with everything about it. There is no dealer to take it too, and you personally do need to become THE problem solver on every little issue, frustrating, perplexing, rewarding, and entertaining, we all go through this as you are are now.

You will get this solved, we will stick with you!

THe ground advice is excellent and, as noted, do not rely on the frame to actually carry the current as per the pem design - make up the separate wires and attach as Dave suggested.

For sale, 73 750. J/K :evil: tomorrow I'll try some new/better grounding and if that doesn't seem to work I'll Hotwire the ignition. Thanks for all your help guys. Batrider lives 20 minutes down the road from me and is good with electrical. Worst case I'll be buying him a lot of beer!

Kevbo, take it easy. These bike are fulls of failures and successes. As time goes by, the failures will subside the the successes will prevail. The more you win, and will win, the more confident you will be out on the road. That is to say, "the better you are, the luckier you get", Ben Hogan.

I have no less than 5 grounding points. The headlight housing, taillight area, timing cover at the mag boss, the head at the headsteady and finally a big braided copper ground at the battery.

As you have found, the low beam conductor is suspect. Those wires in the handlebar switchgear gives everyone headaches at one time or another.

Every elimination gets you closer to the solution. Quite often there are more than one solution to a given problem.

I am rooting for you,
Peter

I'll give you $10 for it. It won't take me 3 hours to get there.

You're almost there. You probably knew when you got this bike it was not a CB750. Get used to it. They need TLC and your attention. That's the best thing about them, you have to connect. Just think what the ride will be like when you figure it out and don't worry about this issue. Not that I don't worry about every bug sound that hits my helmet as I go down the road!!! So far so good.

I think the plugs look fine, carburation is not the issue. It's either fuel or electrics. With the center stand story, I think it's a grounding issue.

When I rebuilt mine, I left some convenient frame places unpainted/uncoated and I can take my Fluke 189 and attach one end to the head and read no more that 0.3 ohms to any other ground point on the bike, even through a switch.\

You will prevail.

Dave
69S

I throw my hat in the ring with broken wires going to the ignition unit, the BK/Y and BK/W.

Remember, most all intermittent failures can erroniously look like a certain condition causes it, simply by coincidence. I deal with this kind of stuff daily.

By far, the most exasperating personal intermittant failure was my 1969 Evinrude 100 HP outboard. Start and run great, except for when it didn't. Leave you stranded miles from the ramp. Long story short, it was an early type of electronic ignition, they all failed that way, good used ones were ultra rare/overpriced, no aftermarket.

concours said:

I throw my hat in the ring with broken wires going to the ignition unit, the BK/Y and BK/W.

Remember, most all intermittent failures can erroniously look like a certain condition causes it, simply by coincidence. I deal with this kind of stuff daily.

By far, the most exasperating personal intermittant failure was my 1969 Evinrude 100 HP outboard. Start and run great, except for when it didn't. Leave you stranded miles from the ramp. Long story short, it was an early type of electronic ignition, they all failed that way, good used ones were ultra rare/overpriced, no aftermarket.

Click to expand...

Those two wires are abandoned in the power arch setup.

kevbo82 said:

concours said:

I throw my hat in the ring with broken wires going to the ignition unit, the BK/Y and BK/W.

Remember, most all intermittent failures can erroniously look like a certain condition causes it, simply by coincidence. I deal with this kind of stuff daily.

By far, the most exasperating personal intermittant failure was my 1969 Evinrude 100 HP outboard. Start and run great, except for when it didn't. Leave you stranded miles from the ramp. Long story short, it was an early type of electronic ignition, they all failed that way, good used ones were ultra rare/overpriced, no aftermarket.

Click to expand...

Those two wires are abandoned in the power arch setup.

Click to expand...

Anything in the cylinder head area touching when the engine moves in the rubber mounts? Assimilator?

I can head over this weekend with my meters and such and we'll get it squared away. I'm taking one of those MSF rider safety courses both mornings but get out at 1-2pm if you will be around. Course is being held at Middle Bucks Vo-Tech so you are on the way home for me. Also Friday I will be around.

Maybe your wife put a curse on it?

Russ

batrider said:

I can head over this weekend with my meters and such and we'll get it squared away. I'm taking one of those MSF rider safety courses both mornings but get out at 1-2pm if you will be around. Course is being held at Middle Bucks Vo-Tech so you are on the way home for me. Also Friday I will be around.

Maybe your wife put a curse on it?

Russ

Click to expand...

Thanks Russ, i'll try again today, and i'll let ya know. I think it's more me in general she cursed than the bike :shock: she must only partially hate it, i told her i would sell it if she quit smoking. She's still puffing...

Ha similar mystery occurred to Wes as we got 160 miles away towards 900 mile Texas trip in October's 40' F rain. We found bad terminals to ignition,, Boyer trigger wire break, fouled plug and wet conducting key ignition [I carry test light] but still stranded hours at a time even after all these faults found and fixed road side, but still interment running only fixed once back at home to dig into loom to find hidden bad ground path connection. Wes got home on our combined pure mental physics will power for conduction. On last leg we'd waited hours for his wife in pu, but i thought [to avoid the load-unload hassle] try it one more time to run 60 miles home on it own.

almost afraid to say it, but i think we got it. of course the last place i would look is at brand new wiring, i made a wire that ran from the head steady to the coil to ground it, turns out when i tightened down the bolt on the head steady, it kinda "flattened" the ring connector and snapped it right where it was crimped. I guess the two pieces were touching enough to work, and as things heated up they would expand and separate? only thing i can come up with because i checked it for continuity when cold and my meter beeped, ran the bike till it cut out again and no continuity.

Good to hear you found the cause.