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Post by 90GTVert on Apr 5, 2010 21:07:40 GMT -5
CHT would be nice, but I dunno if it woulda prevented this or not. I mean I only made it 400ft before it started dying. I guess maybe I woulda known more from temps on other runs to prevent a lean condition though. I'm just not sure how much of it is lean and how much is an engine with 2 miles on it revving 11,000+ RPM I assume. I shoulda hooked my test tach up at least to know how fast I turned it before I blew it up. All I know is it would scream, more than you even hear in that burnout vid.
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Post by stepthrutuner on Apr 5, 2010 23:06:22 GMT -5
CHT would be nice, but I dunno if it woulda prevented this or not. I mean I only made it 400ft before it started dying. I guess maybe I woulda known more from temps on other runs to prevent a lean condition though. I'm just not sure how much of it is lean and how much is an engine with 2 miles on it revving 11,000+ RPM I assume. I shoulda hooked my test tach up at least to know how fast I turned it before I blew it up. All I know is it would scream, more than you even hear in that burnout vid. My bad. I should have known better. Brain fart. I didn't realize this was the new piston. It would be hard to break in a motor that was either 'on' or 'off'. |
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Post by 190mech on Apr 6, 2010 5:55:59 GMT -5
Check your needle taper,a thick needle will run very lean midrange causing 'light switch' throttle action.My VM22 carb
had me in the same tuning situation till I happened to see
the thick needle,dug in the carb parts pile and found a thin
Keihin needle and now it works like it should...
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Post by 90GTVert on Apr 6, 2010 6:56:34 GMT -5
I'll look, but it appears to be rich in the midrange. I had moved the needle up and it crackled worse than before at mid throttle, so I assumed it was too rich.
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Post by 2strokd on Apr 6, 2010 8:58:45 GMT -5
That pipe is huge! Great work John! Sorry to hear she blew so early  , sounded good when it did come on! Looks like the ring got hung in the ex port and broke? Wonder just how many rrr,s you were spinning? We should all chip in and get Brent that nice analog tach he wants and needs sooo bad ;D |
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Post by 190mech on Apr 6, 2010 9:13:32 GMT -5
Im in!Looks like more that a tach is needed though..
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Post by 90GTVert on Apr 6, 2010 17:52:47 GMT -5
I'll get it straight at some point. Don't worry about that. It'll give me plenty of time to figure out what I'm gonna do different.
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Post by 190mech on Apr 6, 2010 18:21:29 GMT -5
52mm ported jug?
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Post by 90GTVert on Apr 6, 2010 19:22:52 GMT -5
No hope for the Polini sport? It shows so much potential when it hits it makes me wonder what it's capable of. I don't have a piston for the 52mm either so it's no more cost effective. Not real fond of all that clearancing without splitting the cases either, and I dunno that I wanna pull it right back apart. A friend suggested maybe trying to break it in on the stand next time. It should be under load, but I suppose I could apply slight pressure with the rear brake. I should be able to get it to rev a little easier to get my part throttle runs and cooldowns in before I let'r loose. I dunno. Makes sense to some degree. I'd have to buy a stand first or straighten the bent one from T1 or something. My paln of making this more budget oriented went straight out the window. lol
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Post by 190mech on Apr 6, 2010 20:24:19 GMT -5
Thought you had the whole 52mm setup..Ya think the bore will be OK with light honing?Are 46mm pistons available?Used to seeing 47 thru 48mm..Saw the grind marks on the cases and assumed it was hogged for the 52mm,it'd be kinda nasty to try to
hog it without splitting it though.The good part about the 52 is that its setup for the longer stroke and would be a more 'matched' build,still would be a bunch more work though!!!
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Post by 90GTVert on Apr 6, 2010 21:06:06 GMT -5
The Polini sport's bore is easily salvageable. I picked up a 3 stone brake cylinder hone (good up to 2 3/4") today in case I wanna go over it. I like the ball hones better, but they are pretty pricey. The one I got for my 54mm cylinder is too big for this. Polini 46mm piston should be Polini PN 204.0090, so I can get a direct replacement when I'm ready.
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Post by drawkward on Apr 6, 2010 21:34:56 GMT -5
Nice that it looks like it's salvageable. I was pretty surprised with the very pronounced power band. Do you think it was the custom pipe that made it rev like that? Seemed to rev a little different in the no-pipe video, but it also wasn't under load. Why would the ring grab and snap like that? Maybe it needed a little bridge to be able to have that big of an exhaust port?
Where did you pick up that brake hone, by the way? Looks perttttyyy useful.
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Post by 90GTVert on Apr 7, 2010 19:47:27 GMT -5
I do think it's the pipe causing it to be so crazy. It's a hard hitter and that usually means a narrow power band. I think this one's gonna be a challenge, but I dare the local scoots to hit a light with me when she's all straight.  I think a bridged port woulda prevented what happened, but the Airsal's stats were crazy. High RPM, probably high temps, plenty of pressure pushing the rings out into the walls (or port in this case), and snap. |
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Post by 2strokd on Apr 8, 2010 7:59:37 GMT -5
Yep, thats what i think too..Not enough 'seat' time on the rings yet for all the pressure?
Oh well man, i woulda done the same thing!
Live and learn!
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Post by 90GTVert on Apr 8, 2010 8:44:53 GMT -5
It might have been more lean than I thought too. It seems to take much more fuel when you have big port durations. T2 with 1 base gaskets runs good from 98-105 main jets depending on temps. On hot days 98-100. I put 3 base gaskets under T2 yesterday and it needed a 112 main at 90 degrees outside for best results. T1 might want a big ole jet with the durations it's got.
I really think the MRP pipe I have would be good for attempting to break in the engine for a bit next time around. I'll try John's pipe after a few miles when the rings, walls, and ports are worn in.
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, sounded good when it did come on!
I think a bridged port woulda prevented what happened, but the Airsal's stats were crazy. High RPM, probably high temps, plenty of pressure pushing the rings out into the walls (or port in this case), and snap.