07-18-2007, 01:57 PM #1
Could cooling have caused this? SL650/750 meltdown
I was talking with ModTodd82 today, and we were discussing possible causes of my piston meltdown. One thing that came up as a possibility is my cooling.
The cooling is different from a '92 650 and a '95 750. For starters there is no water in the lower block on the 750. So when I was putting this motor in over the winter, I talked to a few forum members, and routed it like this:
The water comes in from the pump. It goes to a "T" fitting, and half of the water goes into the 650 "dry" pipe. It connects here, shown in picture 1. The other half continues on to the "Spider", picture 2.
The Spider shown has two hoses on the lower right, on my spider that's just one piece of hose, connecting the two, as no water goes to the lower block. On my spider the water comes in on the short little line at the 9 o'clock position in the photo. The spider sends the water up 3 hoses, which connect to the 3 fittings on the exhaust manifold.
Eventually all the water makes its way to the cooling rail, through the popoff fitting, and exits the craft. Oh, I do have the pisser connected, and it shows good flow from the exhaust pipe.
Is it possible that too much of my water is going into the pipe, leaving nothing to cool the cylinders? As you can see from the underside of the piston, the discoloring says it was getting pretty hot before it holed.... Perhaps I should have routed all water to the spider, and then brought water back from the spider to the pipe?
Does anybody think this could have caused my meltdown? Or does how I have it routed currently sound correct?
Still waiting on my Mikuni 90 jet, so I'm still searching for ideas!
Last edited by delagem; 07-18-2007 at 02:02 PM.
07-18-2007, 02:17 PM #2
I still vote lean. Inadequate fuel supply. That was the Mag cylinder correct? I think an overheat condition would not concentrate the hole right over the electrode.
Last edited by twinstack1; 07-18-2007 at 02:19 PM. Reason: additional info
07-18-2007, 03:34 PM #3
Ok, well here's another thing I discovered today. After starting this thread, I traced out my cooling system, and pulled the popoff fitting. It's got an arrow on it, so I knew it was in the right way, but I opened it up to see if it was stuck anyways. Found some missing plastic.
This break doesn't seem to restrict flow, it just allowed flow in both directions at any time. But it might have prevented full flow when pressurized; I couldn't tell because I took it apart and pieces scattered.
Also, not sure when this happened. I took this apart and cleaned it 2 yrs ago, it was intact then. Perhaps freeze damage? I winterize with RV antifreeze.
07-18-2007, 03:40 PM #4
That is definately a lean condition that caused that.
07-18-2007, 03:54 PM #5
- Join Date
- Jul 2007
I was talking to mike about his engine problems and a question came to mind-he has a 750 and is running the 650 dry pipe, is this different pipe leading to a lean condition. He told me he is jetted for a stock 750 engine. We also explored the possibility of cooling issues, which is what this post is about.
07-18-2007, 03:58 PM #6
07-18-2007, 04:08 PM #7
Stock 1992 650 cdi. I asked if this might be a problem in the original post regarding this holed piston.
I ran this with no issues on the 650 motor for 3 years, and when the "sandblast" look started appearing on my CTR piston, I tried one of ModTodd82's spare cdi's, with no difference. (we thought we were chasing a detonation issue back then)
07-18-2007, 04:28 PM #8
I think you are just lean. Make it fat and blubbering and then back it down.
07-18-2007, 04:47 PM #9
dit da dit ditto w Dart, I'm about to post pics on another thread with a 650 sl I just got w/the same problem
07-18-2007, 08:14 PM #10
I agree, lean condition.
Overheat, I believe will melt the edges of the piston instead of burning a hole in the center.
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