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Discussion Starter · #1 ·
I made a thread a few weeks ago chasing down a lean condition. I melted the same side down last year, rebuilt it a few weeks back and while trying to chase down why its running lean, I melted it down again. I started with 280s and went all the way to 360s with 0 change in either plug color (they are both the same color). I took it out for about a mile after switching to 360s, the egts stayed around 950-1100, I went to hit an end drive and when I landed, I pinned it and it bogged. I looked down and my egts were 2100ish and it was too late. I'm at a loss. Its a newly rebuilt motor, new seals, no leaks, new trail ecu, pj are functional, clean carbs, and 91 mixed 33:1. Also, I can't get my tps to relearn. Even with a 470ohm resistor. Keep in mind, these were a mile runs at a time to check plugs and jetting. I let it warm up 10 min each time also. I'm about ready to throw in the towel.
 

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Discussion Starter · #3 ·
Hot start unplugged, boots are fine. Its a stock 600rs, and I was under the assumption, that they were fine to run 91. I'm not sure on the fuel pump I guess. Is there a way to test that? Obviously its getting fuel, so its working, but how can I tell if its getting enough?
 

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They are OK to run 91 but if the compression is too high itnwill need race fuel. To test the pump I just put the lines into two separate cups and pull it over a few times and compare how much fuel is in each. Should be real close to each other. Did you reuse your existing jugs or replace one or both?
 

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Discussion Starter · #5 ·
I had that one side replated. Being they are both the same color, could the pump simply be weak? Also, how do I tell if the compression is to high to run pump gas. Im assuming a basic compression test won't tell me that. I have to rebuild it anyways, would a thicker base gaskets help this? Im running the .50 mm base gasket btw. Sorry for the dumb questions. I don't have a solid understanding of 2 strokes quite down.
 

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Discussion Starter · #6 ·
Oh, I forgot to mention, this was a factory mod sled. It now has 2-1 exhaust, trail ecu, and tps hooked back up. I don't know if that makes a difference
 

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Did you change the mod domes to low comp domes? And 160 psi is about the limit for pump fuel. The upper limit. Not sure on the base gasket. I always go by the squish and not so much the thickness of the base gasket. I've found it to be more reliable and its just what I'm more comfortable doing.
 

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Discussion Starter · #8 ·
The head that's on it doesn't have replaceable domes. So I never messed with them. I bought the sled as is, and put about 200 miles on it last year before I did any of the above, before it went. And it made it less then 10 miles this year, so I feel like it's a new issue. I will do a compression test once I rebuild it again. I'm trying to get an idea where to start before the same thing happens again.
 

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Based on the fact it was only one side definitely pressure test it before tear down. Air leak or fuel leak. Do you have a pic of the head? The domes should pop out and have a stamp on them.
 

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Pressure test before you do. Double check everything during disassembly. Seal condition, gasket surfaces, carb slides. Think of it like a crime scene and you have to find culprit. I had the corner of my carb slide chip off. Started to destroy the mag piston. But I shut it down before I ruined the cylinder. Also post some pics of the piston, cylinder, plugs, and head. See if the guru's on here will pop up lol!
 
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