I'm missing some good riding

[kcsphil1]

:sick2: I originally posted this in the Classic Shadow forum, but it was wisely suggested I move it here:

SInce we don't seem to have the general repair forum anymore I'll ask the question here: Any ideas why my '83 750 VT won't start? I have (On the good side):
1) replaced bettery and spark plugs with consistant spark;
2) replaced/rebuilt starter clutch;
3) rebuilt starter motor (new brushes, pads, holders, etc);
4) replaced crankcase gasket around the starter clutch assembly;
new fuel filter installed the correct direction;
5) good gas;
6) rebuilt and cleaned carbs.

On the bad side:
1) front cylinder has about 110 psi compression; rear has 125 psi compression;
2) All I get with a full charge on the battery is a lot of backfiring with the choke wide open and nothing but starter sounds with the choke shut down. :furious2:

She so wants to go, and with our mild winter out here I so want to get her going. Could have ridden out to the mountains today - God what scenery.

Thanks in advance!

So on the other Forum the guys put out the ideas of 1) checking the Carbs again (but what needs checked they didn't say) and 2) checking the timing. My Clymer manual syas you need to have the engine idling at normal temp to do that, and I'm not really sure how to get to an engine idling at normal temp if it won't start.

So have at it and Thanks.
:jamming:

[Machinehead]

Sorry to hear you're missing good riding weather.

...anyways...just to get this out of the way...what happens when you jumpstart it using an auto battery (or good booster)?

[M@Man]

I'll post it here too...:happy:

You mentioned it has "consistant spark", and you rebuilt the carbs. An engine needs three things to run...Fuel/Air/Spark (at the right time).
If the carbs were done, and the spark plugs are sparkin', you mentioned that it backfires. So my best guesstimate with the information you have given me is the timing is retarded.
Maybe a little more information can help...
Is it a strong spark?
Can you smell gas at the tail pipe end?
The backfire, is it on the intake or exhaust?

Clymer manuals are just guide lines, they're not written in stone. I have set timing on engines "on the nose" by using just my thumb over the spark plug hole, and watching the timing mark while turning the engine manualy. It's not always exact, but it's a good place to start.
I know it's very agrivating when you hear your engine try to fire and know that you are so close, I've been there before. I see you moved this post into the general area, so maybe someone out there can help.
Anyone?

M@

[amazngrace]

Just two questions I should have thought of earlier:

1. What was it running like before you did the work?

2. Have you tried putting gas down the intake?

[Tangledj]

What about coils,and silinoids?

[kcsphil1]

Lots to answer, so I'll try to get it all in:

1) I get the same response with my car battery as I do with the motorcycle battery.

2) Can't say about the coils and the solinoid - From what I have learned, the solenoid being bad would prevent the starter motor from turning over, so the fact that the starter motor works properly points me to a good solenoid. Coild are another matter - I am trying to get a meter to test the resistance, so we will see.

3) It wasn't running before I started the work - I got it with a broken starter clutch, and had to get that dealt with before I could really look at this other stuff.

4) I don't smell gas anywhere, nbut the backfire is definitely coming out the tail pipe.

I'll have a look tomorrow at setting the timing by hand and see what happens.

And thanks for all the input.

[Machinehead]

At this point you're going to have to determine whether it is a fuel or firing issue. Remove and clean the plugs. Post the condition/appearance. Reinstall all but one and use the last one to test for spark. Install it into the boot and place the end against the cylinder head using a properly insulated pair of pliers. Fat blue spark is what you're looking for when you turn the engine over.

[Machinehead]

Also...I wouldn't be concerned with the timing at this point (unless top end work was performed). The bike is equipped with an electronic ignition and to advance/retard it is not a common procedure used when troubleshooting a no start issue.

[kcsphil1]

So here's where you CAN jump on me for NOOB-ness (Ha, I made up a word on my first cup of coffee :beatnik: ):

What constitutes fat when relating to spark? I have blue spark all the time when I try the block test and it seems to cover the firing area on the plug, but I wouldn't call that fat.

After I get done with Easter stuff today - good church boy that I am, I'll get some digital pics of the plug and post them. And I may ven get a picture of the bike for the GArage - afterall, if it's a garage, then pics of bikes being worked on seem appropriate. :cheers:

[M@Man]

I still don't think the spark is an issue here, becuse it was mentioned that it backfires through the exhaust. That indicates to me that it is firing hot enough to ingnite the fuel (which by the way eliminates the question on weather or not it's getting fuel.) It doesn't matter if it's electronic ignition or points, the ignition still relies on the timing being correct and becuse it was also mentioned that the bike didn't run when he got it we can't be sure if the timing is correct. But...I may be wrong,:headscrat it never hurts to check other things too.

M@

[Machinehead]

I've heard a twin backfire through the pipes when the battery charge was too low.

kcsphil1,
Pick up a can of starter fluid and spray a small amount into the carbs and retry. Also, try with full choke and no throttle then with no choke.

Although I'm begining to believe the fault may be in the IGN system the reason I wouldn't point the finger at the timing is that a timing issue is usually the fault of the ICU and although that or one of the other components in the IGN system may be at fault I find it best to take small steps to eliminate all other possibilities first.

Also it does matter that this is an electronic IGN set-up as there are no settings that can stray from proper adjustment. The only way for the system to faulter is from component failure or improper installation.

[kcsphil1]

Well friends here is the Monday update: I tried the starter fluid trick, and while the backfire gets strong with the fluid in the carbs, choke full on and no throttle, there is no improvement otherwise. I did smell gas in the carbs when I took off the air hood - a good sign I hope. I pulled the plugs, and have included a picture in this post for you to see for yourselves. One of them is a little gray around the ceramic on the electrode, otherwise they look right out of the box. After reinstalling them, I ran the cylinder head test. I still get what I call a consistant spark, which moves back and forth across the metal part of the electorde just like on a commercial on the Speed Channel. Any other ideas?

[Machinehead]

Any other ideas?



Yes, but I'll sleep on them. You have practically removed a fuel issue by using the starter fluid and have given all a new slate to work with.

Do you have access to a DMM?

[amazngrace]

Just as a last check kind of thing. try the starter
fluid with the choke off>
...ED

[fegs]

You need to go in process of elimination:
1. Is there clean fuel
2. Is the fuel getting to the carbs
3. Do you have good spark

I would not worry about the timing, it is adjusted electronically. Backfire on a bike can be created by a defective battery (low on charge or going bad {internal cell failure}). If the bike was running before you laid hands on it, then go back and double check your work. Believe it or not, I had a friend who replaced the plugs and installed the wires incorrectly, did not start.


fegs...

[M@Man]

Okay, I see what you guys are talkin' about now. Boy do I feel a little :stupid: Anyway, what your gettin' at is...what's called the "spark units" on this toublesome bike maybe bad? Causing it not to spark within specs.

M@<----:embarasse

[fegs]

M@man:
How did this problem start? This will help greatly.

fegs...

[kcsphil1]

You need to go in process of elimination:
1. Is there clean fuel
2. Is the fuel getting to the carbs
3. Do you have good spark

I would not worry about the timing, it is adjusted electronically. Backfire on a bike can be created by a defective battery (low on charge or going bad {internal cell failure}). If the bike was running before you laid hands on it, then go back and double check your work. Believe it or not, I had a friend who replaced the plugs and installed the wires incorrectly, did not start.


fegs...


I think the answers are in other of my posts, but for the sake of clarity:

1) The fuel is about a month old but went from the gas station into a new plastic gas can (which I had to buy for the occasion). I put it in the bike, tried to start it, and ten promptly came down with pneumonia (not from the bike). Had to let it sit while I recouped, and have been abck at it since.

2) When I tried the starter fluid idea last night, there was a definite gas smell from the carbs when I took off the Air intake hood/shroud. The backfire is also going to the exhaust, so I am assuming there is fuel in the carbs.

3) I do have a spark on the put it to the block test. It is blue, solid, consistent, and as I posted last night, it dances around really good on the electrode.

4) I got the bike, in part, because its previous owner was storing it outside uncovered and his wife wouldn't let him fix it up. I had it running once or twice before I broke it down. I did replace the plugs, but so far, I have not replaced any of the wiring itself, nor any of the electronic components.

Does that clear it up? :sasmokin:

[RustyJake]

did you have the carb(s) apart? I'm not an expert on carbs but if you are smelling fuel as well as getting that backfire out the exhaust maybe the floats are stuck or not set right.
Just a thought, but I'm sure one of the carb experts will chime in with their input.

[M@Man]

I believe kcsphil1 also mentioned the battery is new, starter & carbs rebuilt...

Just click on kcsphil1's name and veiw his profile, then read all posts by him...ever single post he's left so far is about this problem. So if anyone out there can help, I'm sure he'll post a pic of boobs or sumpthin'. Cuz we all know how frustraiting a no start problem can be.

I think it's still "technically" a timing issue, but know I believe the cause is electronic becuse...(I'm quoting some of Machinehead)..."a timing issue is usually the fault of the ICU" & "
The only way for the system to faulter is from component failure or improper installation."


So it comes down too....anyone?

M@

[kcsphil1]

did you have the carb(s) apart? I'm not an expert on carbs but if you are smelling fuel as well as getting that backfire out the exhaust maybe the floats are stuck or not set right.
Just a thought, but I'm sure one of the carb experts will chime in with their input.

I did have the Carbs apart, and replaced the float components as part of the rebuild. On mine, the float only fits in one way, with the needle suspended from it, so I'd be hard pressied to see how it might have got in wrong - but hey, they keep electing . . . oh right, this isn't a plitical forum. Sorry I forgot myself for a moment. :sasmokin: Serious, I could have them apart again ina jiffy, but I'd rather not unless there is no other alternative - and it sound like there are other alternatives. :help:

[Machinehead]

I really don't think that tearing the carbs apart again will solve the starting issue. You've practically removed that by using the starting fluid. If there is a carb related problem you can add it to the end of the list.

Sorry to back track here, but would it be possible to record and upload a sound clip of the starter turning the engine over? If this isn't possible you should have the starter tested. The starter may be turning the engine over, but I've found that if it isn't spinning fast enough it just won't crank. If you are sure the starting system is in check let us know.

[RAZOR]

had a 85 v445 magna that was doing the same a freind and i diagnosed it as
a bad spark unit and aven got with a honda mechanic and he said that would
be the best and first thing he would do.-(downfall i never did fix it i could not
find a used spark unit nowhere and i was not about to spend 250-300 for
the damn things and it takes 2- so 600 smakers for new ones was not
practical for that old of a bike for me at the time)-
--------spark units i would say is the problem just my 2-cents--------

[kcsphil1]

So I came home today and figured that if i couldn't ride, I'd at least see if icould do something. So I tried the starter fluid, choke all the way open throttle all the way up trick. For about 3.2 seconds she ran faster then she had yet, and sounded on the verge of starting. Then the head light went off, the motor started, and she died. I mean dead. I checked all the friggin fuses and the fusible link, and they are all A-O-Freakin K. Next I pulloed apart, cleaned, and put back to gether every electrical connection I could find. Still nothing. The battery shows a full charge, but put in the key, turn it and punch the starter, and there is no movement at all, no head lights no nothing.

So I came in had a beer, and watched a few minutes of American Chopper - and I thought my family had challenges! SO here's my latest idea - if we can all collectively come up with a diagnosis by this weekend, I've got the time to do the repair right if I start early. Otherwise, I will have to sell her for what i can get for the parts, and start over. Then again, maybe I could get enough dough together to do a decnet cafe' racer repro.

You have all been awsome, and I owe eeveryone a beer some day.

[M@Man]

Oh man! :furious2: I hate electical trouble shooting!!:furious3:

I'm just guessin' here...if you've got a multimeter you can test this....keep in mind I'm guessing. Ignition switch faulty? :headscrat

M@

[Machinehead]

This could possibly be related to a faulty safety switch or one that's posing an intermittent problem or as M@Man suggested, the IGN sw.

Nevertheless, you'll have to pinpoint it .

Can you record the sound of the starter turning the motor over?

[Tangledj]

Wishing you luck bro.I dont get it ,you've got fire,and fuel there should be combustion....wiring maybe?just for the hell of it.undo the switch on the kickstand,and also the neutral if it has one.Im wondering if a ground on a saftey switch might be making some contact.Crazier shit has happened.But im thinking something simple like this might have gone wrong more so than jumping time.

[fegs]

So I came home today and figured that if i couldn't ride, I'd at least see if icould do something. So I tried the starter fluid, choke all the way open throttle all the way up trick. For about 3.2 seconds she ran faster then she had yet, and sounded on the verge of starting. Then the head light went off, the motor started, and she died. I mean dead. I checked all the friggin fuses and the fusible link, and they are all A-O-Freakin K. Next I pulloed apart, cleaned, and put back to gether every electrical connection I could find. Still nothing. The battery shows a full charge, but put in the key, turn it and punch the starter, and there is no movement at all, no head lights no nothing.

So I came in had a beer, and watched a few minutes of American Chopper - and I thought my family had challenges! SO here's my latest idea - if we can all collectively come up with a diagnosis by this weekend, I've got the time to do the repair right if I start early. Otherwise, I will have to sell her for what i can get for the parts, and start over. Then again, maybe I could get enough dough together to do a decnet cafe' racer repro.

You have all been awsome, and I owe eeveryone a beer some day.


OK, based on what I have read, here is what I would do:
1. Start at the battery with a test light or voltmeter and check for voltage at the starter, etc. If this is ok:

2. Make sure (and I know this may sound stupid) that your engine is not locked. You can push the bike (1st engaged, clutch in) and release the clutch. Much like a standard vehicle, the engine should want to start. If this is ok:

3. Go back to your battery and connections. It seems to me that if your light and starter are not worrking you have an electrical open or no voltage to those units. Check every fuse and every connection. Worst case scenario, go by the dealer and get some feedback from one of the techs there. For the most part they are willing to provide some sort of information to get you started.

fegs...

[Machinehead]

I want to add that the headlight circuit is routed through the starter switch. When the starter switch is pressed the power to the headlight is cut. The contacts on this switch may be corroded and need cleaning. You may want to clean the kill switch sw. contacts while the housing is apart as well.

If you cannot post a sound clip of the starter motor I'd have it checked. Most auto parts places can check'em.

The starting system will have to be at 100% before you can move on to any ignition problems.

[fegs]

I want to add that the headlight circuit is routed through the starter switch. When the starter switch is pressed the power to the headlight is cut. The contacts on this switch may be corroded and need cleaning. You may want to clean the kill switch sw. contacts while the housing is apart as well.

If you cannot post a sound clip of the starter motor I'd have it checked. Most auto parts places can check'em.

The starting system will have to be at 100% before you can move on to any ignition problems.


Machinehead: I agree 100%. Glad to see we are speaking the same language, you must have a technical background as well.

fegs...

[M@Man]

Machinehead: I agree 100%. Glad to see we are speaking the same language, you must have a technical background as well.

fegs...

Well, the three of us agree here, it's most likely in the safety switch, starter switch, or ignition switch.

It's an 83 VT750 we're dealing with, so I have to ask, did they have a switch on the kickstand then? Tangledj mentioned it, I know my 86 VT700 doesn't have one, but I just had that problem with Jeannie's Virago about a week ago.

M@

[Tangledj]

I dont know if it has that switch either bro.Just seems like it could be something simple like that.I fucking hate everything about electrical!! grrrrrr

[Machinehead]

Starting circuit and troubleshooter..

[fegs]

Well, the three of us agree here, it's most likely in the safety switch, starter switch, or ignition switch.

It's an 83 VT750 we're dealing with, so I have to ask, did they have a switch on the kickstand then? Tangledj mentioned it, I know my 86 VT700 doesn't have one, but I just had that problem with Jeannie's Virago about a week ago.

M@

It is easy to see it, look at your stand or right behind it. Basically, this switch will not have continuity with the stand down and vise versa.

fegs...

[M@Man]

I was just wondering, could the no start problem he was having before it all went dead be related to a faulty ignition switch?

If I'm reading these schematics right, the "spark units" are linked into the ignition switch too, along with just about everything else.

M@

[kcsphil1]

So I went out last night and got a DMM - don't try to find one at Schuck's they aren't carrying them anymore no matter what the web site said - and got up this AM and tore into it. Every thing points to the ignition switch as the newest culprit! I know, it won't come as a surprise to the jury- There is battery voltage to the switch (same 11.3 volts I read on the battery - and yes it needs a charge), but after tracing down where the starter button plugs into the electrical block, I tested with the ignition switch turned on and got a whopping 0.05 volts! :eek2: So, if the voltgae isn't making it past the ignition switch . . . :sign chil . . . seems like the most likely candidate. I also checked the fuse in the headlight and it was a bit white on the inside - probably oxydized - but I changed it anyway.

So I'm off to the salvaged bike yard to see if they have a switch - I know, used parts in the bike and all, but I ain't got the coin for anew OEM one just now (Unless they are really cheap). Then a new battery just to be safe and a new Battery Tender charger just for this bike - my other charger is a 3 mode and is porbably ok. I did get a $ 100 performance award this week - so it's going to the bike.

I should have itt all back together and ready for another test by tomorrow afternoon - I'll let ya know! :guitarist

[Tangledj]

Sweet,I hope this cures your trouble.I know you've worried alot over this.I hope it
fires right up for ya! :wink_2:

[SmokeShowin]

Great, hope that solves the problem! :luxhello:

[Machinehead]

I'm not very clear on where you actually placed the meter leads to test the IGN SW.

According to the schematic it looks as if the starter sw draws off the headlight fuse. The B/R wire in the housing. You'll have to disassemble the housing to verify what contact is exactly opposite from the contact that the Y/R wire is terminated at. The opposite contact should be hot with key ON (make sure that the (-) lead is properly grounded.

Testing the IGN SW is straight forward. There're 5 wires at the connector or terminated at the switch. The red one is the hot one. The other four should have voltage present when key is ON. Check that all wires are still properly soldered to the switch if you don't read voltage.

[Machinehead]

btw....do you have a schematic/wiring diagram?

[kcsphil1]

I've got the wiring schematics that come in the Clymer manual, so that's what I'm working off of. I basically dsiassembled the whole head light front end complex to get at all the wiring. The ignition switch plug into the panel that has the fuses on it (under the panel lights) with two sets of plugs - one red wire/black wire plug to bring in the power (which matches the voltage reading I get from the bettery, so I know the power is getting that far), and then three seperate red wires in abundle which plug into another part of the panel (to deliver the power after it gets past the switch). I can't figure a way to get into the thing to check soldering, but the new one should be here Wednesday.

I plan to spend some time tonight going through the wiring to see what else reads bad.

[M@Man]

You sound like a man with a plan...Keep up posted (pardon the pun :lol: )

M@

[Machinehead]

I'm still not sure if we are on the same page. I've attached part of the diagram taken from the service manual (Helm) I have.....is it the same?

[kcsphil1]

That's the one, though the CLymer draws it out a little differently - style issue, not substance. My new ignition switch arrives tomorrow, so I'll get it plugged in and see what's next.

On the down side I have continued my testing of those other components I can test with the bike in its present condition. The pulse generators are reading resistance below the manual's values, but since the manual gives the resistance at 60 degree F and we only got to 50 the last two days . . . I am not sure the pulsers are completly up to snuff, but we'll see.

[Machinehead]

The pulse generators are part of the ignition system and will not affect the starting system. Once your starting issues are relieved you'll be able to address the ignition system. We ain't going anywhere or taking a back seat on this.

ok?

[Machinehead]

oh...and btw....the color coding of the insulation is what my main concern was as I don't recall what was "under the hood" of my old 83 and the Helm diagram doesn't list three grouped wires with red insulation.

Is there any way you can crop a shot of the cylmer schematic that displays this?

[Tangledj]

dang man,I hope your getting some head way.I hope the new stuff helps.
If all else fails have you tried undoing everything but the bare essentials.disconnect all the lights,signals,horn.Maybe even the kill switch,neutral
switch,and kickstand switch if it has one.I never heard you say.
Dang buddy,I hope you post with good news!

[M@Man]

Is there any way you can crop a shot of the cylmer schematic that displays this?

I''ve got one here, I'm gonna try to scan it and get it posted.

M@

[M@Man]

Here it is, Machinehead.
Does this help?

M@

[kcsphil1]

SO here's a quick update - the shop I get my parts from f'd the order somehow, so the switch is now supposed to be here tomorrow instead of yesterday! :furious2: Thank God we have good buses here in Seattle, or I might have to put gas in the car and DRIVE!

[M@Man]

Hey kcsphil1, I'm not sure if I missed a post about it somewhere or not, but...
are you up an runnin' yet?

M@

[kcsphil1]

That would be a big NOPE. I did finally get the ignition switch - a week late I will add - and it hasn't changed much. I've put about 10 hours this week into tracing wiring from the Clymer wiring diagram, but to no avail. I'm going away with my daughters fro SPring break next week, and I am supposed to have a real bike mechanic come to the house the week after and doa a real diagnostic - under the table like. I'll start a new thread when that happens.

Og course, I did see a'72 CB 750 tricked out as a cafe racer today - and while it's not a Shadow, is was pretty sick!

[M@Man]

Have fun @ Spring break! Make sure you post pix of that, and (like you said) let us know what was wrong with the bike so we can all smak our head and ask "Now how did we overlook that?"

M@

[Machinehead]

Hey kcsphil1,

Don't get bummed yet, it's kinda difficult at best doin' this over the www and I'm sorry your new switch didn't resolve it.

Anyway, Is there power to the headlight, instrument idicators, tail light etc ?