Reggie08
Petty Officer 1st Class
- Joined
- Mar 31, 2008
- Messages
- 243
I apologize for the long post, but I want to give a brief history of this motor and everything that's been done up to this point.
I picked up this motor (1985 'Rude 90hp E90TLCOS) for free from a guy who said I could have it if I rebuilt it for personal use. The motor had burned the #2 piston. It was initially thought the high speed jet had clogged. At the time, the motor had 140hp carbs and exhaust on it. I rebuilt the powerhead and put new rings, pistons, wrist pins and bearings, rod bearings, t-stats, seals and gaskets on the powerhead. I also changed out the block because the original was bored .030 over and had some substantial scoring on the cylinder walls. Current block is bored .030 over on the #1, 2 and 4 cylinders and .040 on the #3 cylinder. Additionally I replaced the 140hp carbs and exhaust with the 90hp carbs and exhaust. Carbs were thoroughly cleaned and rebuilt and the high speed jets were cleaned as well. Spark was strong on all four cylinders and link-n-sync was done as well. Lastly, I've been using the stock Champion spark plugs gapped at .030.
During break-in, I've been running a 25:1 mix (bypassing the VRO). I had about 4 hours of run time on the motor following the rebuild. Up to this point, I've been checking my plugs following every trip for any signs the motor might not be running right. Friday night I checked the plugs and noticed the #2 and 4 plugs were black while the #1 and 3 were a golden brown. I attributed the black/fouled plugs to the higher oil mixture and a carb that was possibly running rich. The motor had been running great up to this point. There were a few hiccups along the way that I was able to fix but overall, I was happy with how the motor was performing.
Saturday afternoon, we were heading back to the boat ramp running at about 4200rpms. We'd been at that speed for approx 60-90 seconds. Prior to this, I'd been running the motor at about 2500rpms for a couple of minutes as we were trying to find our way out of some flooded timber. During this time I was running at 2500rpms, the motor would act like it was flooded. I could throttle up the motor briefly to clear it then it would run fine. Throttle it back and it would act like it was flooding again. About half-way back to the boat ramp, the motor started to lose power. I pulled the throttle back and checked for a pee-stream. It was putting out a strong pee-stream. Pushed the throttle back up but it started to lose power again only this time I heard a knocking or ticking sound. We slowly made our way back to the ramp (doing around 1800rpms), put the boat on the trailer and called it a day. I started pulling the plugs to check for something major. The #1 and 3 plugs looked good. The #2 was caked in aluminum
Yesterday morning I pulled the head off to take a look inside the cylinder and the #2 piston was burned up. The cylinder walls still look and there seemed to be plenty of fuel/oil mix in the cylinder. The #4 piston was good and the plug appeared to be just fine.
Given the #2 piston burned up (again), I'm wondering if there isn't something else wrong I missed that caused it to do this. Two possibilities that come to me are the VRO/fuel pump isn't working properly causing the #2 cylinder to run leaner or the coil is possibly causing the plug to fire hotter (which I doubt since I haven't heard of that being possible but you never know). Before I replace this piston I need to make sure I have all the bugs worked out first since I obviously don't want to have to replace the #2 piston again every 5 hours
What should I look for when I start to disassemble this motor again? I'm going to break open the carbs and clean/rebuild them again but what else could cause the #2 piston to burn up again? It did the exact same thing it did to the previous owner.
I picked up this motor (1985 'Rude 90hp E90TLCOS) for free from a guy who said I could have it if I rebuilt it for personal use. The motor had burned the #2 piston. It was initially thought the high speed jet had clogged. At the time, the motor had 140hp carbs and exhaust on it. I rebuilt the powerhead and put new rings, pistons, wrist pins and bearings, rod bearings, t-stats, seals and gaskets on the powerhead. I also changed out the block because the original was bored .030 over and had some substantial scoring on the cylinder walls. Current block is bored .030 over on the #1, 2 and 4 cylinders and .040 on the #3 cylinder. Additionally I replaced the 140hp carbs and exhaust with the 90hp carbs and exhaust. Carbs were thoroughly cleaned and rebuilt and the high speed jets were cleaned as well. Spark was strong on all four cylinders and link-n-sync was done as well. Lastly, I've been using the stock Champion spark plugs gapped at .030.
During break-in, I've been running a 25:1 mix (bypassing the VRO). I had about 4 hours of run time on the motor following the rebuild. Up to this point, I've been checking my plugs following every trip for any signs the motor might not be running right. Friday night I checked the plugs and noticed the #2 and 4 plugs were black while the #1 and 3 were a golden brown. I attributed the black/fouled plugs to the higher oil mixture and a carb that was possibly running rich. The motor had been running great up to this point. There were a few hiccups along the way that I was able to fix but overall, I was happy with how the motor was performing.
Saturday afternoon, we were heading back to the boat ramp running at about 4200rpms. We'd been at that speed for approx 60-90 seconds. Prior to this, I'd been running the motor at about 2500rpms for a couple of minutes as we were trying to find our way out of some flooded timber. During this time I was running at 2500rpms, the motor would act like it was flooded. I could throttle up the motor briefly to clear it then it would run fine. Throttle it back and it would act like it was flooding again. About half-way back to the boat ramp, the motor started to lose power. I pulled the throttle back and checked for a pee-stream. It was putting out a strong pee-stream. Pushed the throttle back up but it started to lose power again only this time I heard a knocking or ticking sound. We slowly made our way back to the ramp (doing around 1800rpms), put the boat on the trailer and called it a day. I started pulling the plugs to check for something major. The #1 and 3 plugs looked good. The #2 was caked in aluminum
Yesterday morning I pulled the head off to take a look inside the cylinder and the #2 piston was burned up. The cylinder walls still look and there seemed to be plenty of fuel/oil mix in the cylinder. The #4 piston was good and the plug appeared to be just fine. Given the #2 piston burned up (again), I'm wondering if there isn't something else wrong I missed that caused it to do this. Two possibilities that come to me are the VRO/fuel pump isn't working properly causing the #2 cylinder to run leaner or the coil is possibly causing the plug to fire hotter (which I doubt since I haven't heard of that being possible but you never know). Before I replace this piston I need to make sure I have all the bugs worked out first since I obviously don't want to have to replace the #2 piston again every 5 hours
What should I look for when I start to disassemble this motor again? I'm going to break open the carbs and clean/rebuild them again but what else could cause the #2 piston to burn up again? It did the exact same thing it did to the previous owner.
