Ignition Issues for 1982 BMW R65 (Videos Included)

[stevenrankin]

cable adjustment

I would focus on getting your cables adjusted properly.

If you turn the bars and the idle speeds up, yes, they are too tight.

I will adjust my mantra a bit. First get the cables to the point where they allow the carbs to reach idle. No more than 900 RPM.

Then when you are sure you are actually idling, You can check timing. Yes, timing advances with throttle, So if the bike is not at idle, you will be off on your timing setting if you get my drift.

You can adjust all you want on the idle mixture to no avail if the cables are so tight the carbs are not in the idle position.

Worry about jetting later after you get the cables adjusted, the timing adjusted and finally the idle mixture. Then ride the bike and see how it runs.

That is a different topic. St.

 

[happy wanderer]

I would focus on getting your cables adjusted properly.

If you turn the bars and the idle speeds up, yes, they are too tight.

I will adjust my mantra a bit. First get the cables to the point where they allow the carbs to reach idle. No more than 900 RPM.

Then when you are sure you are actually idling, You can check timing. Yes, timing advances with throttle, So if the bike is not at idle, you will be off on your timing setting if you get my drift.

You can adjust all you want on the idle mixture to no avail if the cables are so tight the carbs are not in the idle position.

Worry about jetting later after you get the cables adjusted, the timing adjusted and finally the idle mixture. Then ride the bike and see how it runs.

That is a different topic. St.

I don't understand "First get the cables to the point where they allow the carbs to reach idle."
This is a confusing sentence because the cables are not used to adjust the idle at all and in fact are in the way of doing so if not loosened off first.

I do it this way with great success every time unless the carbs have serious problems:
-If the bike runs, go ride for at least 20 minutes and have a box fan waiting for your return along with your carb balancer, a 10mm wrench and flat head screwdriver. You cannot balance carbs on a cold engine period. It will change a fair bit once it warms up so doing it cold is a waste of time.
- Once she's good and warmed up set up the fan in front and loosen off the 10mm nuts on the cable adjusters and screw in IN until there is LOTS of free play in the throttle cables. LOTS...
- Now set the idle screws to a reasonable idle
- Now set the mixture screws one at a time to the fastest idle you can achieve and then turn them IN (clockwise) 1/8th of a turn from the highest idle point.
- Now check the idle balance again and make sure it is equal and idling at 950 to 1050 RPM. Some like to set it for just when the charge light goes out. I use the tach reading on my Harmonizer.
- Now turn out (counter clockwise) the adjuster till you have 1.5 to 2mm free play. Tighten down one side.
- Now go to the other side and rev then engine to 3.5 to 4K RPM (where you normally cruise) and adjust the other side throttle cable adjuster until you achieve equal balance at that RPM. This can take several attempts and I find moving the adjuster with a pair of pliers and holding it there while you gently tighten the 10mm lock nut will get you where you need to be faster than using your fingers. The adjuster is affected by the tightening of the 10mm nut when it is tightened so it's a bit of a back and forth dance but getting it bang on brings huge rewards in reduced vibration and a very smooth running airhead.

Go easy on those lock nuts. They are often way over tightened and this just makes adjusting the balance harder since over tightening creates sloppy threads.
And no one likes a sloppy thread!

 

[dretek]

I don't understand "First get the cables to the point where they allow the carbs to reach idle."
This is a confusing sentence because the cables are not used to adjust the idle at all and in fact are in the way of doing so if not loosened off first.

I do it this way with great success every time unless the carbs have serious problems:
-If the bike runs, go ride for at least 20 minutes and have a box fan waiting for your return along with your carb balancer, a 10mm wrench and flat head screwdriver. You cannot balance carbs on a cold engine period. It will change a fair bit once it warms up so doing it cold is a waste of time.
- Once she's good and warmed up set up the fan in front and loosen off the 10mm nuts on the cable adjusters and screw in IN until there is LOTS of free play in the throttle cables. LOTS...
- Now set the idle screws to a reasonable idle
- Now set the mixture screws one at a time to the fastest idle you can achieve and then turn them IN (clockwise) 1/8th of a turn from the highest idle point.
- Now check the idle balance again and make sure it is equal and idling at 950 to 1050 RPM. Some like to set it for just when the charge light goes out. I use the tach reading on my Harmonizer.
- Now turn out (counter clockwise) the adjuster till you have 1.5 to 2mm free play. Tighten down one side.
- Now go to the other side and rev then engine to 3.5 to 4K RPM (where you normally cruise) and adjust the other side throttle cable adjuster until you achieve equal balance at that RPM. This can take several attempts and I find moving the adjuster with a pair of pliers and holding it there while you gently tighten the 10mm lock nut will get you where you need to be faster than using your fingers. The adjuster is affected by the tightening of the 10mm nut when it is tightened so it's a bit of a back and forth dance but getting it bang on brings huge rewards in reduced vibration and a very smooth running airhead.

Go easy on those lock nuts. They are often way over tightened and this just makes adjusting the balance harder since over tightening creates sloppy threads.
And no one likes a sloppy thread!

These Mikuni Carbs do not have vacuum ports for a fancy carb synchronizer. What I do have is one Uni-Syn. In order to use the Uni-Syn I would have to take off the intake side on the carb. The problem with taking off the air intake, is the flow is different in open air as opposed to being in the air box filter. Has anyone had any experience with the Uni-syn?

What I understand is:
So we first get a good idle, then balance them @ ~1025 RPM (idle mixture screw).
-Here we set the idle, then check the Uni-syn has the same vacuum pressure on both sides via a combination of air-mixture and idle dialing?

Then we balance them again at 3.5-4k RPM (slack/tension in cables)?
-At this point idle is set, now we are working at 3.5-4k RPMs, we check Uni-syn has same vacuum pressure on both sides and this is achieved by tightening throttle cables?

 

[20774]

I'm sure you've read about the shorting method in order to synch carbs. You don't really need any "fancy" devices.

There are three steps to synching: 1) idle mixture; 2) idle speed; and 3) throttle cable tension. You go back and forth with 1) and 2) as they effect each other. Once that's satisfied, you move to 3). I don't think that going to 4K RPM is the best way to set the cable tension. You're trying to measure the differences in vacuum or RPM and the carbs are much more sensitive to this at lower RPMs, say 1500-2000. At 4K, your butterflies are open hugely and small changes in vacuum are hard to see.

You want the throttle slides to open evenly which is where setting tension in the cables at a lower RPM come into play. Yes, you don't spend much time running around at 2000 RPM, but by the time you get to 4K, you probably won't notice much difference. If you're big time off on tension at higher RPMs, maybe you need new cables or they need to be routed differently.

 

[stevenrankin]

Clarification

I don't understand "First get the cables to the point where they allow the carbs to reach idle."
This is a confusing sentence because the cables are not used to adjust the idle at all and in fact are in the way of doing so if not loosened off first.

I said this because he said when he turns the handle bars the bike speeds up. The cables are not adjusted properly. If the throttles are being pulled open by tight cables, they are NOT in the idle position.

The throttles have to be in the idle position to adjust idle, what is not clear about this?

Fix the maladjusted cables so they are correctly adjusted before messing with mixture and such.

No way should the bike speed up when the handle bars are turned.

- Once she's good and warmed up set up the fan in front and loosen off the 10mm nuts on the cable adjusters and screw in IN until there is LOTS of free play in the throttle cables. LOTS...

You have just included the step I talk about. The free play is so the carbs are at idle position when they are supposed to be. St.

 

[stevenrankin]

more

In reply to Kurt's advice.

There are three steps to synching: 1) idle mixture; 2) idle speed; and 3) throttle cable tension. You go back and forth with 1) and 2) as they effect each other. Once that's satisfied, you move to 3).

This is true only if the cables are not too tight to allow the carbs to reach idle position.

I think you mean to say you adjust pull off for equal carb operation when throttle is applied. this point number 3. St.

 

[20774]

Yes, ST, I do. I clearly wasn't providing step-by-step instructions. During 1) and 2), there should be 1-2mm of gap in the throttle cables...you don't want them to affect the idle settings. Then in doing the cable tension at low-ish RPM, adjustments are made to the ferrule where the cables go into the cable. This is an important point...if you find one cylinder running faster than the other, SLOW down the fast cylinder. If you decide to speed up the slow cylinder, you run the risk of compromising the 1-2mm of gap that you started with. If you reduce that gap to zero during these adjustments, then you have likely affected the idle settings and you have to start all over.

 

[stevenrankin]

Idle speed versus smooth pull

Hey Kurt,

Thanks for the reply.

Now I must admit, I am thinking about Bing carbs and not Mikunis.

Let me see if I have this straight. With Bing carbs, the idle speed adjustment is made with the idle set screw (once the cables are adjusted to let the bike idle).

. This I believe is number 5 on the diagram.

Once even idle is attained using the screw adjustment. Throttle cables are adjusted to produce proper pull off of idle into the ride area. (not sure of the technical term). (Power band) By adjusting the knurled nut or ferrule where the cables go into the cable. These have to be adjusted properly to give even transition from idle to power. If they are too tight, then the carb will not idle.

As I said, I don't know how Mikuni carbs are adjusted. Perhaps I should have stayed out of this. St.

 

[stevenrankin]

Okay

OKAY,

I should have kept quiet about the idle adjustment on Mikuni carbs.

Looking at pictures of various models, I do not see how they are adjusted for idle speed. Or I should say they don't look like they are adjusted the same as Bings.

I can imagine however the sequence for adjustment is similar.

I suppose I could go to the Mikuni website and find out more but I am not. If I have insulted anyone, I am sorry. St.