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Very Hot Topic (More than 25 Replies) That good old hanging rpm topic again (Read 1538 times)
tunnelrider
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That good old hanging rpm topic again
08/29/17 at 15:14:54
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Hi all, yes I know this same topic has been covered many times (and maybe very recently by BPT) and I have searched and read a couple of posts on this subject so I do feel I've got a good handle on what the problem is, just want a second opinion I guess.
The problem is: While cruising at 4000rpm, if I back off the throttle completely then pull in the clutch lever (actuate the clutch) it takes approx 5 seconds for my revs to drop from 4000 rpm back to idle, approx 1000 rpm.  This has been happening to a lesser degree for a few years but I've just done a timing chain job and it's gotten a little more noticeable.  I'm thinking the ATU (bean can) springs are to blame.  While the ATU was off the bike for the timing chain job I opened the oval plate, saw the springs were pulling the weights to a stop and they seemed to be ok.  Gave a good squirt of CRC5-56 and squeezed in a little light oil.  But symptoms still persist.
- I have adjusted idle speed after a good 20km run to 1000rpm.  Throttle stop screws can be adjusted still. Slack in both throttle and choke cables.
- Idle mix screws adjusted out past what I have normally run at. (Makes no difference at normal or adjusted out further)
- Valve clearances just done
- Timing light shows advance starts approx 1500rpm and stops at approx 3000 rpm
- No air leaks at carb. manifolds
- Clutch drag technique brings idle down faster and idle stays down.

I guess the only two things I think it could be are either stretched/weak ATU springs, or a problem with the carbs, which are one of the few things I haven't had to pull apart yet as I've had no problems with them.

Have I missed something obvious?  Looking at descriptions of pulling the bean can apart it looks a bit tricky, but I believe I could do it ok.  The bike has 115K miles on it and I'm not sure if work's been done on the ATU previously.

Cheers.
P.S. I've just noticed that Barry's posts say he's now an ex member, could I just say that the asylum has lost a truly knowledgeable and kind hearted guru, cheers Barry!
« Last Edit: 08/29/17 at 19:49:47 by tunnelrider »  

 1985 Black R65  -  2001 DRZ400 dirt only
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Re: That good old hanging rpm topic again
Reply #1 - 08/29/17 at 19:45:53
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Holy crap, what happened to Barry??????

Mine was slightly different, at least when I noticed it.  My problem came up when I was coasting to or came to a stop. I'd let off the throttle but it would continue to rev above 2000 rpm.

With my newest problems (possibly ignition related), I've had the been can off.  My local guy was confused as to which one I had and told me to bring it in and they would check it out, expecting points or a variant of those.  I told him I didn't think that's what I had but........   I took it in and he struggled with getting it apart then the old timer there told him they rarely did because it's such a pain.   There are pictures and write ups online and I'm sure the experienced ones here can advise.  I'd say make absolutely sure you need to open it before you do.  For one thing, you have to pound a pin out to get to the inner guts.  Not quite as simple as unscrewing things and just trying to keep them in order.
  

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Re: That good old hanging rpm topic again
Reply #2 - 08/29/17 at 19:51:54
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BTW - I'd mentioned in one of my recent posts that the shop told me I needed my timing chain done and that I probably shouldn't wait as long as I thought I could.  They also told me that could be the source of my idle problems.

Since you say you just did yours, that shouldn't be it?  They told me with mine, kind of like needing the valves adjusted properly, that if the timing chain and/or tensioner is really worn, I'll never be able to get things adjusted correctly.
  

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tunnelrider
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Re: That good old hanging rpm topic again
Reply #3 - 08/29/17 at 20:07:20
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BPT wrote on 08/29/17 at 19:51:54:
BTW - I'd mentioned in one of my recent posts that the shop told me I needed my timing chain done and that I probably shouldn't wait as long as I thought I could.  They also told me that could be the source of my idle problems.

Since you say you just did yours, that shouldn't be it?  They told me with mine, kind of like needing the valves adjusted properly, that if the timing chain and/or tensioner is really worn, I'll never be able to get things adjusted correctly.


No I think if your idle is bouncing up to 2000 rpm again from lower revs then the carbs aren't adjusted properly, usually from doing them before the engine is truly hot. IMHO usually the throttle stop screws would be set too high.  Worn timing chain, or more correctly worn crankshaft sprocket and chain, presents itself as an unsteady, occasionally fluctuating idle rhythm but idle speed is still able to be adjusted to the correct range.  It also causes double (or blurred) images with a timing strobe light aimed through the timing plug hole.

Another reason for you is your ATU/bean can springs might not be bringing the wights back to the stop position.  You can check for this with someone's help.  Get them (or you) to aim the timing light while you have the bike at the high idle, then with the front or back brake on, let the clutch bring the revs down.  If the timing light shows the advanced position still (or at least not back to 'S' non advanced position) then the problem is your bean can/ATU.  Sometimes turning off the bike then restarting it will be enough for the high idle/stuck weights to return to the stopped position/ lower normal idle speed.
  

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Re: That good old hanging rpm topic again
Reply #4 - 08/29/17 at 20:49:21
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I just got my box from EME so will be installing the new coil, wires, etc. tomorrow. Since I've had the bean can off it will most likely need to be timed and the shop will do that for me.

As far as the carbs. I've had them adjusted numerous times.  The first time it happened I'd just come off of a highway ride.  I'd taken the exit and it happened at the stoplight. Coincidentally, I was going to that shop so I told them about it right when I pulled in. At least that time, I'm pretty sure it should have been warm enough.  It's always been up there that I've gotten help adjustin them. Sometimes right when I get there, sometimes after it's sat a bit.   It's been frustrating because it comes and goes so hard to say when or if the carb adjustment made any difference.

I put a couple of drops of oil on the weights in the can.  I can't say I knew exactly what I was looking for but the springs looked ok.  Not stretched or anything obvious and I couldn't get them to bind up messing with them by hand.

After tomorrow I'll have some new ignition parts and then will get it timed and have the carbs adjusted again.  Narrowing things down.......hopefully.
  

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Re: That good old hanging rpm topic again
Reply #5 - 08/29/17 at 21:16:57
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IMHO BPT, you should set the timing and do the carb set up yourself first.  Hire or buy a timing light, they aren't expensive and even cheaper to hire.  You'll learn a lot of useful knowledge, as these two steps are crucial elements of tuning your bike.
  

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Re: That good old hanging rpm topic again
Reply #6 - 08/29/17 at 21:59:29
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I am trying to solve a similar kind of mystery with my 78 R100 - but it (for better or worse) has a DYNA III electronic ignition kit on it, so some of the usual suspects are substituted with other suspects.

I do find that I can get my R65 very nicely idling and returning properly to idle with its stock bean can and ignition module setup, but generally do have to get the bike REALLY quite warm , e.g. 30-40km ride first.  Otherwise, I *think* it is adjusted right and stable, and then later find out after longer rides, the idle is around 1500 RPM instead of 1100.

You seem to be methodically checking all the right boxes, though.
  

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Re: That good old hanging rpm topic again
Reply #7 - 08/29/17 at 22:00:35
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tunnelrider wrote on 08/29/17 at 21:16:57:
IMHO BPT, you should set the timing and do the carb set up yourself first.  Hire or buy a timing light, they aren't expensive and even cheaper to hire.  You'll learn a lot of useful knowledge, as these two steps are crucial elements of tuning your bike.


I second this  Wink
  

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Re: That good old hanging rpm topic again
Reply #8 - 08/30/17 at 00:09:35
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Absolutely agree. I don't have a timing light anymore and when I told the guys at the shop they told me to bring it up there. My intention was to have them show me how.  I figured I wouldn't turn down their offer, especially since I have multiple things going on.

Right now I'm completely down. I'll be getting it rideable then hoping they can show me how to get it to the finely tuned point.

Yep, I do need to get a timing light....
  

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Re: That good old hanging rpm topic again
Reply #9 - 08/30/17 at 04:59:41
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nhmaf wrote on 08/29/17 at 21:59:29:
I am trying to solve a similar kind of mystery with my 78 R100 - but it (for better or worse) has a DYNA III electronic ignition kit on it, so some of the usual suspects are substituted with other suspects.

I do find that I can get my R65 very nicely idling and returning properly to idle with its stock bean can and ignition module setup, but generally do have to get the bike REALLY quite warm , e.g. 30-40km ride first.  Otherwise, I *think* it is adjusted right and stable, and then later find out after longer rides, the idle is around 1500 RPM instead of 1100.

You seem to be methodically checking all the right boxes, though.


Thanks nhmaf that's what I was wanting, some other opinions about similar stuff.  I'm not sure how the Dyna III ingnition set up looks sorry, does it have a similar bean can ATU? But good to hear your R65 set up behaves well stock standard.  How many km has your R65 done?

A bit of an update, with the day off I went for a 70km mixed hilly, twisty and flat open road ride just after starting this post (good for running in new piston rings!).  Had a pie halfway so two 35km runs. Before I left I squirted more lube in the bean can through the oval inspection hole on the top.  Cruising at 4000rpm, throttle off and clutch in my problem of slowly falling revs was basically halved, not time wise but a rapid drop of rpm from 4000 until about 2200, where it seemed to hang up and stay for quite a while then continue down to idle, took just as long to get to idle as before tho, if not longer.  Idle speed when stopped is smooth and steady, didn't have to adjust the carbs.
Will give it another squirt before my next ride.
  

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Re: That good old hanging rpm topic again
Reply #10 - 08/30/17 at 06:52:05
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Mrclubike wrote on 08/29/17 at 22:00:35:
tunnelrider wrote on 08/29/17 at 21:16:57:
IMHO BPT, you should set the timing and do the carb set up yourself first.  Hire or buy a timing light, they aren't expensive and even cheaper to hire.  You'll learn a lot of useful knowledge, as these two steps are crucial elements of tuning your bike.


I second this  Wink


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Re: That good old hanging rpm topic again
Reply #11 - 08/30/17 at 22:10:31
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Quote:
Thanks nhmaf that's what I was wanting, some other opinions about similar stuff.  I'm not sure how the Dyna III ingnition set up looks sorry, does it have a similar bean can ATU? But good to hear your R65 set up behaves well stock standard.  How many km has your R65 done?


The DYNA III was advertised as the bee's knees back in the day, but they can have their own sets of issues.  Our venerable airhead specialist, "SNOWBUM" a.k.a Bob Fleischer considers that they can be inconsistent/unstable.   I may try to revert back to the old points setup, but this is what the ol girl came with and I'm trying to get it as right as it can be before giving up.

My 1982 R65LS spent at least 15 years in a damp storage shed which took alot to recover from, but it had less than 13,000 miles on it when I got it.  It is now up to about 28,000 miles and running great.   The longest trip I have taken on it thus far has been about 2400 miles (round trip) from NH down through to Tennessee and thereabouts, and back home.   I've done a couple 600 mile days on it, but the stock seat left me kinda stiff afterward.
  

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Re: That good old hanging rpm topic again
Reply #12 - 08/31/17 at 00:34:16
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nhmaf wrote on 08/30/17 at 22:10:31:
It is now up to about 28,000 miles and running great.   The longest trip I have taken on it thus far has been about 2400 miles (round trip) from NH down through to Tennessee and thereabouts, and back home.   I've done a couple 600 mile days on it, but the stock seat left me kinda stiff afterward.


Far out, she's a spring chicken nhmaf!  Those are some good long trips on her, the most I've done in one round trip is about 1500miles, 2500km, a couple of times and ridden 350 mi (550km) in a day a couple of times.  Many times I've stretched my legs out and ridden with them resting on the crash bars, what a relief!
  

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Re: That good old hanging rpm topic again
Reply #13 - 08/31/17 at 04:17:32
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Hello !
As you have sorted the bean can and ascertained it was not seized,I would add that the carburetor are the problem.
The combination of idle stop position and idle mixture screw make the engine too much fed to return to idle correctly.
I suggest you run the bike until hot, return the idle screws to the factory setting and do an idle synch and set up. When done, adjust the idle screw mixture a very tiny bit to have a smooth idle.
I bet that the problem will disappear but when cold the idle will be too slow and the bike will stall. You will have to run the bike for a few hundred meters for the engine to get to proper temperature. Not a big deal Wink
Last but not least, if you are new to engine tune-up you can learn a bit with the Colortune plug (it ias a transparent plug which allows you to SEE if you have set the idle screw correctly... Sort of a gadget but will help you to relate the combustion in the cylinder to the noise the engine makes and the way the idle screw works.
  
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Re: That good old hanging rpm topic again
Reply #14 - 08/31/17 at 04:41:55
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georgesgiralt wrote on 08/31/17 at 04:17:32:
As you have sorted the bean can and ascertained it was not seized,I would add that the carburetor are the problem.
The combination of idle stop position and idle mixture screw make the engine too much fed to return to idle correctly.
I suggest you run the bike until hot, return the idle screws to the factory setting and do an idle synch and set up. When done, adjust the idle screw mixture a very tiny bit to have a smooth idle.


Hi George, thanks for the info.  What you describe is how I have set up the carbs usually for a while now but it has been giving this hanging rpm.  In the past I've kept to the initial idle mix setting of approx 3/4 turn or a couple of clicks further out.  Then adjusted the stop screws.  This gives me the slowly falling rpm. Another popular method goes, which I'm trying now, by adjusting the mix screws to obtain highest rpm then adjusting the revs down using the throttle stop screws.  I should really bite the bullet and get a plug shorting set up as I think Mrclubike described this week and do it that way.  However I'm still suspecting the bean can springs also, they've probably done 185K km over 32 years now.  I could also try going leaner than 3/4 turn of the idle mix screw, which would be along the lines of what you're suggesting.  I've done that before too, but a couple of years ago now.  Gave good fuel economy but compromised open road speeds. 
Thanks George for reminding I can always go back and start again!  As far as I can remember, the initial setting for the throttle stop screws is one full turn from contact?
  

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