plain and simple, why does overjetting increase heat? pipe flow is too slow? or more gas in the mix makes it burn slower? i was jetted at a 80-82 with my 20phbg and mildly ported kstar and biturbo (uni filter) and barely kissed 400 on long uphills, and im geared damn tall (20x40), threw a 86 in there and my temps went up to 410 within a few minutes of riding from a cool engine? and the 78/77 jets i have push the temps down to 350! i thought it was supposed to be the other way around? im timed at 17btdc.
upjet = more heat? whats going on here
Re: upjet = more heat? whats going on here
what is your oil ratio?
Re: upjet = more heat? whats going on here
Needle bearing crank right? Gear way way down, bi-turbo is a higher revver, and the porting you did should work well to make a high revver.
Re: upjet = more heat? whats going on here
Tuned length of a biturbo is like 25.6in according to the exhaust monograph, which is even shorter then a boss. Try 15 or 16x40 and see what happens. You've tuned your clutch already right?
Re: upjet = more heat? whats going on here
50:1 synth stock crank for now (hence the temporary high gear, im usually at 17/40 but decided to throw the 19 on for shits and it made me go FAAST, clutch shoes are lightened about 10g from what they were i think, a little more then 720 out from all the way in on the adjustment. i juuuust got my clutch brace and kickstart springs yesterday, i know the pipe combo is very mismatched with gearing, my plan was to get a lower hitting pipe like a bk100 but i didnt yet. i have a techno circuit with a dent in the chamber laying around...but i cant get it to seal up at the exhaust flange
full setup
kstar 70
b7hs@.018
intake widened, ex widened and raised 1 mm
my compression is pretty low around 130psi even with the hihi comp head due to my squish being sooooo off thanks to the basegaskets...
2 basegaskets so piston clears ex port, also running a headgasket.
takeoff is GREAT, screams up to top speed then nothing....ive always kinda battled with heat. am i just not hitting the pipe at all so the heat is staying in the engine?
Re: upjet = more heat? whats going on here
” screams up to top speed then nothing”
Which is...?
Re: upjet = more heat? whats going on here
48-52 ish according to iphone gps
Re: upjet = more heat? whats going on here
forgot to mention, au262 atomizer, w7 needle, at a 77 main and 45 idle
Re: upjet = more heat? whats going on here
forgot to mention, au262 atomizer, w7 needle, at a 77 main and 45 idle is what im running now.
Re: upjet = more heat? whats going on here
this talks about rich and lean temps
http://flighttraining.aopa.org/students/solo/special/mixture.html
i was trying to find this article that mentions a book. In the article it talks about going past 12.3:1 to cool the engine with extra fuel but in fact that doesn't work. idk. Hopefully all you did was a jet change and didn't mess with anything else to get your temp reading. Change one thing then test and repeat, sucks not to be able to change a bunch of stuff at once sometimes but that's what you gotta do to learn.
Re: upjet = more heat? whats going on here
Too advanced timing is why your battling hi temps
Re: upjet = more heat? whats going on here
yup all i did was change main jet, gonna read that article now!
Re: upjet = more heat? whats going on here
http://www.rbracing-rsr.com/waterinjection.html
this is the article I was searching for. it mentions the book under the heading "Don’t Drink the Purple Cool-Aid"
Re: upjet = more heat? whats going on here
ken im at 17 degrees and have gone so far as 15 and its no different. so i just set it to 17 because it ran better.
Re: upjet = more heat? whats going on here
Have you reworked the squish band on the hi-hi head? That'll kill higher rpms with heat and give you nice low end.
Re: upjet = more heat? whats going on here
Ya 17 deg is ok
Ya too much compression or air leak could spike temps .
You could have knocked off a plug on your carb or something when you changed your jet
Re: upjet = more heat? whats going on here
yes the head is reworked, the plug cup lip has been taken way down, squish border also was pushed back 3-4 mms. absolutely no airleaks, i have the two holes on the non idle adjustment side plugged....maybe one is leaking ? ive sprayed carb cleaner directly on the holes with no rev loss though.....
Re: upjet = more heat? whats going on here
oh and.... i went for another late night ride last night to confirm with the 77 main its running better then ever and i didnt break 350 at WOT on a mild hill
Re: upjet = more heat? whats going on here
Well its sounds to be jetted perfect to me. You can actually run hot when running rich...
Re: upjet = more heat? whats going on here
i never really considered that i wasnt hitting the pipe, im going to regear to 17/40 and see what that does to my top end. hopefully ill actually get some more speed.
Re: upjet = more heat? whats going on here
Same thing happened with me.Just run with it.
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