Topic: Spark plug cap resistance and whole lot more

[topperharley]

How important is that?  Iv been having some issues at cold start. I just measured them and they were 0.8k ohms. Iv read that it should be close to 5 k ohms. Would this make a difference about running cold and warm.
I have a custom coils and i think they are around 7kohms.
Iv got new ignition condensators and i have set timing allso.

What type of spark plugs should i use if i buy the 5kohms caps?

Ps. For some idiot reason i did set the contactor braker gap to 0.6 instead of 0.3.
Now its 0.3 but i havent driven yet.

[Deltarider]

How important is that?  Iv been having some issues at cold start. I just measured them and they were 0.8k ohms. Iv read that it should be close to 5 k ohms. Would this make a difference about running cold and warm

Now exactly what have you measured? Caps separate or caps attached to the HTleads to the coils? Would you mind informing us what bike?
Could it be you've selected the wrong scale on your ohmmeter?

I have a custom coils and i think they are around 7kohms.

Think or did you measure? Are you aware there's a primary circuit that you can measure and a secundary?

What type of spark plugs should i use if i buy the 5kohms caps?

In that case preferably spark plugs without R(esistor).

Ps. For some idiot reason i did set the contactor braker gap to 0.6 instead of 0.3.
Now its 0.3 but i havent driven yet.

I'd start with 0,4 mm as breakerpoints gap tends to decrease.

[Jerry Rxman Griffin aka MuthaF'er]

If they now have too much resistance your electrical charge will not cross over to the spark plugs as well. Lesser/no spark results.

Replace the 40+ year old caps as a set and be done with it.

[topperharley]

The bike is cb 750 k2. Std bore. Custom air cleaners and straight pipes. Runs fine when warm. Cold start is hard. It starts with full choke and throtle but only with 3 cyl.
Cyl. 4 is missing that inner flap on the choke. According to plugs it isnt running lean. I would say maybe a bit ritch.




I measured the caps only. Those are 0 ohms caps. 0.8 readings with a bit of wear.

I have these coils

http://vi.raptor.ebaydesc.com/ws/eBayISAPI.dll?ViewItemDescV4&item=171142438255&category=177961&pm=1&ds=0&t=1461518665485

Primary 4.2 ohms and secondary 11k ohms.
No. I dont know how to measure coils.

[jonda500]

I think 8000ohms should be fine - all I worry about is having the same or similar readings for 1 and 4, same or similar for 2 and 3 and that they are somewhere between 5000 and 10000 ohms!
John

[topperharley]

If i use plugs with R then 0 hms plug caps are fine?

Lähetetty minun SM-G903F laitteesta Tapatalkilla

[Deltarider]

If i use plugs with R then 0 hms plug caps are fine?

Yes.

[przjohn]

You have a cold start issue and you have 1 cylinder that is unable to choke, I would start there. Fix the obvious before anything else.

[topperharley]

S***. This morning it started with only one cylinder #2.  Whats going on?  It takes a strugle to get all cylinders to fire. After warm up it starts and runs great. Where to start finding the solution?

[flybox1]

at 8000ohms, your caps are shiit (if supposedly 5kohm rated)
install new ones.
when was your last carb vacuum sync?

[topperharley]

Yea. Im gonna get new caps for sure.
There is somethibg fishy about the carbs or something. If i set the carbs lock nuts and the rod like the manual says before sync, it just revs madly.

I have to put #1#2 cylinders "slider" closer then #3#4. After that it setles down.
Can someone gimme specific working order and advise. I couldnt be more thankfull.

[flybox1]

Yea. Im gonna get new caps for sure.
There is somethibg fishy about the carbs or something. If i set the carbs lock nuts and the rod like the manual says before sync, it just revs madly.

I have to put #1#2 cylinders "slider" closer then #3#4. After that it setles down.
Can someone gimme specific working order and advise. I couldnt be more thankfull.

What bike and model carbs do you have?
I dont know the terminology you are using here.....Carb lock nut?  Slider? 
Have your carbs been thoroughly cleaned? did you do a bench sync?
have you 'rebuilt' your carbs with some sort of aftermarket carb 'kit?'
we need more details, pls.

[topperharley]

Sorry about my english.
I mean that if i set the carbs like the manual says the idle is something like 3000rpm.


The picture that has the rod Bad and Good i have to set cyl #1#2 like bad. Otherwise it revs madly.

[topperharley]

Sorry. Cb 750 k2.

[flybox1]

No worries.
as you described, your hanging/high idle indicates all the slides are not the same height.
please do a bench sync (manually set all slides to the same height), and then do a vacuum sync (to fine tune the slides individually to get them all to pull the same vacuum)
This will allow you to lower the idle using the idle set screw.

[topperharley]

What would be a good gap from slider to carb body. Like i wrote i cant put them like manual gives. If i measure the gap from slider to body. Is it a bad idea to start from zero gap and try to get some idle with idle screw and then do the fine sync?

Lähetetty minun SM-G903F laitteesta Tapatalkilla

[flybox1]

turn your idle screw out so it no longer touches.
Bench Sync - loosen and then lower your slides all the way to the bottom, and secure them in place.

----or, if you have a 'slave' or 'un-adjustable' #2 carb, lower #2 slide (turn out the idle set screw) so it gently pinches a 3-4mm drill bit or pin.
Leave the idle set screw where it is, pull out the pin/bit, and individually lower the other three slides down to get them to the same height as your #2.  they all should now be at the same height.
Check this by turning out the idle screw....all slides should bottom out at the same time.
Now you can vacuum sync them.
 

[topperharley]

I have done the hard sync once but i will try it again. This time im gonna use a 2 or 3mm drill bit. Last time i did that i used 4mm nail and when i started the bike it took crazy revs. I had to screw cyl 1 and 2 sliders down to get the idle to setle down.  I am doing something wrong and i have to try it again.
It just makes me wonder that why does it run so good when its worm. It wont budge or choke even on extremely low revs on first gear. 
I take the carbs out this evening and hard sync and set the float levels again tomorrow.
How much revs should i have on the bike when syncronizing?

[flybox1]

I have done the hard sync once but i will try it again. This time im gonna use a 2 or 3mm drill bit. Last time i did that i used 4mm nail and when i started the bike it took crazy revs. I had to screw cyl 1 and 2 sliders down to get the idle to setle down.  I am doing something wrong and i have to try it again.  once sync'd, you use the idle set screw to lower the idle, not the individual carb top adjusters...
It just makes me wonder that why does it run so good when its worm. It wont budge or choke even on extremely low revs on first gear. 
I take the carbs out this evening and hard sync and set the float levels again tomorrow.
How much revs should i have on the bike when syncronizing?  as low as the bike will comfortably idle.  for my 78, its around 1200rpm

[topperharley]

oh, and all carbs are adjustable. Instead of leaving 2mm gap i will set sliders all the way to the bottom and start there.
thank you very much flybox1

[flybox1]

oh, and all carbs are adjustable. Instead of leaving 2mm gap i will set sliders all the way to the bottom and start there.
thank you very much flybox1

OK
in figure 2.2----set each carb to GOOD
turn idle screw OUT, to where it just loses contact.
adjust each carb to bottom,  and tighten in place.
turn in your idle set screw, and vacuum sync.

[topperharley]

#$%*. K just downloaded the real service manual. There is so much more stuf then in haynes.

Lähetetty minun SM-G903F laitteesta Tapatalkilla

[flybox1]

#$%*. K just downloaded the real service manual. There is so much more stuf then in haynes.

Lähetetty minun SM-G903F laitteesta Tapatalkilla

lol.  get HondaMan's book, too    Helped me rebuild my 750.  Its worth its weight in gold.
http://forums.sohc4.net/index.php?topic=65293.0

[topperharley]

Thanks. Im definetly gonna buy that.

Lähetetty minun SM-G903F laitteesta Tapatalkilla

[topperharley]

Bench sync is done. Float level adjusted. They were way off. Only cyl 2 was on the spot. I have to stop taking Jack when i deal with the bike.

Plug caps and plugs equaled total of 10kohms. Way to much. I bought d8ea plugs and Beru 5 kohm caps.

Sum. Bench sync done with care. Float level adjusted 26mm. Jets and lines cleared. New plugs and caps.
Lets what happens this evening.

This doesnt involve idle but i have 135 main jets becouse i had that 900cc before.
Bike runs nice with these but is there a huge difference in fuel mileage if i install 110's