tonyown Posted August 4, 2009 Report Share Posted August 4, 2009 Hi, one of my spark plug came out and I'd like to have your opinion... is it necessary detonation or was it just not tight at start... I normally tight them a lil but not to much I dont know my compression but im at 1000ft elevation run 21 cc domes and +4 timing 91 octane fuel i ran the same before my 4mm stroker and bigger carb setup and I didnt have any detonation Quote Link to comment Share on other sites More sharing options...
DallasGDub Posted August 4, 2009 Report Share Posted August 4, 2009 What does the plug look like? Melting at the top, and also black spots or silver specs around the base. Thats also a sign of deto. Quote Link to comment Share on other sites More sharing options...
tonyown Posted August 4, 2009 Author Report Share Posted August 4, 2009 I'll take pics tomorrow but I'd say they look nice... Quote Link to comment Share on other sites More sharing options...
yamahaman244 Posted August 4, 2009 Report Share Posted August 4, 2009 I'll take pics tomorrow but I'd say they look nice... sorry im stupid lol but wat is that dentonation Quote Link to comment Share on other sites More sharing options...
T_Shee Posted August 4, 2009 Report Share Posted August 4, 2009 did you have your domes cut or are you running a spacer? i saw one case where the domes werent cut right and caused the plugs to back out Quote Link to comment Share on other sites More sharing options...
AKheathen Posted August 4, 2009 Report Share Posted August 4, 2009 if you aren't running a spacer on the bottom, then the 21's just became MUCH smaller, realatively, because the extra stroke really changes the cr. and, yes, you are detonating. new plugs= +5/8 turn after gasket ring touches. Quote Link to comment Share on other sites More sharing options...
tonyown Posted August 5, 2009 Author Report Share Posted August 5, 2009 im not running spacer plate I run 21cc 2mm cut domes by FAST Quote Link to comment Share on other sites More sharing options...
dajogejr Posted August 5, 2009 Report Share Posted August 5, 2009 Measure your squish please...need to know that first and foremost. Quote Link to comment Share on other sites More sharing options...
tonyown Posted August 5, 2009 Author Report Share Posted August 5, 2009 did a search and cant find what is the squish can u explain or give me a link? lol Quote Link to comment Share on other sites More sharing options...
dajogejr Posted August 5, 2009 Report Share Posted August 5, 2009 You take a piece of solder. You bend it and place it through the spark plug hole and make sure it lines up left to right if you're sitting on the bike. You push the kick starter down by hand. It smashes the solder, and you use a micrometer to measure how thick the solder is (how much it's squished) That will tell you how close the head is to the combustion band in thickness. Quote Link to comment Share on other sites More sharing options...
tonyown Posted August 5, 2009 Author Report Share Posted August 5, 2009 hm k and if i dont have a micrometer can i just run racefuel will it be safe or i must know squish Quote Link to comment Share on other sites More sharing options...
spurdy Posted August 5, 2009 Report Share Posted August 5, 2009 hm k and if i dont have a micrometer can i just run racefuel will it be safe or i must know squish Just FYI. I run a 21cc dome in my 4 mil and am around 195 psi static compression. I run 110 octane fuel and set it up this way intentionally. We started with 19cc domes cut for the 4 mil crank but they ran about 235 psi static compression. The porting of the exhaust will effect your static compression also. Yes, you should also know your squish clearance. Too tight of a squish clearance can cause you problems. You can pick up a cheap pair of calipers for $35 or a nice set for around $100. Every mechanic should have a couple of sets! SP Quote Link to comment Share on other sites More sharing options...
dajogejr Posted August 5, 2009 Report Share Posted August 5, 2009 hm k and if i dont have a micrometer can i just run racefuel will it be safe or i must know squish No. If you are backing a plug out, you need to know this information, simply adding octane may not solve the issue. As said, porting can change the cranking compression, but the true need from octane comes from compression ratio... Checking the squish and cranking compression is where you need to start. You could have 150 PSI cranking compression...but have a .020 squish and it will cause problems. Every motor is different, so you need to know this info. Quote Link to comment Share on other sites More sharing options...
tonyown Posted August 5, 2009 Author Report Share Posted August 5, 2009 okok I see but can someone explain me what is a piece of solder cuz I speak french and cant figure out what it is.... I used translator but it tells me it's weld.... I'd like to be bilingual :ermm: I'll measure it when I will know what to use lol Quote Link to comment Share on other sites More sharing options...
spurdy Posted August 5, 2009 Report Share Posted August 5, 2009 okok I see but can someone explain me what is a piece of solder cuz I speak french and cant figure out what it is.... I used translator but it tells me it's weld.... I'd like to be bilingual :ermm: I'll measure it when I will know what to use lol A solder is a fusible metal alloy with a melting point or melting range of 90 to 450 Quote Link to comment Share on other sites More sharing options...
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