|
|
Post by 2strokd on Jul 6, 2012 8:50:32 GMT -5
Great info! Ever seen the pistons with holes like that cast into them?
Makes no sense to me?...
|
|
|
|
Post by 90GTVert on Jul 6, 2012 9:13:20 GMT -5
Yeah, I cleaned those up and sold 'em after the last time I messed with timing. lol j/k
No, actually I don't think I've seen them made like that.
|
|
|
|
Post by 2strokd on Jul 6, 2012 10:44:06 GMT -5
|
|
|
|
Post by 190mech on Jul 6, 2012 15:00:14 GMT -5
That is a "center" drill hole so a lathe center can be used to engage in the piston top during the ring groove cutting operations.Many of the older style pistons had them...
|
|
|
|
Post by 2strokd on Jul 6, 2012 15:52:50 GMT -5
That is a "center" drill hole so a lathe center can be used to engage in the piston top during the ring groove cutting operations.Many of the older style pistons had them... That clears that up for me. Thanks :cheers: |
|
|
|
Post by 90GTVert on Jul 9, 2012 14:34:04 GMT -5
I got the new piston in today. I'm very glad I made sure to get the exact same piston I had. It cleared something up. I'm now completely sure that I'm an idiot.  Yup, there's the hole in the new piston. I hadn't seen one before because I have a horrible memory. I'm sure I noticed it, I just didn't remember it. This is why I make notes and take pics. My memory is broken sometimes.  I saw the spark plug with chipping and the built up spot on the head when I removed it and even though the hole looked really clean, it had to have been burnt in. Where else would the thin line of aluminum on the head be from? Carbon. When I've looked before it's always thin and black. This time it was raised and a different color. That's what I get for jumping to a conclusion and being in a hurry to get results and video up. I did look back at pics of the piston new, and it just looked like a dimple to me. On top of being dumb, I have a terrible memory. So I'm sorry for the mistake. I seem to be full of them lately.  I've edited the video on YouTube so as not to spread this mistake to everyone that doesn't follow here. I just chopped off the end of the vid for ease. Since the pics will be gone once YouTube passes the edit, here are the pics of what made me think the piston was damaged again. The spark plug pic is sorta hard to see, but theres a chipped off bit kinda on the front/left of the insulator.     I'm not sure if I've ever felt this stupid before. Mostly I'm embarrassed and sorry for giving out bad info, even if it is being corrected. I thought it was so weird that I had ran at 28 degrees briefly and never had any major problem then. Never heard spark knock at all, no major overheating on the head, but dammit it looked like it was burnt in my haste. Again, I'm sorry, but once again I'm proving I'd rather look stupid than give anyone bad information if I can help it... if that means anything.  |
|
|
|
Post by stepthrutuner on Jul 9, 2012 15:16:00 GMT -5
Maybe think about a cooler plug whilst playing with the iggy clock?
|
|
|
|
Post by lshigham on Jul 9, 2012 15:22:53 GMT -5
Ah well! I took the top end off my brothers Senda yesterday and it has the same mark in the top of the piston. The cylinder kit was of Chinese origin, so maybe it's a method they still use there - never seen it on the European made cylinders I buy.
|
|
|
|
Post by 90GTVert on Jul 9, 2012 19:50:32 GMT -5
Since I have the engine apart for no good reason, I did at least get a measurement of the piston crown to use for future compression ratio calculations.  40.02mm bore with the piston 7.22mm deep gave 8cc. That bore and stroke calculated would be 9.08cc. That leaves the piston crown at 1.08cc. I'm thinking I may try 225psi compression once more. I last reported it felt resistant to increase speed over a certain point when I altered compression. Of course that was the last test I did before the torque driver screwed up and I had to replace it. After replacing it I noticed it picked up the last few MPH easier than it had before. I still think it'll show too much heat increase vs gain, but thinking isn't knowing. I suppose I'll set it back to stock timing for that. |
|
|
|
Post by tygertung on Jul 10, 2012 2:54:33 GMT -5
You have inspired me to go crazy with the head machining on my Suzuki, as I only have 100 PSI, so I need to be doubling it.
|
|
|
|
Post by 90GTVert on Jul 10, 2012 7:09:05 GMT -5
lol Might wanna work your way up instead of going crazy all at once, but you should see gains. 180psi is where I settled last time, right where this engine is stock.
|
|
|
|
Post by 2strokd on Jul 10, 2012 8:03:44 GMT -5
Well, i guess thats good news..? About the piston.
I bet if our stock CDI would pull more timing at higher RPM it wouldnt feel flat as it revs.?
|
|
|
|
Post by 90GTVert on Jul 10, 2012 13:13:28 GMT -5
It's good news that I have a spare piston now. I'd rather screw up a piston and not be a dumbass I think.  I dunno that it really does feel flat. It doesn't with the timing. It did with compression, but then I tested it right before the TD started acting funny and after swapping the TD it seemed like it pulled the last few MPH much easier... but by then I had the compression back to stock. That's what I wanna try it again. I was gonna get it together today, but I have had other stuff to do. I visited my favorite place ever, the Motor Vehicle Administration. 50 minutes in line, 5 minutes or less to renew my license once I got to the counter. |
|
noday
Scoot Enthusiast
Posts: 149
|
Post by noday on Jul 10, 2012 17:58:08 GMT -5
a newb question: when you work on the TD and reassemble for testing, , do you torque the nut ?
do you use loctite ?
do you mark the nut and shaft ?
thanks
|
|
|
|
Post by 90GTVert on Jul 10, 2012 18:40:56 GMT -5
I don't torque the nut, I don't use loctite, and I don't mark the clutch and nut. Those are good things to do though, minus the loctite if tuning and removing often. If I'm going to loctite something I will usually wait till I have it tuned and then take it back apart and loctite it. I don't really think that particular nut needs loctite though. Won't hurt to use a non-permanent loctite though if that gives you peace of mind. The most important thing I've found is to thread the nut on for the rear pulley assembly by hand a good bit. Maybe it's just me, but I find those easy to crossthread if you aren't careful.
|
|
