Nearly everything I've seen or read about involving examine the plug as a diagnostic tool are always about the elusive and magical 'tan' colour that we long to see when we remove it or the oil or soot or white ash or whatever that indicates other stuff.

This post is not about that. It is about the one time I read of how it should be inspected as opposed to how it usually is. Usually the method for inspecting is simply removing the plug and having a look at it, then comes the analysis. There is no preparation for this, meaning you just pull it out and you'll get your answer. One time though I read that in order to do this test, you need to get your bike up to speed then clutch in a bring it to a stop quickly, do not coast to a stop.

Why. What is the precise purpose of this second method.

Cause there are different ranges that jetting Covers in the carb , idle , pilot , needle , main.  And as plug cools the color changes. Yes it's something that is complicated and simple at the same time.
Are you having a problem? Are you jetting the carb ?
I use throttle indexing technique to find and correct problems and for jetting too.
I almost never go by the plug until I'm done with the corrections , it's a pita !

OK, that's good, but it begs the question does that mean that the plug needs to be removed immediately after coming to a fast stop, or is the fast stop itself enough and it's then OK for it to cool off?

@Gary_in_NJ, OK thanks for that, makes perfect sense. In other words I will be taking Rutty's advice and not bother about the plug till the end.

@Ruttly, at the moment I am jetting the carb but I'm not having any problems and I'm not going to get as intricately involved as IslandRoad has recently, the bike is running fine and I'm happy. Having said that though I want to take a step back and do my best to *slowly* do some jet tweaking over the next few months.

Maybe I can convince you to do a more detailed analysis of how you precisely determine the jetting. My experience so far is that having bought the bike in showroom condition having ridden only 500 miles in 11 months, when I got it, it was running very very hot, tiny shutdown poof, but annoying low speed surging, but it was the heat that bothered me. Did a pilot mix adjustment from what it was on 1 3/4 to 2 3/4 and that instantly solved the overheating and surging problem too. So all was good.

I decided to put in a 55 pilot from the standard 52.5 which took the pilot screw back to 1 3/4. However with my limited experience I didn't really notice any difference between the 52.5 adjusted correctly and the 55 adjusted correctly, while some people suggested that the 55 pilot (I'm at sea level btw) was too much I left it in as I was about to install a Dyna which would need more fuel anyway.

After putting on the Dyna and before riding the bike I installed a 150 main from the standard 145 because there seems to be a general consensus that 145 is definitely too small. I did a lot of the roll on WOT drop back an eighth of throttle looking for the telltale surge which was not there. Nevertheless I still went for a 150 main. I'm still wondering why the 145 did not give me the surge when backing off WOT an eighth. I marked the throttle position from slack removed to WOT and all the in-betweens. So that's a question for anyone, how come that 145 is considered definitely lean even at sea level but there is not indication of this for me at least.

I also did the spacer mod and as I am in Australia I have the notched needle. I was surprised to measure the nylon spacer at 2.5mm as I had been let to believe it was more like 4 or 5 metal washers or 4 or 5mm. It began on middle and as the notch difference is 1mm that means that just moving it to the bottom notch and leaving the spacer was almost the equivalent of thinning the spacer by 1/2, in fact the difference was only a 1/4mm and I'm pretty well certain that absolutely no one no matter how anal is ever going to do a 1/4mm needle position adjustment.

Now I don't know if the AUS needle is the same as the US needle (without notches) but it has notched machined into it, OR if's it's a different needle so I don't if the single clip position on the US needle is equivalent to the middle notch in Australia, or not. I don't suppose anyone can answer that without a side by side comparison. In the event as it is also general consensus that a bit more gas on the needle is definitely a good thing. Removing the spacer completely (for US) is bad for some but half a spacer is pretty well de rigueur.

If you want to illuminate me to your very specific needle fine tuning then I'd look forward to reading it.

OK so where I am at the moment is that I'm not unhappy with how it is there's no surging, no shutdown poof, no overheating, and there's a tiny bit of throttle shut down pops and crackles which I deem a good thing because I wasn't getting any of that before the dyna and that meant to me that it was not tuned to it's best because deceleration pop is normal.

Right now I'm wondering whether I should go back to the 52.5 pilot and put the clip back to the middle with the spacer removed completely meaning that I'm giving it a further 1.5mm from what it is now (bottom clip with spacer) or not.

But mostly I'm concerned with how to tell the difference, what to look for because as I said, I'm not even seeing a difference between the 55 pilot or the 52.5 pilot as long as they are both adjusted properly.

Hi, IslandRoad,

Believe me I've read all your tuning threads and the responses with care. I could see that it was beginning to mess with your mind and I was mindful of falling into that. Yep I've turfed the limiter.

Just got back from a 100 kilometre highway run, which was a bit tricky because poppo was out in force. The only time I could get a deceleration pop was sometime when I shifted from 1st to 2nd and then to 3rd, but this was only occasionally and I could not make it backfire or pop no matter how fast I shut the throttle off at high speed.

To my untrained mind I could not locate any dead spots.  Do you know what milage you get with your current set up and when you say spacer at .6 do you mean you've taken 40% off the spacer thickness and left the clip in the middle position?

5,500 between gear changes, must be pretty intense. I was cruising on the highway at 100kph in top and shifted down one with not much difference, so I shifted down to third at that speed and the bike was buzzing and vibrating like a maniac, checking on the rpm chart, I see that 100kph in 3rd is 5200! I think the Savage really begs for early gear changes.


EDIT: just read a few old top speed and milage posts and my current 52mpg (us gallons) and top speed of 145 pulling hard all the way, seem to be normal. So all I'm really wondering at this stage is what the difference would be if I take the pilot back to 52.5 and give it more gas at the needle. However I'm not in a hurry to do anything.

The difference between the 52.5 & 55 pilot jets is not just one huge step between them.  The jets are closer to each other than that.  There is overlap from 50 to 52.5 to 55, etc.  If you have the 52.5 installed and have tuned properly and the setting is at say 2.5 turns out, then switched to the 55 pilot jet and when tuned you find you are at 1.5 turns out...the end result of the change is the same, the fuel flow is the same, this is the overlap you are seeing.
The general rule of thumb is that when changing one main jet size you will be adjusting one full turn on the pilot screw.  
If you go up or down 2 jet sizes you can expect about 2 full turns on the pilot screw.
Keep on mind that the pilot screw can only safely be turned 3 turns out.
You might go beyond that but if you do it is possible that the screw may fall out as the spring is loosing tension on the screw.
The "ideal" setting on the pilot screw is at 1.5 turns out, but if you have a setting somewhere between 1 & 2 or even .5 & 2.5 turns out, and the engine is running good, then you have done well.
It is all about how WELL the engine is running, regardless of the exact setting of the pilot screw, just don't go beyond 3 turns out.

I hope this is helpful.

eau de sauvage wrote on 02/25/17 at 17:38:18:


Get to desired speed/rpm that you want to check and ride at that pace for a bit, THEN, pull in clutch AND cut engine ASAP, THEN coasting to a stop is OK.

Ruttly wrote on 02/26/17 at 08:41:11:



While I think that the physical throttle position is valuable for some things, it has some drawbacks for what you suggest.  Throttle position is NOT the same as the throttle slide position in the carb.  The slide is controlled by vacuum which is controlled by the throttle plate, which IS directly controlled by the throttle position at the handlebars.  However, depending on air/fuel flow, leaks, and various other factors, the vacuum above the slide could vary - meaning that for example, 1/2 throttle position does not necessarily translate into 1/2 slide position.

Having said that, the throttle position is going to be dog-gone close and will approximate enough to be very helpful in re-jetting, since there is no EXACT position where one jet system transitions into the next jet system and so on.  I always start with idle jet, then go upward from there.  One place that is extremely valuable to have correct is the RPM where you most often ride/spend your time.  I have seen pistons that have huge holes burnt through where this spot is too lean!

@Gary_in_NJ, No far from it. I'm glad to hear some pops!

@piedmontbuckeye, OK thanks got it! on the correct method, will do that once I'm happy with it, which I almost am. Right now I'm just tossing up whether to put pilot back to stock 52.5 and raise the needle another 1.5mm.

However the problem is that I don't really have enough experience to be able to feel where a flat spot is. What I did discover was that I could be cruising on the freeway at 100kph (62mph) with the throttle at 1/4 then I just rolled the throttle on to WOT and it pulled strongly all the way to about 90mph (actual speed not indicated speed) Not sure if that tells me anything about the main or the needle.

What precise test would I need to perform if I wanted to check if the needle needed to be raised a tad or not?

@Ruttly "I just spent 9 nine months messing with jetting" That's dedication. What is your opinion on completely removing the airbox and filter and just putting a cone filter on with the Dyna? Are there any downsides to this?