Ignition setup

If it's broken or just needs tweaked

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B4
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Ignition setup

Postby B4 » Tue Mar 06, 2007 6:50 am

**After posting realised this should have gone in technical**
Guys...thanks for the warm welcome and the help/advice already...online manual brilliant! Have done valve clearances, new plugs, Cleaned carbs/set float heights. According to the online manual the ht leads were sut up wrong when I got it. Picture not too clear in online manual and haynes crap. Can someone confirm that
coil 1 (bottom left) to cyl 1
coil 2 (top left) to cyl 4
coil 3 (bottom right) to cyl 2
coil 4 (top right) to cyl 3
wont idle particularly well (havn't set up throttle cables, fast idle, choke yet) but revs cleanly and freely with no smoke. Synchronising carbs tomorrow night :D Thanks
dont put a blanket over me...I was only blinking!!

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Volker_P
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Re: Ignition setup

Postby Volker_P » Tue Mar 06, 2007 9:38 am

Here it is in the technical section now :)
The left coil for 1+4, the right one for 2+3 seems allright. The coils do not distinguish between both outputs, so bottom or top plays no role and may be interchanged. The circuit is just in series for each pair and one spark is just "wasted".
(Piston) carb synchronization bases on carb 2 (with the accelerator pump) which is not adjustable.

B4
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Location: Shellield, UK

Postby B4 » Tue Mar 06, 2007 9:53 am

Thanks for that, makes sense...I have a double vacum gauge form owning a twin so a forum member from www.sheffieldbikers.co.uk (friendly local bunch) is bringing a 4 gauge wed night. Do you think synchrnisation could be the source of my rough idle or could it simply be throttle/choke/fast idle set up. Needles and floats looked good, although float heights out. No obvious vacum leaks. valve timing good. New plugs, new HT lead and good caps. Mixture srews well out on each varying from 2 1/4 to 3 1/2 turns out. Set all back to 1 1/2 turns out. My theory was that with float height and mixture srews not in spec someone has been trying to compensate with synchronising??????? Any thoughts on my poor idle? Wont Idle bellow 1500-1800 becomes very lumpy and cuts out. Plug colour good on all four. :)
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Ibsen
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Postby Ibsen » Tue Mar 06, 2007 1:59 pm

Before synchronizing the carbs you should make sure the float level is correct on all carbs and fine tune the idle mixture screws according to the manual. The last step in a tune up procedure is the carb synch.
But to answer your question, carbs out of synch will cause a rough idle, and the off idle response will also suffer. The engine can get amazingly smoother after a proper carb synch.

B4
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Location: Shellield, UK

Postby B4 » Tue Mar 06, 2007 2:29 pm

thanks for the reply Ibsen...when I stripped the carbs Ive set all floats to 12.5mm and all mixture srews out 1 1/2 turns...so I guess next step is synchronisation. In your experience does setting up the choke / throttle cables correctly improve the situation?? :)
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Ibsen
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Postby Ibsen » Tue Mar 06, 2007 3:05 pm

What's important regarding the throttle cables is to have some free play. If not, the idle speed will be unstable. Also make sure there are a small amount of free play in the choke cable. The free play in the choke cable is adjusted by loosening the clamp for the cable located between carb #2 and 3. You can also adjust the fast idle with a small adjustment screw on the choke mechanism between carb 2 and 3, but it has to be done when the engine is cold.
Another thing I have experienced (and take it as warning that it's time to synch the carbs), is that the engine won't fire even on all 4 cylinders when starting the engine cold. After a carb synch this problem are normally gone.

B4
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Postby B4 » Tue Mar 06, 2007 4:30 pm

Ok ...noted. Adjusted all cables and got it to run smooth at around1600-1800. But still variable and uneven, especially on startup. Might have suspected an air leak on the intake side but spraying WD40 around the intakes produced no change, so I think not. Synchronisation it is. I know from synchronising my twin that it can be dramatic so fingers crossed. If it fails, im going to be unhappy and have to pull the carbs again...oh joy!!! Will keep you updated. Wish me Luck. Cant wait to get to the same stage as most of you...even a maiden voyage. Having my cast removed a week on Thursday so hopefully soon. The insurance company will be giving me a loan bike as soon as its off so I can still tinker with the cb650...no pressure. Cheers Pete
dont put a blanket over me...I was only blinking!!

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Volker_P
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Re: Ignition setup

Postby Volker_P » Wed Mar 07, 2007 2:01 am

Ibsen wrote: Another thing I have experienced (and take it as warning that it's time to synch the carbs), is that the engine won't fire even on all 4 cylinders when starting the engine cold. After a carb synch this problem are normally gone.

Although that sounds logic and reasonable, mine rarely started cold on all four. Neither before nor after carb synchronization. Depending on temperature and standing duration, it may take about half a minute until all cylinders fire. But I guess it is because I never cared for the fast idle at the choke mechanism. Warm it idles quite smoothly even below 1000rpm if one likes to try. Well, all that may be not very representative as my engine is quite worn now. :cry:

B4
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Postby B4 » Wed Mar 07, 2007 3:39 am

Mine wouldnt idle below 15000 even after 10 mins running. Set the choke last night. started it on choke to 2500, adjusted the choke mechanism screww until it was just touching the cam of the choke assembly. Switched off and unnscrewed by 2 1/2 turns. Full choke now takes it to 45000rpm where as before the maximum with choke was 2500. I guess it king of Zeros the choke setup and gives it a reference point and makes sure theres no choke on when its fully in :) If mine would idle at 1000 or under after 5-10 mins I would be very happy whatever the mileage and wear :D
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Volker_P
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Re: Ignition setup

Postby Volker_P » Wed Mar 07, 2007 4:07 am

As Ibsen wrote, first make sure you have free play in gas and choke cables. It should also stay free when you turn the handlebars!
You also should be sure that the choke mechanism always returns to choke flaps being horizontal.
Your procedure is all right, after clarifying the important points now it is time for carb synchronization. No need to worry about idle properties or turn again at screws until you did that. As you already had a look into your carbs and found nothing obviously being worn out or damaged, I would guess it will run just great afterwards.

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Ibsen
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Postby Ibsen » Wed Mar 07, 2007 11:27 am

Did you check the return cable as well? Normally you should be able to adjust the idle down to zero with the idle stop screw. Also check for any air leaks in the intake manifolds.
And despite the choke cable, the choke mechanism between the carbs are spring loaded and the choke shafts that is running through the carbs has to be exactly in line. If not they tend to bind to the bushings and won't open and close fully.

But as Volker said, a carb synch might solve the high idle problem. If not, either the cables are binding, the return spring on the cable pulley doesn't work properly, or the slides are prevented from closing all the way for another reason.

B4
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Postby B4 » Wed Mar 07, 2007 11:41 am

Ok Ibsen...synchronising in the next 3 hours :D
dont put a blanket over me...I was only blinking!!

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Ibsen
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Postby Ibsen » Wed Mar 07, 2007 2:30 pm

Good luck with the synch job. :D

B4
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Postby B4 » Wed Mar 07, 2007 5:06 pm

Right...update time. good and bad really. Put the guages on and all 4 cylinders spot on. Still wouldnt idle below 1500-1800 sounded like it was lean and needed fuel. Revs hanging up an taking ages to return...also choke improving throttle response. Resorted to turning out the mixture screws out in 1/4 increments. Ended up all 4 at 2 1/2..smoothe idle at 1100 and good throttle response with revs returning to idle immediately. When I set the mixture screws all to 1 1/2 from 'lightly seated' on the bench at carb cleaning. Only explanation that I can think of is that my 'lightly seated' and a 1970's honda production line technicians 'lightly seated' differs greatly. Any other ideas or explanation? Can wait for my first ride on it. will the mixture screws at 2 1/2 on all 4 lead to MOT failure on the emissions test? Anyway, getting somewhere. :D
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Ibsen
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Postby Ibsen » Wed Mar 07, 2007 5:26 pm

It's good to hear that you got the idle right. :)
It's impossible to tell what the result will be at the emission test really, unless you have a chance to measure it and correct the mixture in advance.


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