hanging idle

[Steve]

Forgive my ignorance, but timing is pretty much fixed by the cam chain & sprockets, right? If so I'd think that being off by one tooth on either cam would present a bigger issue than a hanging idle.

You are correct in that VALVE timing is fixed by cam chain and sprockets, but the issue being discussed here is IGNITION timing, which is controlled by the point gap(s) and the position of the timing plate on the right end of the crank.

He mentioned that the gap was rather small. That means they are being opened later than normal, which means retarded timing, which can definitely affect throttle response.

.

 

[Guest]

i love happy endings

 

[Nessism]

So, final verdict is the points were causing the issue. Set them to spec and the hanging throttle almost disappeared. Did a final adjustment on the carbs and the problem is gone. Thank you everyone for your wisdom and advice.

Newbie Mistake #1 strikes: trying to diagnose running problems on a bike that doesn't have all the maintenance up to date. Glad you got it sorted but you might want to go though the entire maintenance table to make sure you don't miss anything else.

 

[1978GS750E]

Checked my points today and they were burnt up! Trying to decide if I want to spend the money and put a Dyna S ignition in it or just go back with points...?..decisions, decisions...??..$20 for points , $115 for a Dyna S. Anyone have any comments on the Dyna systems, good or bad?

 

[Steve]

Is that $20 for one set of points or both? :-k

Don't forget that you should also replace the condensors.

Do you have Nippondenso or Kokusan? It makes a BIG difference.

ND points are different prices, but are basically $30 each, condensors are just under $15 each, for a total of about $90.

Kokusan points are $72 each, condensors are $65 each, for a total of almost $275.

Where are you finding points for $20?

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[1978GS750E]

I have a ND ignition. Points on ebay!
https://www.ebay.com/itm/1977-79-Su...h=item5b31be35ed:g:KsQAAOSwWxNYx2vI:rk:6:pf:0

Thinking I may just go with the Dyna S and be done with points altogether. Sad thing is that I sold a bike last year with a Dyna S system on it! Hindsight is always 20/20!

 

[Spoonz]

Newbie Mistake #1 strikes: trying to diagnose running problems on a bike that doesn't have all the maintenance up to date. Glad you got it sorted but you might want to go though the entire maintenance table to make sure you don't miss anything else.

In 15yrs of working on older bikes, I have never had an issue like this happen with the points being the cause. When every symptom points to an air leak, and you are trying to figure out what the last 3 people have done to it. Last person that was in it broke an idle mixture screw in the carb body. So started there and apparently someone at some point was in adjusting the point to “make it run”. All maintenance has been done as that was part of the total repairs being done while it was in my shop. This issue stumped at least three people on my end. I will say that he who says they know everything is a liar as no matter how many times I have the same symptoms on bikes that come in, not one of them is ever the same exact repair.

 

[Spoonz]

But needless to say it?s running great

 

[Guest]

And, I feel kinda humbled for 'throwin' it out there' and have added checking my bike's point gaps, ya know...'for sh*#s & giggles' Glad it worked for you, Spoonz!

 

[aclaytonb]

Glad I found this. Just rebuilt my top end and was having similar issues. New boots, everything. Adjusted the plate holding the ignition and problem solved. Weird.

I've pulled those carbs so many times for cleaning that I can get them off from a fully assembled bike in under 5 minutes. Was about at wits end with this.

 

[canuckxxx]

One last thing to check, with the points, is the timing for 1-4 vs 2-3. it should be the same for both, but may not be because the 2-3 points are on a separate sub-plate from 1-4.

 

[KEITH KRAUSE]

I once had a similar "hanging idle" issue that was also electrical related.
When my bike was 1 year old ('79 GS1000E), I converted the points to a system made by Martek. It used a collar that slipped onto the shaft and was held by a small set screw. The set screw came loose and allowed the collar to rotate. I'd pull up to a stop and the rpm's would hang about 400 rpm's higher. If I "blipped" the throttle, the rpm's would quickly fall to normal idle (1,000 rpm's) and stay there as long as I didn't touch the throttle. It had me confused for a bit but since the Martek system was just installed a few weeks earlier I kind of suspected it. I ended up tossing the Martek for a Dyna system.
Though the slipping collar mimicked an intake leak, the difference is a true intake leak will result in a constant higher "idle" when the engine has reached full warm up. Blipping the throttle won't settle the rpm's beyond a moment or two, if that.