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Post by kevink16 on Jul 19, 2011 2:05:43 GMT -5
I decided to pull the bowl off my carb to see what main jet is in my carb. The only marking on the main jet is the number 70. Am i correct in thinking that means 0.70mm? This would mean I'm running a jet smaller than 0.028in. That's what i figured after looking at this www.mhpsonline.com/catalog.php/milehigh/pd2094015I'm thinking about buying some larger jets since the rules allow us to run up to a 0.042in jet. Has anyone else played about with jetting? What are good sizes to start with add power but not make the engine too rich? |
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Post by Simon on Jul 20, 2011 1:34:47 GMT -5
Hi Kevin, I'm not sure what the 70 means, but I used to generally run a 0.037" with a non-cheater cam. I only tried the CL-1 cam once and it seemed to run fine with a 0.037", but I suspect it might work with a 0.038". I went down to a 0.036" up at Reno.
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Post by markofzero on Jul 20, 2011 11:08:52 GMT -5
Hi Kevin,
I bought a range of sizes from ARC Racing. Several of them had a 70 on them. I believe they take the closest (smaller) size to the size desired, and drill it out to the exact 1/1000th.
There are pin gages (I don't know why they spell it like that) for sale on eBay that can be used to identifiy the actual size of the jet hole.
You probably know this but, as you reduce the jet size, you make the mixture leaner. This will increase EGT and CHT.
(Exhaust Gas Temperature and Cylinder Head Temperature)
If you get too lean, engine damage can occur. That said, increasing the jet size may reduce (or increase) power. I hope this helps.
Mark
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Post by kevink16 on Jul 20, 2011 13:33:55 GMT -5
thanks for the help guys, I think I may hold off on playing with the jetting now until I can pick up mychron so that I can watch my temps while experimenting. My spark plug also seems to look pretty good after a full day of running, a nice tanish brown, so it may be my jet is just fine to leave the way it is for now.
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Post by tommy toro on Jul 20, 2011 20:49:59 GMT -5
last I checked 40 was a no go, and 19 on the idle jet, as I 'm pretty lazy I've been running a 37 for as long as I can remember, at least I'm pretty sure its a 37, and I fought the heat thing for awhile with the jetting with no luck, 470 at PC yikes! found that lowering the heat range of the plug solved the problem, but without the mychron your only guessing,
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