Author Topic: Spark plug cap resistance and whole lot more (Read 16925 times)

flybox1 · « **Reply #25 on:** April 27, 2016, 06:40:59 AM »

yes, gas mileage will change if your main jet is too big, AND if its too small.
your main jet should be chosen based on obtaining the proper air/fuel mixture when you are in that throttle range, not because of fuel economy.
accidentally going too small can definitely burn up your engine.

It would be great if you'd describe your intake (airbox or pods) and exhaust setup, mixture screw setting, and any other engine mods you've done so we can assist you in finding the right jetting for your bike.

topperharley · « **Reply #26 on:** April 27, 2016, 08:34:52 AM »

First. The bike cold started really good. +4c°. Just a small pop few times then it setlet.
It runs good and idles pretty good. It takes realy low revs and still wont stall. I know it could be smooter but im out of ideas. Il try the vacuum sync next.

Engine is std 750 with open exhaust. Intake is just cones with filter. Needle is set in the middle and the jets 135. Mixture screw is still finding his place. 3/4 to 1 1/8 thats the richest and leanest iv used. Doesnt seem to make a difference. I couldnt find the low jet size.

flybox1 · « **Reply #27 on:** April 27, 2016, 08:47:42 AM »

Thank you for that. How does your bike ride?
Does it have good throttle response throughout the RPM range?

topperharley · « **Reply #28 on:** April 27, 2016, 08:55:10 AM »

Yes it has. Only thing that make wonder is the time when i cruise on high gear and low revs it seems like it missing a pace now an there. Nothing major but still.

Lähetetty minun SM-G903F laitteesta Tapatalkilla

topperharley · « **Reply #29 on:** April 27, 2016, 08:58:34 AM »

And a bit rough idle

flybox1 · « **Reply #30 on:** April 27, 2016, 09:13:36 AM »

We need to see plug color after idle first.
Make note of your current mixture screw setting. If they all are different, set them all to 1 turn out.
Warm up the bike, ride around the block. Shut it down.
Install a NEW, clean set of NGK D8EA plugs, start the bike, and let it idle for 4-5 minutes. Place a fan on the engine during.
No blipping of the throttle, just an idle. Shut it down.
Pull out all the plugs, line them up 1-2-3-4, and take a closeup picture of the ceramic insulator and tip electrodes.

topperharley · « **Reply #31 on:** April 27, 2016, 09:17:14 AM »

Damn. I just bought and installed new plugs but i have driven 30km or so. Maybe this weekend i buy new ones.

Lähetetty minun SM-G903F laitteesta Tapatalkilla

flybox1 · « **Reply #32 on:** April 27, 2016, 09:20:16 AM »

yes, you will want a new set of plugs to better tune your idle sircuit, but tell us about your ride. freeway?town?around your neighborhood? and post a picture of what they look like.
line them up like this.

Deltarider · « **Reply #33 on:** April 27, 2016, 10:01:33 AM »

But new spark plugs is not manditory at all. It's enough that they function well and they will tan pretty quick according to what's happening to them. I don't know where this new plugs thing comes from but it is echoed over and over again.

flybox1 · « **Reply #34 on:** April 27, 2016, 10:04:45 AM »

Quote from: Deltarider on April 27, 2016, 10:01:33 AM

But new spark plugs is not manditory at all. It's enough that they function well and they will tan pretty quick according to what's happening to them. I don't know where this new plugs thing comes from but it is echoed over and over again.

correct, unless the plugs look like this to start with, and you have access to a soda blaster to clean the porcelain before an idle chop.

topperharley · « **Reply #35 on:** April 27, 2016, 11:00:55 AM »

Well well. Here are the plugs. Could be better.
Cyl #1 on the far right.

Mixture screws 3/4 open
I was driving in hoods. Few lights and accelerations.

flybox1 · « **Reply #36 on:** April 27, 2016, 11:12:53 AM »

as i suspected, different on all. no worries.
first comment...i hope it is just the plug angle, but #2 looks strangely short compared to the others

First task, clear tube test to see what the existing bowl fuel levels are. post the results from each.
see this thread
http://forums.sohc4.net/index.php?topic=149299.0

Deltarider · « **Reply #37 on:** April 27, 2016, 11:20:02 AM »

The idea is this: temperature in the combustionchamber is many hundreds of degrees. As long as a sparkplug fires, whatever deposit is on the insulator nose, it will tan accordingly to the ambient (infernal) temperature. As a matter of fact used sparkplugs show better what is going on than new plugs that hardly show anything. Bottomline is that the sparkplug must fire OK. If the current is leaking away over the insulator nose, it's another story ofcourse but then you will have an irregular running engine that you will notice. Another thing is that todays unleaded gasolines don't show much coloring anymore. You can overcome this by adding a spoonful of castor oil to the fuel in your tank. Succes.

topperharley · « **Reply #38 on:** April 27, 2016, 11:22:06 AM »

Thanks Fly and Delta

topperharley · « **Reply #39 on:** April 27, 2016, 11:56:47 AM »

http://forums.sohc4.net/index.php?topic=152670.0

The one having these issues.

topperharley · « **Reply #40 on:** April 28, 2016, 06:55:17 AM »

What kills spark plug? Today i drove to work and cyl 1 didnt ignite every time. It made driving terrible. I came home and put old plug and plug cap to cyl 1. It worked fine again.
Old setup is R plugs and 0ohm caps.
So why did the plug die?
Could it be too rich mixture?

flybox1 · « **Reply #41 on:** April 28, 2016, 07:04:15 AM »

since you changed back to the old cap AND the old plug, its hard to say which was really at fault

i bet the plug was just fouled, if you didnt clean it after you took the picture above.
your new caps are fine. check their resistance if you need...i'd continue using them.

Its time to get your carbs sorted out. clear tube test.

topperharley · « **Reply #42 on:** April 28, 2016, 09:01:34 AM »

What is the size of that drain plug hole. Is that m5 or m6?

flybox1 · « **Reply #43 on:** April 28, 2016, 09:04:46 AM »

Quote from: topperharley on April 28, 2016, 09:01:34 AM

What is the size of that drain plug hole. Is that m5 or m6?

Sorry, I dont know.
On my 350F I used some small (3/16" i think) OD tubing and knife-tapered the end. Screw'd it into the drain hole to do the test.

topperharley · « **Reply #44 on:** April 28, 2016, 10:11:28 AM »

I think that the plugs are fouling becouse rich mixture. The surface is black and fluffy. The plug is like an example on ngk page.

I try to get that clear tube test done on weekend.

Lähetetty minun SM-G903F laitteesta Tapatalkilla

flybox1 · « **Reply #45 on:** April 28, 2016, 10:20:17 AM »

Yes, a fouled plug can cause irregular running.
We also need to know what size pilot jets you have, and if the needle clip position has been changed.
These have not been provided to us yet. We only know mixture screw setting and 135 main jets.
Thanks

topperharley · « **Reply #46 on:** April 28, 2016, 10:26:55 AM »

Needles are at center. By pilot jet you mean slow runnig jet? Coudnt find a reading on those. There is a carb kit for good 38$ price on ebay that has all spares. 110 main jet and std slow running set + all else. Would it be a wice decision to buy it?

flybox1 · « **Reply #47 on:** April 28, 2016, 10:30:57 AM »

Quote from: topperharley on April 28, 2016, 10:26:55 AM

Needles are at center. By pilot jet you mean slow runnig jet? Coudnt find a reading on those. There is a carb kit for good 38$ price on ebay that has all spares. 110 main jet and std slow running set + all else. Would it be a wice decision to buy it?

no....aftermarket jets are notorious for causing tuning issues. buy OEM Keihin Jets only.
you have a bit of exploring to do before you can settle on a correct main/pilot jet size. ordering them now you'll most likely be throwing your money away.

topperharley · « **Reply #48 on:** April 28, 2016, 10:54:25 AM »

Ok. Lets continue with clear tube test.

flybox1 · « **Reply #49 on:** April 28, 2016, 10:58:58 AM »

Do your pilot jets have any markings on them?
Look for a K stamped in the brass to indicate they are Keihins

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Author Topic: Spark plug cap resistance and whole lot more (Read 16925 times)