DAG
Yes, my balls tickled from that landing
- Location
- Charlotte, NC
I'm in need of some diagnostic help. I'm getting excessive wear in the sleeves of a DASA 970 10mm. Its hard to tell from the pictures I took so I'll try my best to explain the details. Sorry in advance for the wall of text and I appreciate any tips/advice/constructive criticism.
A little background info: Bought the 970 and crank new over the winter and built it up myself. As there was a 3 month wait on a PFP I took my time assembling checking ring gaps, break cleaning gasket surfaces, pv clearances, air leaks, & proper squish. Everything checked ok, water test time. Did several heat cycles over about a 3-4 hour period maybe a gallon of fuel and it locks up. I figured I cold seized it as the cycle that it locked up on I was in the 1/2-3/4 throttle range (but I did not go as easy on it as I did the other cycles, a lot more blips vs steady). Pulled the head at the ramp and sure enough the rear cylinder was scored opposite the exhaust port tapering from 1.300" wide into a .7000" over a distance of about .5000". As I did not try and restart the motor on the water when it locked up you could see some galling which I've never seen on a cylinder before. The front cylinder had much lighter scoring but it was the same size and shape of the rear.
Took the cylinder to the local auto machine shop for a bore/hone. Got a call from them that their boring rod broke due to the sleeves gumming up. Jug and sleeves were sent to NW sleeve and they came back saying the sleeves were faulty due to high chrome or nickel (The machine shop forgot what NW told them...) but anywho NW replaced the sleeve free of charge. Since I already bought the .50" over pistons they just bored the new sleeves to .006" over the piston size per DASA recommendations. Only difference being is hone was 400grit vs DASA's 150grit recommendation. Got the jugs back and had to port match the sleeves to the CNC'd jugs and gave all inside leading edges a good chamfer to prevent ring damage. I don’t own accurate bore mics or spring pins so I check the bore using 2 .0030"
shim on each side of the piston prior to installing the rings (front and back, and intake and exhaust) and it went but was snug so the bore is somewhere between .006" and .007" over. Ring gaps checked ok and had to clearance the PV's as it was slightly hitting the rings.
Got that all assembled and compression checked 175 cold with the PV's closed. (still not sure if you check compression with PV's open or closed, I get different answers from different people...) As I just sunk more money into this 'new' motor with new pistons/gaskets and the machine shop work I really wanted to take my time. This time I fired up the motor on land (without hose) and let it idle for about 15-20 seconds and checked the compression warm. 180psi warm w/ pv closed. Pulled the head just to check things out and nothing obvious. Let it completely cool and idled it again in the drive way about 30 seconds this time and rechecked everything ok.
Next day took it to the ramp and left it on the trailer but backed it completely into the water. Let it idle about 2 minutes before rechecking compression and pulling the head. (cylinder got warm but I could hold my hand on it for several seconds, pisser water is luke warm at best. Compression still at 180 and the honing was slightly starting to disappear on the exhaust and intake side in both cylinders. Since compression was still 180 I figured I'd give it another dip on the trailer thinking there is probably not enough run time on the cylinders to even make a call that something might not be right.
After it completely cooled down, back into the water and let it idle for about 2 minutes then started blipping to about 1/4 throttle for another minute. Compression checking 180 rear cylinder and the front cylinder it went up to about 185-190 (checked 3 times). Pulled the head, the front cylinder with high compression didn’t find anything out of the ordinary, however the rear cylinder was defiantly progressing for the worst. Hone marks opposite of the exhaust port were nearly gone and it started to become shiny and the hone above the PV's are barely visible. There is also vertical scratch/scoring like marks about the width of sand .008" at most but not deep at all (my calibrated eyeball says maybe .0005" to .0010 DP) Front to back on both cylinders are not showing any ware in the honing at all.
At this point I have a feeling I'm on my way to locking up another motor if I don’t make some kind of change. But I'm out of ideas. Compression is still perfect and I cant even feel the scoring or shiny marks in the cylinder. I cant convince myself if this type of wear is normal in a stroke motor? I haven't even ran 16oz of fuel through it... The only thing I can think of is piston slap being that it’s a 10mm stoker and the wear is high in the jug or prehaps yet another set of defected sleeves... I really enjoy working on the motors but I'm at a frustration level where if I loose another motor I'm going to take a break from the sport for a few years being that I've only had about 10hrs of ride time over the last 2 years as its apparent the jetski Gods do not want me on the water. Help.
A little background info: Bought the 970 and crank new over the winter and built it up myself. As there was a 3 month wait on a PFP I took my time assembling checking ring gaps, break cleaning gasket surfaces, pv clearances, air leaks, & proper squish. Everything checked ok, water test time. Did several heat cycles over about a 3-4 hour period maybe a gallon of fuel and it locks up. I figured I cold seized it as the cycle that it locked up on I was in the 1/2-3/4 throttle range (but I did not go as easy on it as I did the other cycles, a lot more blips vs steady). Pulled the head at the ramp and sure enough the rear cylinder was scored opposite the exhaust port tapering from 1.300" wide into a .7000" over a distance of about .5000". As I did not try and restart the motor on the water when it locked up you could see some galling which I've never seen on a cylinder before. The front cylinder had much lighter scoring but it was the same size and shape of the rear.
Took the cylinder to the local auto machine shop for a bore/hone. Got a call from them that their boring rod broke due to the sleeves gumming up. Jug and sleeves were sent to NW sleeve and they came back saying the sleeves were faulty due to high chrome or nickel (The machine shop forgot what NW told them...) but anywho NW replaced the sleeve free of charge. Since I already bought the .50" over pistons they just bored the new sleeves to .006" over the piston size per DASA recommendations. Only difference being is hone was 400grit vs DASA's 150grit recommendation. Got the jugs back and had to port match the sleeves to the CNC'd jugs and gave all inside leading edges a good chamfer to prevent ring damage. I don’t own accurate bore mics or spring pins so I check the bore using 2 .0030"
shim on each side of the piston prior to installing the rings (front and back, and intake and exhaust) and it went but was snug so the bore is somewhere between .006" and .007" over. Ring gaps checked ok and had to clearance the PV's as it was slightly hitting the rings. Got that all assembled and compression checked 175 cold with the PV's closed. (still not sure if you check compression with PV's open or closed, I get different answers from different people...) As I just sunk more money into this 'new' motor with new pistons/gaskets and the machine shop work I really wanted to take my time. This time I fired up the motor on land (without hose) and let it idle for about 15-20 seconds and checked the compression warm. 180psi warm w/ pv closed. Pulled the head just to check things out and nothing obvious. Let it completely cool and idled it again in the drive way about 30 seconds this time and rechecked everything ok.
Next day took it to the ramp and left it on the trailer but backed it completely into the water. Let it idle about 2 minutes before rechecking compression and pulling the head. (cylinder got warm but I could hold my hand on it for several seconds, pisser water is luke warm at best. Compression still at 180 and the honing was slightly starting to disappear on the exhaust and intake side in both cylinders. Since compression was still 180 I figured I'd give it another dip on the trailer thinking there is probably not enough run time on the cylinders to even make a call that something might not be right.
After it completely cooled down, back into the water and let it idle for about 2 minutes then started blipping to about 1/4 throttle for another minute. Compression checking 180 rear cylinder and the front cylinder it went up to about 185-190 (checked 3 times). Pulled the head, the front cylinder with high compression didn’t find anything out of the ordinary, however the rear cylinder was defiantly progressing for the worst. Hone marks opposite of the exhaust port were nearly gone and it started to become shiny and the hone above the PV's are barely visible. There is also vertical scratch/scoring like marks about the width of sand .008" at most but not deep at all (my calibrated eyeball says maybe .0005" to .0010 DP) Front to back on both cylinders are not showing any ware in the honing at all.
At this point I have a feeling I'm on my way to locking up another motor if I don’t make some kind of change. But I'm out of ideas. Compression is still perfect and I cant even feel the scoring or shiny marks in the cylinder. I cant convince myself if this type of wear is normal in a stroke motor? I haven't even ran 16oz of fuel through it... The only thing I can think of is piston slap being that it’s a 10mm stoker and the wear is high in the jug or prehaps yet another set of defected sleeves... I really enjoy working on the motors but I'm at a frustration level where if I loose another motor I'm going to take a break from the sport for a few years being that I've only had about 10hrs of ride time over the last 2 years as its apparent the jetski Gods do not want me on the water. Help.
