Jetting problem - JD / spooge / spluttering

[Jakobi]

Don't just whack another insert in and guess. At minimum take note of where the piston edge sits in relation to the bottom of the exhaust port. That will give you some information about the base gasket stack. Then take a squish sample.

The way the S3 head inserts are made, they are all the same volume. It's just the deck height that changes which reduces squish and increases compression. This creates a situation where the ideal squish clearance very well could have too much compression or vice versa.

Also, don't get hung up on the plug unless if it was an old crusty one that has been burnt clean white. Throttle response will generally tell more of the story than the colour of the plug.

 

[jocser]

Don't just whack another insert in and guess. At minimum take note of where the piston edge sits in relation to the bottom of the exhaust port. That will give you some information about the base gasket stack. Then take a squish sample.

The way the S3 head inserts are made, they are all the same volume. It's just the deck height that changes which reduces squish and increases compression. This creates a situation where the ideal squish clearance very well could have too much compression or vice versa.

Also, don't get hung up on the plug unless if it was an old crusty one that has been burnt clean white. Throttle response will generally tell more of the story than the colour of the plug.

Hello Jakobi,

Thanks for this reply. I d really like to follow your advice, but really is where my technical knowledge stops.. You confirm what I was thinking but I really dont know how to see abd measure this.

You say only the height varies, so wouldnt the Red be already better compared to the stock Grey one thats in now?

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[barossi73]

If you dont measure squish you have 2 options-
1.assume it was set up ok with black insert and revert,then try diff needles etc to tame the storming beast.run at least 95ron(if poss,check with previous owner about setup/fuel)
2.compression test with the diff inserts,and avoid anything higher than 185-190(guages vary so allow a margin,maybe target 180) unless you go higher octane on fuel.you could finetune the cr with base gaskets if necessary,but be aware you slightly alter port timing also
If it was me id start with the previous owner and find out everything you can,what changes had been made,fuel requirements etc,before you decide which direction to head
Also if you are comfortable changing inserts youll be fine measuring squish.search and read up.its pretty simple,just be sure to avoid using kicker/starter when bringing piston to tdc

 

[Jakobi]

In regards to comp testing you need to know the actual gauge that you are using to see what number it blows. I have one with an adapter, and my engine that is high comp blows low psi as it's accounting for the volume of the adapter as well as the volume of the combustion chamber. Unless if you have a benchmark to work from a test alone doesn't give much insight.

With the squish there is a write-up here: http://www.gasgasrider.org/html/measuring_squish.html


The gas gas 300, by design, is lower comp than the 250. You should be able to run the black insert with squish around 1.6-1.9mm and be OK on the compression front. If you try to tighten in up to the suggested 1.3 or less you'll definitely run into issues. The point is, that regardless of which insert you use, if you bring the squish in too tight, the compression ratio will be too high as the volume of the head inserts are still the same from one to another.

 

[jocser]

Hey Guys,

big big big thanks to you for your extremely good help. I've been reading the articles and now I get the whole squish thing!
So my bike likely was set up for the black insert (maybe with other base gaskets), I was thinking, power is too much so I'll swap the heads, but that wasn't a good decision because I was making the squish bigger and the compression lower. So that might be the reason my bike doesn't respond well in the lower rev's, because compression is important there.
The previous owner and inter-enduro rider is an ex-MX rider who probably likes the explosive power and top power, so the jetting was set up that way.

With the JD needle the power delivery is more in the low rev's I could already feel that, so maybe I'll better switch back to the black insert, cause the bike ran fine, bet rejet with the JD red #4, fuel will burn as it's supposed to be and maybe it will be perfection for me.

Maybe to be sure I better insert the "medium" red insert first, measure squish and when thats around 1.6-1.9, leave it that way? But I am short in time for a long and heavy ride on sunday, so maybe for now just re-insert the black one and JD jet and see what happens. But with the head off, measuring squish with the different inserts isnt a big big big job so I'll see how far I get.

thanks and I'll keep you updated!

 

[Jakobi]

That's the approach I would take.

Drop the coolant, pull the head. Compare the inserts. You could measure the volume of each to confirm if you were that way inclined as well. Then pick the one which works best.

The base gasket stack (cylinder and port height) will also effect the power curve. A thinner gasket that drops the ports will move the power curve down to favour bottom end, where raising the ports will give a stronger top end. It's about balancing the port timing, compression ratio, and squish clearance to achieve the best outcome.

When we speak about having heads modified, it's the process of setting the port timing for purpose and preference, machining the head to tight tolerances, and then correcting the volume to achieve a particular compression ratio. It takes the balancing factor out and gives specific results. In my case I used an S3 black insert with .5mm base gasket to give 1.25mm squish, however had quite a few cc's machined out to still end up with a relatively high compression engine.

A strong engine is good. You can always gear it taller and make the power work over a larger range. It'll allow you to be a bit lazier on the shifter while also taking some of the snap out of the response.

 

[jocser]

That's the approach I would take.

Drop the coolant, pull the head. Compare the inserts. You could measure the volume of each to confirm if you were that way inclined as well. Then pick the one which works best.

The base gasket stack (cylinder and port height) will also effect the power curve. A thinner gasket that drops the ports will move the power curve down to favour bottom end, where raising the ports will give a stronger top end. It's about balancing the port timing, compression ratio, and squish clearance to achieve the best outcome.

When we speak about having heads modified, it's the process of setting the port timing for purpose and preference, machining the head to tight tolerances, and then correcting the volume to achieve a particular compression ratio. It takes the balancing factor out and gives specific results. In my case I used an S3 black insert with .5mm base gasket to give 1.25mm squish, however had quite a few cc's machined out to still end up with a relatively high compression engine.

A strong engine is good. You can always gear it taller and make the power work over a larger range. It'll allow you to be a bit lazier on the shifter while also taking some of the snap out of the response.

Hi, I started and measured squish with the grey insert which was in it but the squish was bigger than the 2,7mm solder I bought. Tried the Black one, which was in when I bought the bike and that gave me a result of 1.6 to 1.85. So that should Be quite good?

I'll try it that way and try to find the time to rebuild the bike this evening, with the jd Red. Lets hope he 'll have torque as hell.

Yesterday I screwed up the m6 Bolt on top of the Head... (Dumbass too tighten...) so I went to a friend to make it An m7... So last Chance!

Another big thanks for All your help Here!

Grts

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[Jakobi]

The M6 bolt for the coolant inlet? Those little fellas would be lucky to need 8Nm on a good day.

Based on what you found I'd say the ports have probably been lifted for top end performance. Did you note where the piston was in relation to the exhaust port at bottom dead centre?

1.6mm squish clearance is still on the large side if you were specifically aiming to set up tight tolerances and improve efficiency, however given you aren't doing that I would be quite content with 1.6mm clearance, high comp, and ports for top end. Should give a nice spread. It's actually very similar to how I had my engine setup when I was running a 300. Been on 250's for some time now though.

 

[jocser]

The M6 bolt for the coolant inlet? Those little fellas would be lucky to need 8Nm on a good day.

Based on what you found I'd say the ports have probably been lifted for top end performance. Did you note where the piston was in relation to the exhaust port at bottom dead centre?

1.6mm squish clearance is still on the large side if you were specifically aiming to set up tight tolerances and improve efficiency, however given you aren't doing that I would be quite content with 1.6mm clearance, high comp, and ports for top end. Should give a nice spread. It's actually very similar to how I had my engine setup when I was running a 300. Been on 250's for some time now though.

Hi Jakobi, I ll take notice of the piston on dead End, I think i was about 1 cm under the exhaust Port. I'll take a pic!

Grts

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[Jakobi]

The points we want to compare (simply for reference points), are the edge of the piston dome, and the bottom edge of the exhaust port, when the piston is rotated through to it's lowest point. It'll either sit flush with the bottom of the port (which is what I expect), or up to 1mm above (roughly).

 

[jocser]

Hi Jakobi, what you said was correct. The piston sits on dead end about flush with the exhaust port. Yesterday I did a 160km quite hard enduro ride and my bike has never been as good as it is now. I didnt have the time to test it thoroughly but it was really good.
It might need a little optimisation because I have the idea he s running lean when idling. Maybe the Air screw needs another adjust and the idle was also too high, what might have caused the idea of the bike being lean.

I ve never known the squish was so important, now my bike pulls like a tractor uphill, very very strong! The explosion thing when powervalve opens is also tempered with the jd needle.

I m going to test some more needles in the future. For what I have Read Here, I think the Suzuki needles match my riding style perfectly?

Another Big Big thanks for all your answers, they were really helpful!

Only spooge is still there but I dont care.

Grts!

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[Jakobi]

Great work mate! Enjoy

 

[adriano.ro]

Usually when head mode is done,the jetting part will go in lean or rich side?

 

[barossi73]

One thing to consider with spooge is that it means a little oil is remaining as oil (not ash) throughout the combustion process.
Thats not a bad thing,think of it as insurance or a little safety margin for those times when you work the engine harder/hotter.imo this is preferable to zero spooge.
if you are still getting too much consider running a different,quality oil,with a lower flash point.be aware that some oils/additives will skew the plug colour a few shades either way.

 

[Jakobi]

It's also largely a feature of the huge FMF Q silencer too. I couldn't jet the spooge out with it, until after cutting it down and repacking it. Even still, I have enough excess oil that I can get some show up at the join between the pipe and silencer if the seal isn't 100%, but only ever get a nice small oily ring at the back of the silencer as opposed to the spooge running back down the can.

Like barossi said. It's not so bad as long as the bike is running as clean and strong as it should.

 

[Jakobi]

Usually when head mode is done,the jetting part will go in lean or rich side?

It depends where you are starting from, but typically with the improved efficiency of the head you'll be able to jet down a little more, while still using all that fuel to create power instead of having incomplete combustion and pushing it out the exhaust. However, if you end up significantly higher on the compression side of things you may need a little more fuel too.

 

[jocser]

It depends where you are starting from, but typically with the improved efficiency of the head you'll be able to jet down a little more, while still using all that fuel to create power instead of having incomplete combustion and pushing it out the exhaust. However, if you end up significantly higher on the compression side of things you may need a little more fuel too.

So Jakobi, does that mean I better try to go a little leaner on the main jet? With the N1EF needle that was in, the previous owner used a 172 while I am now on an 180 with the JD red. Yesterday I rode a large ride with slow and faster parts and the spark plug looks way better than before when it was kind of white, now it's brown butte the upper "lath" (dont know the english word) is more black. Picture of my spark enclosed, does this looks better or too rich?

Maybe I'll try another oil, what do you guys recommend? With my previous gasser I used Castrol Power RS (ex TTS) but someone told me that it is a rubbish scooter oil. I had never had a problem with it and that's the reason I switch to an ester based oil, Motul 800 so I thought that would be better.

 

[jocser]

another addition, retested the compression with the black insert and could get it to +- 135psi with engine cold.

 

[Jakobi]

I don't really bother with reading plugs too much. Too many variables, particularly unless you're testing and reading based on sustained throttle positions.

Motul 800 won't be helping your spooge. High flash point.

JD needles are quite thick towards the pointy end, and as such require larger mains to achieve the same fuelling at WOT. The N1EF tapers down much more.

 

[barossi73]

You have the as2 carb so the ned? Suzuki needle should be fine.you would need the same diameter as youre n1e?/noz? that u started with,same main,pilot same or 1 richer than the original.
For eg.my 13(200) ran noz(h)clip 2/3 p40 m175.stock needle
Now ned(h)clip2/3 p42(40 ok),m175
For fine tuning nec(h) is half clip leaner than ned(h) so nech clip 3 is =nedh clip2.5.
Note,the (h)is diam for 200
I settled on clip2 nedh for warmer months,now we are into cooler weather iv moved half clip richer nech3.
On oil i began with belray h1r,im currently running castrol tts power1(50hrs no prob)
At first topend on belray engine was perfect internally but too much spooge.
Your friend may have been referring to the old castrol tt which is inferior.until i do my next topend i cant comment on protection/internal condition.
Also consider that if the bike was rich for some time it may take a couple rides to clear out the excess oil in the system,esp if you are not wot much