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Continued starting issues

  • Thread starter Thread starter Topman
  • Start date Start date
T

Topman

Guest
After some real trouble, I finally got the 750 running pretty regularly, still not riding her due to an as of yet unsolved clutch problem. Got the tach to stop jumping around, and figured I'd do a vacuum sync one of these days. Got off work too late to wrench last night but was showing my progress to a buddy. Cranked her up and she started and idled for a bit around 1k and unfortunately I had something in my other hand so I didn't have the opportunity to play with the throttle as I've had to in order to get her to stay at a consistent RPM in order to warm up enough to idle properly. Consequently she slowly but surely dropped in RPM before completely dying. That's not where I was surprised, it was when I couldn't get her to start again that I became confused. Even hooked her up to the tender for a few minutes just in case I had drained too much of the battery to get a good spark so soon, but nothing. He mentioned it smelled like it was running too rich, after making some adjustments with the mixture screws and such, I ended up giving in for the night.

Went back to her tonight to try and do the sync, she cranked up nicely, I had to play with the throttle a bit as usual in order to get her to a comfortable RPM for long enough to warm up to a point where I could let go and she would idle without dying. Had her run for several minutes to warm up in order to do the sync, shut her down and prepped everything for the sync, and as per usual she started up fine being warm and all. Calibrated the tuner, and did the sync as best I could, during which the idle was a regular problem, it would every once in a while start to creep very slowly up to around 2k, I'd lower it back down to around 1.25k, work on syncing them and notice it creeping one way or the other (up around 2 or down around 900). Needless to say this made it quite difficult to sync. I got it as close as I could and got fed up, shut her down and thought about it. The more I thought, the more I noticed that when she is running, there does seem to be a constant issue with the idle staying in one spot. Obviously I'm not riding so I do a lot of observing as it idles and realized I tend to play with the idle screw a lot. In any case, I let her sit for a while as I made some dinner to think it over, by the time I got back out there, she had pretty well cooled down. I went to start her again and see what I could do assuming she would start right up, she wanted to die again, and me not expecting it, I wasn't ready to grab the throttle before she died down. Once again, wouldn't start again after that.

I'm at a loss for what's happening with this one. Tried to do some research before posting, but as for the idle not staying, all I've got is potential air leaks. I replaced all the boots from the air box to the carbs, the carb boots to the engine are in great shape, replaced the boot connecting the two air boxes, replaced the air filter, and sealed air box with new weatherstripping. As for not starting if the first cranks doesn't fully succeed, I can't even fathom where to begin with that.

Any suggestions are truly appreciated, I want so bad to ride this baby before it's too cold up here.
 
Hi,

Can you adjust the idle with the main idle set knob? Have you adjusted the valves? Have you cleaned the carbs? Have you replaced the intake boots and O-rings? Is the air intake system (air box, air box boots) tight, no leaks? Have you tested the charging system?


Thank you for your indulgence,

BassCliff
 
After you get your mixture screws set to three turns out, you need to work on your starting technique. :-k

First rule: Do not touch the throttle. :eek:

Second rule: DO NOT TOUCH THE THROTTLE. :-k
Third rule: DO NOT TOUCH THE THROTTLE.
well1.gif


You get the idea yet? You set the "choke" to whatever works for your bike, then hit the button to start it.
If you need to modulate the engine speed, do it with the "choke" control.
When it is running well enough (when you get your mixture set, you should be able to ride in 30 seconds :p),
THEN you can put it in gear and use the throttle to to leave.

.
 
when it doesnt start did you check for spark my bike had similar symptons to yours.I too buggered around with the screws and carbs checked for spark and found I only had spark every now and then changed to dyna-s ignition and havent had a problem since cheers.
 
Mixture screws are 3 turns out.

Steve, I wasn't starting with the throttle. I'd start the bike and then blip the throttle just to keep the rpms up enough to keep her running. If I need to do that regulation with the Choke, then I have another question for you... My choke doesn't stay out, I can pull it all the way out but as soon as I let go it starts on it's way down. I'm at work but if I recall correctly, it doesn't go all the way down it'll stop with about 1/4 of the choke open. Could a worn choke cable cause that? I've heard of others having that problem, but I never heard anyone explain fixing it. Thanks for your help.
 
Topman said:
I wasn't starting with the throttle. I'd start the bike and then blip the throttle just to keep the rpms up enough to keep her running.
Click to expand...
"Blipping" the throttle opens the butterflies, yes? Opening the butterflies reduces the vacuum that is necessary to pull the fuel through the enrichener system (the "choke"). When you "blip" the throttle, you are bypassing the "choke" and forcing it to run on the leaner "normal" systems, only aggravating your problem.


Topman said:
then I have another question for you... My choke doesn't stay out, ...
Click to expand...
Have you tried twisting it a bit? It is supposed to lock in place if you pull it out and give it about 1/8 twist to the right. If it does not lock, a new cable will fix that.

.
 
Guess I'll have to get ahold of a new choke cable one of these days. Just to check what Nahoo stated, I pulled my plugs and checked them again, but again, I'm not sure what to expect. So, I scrounged up a camera (very crappy) that is capable of shooting video so perhaps I'd have a decent enough video to demonstrate my spark to everyone. I keep watching the video and thinking it just doesn't look right, everyone talks about the spark as a "nice fat spark". Just to remind everyone I've done the voltage tests at the coils and all and had my results confirmed in another thread as "satisfactory".

Here is the first video, it was hard to get a good angle so I shot a couple: (The sparks laid out from left to right are #4-#1)

http://www.youtube.com/watch?v=APMjdbkPfPU

Here's the second:

http://www.youtube.com/watch?v=kqiA8hokkyA

And here's one I shot while I had the camera out, it's just of what she sounds like after the first crank should she fail to start, or not get enough of the choke to stay on long enough before dying:

http://www.youtube.com/watch?v=DA3b6WydcNU

I really appreciate anything anyone can decipher from these videos, I really don't know anyone in the area who can give me a hand so I'm stuck trying to assign my symptoms to other peoples' videos and threads. It really doesn't help that because of my inexperience I lack to ear for these beautiful machines just yet.

Thank you again.
 
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In the spark plug videos I didn't see consistent spark on #4. If you have a timing light with a magnetic probe that just goes around the spark plug wire you can run that probe on each of the plug wires (with the plugs installed) and watch the light for a consistent rythum. It helps look for some ignition issues.

Is it just me or when cranking it in the last video the bike sounded like it only had compression on 1 or a matched pair of cylinders. Makes it sound like a single cylinder motor cranking over. Have you checked compression on all cylinders?

If you have a pull choke then there should/may be a ring just below the pull knob with serrations on it. If you tighten that ring it should put friction on the shaft of the choke knob and hold it in place.

Chris
 
I had a friend happen across town today, showed him the sparks in person. It didn't take him long to determine that they're just fine, I reiterate how terrible the quality of the video camera that I used was. Also unfortunately don't have access to a timing light. The conclusion we came too is that it's a fuel starvation issue. I pulled the plugs and put a nice shot of fuel right in the cylinder and she started up promptly. There's got to be an issue in the carbs. I plan on pulling them tomorrow, but if anyone's got a clue where I should begin I'd really appreciate it. They were dipped just a few weeks ago, and all passages cleared as per the guide on Basscliff's website. My floats were very low before (19mm) and I knew it prior to cleaning because at one point the carbs overflowed. The specs call for 21.3-23.3mm so I naturally adjusted them. One thing I'm not certain of, if per chance I adjusted above spec, would that cause any level of fuel starvation? Other than that, I plan on clearing every passage with a very thin guitar string or the sort.

Thank you again for everything
 
The float level actually is very important. It must be spot on. Especially for low speed running.

I just learned the importance of this recently myself. I installed good new float needles and seats then raised (meaning increased fuel level) the floats to the correct level and made sure all four were the same. It made a huge difference how it idles, how it runs at low throttle openings and also how quickly/smoothly it comes off of choke. The bike runs MUCH better.

Chris
 
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