Help a newbie...mechanical issue on recently acquired '99 M750

[Ddan]

Ok, I'm seriously stumped again. I thought it was feasible that I was out of gas. Engine sounded like it was trying to start but just wouldn't turn over. I know I got the bike when it was low on fuel and as a rocked the bike back and forth I didn't hear any swoosh of liquid in the tank. So I put about a half a gallon of premium gasoline in there. As I've been trying to start it up, it sounds weaker and now all I hear is clicking (perhaps my spark plugs clicking). Looking at the Haynes guide indicates it could be many issues, none of which presented themselves until now. I feel like the most obvious thing would be something I just adjusted/fixed myself, a user error. But who knows? Any ideas?

Did you put gas in it?

[Saxofoto]

Yes, as indicated by the very sentence you've highlighted.  Am I missing something?

[motoxmann]

check my last post on page 3, I'm guessing you missed that one 

[Ddan]

Yes, as indicated by the very sentence you've highlighted.   Am I missing something?

I meant to say did you put more gas in it   

[Saxofoto]

I didn't but I probably will after I've tested a few things I should test anyway, namely the resistance measures for the coils, both pickup and ignition.

[Saxofoto]

Well, today I got to run through the critical resistance checks, thanks to the help of Motoxman, but unfortunately to no avail. The pickup coils, ignition coils - primary and secondary - and spark plug cables and boots all tested within spec. I was rooting for failure of the ignition coils or at least the cables (which, by the way, appear to be glued into the coils) so I could a) solve this problem and b) upgrade my ignition coils. So I'm back to square one, or worse, actually, because before I could at least start half the engine, plus my bike is stranded a mile away from my house/garage. Looking like tow trip to the dealer is inevitable. But I'll ask one more time for any suggestions now that I've run the resistance checks.

Quick recap: bike started like a champ when I got the bike a month ago (with no choke or throttle); one day I'm riding and it drops a cylinder; engine starts reliably but can't fire the vertical cylinder; I switch the spark plugs and the problem switched to the horizontal cylinder; I replace both spark plugs with the same NGK's that were in for the previous year and the bike fires up like it did when I first got it; I ride one mile down a straight road up to 35/40mph and something fails so I pull over and the bike stalls before I get to a stop; trying to restart it drained the battery; I recharge battery and put 2/3 gal prem gas in the tank; bike won't start at all, engine turns, ignition circuit tested for resistance with engine cold, fuses checked, got Champion spark plugs as well with no difference.

What's the next most likely culprit and/or the easiest thing to check myself before I have it towed?

 

[koko64]

What color were the plugs?

[WTSDS]

Take out the sparkplugs, connect them to the HT leads and rest them on some metal part. Crank the motor over with the starter and take a peek at the plug gaps. If there's no sparks happening you have ignition problems.

If you do see a spark at each plug pour a few mls. of petrol into each plug hole, replace the plugs and crank the motor. It should at least give a cough or even fire up. If the motor does fire up and then dies you have a fuel delivery problem.

[koko64]

Take out the sparkplugs, connect them to the HT leads and rest them on some metal part. Crank the motor over with the starter and take a peek at the plug gaps. If there's no sparks happening you have ignition problems.

If you do see a spark at each plug pour a few mls. of petrol into each plug hole, replace the plugs and crank the motor. It should at least give a cough or even fire up. If the motor does fire up and then dies you have a fuel delivery problem.

I'm startimg to think that. That could have been an excellent first reply.

Dont give up yet.

[motoxmann]

I listened to your sound file. it sounds like its getting absolutely no spark, or absolutely no fuel. do what the above guy said to triple check it's actually getting spark. if it has spark on both plugs (which I'm assuming it will due to all the tests we went through), it must be having a serious fuel supply issue; either nowhere near enough fuel, or way too much fuel (flooding).

as for what the guy above asked in reference to what color the plugs are, part of that question is also: after cranking it to try to start it, take the plugs out and look at the tips. what color are they? are they wet or dry?

[Saxofoto]

Ok. I tried these tests. Spark plugs looked like they were sparking. Tried the fuel test but didn't get it to start and I don't think I heard any "cough" either. Spark plugs appear dry after testing, and they are the same color as when they were new. My gut is leaning toward fuel supply as well after the resistance checks yesterday. When the plugs were out of the sockets, I did feel gusts of air coming out of each cylinder. Maybe it just needs more gas in the tank? If it was empty before, there's probably only 1/3 gal in there at the most (previous estimate was high). If I have a fuel issue, will it be harder to fix with more gas in the tank? While I think i can fix this, I leave town Saturday and get back Tuesday, and my diagnostic test is Wed, and I don't want to postpone that. Need to fix or tow the bike by tomorrow, basically.

[ducpainter]

Follow the fuel line down to the pump and disconnect it to see if there is enough gas to feed the pump.

If this bike has a vacuum petcock it too could be faulty even if there is gas in the tank.

[Saxofoto]

Scratch that...retried the whole test and put a little more fuel in. Got it to 'cough' but it didn't start. Tried once more with choke engaged and it started weak at first, then revved really high so I gradually let out the choke until it held on, and I gave it a little throttle. Killed the engine, waited 5 min and just restarted instantly with no choke. Looking good for now but I spoke too soon last time I thought I was in the clear. Hopefully I can get it home now and maybe try some more testing before I leave town. No need to tow til Wed if at all.

[BastrdHK]

Puts some gas in the tank!  You can always drain it out into a container if needed. When the bike is cold/first start use the choke.  I hope it is that simple for you.

[stonemaster]

reviving this old thread as it somewhat relates to my problem, the op and I have similar problems but my cylinder loss is intermittent, I had a bad coil in the past that would cut out when it got hot, on another bike, but it didnt have a pickup sensor to deal with, does the fact that it is intermittent narrow down the possibilities mention in this thread ? I to have a 99 m 750, I dont have a haynes manual yet (its on its way) but I do have a same year 900 service manual and I read that they are about the same, please advise thanx