Husaberg 550E purchased new in 2007.
On the very first startup, the engine made some horrible grinding noises. It turns out the the snap ring for the kickstart idler gear was missing or improperly installed. The idler gear bearing cage and rollers passed through the all primary gears damaging many teeth. The dealer replaced the damaged parts. The oil was changed several times to remove the leftover bits.
Not long after the bike was put in service the engine started making a humming noise when it was under load. This was most noticeable when travelling on forest roads in third or fourth gear at 1/3 to 1/2 throttle. I knew something wasn't quite right, but since I mostly ride singletrack just off idle, I rode it for the rest of 2007. There were tiny bits trapped in the oil filter at each oil change. The magnet was only normally fuzzy. The particles in the drain pan were not magnetic.
Over the winter of 2007 I took the engine apart to investigate. I have a complete machine shop and made up the required tools. The Berg engine is easy to work on. One thing I needed to check out was the crank. I could tell the engine had more vibration than necessary. The .008"crank runout was the result of me keeping the revs too high one time climbing a hill. I trued the crank, then welded the crank pin. The runout was .0025" when done. I expected this to be adequate for the next season.
There was substantial scoring of the bore. The piston had heavy scratches and the rings were marked up. This was obviously the source of the humming noise. The particles in the oil were tiny bits of nikasil. At this point I figured the failure started as a result of all the bits in the engine from the original kickstart idler gear issue. Here is a picture of liner number one:
I could not find anything else wrong with the engine, so I blew out all the oil passageways with compressed air and wiped off the insides of the engine cases. I did not remove the transmission gears, they stayed in place in the left engine case. The piston and liner were replaced (second set) and the engine went together well.
Here is where the problem begins. On my first ride in 2008, after an hour's operation the humming noise was back. The engine ran smooth when I started it, but after a bit I could tell there was some extra vibration. I pulled the engine apart to check things out. Dialing the crank shows that it had relaxed some despite the welding. I figure the original large .008" runout deformed the crank wheel bores and it had settled at .005". This does not concern me as I knew welding the used parts might not work out. The real issue is that the piston and bore were both damaged by scoring. You can see that the compression ring is not very good as it fails to make full contact around the bore. You can also notice how coarse the honing is. Here is a picture of liner number two:
More investigation was needed. The oil pump had slightly more clearance than recommended. Radially it varies from .006" to .007" compared to the .005" limit stated in the repair manual. While the oil pressure may be reduced some, this engine has no plain bearings and should not need extremely high oil pressure. The oil pump wear likely occurred from the particles that passed through the coarse strainer screen.
I wondered if rich jetting might be reducing bore lubrication, but on the second piston/liner I had already installed a 42 pilot jet in place of the overly rich 48 that Dale supplies with his kit. I tried a 38 but the idle would hang up too much. Main jet at 160 and clip in #4 worked OK. TPS disconnected and no pump squirt. I doubt the jetting caused any problems.
The only conclusion I could make was that I should have totally stripped each part and manually washed every piece to guarantee cleanliness. I think there must have been some tiny grains of nikasil left somewhere that came out after the engine was run. While this train of thought seemed logical, what I found during the next disassembly proved that cleanliness was not the problem.
OK, so now I am ready to install the third piston and liner. I also replaced the crank while I was at it. I checked the new crank before installing it. I dialed the crankshaft with the support bearings close to the crankwheel cheeks. It came in at .003", which is only slightly less than their published limit of .004". I installed the balancer and bearings and checked it again. With the support bearings now farther out under the main bearing races, the crank ends dialed in at .002". Since it was a combination of twist and parallel, I decided to leave it alone. Now that I know to limit a Husaberg engine to moderate revs, it should be adequate for my needs (although it's not very impressive as to new part quality). I had to return a brand new oil ring that was tight in the piston. It had a twist in it. Also one liner had to go back as it had a bad spot in the plating.
Because I'm on the third set of piston/liner parts, I do a meticulous teardown and complete cleaning. Here is how I do the assembly: I inspect the new piston to see that the rings slide OK. I coat the piston and rings with fresh oil. I coat the liner and the assembly sleeve with oil. The assembly sleeve is made of bronze and has a tapered bore. The rings compress gradually as the piston is pushed through the sleeve into the liner. Only a slight thumb push is required to install the piston. I slide the piston down to the bottom of the liner and install the wrist pin through the rod.
I "time" the balancer when the crank/liner/piston assembly is put into the left engine case. The joint surface is coated with sealer and the right engine case is assembled. Everything goes together with no problems and I torque the case bolts. I put more fresh oil around the piston above the top ring. The oil ring is still saturated from the initial assembly. I turn the flywheel back and forth multiple times to move the piston halfway up the bore and back down. It slides freely. After a few minutes I wipe the oil out of the bore. The rings are already marking the bore. Here is a picture of liner number three:
Because the previous engine problems were due to nikasil failures, I'm not bolting the rest of the engine together unless I'm sure the bore is fine. When I run my fingernail around the bore, it catches on some of the scratches you see in the photo. This is not good so I take it all apart again.
While researching nicasil coatings I found one article with a lot of good information. The author states that best success is had using some additional finishing AFTER diamond honing.
http://www.babcox.com/editorial/ar/eb110242.htm
Now let's move on to where I think the problem is. I have to say the compression ring is the culprit. Using a file on an old top ring, I can tell it's very tough. The chrome moly ring has a very slight chamfer on top, but is quite sharp on the bottom edge. The real issue is the amount of taper built into the ring face. Look at this picture of the top ring from liner #3 rebuild.
You can see how only the lower portion is touching the cylinder wall. I believe this tiny area puts extreme pressure on the bore. This pressure rips off the honing peaks quickly and creates the scratching problem. Keep in mind, the top ring face is only .048" wide, thus the initial contact area is much less than that. The oil ring is softer and feels like cast iron. It shows an even wear pattern. I doubt it has any effect on the coating/ring problem.
I have made up a piston ring clamping fixture for the lathe so I can machine the top ring OD. I might rig up a Dremel as a tool post grinder and grind the OD instead. Providing the top ring with a full width contact surface is the only way I can see to fix the problem. This will apply whether I replate the liner or have a custom cast iron liner made. I am leaning toward cast iron, but I will need to discuss the application details more with LA Sleeve before proceeding.
I suspect that bore scratching on Husaberg liners is quite common. In most cases the rings wear in quickly enough that the scratching is minimal. Replated liners may perform better than OEM parts by having higher quality coatings and/or better surface finishes.
I had inteneded to buy a Wossner/Atena piston and send it to LA Sleeve hoping that Wossner's ring quality is better than the OEM parts. Since the OEM piston is still OK, I will do some experimenting with ring finishing. Buying a set of rings is more economical than buying the entire piston assembly.
I will update this thread when I find out anything noteworthy.
On the very first startup, the engine made some horrible grinding noises. It turns out the the snap ring for the kickstart idler gear was missing or improperly installed. The idler gear bearing cage and rollers passed through the all primary gears damaging many teeth. The dealer replaced the damaged parts. The oil was changed several times to remove the leftover bits.
Not long after the bike was put in service the engine started making a humming noise when it was under load. This was most noticeable when travelling on forest roads in third or fourth gear at 1/3 to 1/2 throttle. I knew something wasn't quite right, but since I mostly ride singletrack just off idle, I rode it for the rest of 2007. There were tiny bits trapped in the oil filter at each oil change. The magnet was only normally fuzzy. The particles in the drain pan were not magnetic.
Over the winter of 2007 I took the engine apart to investigate. I have a complete machine shop and made up the required tools. The Berg engine is easy to work on. One thing I needed to check out was the crank. I could tell the engine had more vibration than necessary. The .008"crank runout was the result of me keeping the revs too high one time climbing a hill. I trued the crank, then welded the crank pin. The runout was .0025" when done. I expected this to be adequate for the next season.
There was substantial scoring of the bore. The piston had heavy scratches and the rings were marked up. This was obviously the source of the humming noise. The particles in the oil were tiny bits of nikasil. At this point I figured the failure started as a result of all the bits in the engine from the original kickstart idler gear issue. Here is a picture of liner number one:
I could not find anything else wrong with the engine, so I blew out all the oil passageways with compressed air and wiped off the insides of the engine cases. I did not remove the transmission gears, they stayed in place in the left engine case. The piston and liner were replaced (second set) and the engine went together well.
Here is where the problem begins. On my first ride in 2008, after an hour's operation the humming noise was back. The engine ran smooth when I started it, but after a bit I could tell there was some extra vibration. I pulled the engine apart to check things out. Dialing the crank shows that it had relaxed some despite the welding. I figure the original large .008" runout deformed the crank wheel bores and it had settled at .005". This does not concern me as I knew welding the used parts might not work out. The real issue is that the piston and bore were both damaged by scoring. You can see that the compression ring is not very good as it fails to make full contact around the bore. You can also notice how coarse the honing is. Here is a picture of liner number two:
More investigation was needed. The oil pump had slightly more clearance than recommended. Radially it varies from .006" to .007" compared to the .005" limit stated in the repair manual. While the oil pressure may be reduced some, this engine has no plain bearings and should not need extremely high oil pressure. The oil pump wear likely occurred from the particles that passed through the coarse strainer screen.
I wondered if rich jetting might be reducing bore lubrication, but on the second piston/liner I had already installed a 42 pilot jet in place of the overly rich 48 that Dale supplies with his kit. I tried a 38 but the idle would hang up too much. Main jet at 160 and clip in #4 worked OK. TPS disconnected and no pump squirt. I doubt the jetting caused any problems.
The only conclusion I could make was that I should have totally stripped each part and manually washed every piece to guarantee cleanliness. I think there must have been some tiny grains of nikasil left somewhere that came out after the engine was run. While this train of thought seemed logical, what I found during the next disassembly proved that cleanliness was not the problem.
OK, so now I am ready to install the third piston and liner. I also replaced the crank while I was at it. I checked the new crank before installing it. I dialed the crankshaft with the support bearings close to the crankwheel cheeks. It came in at .003", which is only slightly less than their published limit of .004". I installed the balancer and bearings and checked it again. With the support bearings now farther out under the main bearing races, the crank ends dialed in at .002". Since it was a combination of twist and parallel, I decided to leave it alone. Now that I know to limit a Husaberg engine to moderate revs, it should be adequate for my needs (although it's not very impressive as to new part quality). I had to return a brand new oil ring that was tight in the piston. It had a twist in it. Also one liner had to go back as it had a bad spot in the plating.
Because I'm on the third set of piston/liner parts, I do a meticulous teardown and complete cleaning. Here is how I do the assembly: I inspect the new piston to see that the rings slide OK. I coat the piston and rings with fresh oil. I coat the liner and the assembly sleeve with oil. The assembly sleeve is made of bronze and has a tapered bore. The rings compress gradually as the piston is pushed through the sleeve into the liner. Only a slight thumb push is required to install the piston. I slide the piston down to the bottom of the liner and install the wrist pin through the rod.
I "time" the balancer when the crank/liner/piston assembly is put into the left engine case. The joint surface is coated with sealer and the right engine case is assembled. Everything goes together with no problems and I torque the case bolts. I put more fresh oil around the piston above the top ring. The oil ring is still saturated from the initial assembly. I turn the flywheel back and forth multiple times to move the piston halfway up the bore and back down. It slides freely. After a few minutes I wipe the oil out of the bore. The rings are already marking the bore. Here is a picture of liner number three:
Because the previous engine problems were due to nikasil failures, I'm not bolting the rest of the engine together unless I'm sure the bore is fine. When I run my fingernail around the bore, it catches on some of the scratches you see in the photo. This is not good so I take it all apart again.
While researching nicasil coatings I found one article with a lot of good information. The author states that best success is had using some additional finishing AFTER diamond honing.
http://www.babcox.com/editorial/ar/eb110242.htm
Now let's move on to where I think the problem is. I have to say the compression ring is the culprit. Using a file on an old top ring, I can tell it's very tough. The chrome moly ring has a very slight chamfer on top, but is quite sharp on the bottom edge. The real issue is the amount of taper built into the ring face. Look at this picture of the top ring from liner #3 rebuild.
You can see how only the lower portion is touching the cylinder wall. I believe this tiny area puts extreme pressure on the bore. This pressure rips off the honing peaks quickly and creates the scratching problem. Keep in mind, the top ring face is only .048" wide, thus the initial contact area is much less than that. The oil ring is softer and feels like cast iron. It shows an even wear pattern. I doubt it has any effect on the coating/ring problem.
I have made up a piston ring clamping fixture for the lathe so I can machine the top ring OD. I might rig up a Dremel as a tool post grinder and grind the OD instead. Providing the top ring with a full width contact surface is the only way I can see to fix the problem. This will apply whether I replate the liner or have a custom cast iron liner made. I am leaning toward cast iron, but I will need to discuss the application details more with LA Sleeve before proceeding.
I suspect that bore scratching on Husaberg liners is quite common. In most cases the rings wear in quickly enough that the scratching is minimal. Replated liners may perform better than OEM parts by having higher quality coatings and/or better surface finishes.
I had inteneded to buy a Wossner/Atena piston and send it to LA Sleeve hoping that Wossner's ring quality is better than the OEM parts. Since the OEM piston is still OK, I will do some experimenting with ring finishing. Buying a set of rings is more economical than buying the entire piston assembly.
I will update this thread when I find out anything noteworthy.
