Author Topic: What gives?!? (Read 11150 times)

KingCustomCycles.com · « **Reply #25 on:** January 04, 2009, 03:04:28 AM »

Quote from: 754 on January 03, 2009, 08:05:52 PM

did you change plugs?

+1 Do you hear me now? I love your persistence on this one.

TheHun · « **Reply #26 on:** January 04, 2009, 06:20:04 AM »

Yes I have changed them yesterday sorry. Got some NGKs. Same problem

eldar · « **Reply #27 on:** January 04, 2009, 10:11:08 AM »

Stock plugs are d8ea ngk. If you got dr8ea then you got the wrong plugs and will most likely continue to have goofy little issues.

TheHun · « **Reply #28 on:** January 04, 2009, 03:28:56 PM »

Ok. Got the bike running somewhat. Here are my findings today. New plugs

1. Number 2 cylinder is not firing
2. 1/3/4 cylinder are hot to touch once ran for a while, 2 is just barely mild
3. 3/4 cylinder is a little bit hotter than the others
4. timing is off I believe quite bad

I went ahead and took the carbs off and disassembled #1 carb, float bowl had all kinds of gunk, also on the main jet and such...I am going through it all to make sure it is cleaned.

Accel pump was filled with particles..needs cleaning/rebuilding.

Air screws were out way too much I think, over 3 turns.

So the whole bike is getting a whole full tune up. Number 2 is not wiring, I am thinking its a coil problem.

I also have one question, on the carbs right by the main fuel line there is a line, on my bike it is not connected to anything does anyone know what that line is for?

cbr-eric · « **Reply #29 on:** January 04, 2009, 03:43:36 PM »

vent line. I wouldn't rule out that the carbs are just soo bad to be causing your problems. start with that and see how it runs. make sure to pull those slow jets, I just found that out

are you getting spark to your cold cylinder? wet plug?

TwoTired · « **Reply #30 on:** January 04, 2009, 03:57:15 PM »

If you have crap in the carbs, the idle or slow jet most likely get stopped up (it's only about 0.016 in. in diameter). Since they supply most of the fuel at idle settings, the pipe stays cold. The PD carbs have pressed in slow jets. To clean you must remove them (yank them out) then tap back in after cleaning. Quite a few posts have been made about cleaning these carbs.

I doubt your coil has a problem. A single coil fires two plugs. If one is firing the other must also, if the plugs are good. One coil fires 1-4 the other 2-3.

The smaller nipple next to the fuel inlet is a carb vent line. A tube runs from there and back to between the engine and swing arm. Any debris that gets into that nipple settles into the carb bowls, or clogs fuel jets.

Cheers,

TheHun · « **Reply #31 on:** January 04, 2009, 04:01:06 PM »

No spark to the plug. I tried all my plugs on it old and new ones. It is wet from fuel but thats it. No oil residues on any of the cylinders on the spark plugs either. All cylinders are getting fuel, I checked by the redneck way-place my hand over the carb when it was running and my hand got wet from gas..so the carbs are getting fuel.

Yeah I am tearing into the carbs to make sure everything is good and clean. I am getting a accell pump rebuilt kit too...it is dirty...didnt have much chance today to work on it..it is super cold outside, but what better way to learn about carbs then just doing it yourself and ask questions as you go. I am mechanically inclined so I don't see much problems.

I narrowed my problems down to three things:

1. Timing Off
2. Something in the 2/3 coil is bad. Number 2 doesnt get spark but Number 3 does.
3. Dirty Carbs

TheHun · « **Reply #32 on:** January 04, 2009, 04:03:06 PM »

Why would number 2 dont fire then? The other mysterious part about Number 2 is when I try to test it, it shocks me, none of the other cylinders does that when I try to test for spark..only #2

Patrick · « **Reply #33 on:** January 04, 2009, 04:09:37 PM »

Check your No. 2 wire for breaks in the insulation. Pull off the spark plug cap, trim back the wires about 1/4 of an inch and screw the cap back on. This will eliminate oxydation at the end of the wire as the problem. If still no spark, switch the spark plug caps between 2 and 3. If the problem follows the cap, then you need a new plug cap.

Patrick

TheHun · « **Reply #34 on:** January 04, 2009, 04:17:17 PM »

Love this site. Thanks for the help again...more brains=better problem solving skills

TwoTired · « **Reply #35 on:** January 04, 2009, 07:01:02 PM »

The coil is aptly named as it is two windings of wire; a primary and a secondary. The part that goes to the spark plugs (secondary) is a single coil of wire with one end going to one spark plug and the other end going to another spark plug. In order for current to flow in that secondary coil the two ends must connect together somehow. Normally, the plasma at each spark plug tip completes the conductive path through the cylinder head when spark occurs.

If your report is accurate and only one spark plug is sparking, then the other lead wire is shorting to the head, or the spark plug itself is shorted.

You should look for arcs in a darkened environment to see where the new plasma path is being formed. You'll see it in the form of an arc. I'd guess the insulation is cracked at the coil juncture, and you'll find it arcing to the frame there. When you touch the lead, you are offering an easier path for the current, so it goes through you (unless you insulate yourself from completing a circuit path by using one hand only and keeping all other parts of your body from touching any other part of the machine besides the ignition lead).

Cheers,

eldar · « **Reply #36 on:** January 05, 2009, 10:07:58 AM »

Well as I said, clean the carbs! Now you know why!

The idle jets can be pulled out. You wrap them with a piece of rubber and then grab with pliers. Twist and pull, they should pop out. Make sure all the holes are clean.
The FUEL screws should be set at 1.5 turns out. I say fuel screws as that it what they are. They are not air screws on these carbs.

If the wire is shorting out, you can either replace the wire OR get a new coil. A could will run about $35 or so from partsnmore with the leads, you just have to screw on your plug caps. A new wire would be about 7 or so and you have to drill out the old wire and strip the new one and epoxy it back in. I think it is too much work but it may be worth it if you are a purist.

TheHun · « **Reply #37 on:** January 05, 2009, 10:11:09 AM »

Would any coil with a dual output work?Say a CBR F2? I looked at the CBR F2 diagram and its the same wiring setup as our CB750. It might not be 100% fitment but it should work

Patrick · « **Reply #38 on:** January 05, 2009, 10:22:38 AM »

You need to check the ohmage of any coil you would want to use. Stock 750 coils run at 5 ohms. Many, including me, run 3-ohm coils, but you should install a 1-ohm resistor if you go with the hotter coils. The electrical system on these old bikes can be taxed too heavily with hotter coils. if the coils are any hotter than 3 ohms - any lower ohmage - don't use them. Your electrical system won't support them.

On my K0 750 I have the coils frtom an 80s VT750 (3 ohms) along with a Hondaman ignition and a Hondaman resistor. It gets good strong spark and the system charges just fine.

Patrick

TheHun · « **Reply #39 on:** January 05, 2009, 10:31:58 AM »

CBR f2 coils are around 3 ohms stock

eldar · « **Reply #40 on:** January 05, 2009, 11:28:03 AM »

the coils I am talking about are 5 ohm which will do dandy if you have the stock system.

https://www.partsnmore.com/cat_index.php?model=cb750_sohc&category=electrical

check on this page about midway down.

Duke McDukiedook · « **Reply #41 on:** January 05, 2009, 11:48:22 AM »

Hey Hun,
I would definitely change the plug wires, that's where I had my problems when I was getting ticking/misfiring/bad idle. If you keep getting your plugs wet after clearing up the spark problem you may want to switch to D7EA's for the Mizery cold. I have been running those so far this winter and no problems here. Watch those coils from partsnmore, I got a bad one and it took a while for me to figure out I received a bad, new coil from them. Went with the green dynas after that and no problems.

eldar · « **Reply #42 on:** January 05, 2009, 12:11:09 PM »

Well 30 versus double or more. The dyna had better be good!

Terry in Australia · « **Reply #43 on:** January 05, 2009, 03:17:11 PM »

Quote from: eldar, Master of the K8 Thunder! on January 05, 2009, 12:11:09 PM

Well 30 versus double or more. The dyna had better be good!

They are Eldy, and worth every penny.

eldar · « **Reply #44 on:** January 05, 2009, 09:13:37 PM »

I am sure they are. The partsnmore are basically the same as stock. I would like to get the dynas too as my wires are also getting old.

TheHun · « **Reply #45 on:** January 06, 2009, 02:02:26 PM »

UPDATE:

Wow..all I can say is wow. A tip for people, if you think your carbs are somewhat clean because they look clean on the outside...it was a

awakening when I opened the carbs. Everything from the main jet to the accell pump had crud all over it. Little sediments here and then, rust built up etc, the nasty stuff just kept coming out and out. I would let the carb cleaner sit for a little bit, more crud came out. Did that until nothing but the carb cleaner was coming out. Now my carbs are clean as it can be.

I spent a good 5-6 hours cleaning the carbs. They looks fantastic compared to how they were before. Everything was cleaned. Nothing comes with a price..I tore apart one of the gaskets for the top carb cover..good thing I have gasket making paper at the garage

My newer coils are coming in this week, so are my new points/condensers/filters. I should..should have it running soon. Valves are going to be checked too while I am at it, but my feeler gauge only goes to .010 and I need it down to i believe .002 according to the shop manual.

What I have learned- learned my carburetor a lot better from digging in myself, using info from here and the shop manual. To put an inline fuel filter on the bike $3.00 every two months or so is a wise investment for that to keep most of the crude out of carbs. When the bike is running good, periodically run b-12 carb cleaner when a tank of gas.

Thanks for all the help i got from this site.

Plus I found out I got PD42B carbs not A, like other Ks. According to my manual I should have PD42As. Also it has a 110 jet instead of a 105 like how it should.

cbr-eric · « **Reply #46 on:** January 06, 2009, 04:09:21 PM »

have you tried running it with the carbs on? I bet it runs a LOT better now

TheHun · « **Reply #47 on:** January 06, 2009, 04:26:51 PM »

Nope. not yet..waiting on all my other tune up parts to come in. I bet she will run good once its synched and timed

cbr-eric · « **Reply #48 on:** January 06, 2009, 04:34:11 PM »

you should try with just the carbs cleaned, to see the difference that alone makes

OldSchool_IsCool · « **Reply #49 on:** January 06, 2009, 05:39:57 PM »

Tappet Feeler Gauges: You need a little gizzmo like this:

http://www.motionpro.com/motorcycle/tools/view/tappet_feeler_gauges/

Maybe the place you ordered from has them and can toss one into the package if they haven't shipped it yet.

A note on in-line fuel filters - make sure you mount it standing upright. A horizontally mounted in-line filter can trap air and restrict your fuel flow.

News:

Author Topic: What gives?!? (Read 11150 times)

KingCustomCycles.com

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