Plug Colour and the new Hmf System

[Def-e-nition]

Morning .

Guys Im in a bit of a fix .
I had the Rex at a Dyno shop to once and for all have the Air fuel reading sorted out . This was done about two months ago .

Last month I had my Car serviced , and , along with a chip , it makes the Plugs burn a nice tan colour - perfect actually , but nothing close to what i should be gettting out of the Quads plug .

My problem is the following : after the dyno , the plug still burns a smoke blackish colour , and according to the dyonoJet reading the co is fine ...

I fitted a full HMF system last week , and the exhaust opening is substantially Larger than the present set-up .

NOW - the guys have said i should consider lifting my main to a 170 , the kit also recommends this . I have read elsewhere though of guys with similar mods running 155 and 160's at Sea elevation , which is in line with me .

SO - if i go up a jet size , to compensate for the bigger header diameter , plus the freer pipe- and the Plug is currently burning smoky black (but not Wet ) - wont I be adding to the problem and making it even worse , than solving my problem ????

I currently run a 165 and the bike pulls fine , hence my catch 22 situation , as Im between the 155/160 and 170 that the kit says to use .

My personal feeling is to sit tight and see what the Plug does , or how the bike runs with the new pipe . i have not ridden yet . The bike was set up for 13.9:1 yet the plug shows a SLIGHTLY rich mixture ....


???? Help ????

[Eviltanker]

Do a plug chop and see how the plug looks.go from there.

[Def-e-nition]

Plugf chop meaning ride the bike on new plug and assess ??
ok . tomorrow Ill go fetch one and do the chop .
flat out , then clutch in and coast . Remove plug and check .

This baffles me man , as I had the damn thing set up , and it contradicts what i am told to do regarding main jet ....

[hornetgod13]

Sounds like a 165K may be a tad rich. If you go to a 170K than your set up will definitely be rich. I'd put a fresh plug in and run a 162K and see what the plug look like. Is your air box lid on or off?

[Kaleigh]

the way i jet is like this.. i will size up as much as i can go.. the take it for a nice ride at WOT.. if it bogs out at WOT then drop down a jet size.. keep doing this til it doesnt bog at WOT then you should be really really close to the perfect jet size.. I do this everytime and works great for me.. did this a few times with a few quads and i see a nice tan colour plug all the time..

[Def-e-nition]

sup kaleigh .

Its a dyno 165 at the moment , and i do think that going UP will richen it too much .

By bog down - you mean it hesitates a little each time in top gear ?

Ill check for that today - im going to nail its *** to the Wall this afternoon on the track - I cant WAIT to hear that hmf in Full cry !! Friggin thing is perhaps a littel too loud !! but I suppose they are not here to please evryone . They are going to implement noise-level by-laws soon , and that means South africa will importing a crate full of Quiet cores .........

so you all agree with me then - I mean , even after riding with ones plug in for a month man , if the mixture is correct - eventually it WILL turn the brown tan colour we want it to be . the new plug test is simply a quicker way to obtain a reading - Correct ?? ??

and this bugger is still burning smoky black .

162K - What would that size be in Dyno again ? I've left my chart at home , so i cant look it up .

[GPracer2500]

Originally posted by Def-e-nition
....even after riding with ones plug in for a month man , if the mixture is correct - eventually it WILL turn the brown tan colour we want it to be . the new plug test is simply a quicker way to obtain a reading - Correct ?? ??....

No. For the kind of fine tuning you are doing, you'll never get good info from an old plug. The problem with old plugs is they've been run at all different throttle positions. You could be rich on one circuit and lean on another. An old plug won't help you distiguish what's what.

When you do use a new plug, remember to look way down inside the plug at the very base of the insulator. The mixture ring at the base is what you're looking for. They're called "plug chops" because you'll often need to actually "chop" (cut) away the threads of the plug to see the area that's important.

Here's a couple examples of plug readings. These are from a dirt bike not a 400ex but the idea is the same.

With a 148 main (just right):
http://img62.imageshack.us/img62/4870/plug148mainmediumrh3.jpg

With a 152 main (a little rich):
http://img62.imageshack.us/img62/1542/plug152mainmediumoi2.jpg

The part we're looking at is the "mixture ring" right at the base of the conical portion of the ceramic. Each was colored with a trio of 7 second WOT passes. Rememeber to spend as little time as possible at anything other than WOT when doing the tests (no idleing or soft riding if you can help it).

Plug readings introduce the variable of different fuels. All pump fuels are not created equal and they can skew the readings some. Personally, I don't use plug readings (much).

[Kaleigh]

Originally posted by Def-e-nition
sup kaleigh .

Its a dyno 165 at the moment , and i do think that going UP will richen it too much .

By bog down - you mean it hesitates a little each time in top gear ?

Ill check for that today - im going to nail its *** to the Wall this afternoon on the track - I cant WAIT to hear that hmf in Full cry !! Friggin thing is perhaps a littel too loud !! but I suppose they are not here to please evryone . They are going to implement noise-level by-laws soon , and that means South africa will importing a crate full of Quiet cores .........

so you all agree with me then - I mean , even after riding with ones plug in for a month man , if the mixture is correct - eventually it WILL turn the brown tan colour we want it to be . the new plug test is simply a quicker way to obtain a reading - Correct ?? ??

and this bugger is still burning smoky black .

162K - What would that size be in Dyno again ? I've left my chart at home , so i cant look it up .


I have dyno and Im using 160.. anyways.. dont go by my plug.. dont know why i told ya.. but oh well.. lol..

yea im talking about hesitation at the top end.. seems like you hit the rev limiter and it cuts out for a second and kicks back in.. this is usually caused by being rich.. also black smoke it rich too.. keep dropping jets til it doesnt bog at WOT.. then if it backfires after you found the right plug.. turn your mixscrew up 1/4 at a time til the backfiring goes away if there is any.. anyways.. good luck with that Def.. let us know how it turns out for you..

Take Care Bud..

[Def-e-nition]

So much for taking care .

Did a figure S loop track yesterday with the Bike absolutely screaming - and Rolled it .

Concussion, Shoulder , Pelvis . Front Light ,its bracket , & steering stem . I got a Vfr Friday , Now I cant even go and RIde THAT . .

Plug chop- amazing .Hey .. Gp , good to have some input from you again . First time I've seen something like that . Im not even sure any of the guys have seen something like that around here . Ill give that a try for sure . Im so Miffed at falling yestarday with myself I should ban myself for 3 weeks from riding for being so stupid this yesterday - I should have checked the surface BEFORE going out for a ride , but hwo knoew man , Who knew ??

Bike , with 450 shocks , seems a little too rigid and unforgiving , but yesterdays major fall was simply because the new track was laid out over a compacted section (about 7meters) , with the rest of the track ploughed and grippy . I belted it around that corner , and that was the last thing i remeber besides seeing the quad do 2 complete rolls to its right before coming to a stop on its wheelss .

Jussttt Great ...