25 replies [Last post]
acerynes
acerynes's picture
 Offline
VBMWMO #9334
Seattle
Joined: 10/07/2015
Posts: 23

Hello all,
Just asking a general question to see if its something Im doing or if I need to do some adjustments still. When I come to a complete stop and then put the bike in neutral. When I give it gas, it feels as if its stumbling on itself. I cut the throttle, blip it a few times and then it idles normally and then I can start moving. Do I need to adjust the idle speed? ie is it idling to slow and then trying to play catch up?
input would be extremely appreciated. Thanks

johnpst
johnpst's picture
 Offline
Hawaii
Joined: 03/22/2016
Posts: 82
SIMPLE SYSTEM IF...

Aloha,

Like you'll hear from many of us, we're not there so, we don't know and can't see what's going on so, we'll advise the best we can with what we know.

Any time these engines run different, something changed. Obvious, right? The question is, what changed?

Have you done anything to it recently? Always start with what changed. If not, do a visual inspection of everything. There are many guides on how to inspect the carburetor and ignition system so, I won't rehash it here but,

Next is, systematically, verify each of the systems is working correctly. What you are describing could be anything including maladjusted carb float, leak at the carb to cylinder head joint, dirty carb, spark plug wire arcing to the engine case, coil safety gap maladjustment, bad coil, dirty points, bad condenser, and many more.

Start at each system and go through it until you are confident it is working correctly. If you disassemble the carbs, clean them, inspect them for blockages and damage, then you can be confident they are correct. Move on to...

It takes a couple of hours for an unpracticed person to go through the carbs. Parts are less than $15.00. Running through a static then dynamic timing job will take an hour or two, and visually inspecting the ignition system will take a minute or two, looking for arcs and sparks where they shouldn't be. Verifying the coil condition can be done but, I caution, it is subject to change with temperature so, unless you are really confident in your ability to troubleshoot it, a new one can surprise you on how much better the engine will run, even it it wasn't the root cause of the failure.

Hope this helps. I'm a big believer in pulling up a chair, the instruction manual, loud music, a beer, then digging in. I have always been disappointed in partial efforts that I have to revisit.

John

__________________

John
55 - R50, 06-R1200RT, 96-M900, 10-TU250x

acerynes
acerynes's picture
 Offline
VBMWMO #9334
Seattle
Joined: 10/07/2015
Posts: 23
more info

I was at work when I wrote the previous post. The carbs have been rebuilt, the engine has been completely rebuilt, everything is brand new or as new as can be. BING serviced the carbs, and the "official" term I've seen is the bike has a flat spot just off of idle

Thanks for taking the time to write

malmac
malmac's picture
 Offline
VBMWMO #8751
Toowoomba, Australia
Joined: 06/29/2014
Posts: 300
if you think its carbies .......

My old boss used to say, "If you think its carbies its probably timing, and visa versa"

However in this case I think carbies.

Even though Bing serviced the carbs, did they refit them to your bike and synchronise them? I am assuming they did not.

I would check that the idle on both cylinders is even, and that one cylinder is not doing most of the work.

If that checks out OK the next thing I would look for is, are the slides pulling open at exactly the same time?
If one cylinder is trying to pull the other cylinder then I would expect the result to be a flat spot.
If they are opening at exactly the same time from an even idle speeed, then you would want to backtrack and check things like compression, spark and all the things that John suggested..

Broadly speaking I agree with John however since everything has been changed you have to start somewhere.

I am sure both John and myself will be interested to see how your investigations progress.

__________________

mal - R69s
Toowoomba- Australia

schrader7032
schrader7032's picture
 Offline
VBMWMO #7032
San Antonio, TX
Joined: 10/27/2006
Posts: 6901
I think what Mal has said

I think what Mal has said makes sense. The carbs can be speced out on the bench, but they must be synchronized to work together when mounted to the engine. It's kinda like the BMW motorcycle consists of two engines that share a common crankshaft. So, adjustments need to be made to get them to work together.

I can probably see where the idle mixture setting could be adjusted to help your situation. Which the bench setting is "1-1/2 turns out" or what ever it is. That's only a starting point. As part of the synching process, you must find the spot where the mixture results in the best idle speed....for that cylinder. And the way the cylinder runs is influenced by ignition, compression, health state of plugs/wires, etc.

So, an on-bike synching should really be done.

__________________

Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

808Airhead
808Airhead's picture
 Offline
VBMWMO #7677
Joined: 08/05/2009
Posts: 1025
Needs to be fine tuned more

Needs to be fine tuned more than likely. Idle mixture or jetting needs adjustment,maybe even needle position on slide. The biggy is the carb synch and throttle cable synch. I use the EMPI air flow meters and these bikes run sweet when setup right.

__________________

Thomas M.
R69s - R60/2 - R67/2 - R51/3

johnpst
johnpst's picture
 Offline
Hawaii
Joined: 03/22/2016
Posts: 82
AGREE WITH JETS / NEEDLE JET POSITION

Aloha,

A flat spot, given all other things are correct, indicate jetting or needle position.

Slide carburetors work on three circuits. Idle, pilot and the main. Each of these are designed to transition, one to the other, to give smooth acceleration. The jet size, needle position, and float level all play a role.

If all other things are correct, we or Bing can guide you through evaluating an adjustment/jet replacement to get things in order.

My caution is, since things worked then they didn't, I wouldn't make the conclusion that jetting is the issue unless you are certain all other things are correct.

Let us know how it's coming. We're all root'n for ya.

John

__________________

John
55 - R50, 06-R1200RT, 96-M900, 10-TU250x

acerynes
acerynes's picture
 Offline
VBMWMO #9334
Seattle
Joined: 10/07/2015
Posts: 23
Update

First off, Id like to thank the people who responded with helpful info. I had been overthinking it so much that I overlooked a few obvious things. The left hand throttle cable was tighter then the right hand side-has been fixed.
The carbs weren't 100% in sync with each other- fixing when I have off time.
The left hand carb is also burning a little rich and the right hand carb is close to spot on according the color of the plug.

Again, big thanks to the people who took the time to write back.

312Icarus
312Icarus's picture
 Offline
Joined: 07/15/2016
Posts: 436
Not to overlook the

Not to overlook the obvious...assuming ignition tune is right, consider dirt in the carbs. A 50+ year old fuel tank can have lots of rust, gunk etc in it. The idle needle jets are tiny and very prone to plugging. (This also assumes that the carbs have been tuned and synced). You can easily blow them out by removing the needle valves (remembering where they are currently set!) an then blowing compressed air into he needle bore). Then start the engine, adjust idle mixture by ear on both carbs and then try it. A flat spot often indicates a lean mixture, which dirt can cause. You may have to do this quite often with an old bike.

Icarus

PS Sorry for the duplicate, don’t know how that happened, happened.

Icarus

schrader7032
schrader7032's picture
 Offline
VBMWMO #7032
San Antonio, TX
Joined: 10/27/2006
Posts: 6901
Duplicate is deleted.

Duplicate is deleted.

__________________

Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

acerynes
acerynes's picture
 Offline
VBMWMO #9334
Seattle
Joined: 10/07/2015
Posts: 23
What mine looks like today

R69s
Above should be a link of what my bike looks like today.

schrader7032
schrader7032's picture
 Offline
VBMWMO #7032
San Antonio, TX
Joined: 10/27/2006
Posts: 6901
Facebook doesn't let me see

Facebook doesn't let me see anything.

__________________

Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

acerynes
acerynes's picture
 Offline
VBMWMO #9334
Seattle
Joined: 10/07/2015
Posts: 23
I got the picture to work,

I got the picture to work, disregard the post with the link.
Thanks

  • bmw.jpg
malmac
malmac's picture
 Offline
VBMWMO #8751
Toowoomba, Australia
Joined: 06/29/2014
Posts: 300
stunning bike.

What a beauty. given enough time I hope mine can look something close to yours when finished.

A lot to do, so I had better get on with it.

Mal

__________________

mal - R69s
Toowoomba- Australia

butch housman
butch housman's picture
 Offline
United States
Joined: 03/23/2015
Posts: 244
wow, a white one what yr? was

wow, a white one
what yr?
was it white originally?
looks great
is that the original seat?

for $20 or so u can buy a harbor freight ir thermometer that is nice to check if both sides run at the same temp
with enough tampering & rejetting mine r now within 2 degrees f of the same temp abt any place
beats going by the blue color of the pipes

312Icarus
312Icarus's picture
 Offline
Joined: 07/15/2016
Posts: 436
I second the idea of using a

I second the idea of using a IR thermometer to check carbs and tuning. Mine are currently misjetted, so one side runs ~10f higher. Gotta order some new jets that match.

Icarus

butch housman
butch housman's picture
 Offline
United States
Joined: 03/23/2015
Posts: 244
i was seeing 30-50-degrees

i was seeing 30-50-degrees difference at the cylinders at one point!

acerynes
acerynes's picture
 Offline
VBMWMO #9334
Seattle
Joined: 10/07/2015
Posts: 23
IR therm

Hello,
I have purchased one of those HF therms and my cylinders are at where they should be.
Mine is a 1964,

The original color from factory was black, but dover white was one of the colors you could get.

That is one of the seats you could also get, but mine from factory had one of the bench seats.
She is a real treat to ride.

butch housman
butch housman's picture
 Offline
United States
Joined: 03/23/2015
Posts: 244
glad u enjoy ur old bike how

glad u enjoy ur old bike
how do u rate the brakes?

black w/ a bench seat...wide or narrow?

ur's was like most, mine had a wide seat but is a US model & had a wixom habdlebar fairing...I've never seen another US in person

in the day i never saw a solo seat except maybe on a single & i'm not sure abt that
i did see a FEW white ones, they did exist but uncommon

i saw one blue one in the window at flanders in pasadena i think
PS. love the helmet Smile

  • dsc_6657.jpg
312Icarus
312Icarus's picture
 Offline
Joined: 07/15/2016
Posts: 436
I’ve got a 68 R50 US, with

I’ve got a 68 R50 US, with both a wide and a narrow dual seat, all black. I’ve owned it for over 40 years.

Icarus

acerynes
acerynes's picture
 Offline
VBMWMO #9334
Seattle
Joined: 10/07/2015
Posts: 23
mine

I believe mine was the narrow seat. If you go to the member gallery page and type in my username (acerynes) you can see a picture of what the bike was when I brought it home.

The brakes are shockingly pretty good for what I expected. I had a lot of help by Kevin Brooks and he uses a good brake material and I've been pleased with it. I naturally give it more room to stop then I would my 2012 Triumph. But I just started restoring a 1939 R12 and Im expecting those brakes to be really soft.

acerynes
acerynes's picture
 Offline
VBMWMO #9334
Seattle
Joined: 10/07/2015
Posts: 23
new question

Hello, so a friend and me adjusted the carb and the flat spot is now gone completely. However a new random issue has cropped up... when I am in first and NOT going to shift into neutral but going to go to a stop for like sitting into a turn lane to make a turn when traffic allows the bike will just die but not die and jump as if the clutch was released. It just calmly dies as if I turned it off myself.

Was just curious is this a idle screw adjustment issue? or is this something else and timing has been checked and is good.
Thanks

schrader7032
schrader7032's picture
 Offline
VBMWMO #7032
San Antonio, TX
Joined: 10/27/2006
Posts: 6901
So what steps have you done

So what steps have you done in order to do a full synch with the carbs. It's not really proper to just start changing this or that...all of the jets/settings work in concert with each other.

__________________

Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

acerynes
acerynes's picture
 Offline
VBMWMO #9334
Seattle
Joined: 10/07/2015
Posts: 23
what we did

what we did was take the air tubes off and look at the needles and made sure that it was even. We did the whole adjustments per the manual and the generator light is flickering at idle.

schrader7032
schrader7032's picture
 Offline
VBMWMO #7032
San Antonio, TX
Joined: 10/27/2006
Posts: 6901
Can you detail those

Can you detail those adjustments? Just making sure the needles are the same isn't the process. You need to determine which hole/position they're in.

Synch involves:

- warm engine
- 1-2mm slop in the throttle cable at the adjustment ferrule
- idle adjustment on each carb to get the best RPM, then turn the mixture screw a skoosh to the rich side
- idle speed the same on each engine; might have to go back and recheck mixture
- ensure tension in each cable gives the same RPM at say 1500 RPM...definitely off idle
- if one cylinder is running faster than the other, slow the faster cylinder down...don't speed up the slow cylinder

__________________

Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

acerynes
acerynes's picture
 Offline
VBMWMO #9334
Seattle
Joined: 10/07/2015
Posts: 23
so I found

so I found my left hand airtube not all the way onto the carb. im hoping that's the issue.

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.