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Message started by ThumperPaul on 04/23/24 at 08:57:00

Title: Spark Plug Evaluation
Post by ThumperPaul on 04/23/24 at 08:57:00

Who puts an Autolite spark plug in a Japanese bike? (nevermind :o)

Anyway... She's running a little rich wouldn't you say? I don't know how long the plug has been in the bike, but a definite sign the bike was running a bit rich. And/or perhaps some oil fouling. It seems to be mostly carbon to me. And the plug wasn't exactly tight (about 1/4-1/3 turn shy of tight).

Upon carb disassembly, I found a 145 main jet and 47.5 pilot jet in the carb. So, it's not the smallish jets. I found the needle setup very rich and not assembled correctly. That will have to be addressed.

Title: Re: Spark Plug Evaluation
Post by Savard 05 on 04/24/24 at 03:41:37

I would say definitely rich

Title: Re: Spark Plug Evaluation
Post by Savard 05 on 04/24/24 at 03:46:19

Those are stock size jets I'm using in my s40 ID say maybe the carb setup being wrong had something to do with it running rich on mine I just messed with idle speed and air valve 2 1/2 turns out and my plug was nice tan color with those same jets.

Title: Re: Spark Plug Evaluation
Post by Dave on 04/24/24 at 04:57:48

If the engine hasn't been run in a while - you really can't judge the carbon color to mean anything.

For some reason the tan and white carbon on spark plugs and exhaust valves turns black over time.

Title: Re: Spark Plug Evaluation
Post by ThumperPaul on 04/24/24 at 05:05:25

0723212B3623217625372A25440 wrote:

The needle on mine was assembled incorrectly and setup rich. I’m fairly confident that’s the cause of my rich condition.

FYI - the 47.5 pilot jet is for older models that also had idle jets. Newer models use a 52.5 as stock and don’t have the extra idle jets. The 145 main is stock for newer models, but the older models used a 155 main jet.

I’m rebuilding the carb with a 52.5 pilot, 150 main, and I’ll be setting up the needle closer to the middle (move the clip up and lean out the midrange). See my other post about the needle and white spacer location for more details. Hopefully I can get it right (or close) on the first try so I don’t have to repeatedly tinker with it to get it right.

Title: Re: Spark Plug Evaluation
Post by ThumperPaul on 04/24/24 at 05:13:52

Thanks Dave. Interesting and didn’t know that. Seeing the plug and how the needle was setup beyond the richest 3-groove setup, I’m pretty sure it was running rich before the bike sat up.

Title: Re: Spark Plug Evaluation
Post by DragBikeMike on 04/24/24 at 12:06:25

The spark plug heat range is also a consideration. What number is that Autolite plug? You are correct in assuming your needle was set way too high, but a cold plug won't help the situation.

You should probably get an NGK DPR8EA and install it to make sure you have the correct heat range.

Title: Re: Spark Plug Evaluation
Post by ThumperPaul on 04/24/24 at 15:22:39

Thanks Mike. I hadn’t thought about that.

The Autolite is a 4163. The last digit is heat range - so heat range of ‘3’. Autolite doesn’t have a standard set of numbers for heat range and their plugs are in ‘families’. For the 416 family, they have 2,3,4 heat range for this family. So it’s in the middle heat range at a 3 for this family. (In a different family, a 3 might be the coolest in a 3,4,5 heat range numbering). Autolite couldn’t make it easy.

And I installed a NGK DPR8EA-9. This ngk has worked well in other ls650s I’ve had.

EDIT: I just found a cross-reference chart for the Autolite plug that shows a match to the NGK DPR8EA-9. So presumably it's not too far off. (??) It's copper core with nickle electrod material (center and ground).

Title: Re: Spark Plug Evaluation
Post by Savard 05 on 04/25/24 at 05:04:34

Thumper paul you are right mine is a 05 and yes it's 145 main and 52.5 pilot for some reason always forget sizes. In the warm months my bike does good i did white spacer mod took it down 1/3 of size and really helped the low end surging but how is the 150 main jet do ? I've been thinking about it but my plug was good color and mpg is avg.Im In ohio so not alot of elevation for bigger jet size and stock setup exhuast and air filter wise. Anyway was wondering how the 150 does on your bike if you think it's something worth trying?

Title: Re: Spark Plug Evaluation
Post by ThumperPaul on 04/25/24 at 05:31:31

Savard05 - I’m going with the 150 based on other forum members experience and advice. I’ve had 3 of these bikes before my current one and none of them were stock until this one. So, this is a bit of an experiment for me. I don’t run wide open throttle very often, but I’m hoping for a little extra grunt and top end with the 150 when I do. On previous bikes I’ve had with more open exhausts, I did ‘jet up’ a bit to accommodate.

If I find that the 150 is too rich and bogs acceleration up top, or it gets crappy gas mileage, I have the 145 cleaned up and ready to plug in.

Part of my thought process and rationale is that these bikes are set up as lean as functionally possible from Suzuki to meet EPA and other regulations. That’s fine, but if there’s something left on the table, I want it. And if the bike can run a bit cooler by jetting a bit bigger, I want that too. I’m in the heat swamp known as Houston.

Title: Re: Spark Plug Evaluation
Post by Savard 05 on 04/27/24 at 03:27:28

Thanks for the response thumper Paul. I've read through these forums alot when I first got my bike and alot of people seem to jet 150 main with stock setup and some stay with stock jetting. I like the way she runs now so why change it right. And yes alot of it does have to do with where your at location wise. Anyway you'll have to let us know how she does when all setup and thumping!!!

Title: Re: Spark Plug Evaluation
Post by ThumperPaul on 04/27/24 at 05:54:48

I hear ya. All this was carb timing talk was in vain now that I’ve managed to trash the stock carb. It’s a cleaned up $500 paperweight now with new authentic Mikuni jets and a few pieces from a cheap aftermarket rebuild kit.

Stay tuned for a future post on my trials and tribulations installing a PWK38 Air Striker carb. I’ve installed a PWK40 on a different S40 I had so I have some idea about jetting from the slightly larger PWK40 and DragBikeMike’s tuning and testing with the PWK38.