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January 19th, 2017, 04:21 PM   #1
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I Ride: 99 FC600, 95 FC501, 94 FE501
94 FE 501 Rebuild

I picked up a 94 FE 501 a few months ago. It had sat outside in the weather for over a year, and was looking pretty rough. I was able to get it running a couple weeks ago, with just a good cleaning of the carb and rinsing the tank out. I am doing a mild restoration - essentially, just getting it into good working order. I was going to wait until further along in the project to start a thread, but have already reached a point, that I need some help/guidance.

The motor started easily, 1-3 kicks and ran well. However, I decided to tear down the motor, to inspect everything.

First, from what I can tell, it seems to maybe have a piston from a KTM rfs motor in it. Pro-X Technical catalog has all the dimensions for their pistons (and connecting rods, etc - good resource) and all the measurements of this piston are similar to the KTM 520 / 95mm piston. And it only has 1 compression ring and the oil ring. Piston has 94.95 on stamped on top. Piston has a couple spots you can see at 6 and 7 o'clock in the pic below, where it looks like it has been dropped and flattened out the top edge. Had the original titanium nitride wrist pin, however it took considerable effort to remove it from the piston.

[IMG]
[/IMG]

[IMG][/IMG]


Where I am really needing some help, is with the rockers. I have researched this site, and most information I have seen is related to the newer motors. But from what I understand, the original rocker arms on these early Husabergs had replaceable bushings. These have no bushings. They do have one small hole on top of each rocker. They also appear to have had the rollers and roller bearing replaced, as they have peening. However, I am concerned that one roller is almost flush with the mounting flanges. The cam has not contacted the rocker, but it is awful close. Is this normal? Seems like the roller should be sticking further out. The roller on the other rocker sticks out maybe 1-2mm.

[IMG][/IMG]

Removing the rocker arm shafts took some effort. Once I got them out, I found out why:

[IMG][/IMG]

[IMG][/IMG]


The rocker arms / shafts were clearly not getting any oil. What is the proper rocker arm / shaft setup for these early Berg motors? These rocker arms each have a very small oiling hole on top, and the shafts are both hollow.

Last edited by VOR165; January 19th, 2017 at 04:25 PM.
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January 20th, 2017, 03:03 AM   #2
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so the rocker shafts are tight in the rocker arms right? so what is the OD of the shafts / ID of the rocker arm?

the rocker always moves away from the rocker end cap. the more you push the end cap in - the further you wedge the rocker arm over to the left.

Taffy
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January 20th, 2017, 05:37 AM   #3
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The shaft OD is 12mm, and the rocker ID is 12.20mm. The undamaged ends of the shafts insert cleanly into the rockers and rotate smoothly. The insides of the rocker do not appear to have been damaged - just the shafts.

However, I am wondering if the damage to the shafts was caused by lack of oiling, due to improper set up (either incorrect rockers, and/or shafts) or if this is normal long term wear.
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January 20th, 2017, 10:38 AM   #4
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I Ride: "2000" FE600, 1996 FC600, 1984 Husky WR400, 2015 Beta Xtrainer
The only difference that I've noticed between a KTM 520/525 piston and a Husaberg 501 piston is the compression height. Husabergs were 23mm from center of the wrist pin bore to the top of the piston and the KTM piston is 23.5mm. I'll bet that the piston you have measures 23mm.

I would presume that the 520/525 piston could be used in the Berg 501 if the crown was machined down .5mm and the valve reliefs deepened. However, that should be unnecessary since, at least the last time I checked, Wossner makes the correct piston for the Berg with the 23mm compression height.

Incidentally, if you bore your cylinder and install a sleeve with a 100mm bore, you can use the piston from a newer 550 (Wossner p/n 8551DA) and end up with a 551cc engine!

Thumper Racing is experienced with sleeving Husaberg cylinders out to 100mm now since I just had them do it for my 600 cylinder.

As for your rocker shaft issue...these are splash oiled engines and damage like that can easily occur if a previous owner didn't change the oil often enough. The little hole on the top of each rocker is the spot where the oil is supposed to access the shaft. Seeing the damage you've got there has me thinking about machining a wide angle chamfer around those little holes for each of my engines in an attempt to collect more oil. Maybe I'll have Microblue work their magic on the shafts as well. Thanks for the heads-up.
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April 4th, 2017, 04:26 PM   #5
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Well, progress has been slow - but I am getting there.

The insides of the rocker arms did have some slight damage - I bought a fine 1/2" ball hone and refinished the insides.

[IMG][/IMG]

After that, I used a dremel and metal polish and polished out the insides of the rocker arms to a mirror finish.

[IMG][/IMG]


I bought new rocker arm shafts from a KTM RFS motor. The KTM's have a long and a short shaft - the longer shaft is identical to the Husaberg shafts. I also polished out the shafts to a mirror finish. Inserting the new shafts into the refinished rocker arms, after the polishing, the action is smooth as glass. Hopefully this will assist in reducing wear.

I was also concerned with the clearance, or lack thereof, between the rocker arms and the cam lobes. I clearance ground the rocker arms, so that the cam lobes will not contact the rocker.

[IMG][/IMG]

Next, the cylinder had major wear in the front and rear, from the piston skirts. The was also slight wear, either into the plating or the actual cylinder, from perhaps piston slap.


[IMG][/IMG]

I sent the cylinder off to US Chrome to be re-plated. I am impressed with the results:

[IMG][/IMG]

For a piston, I decided to go with a Pro X piston from a KTM RFS motor. I sent it to US Chrome and had their coating applied to the skirt. The KTM piston is .5mm taller compression height, as previously mentioned. In order to add back the .5mm height, and retain normal clearances, I had a custom .5mm copper shim made.

[IMG][/IMG]

[IMG][/IMG]


Now, I am well aware that Wossner makes a direct fit piston for these early motors. However, using a KTM RFS piston opens up a lot of options: Wossner, Vertex, Wiseco, JE, Pro X, as well as different compression ratios: 11:1, 12.5:1 and 13:1. My intake valves were worn pretty bad. I used Pro X intake valves from an RFS motor as replacements ($20 each). The RFS valves are 1mm shorter, but my adjusters had plenty of length to make up the difference. After I reassembled the head, I test fit the cam and rocker cover and set the valve clearances - just to check everything out. Exhaust valves look like new after I cleaned the carbon build up from them.

I ordered an RFS head gasket, but the water jacket holes were a bit smaller than the original, so I returned it and ordered an Athena head gasket. Unfortunately, they sent me a 93mm gasket from an early MC501 motor and not a 95mm gasket like I ordered. This is likely going to cause a significant delay, with the international shipping involved.
Thanks from zaga

Last edited by VOR165; April 4th, 2017 at 06:47 PM.
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April 4th, 2017, 04:38 PM   #6
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I also purchased cam bearings, water pump seals and orings from an RFS motor. These items were identical to the Husaberg parts. I bought KTM valve seals, but they were not the same. I ended up buying valve seals from a 03 VW Jetta 1.8 gas motor from a local auto parts store for $1.49 each and they were identical to the Husaberg seals.

I may have to elongate the cam sprocket mounting holes to position the camshaft correctly at TDC, as I understand raising the cylinder and head with the copper shim I am using will advance the cam timing slightly.

Last edited by VOR165; April 5th, 2017 at 04:39 AM.
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April 19th, 2017, 09:48 AM   #7
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I got the motor reassembled with the KTM head gasket.

This is the first Husaberg motor I have worked on. While the top end was off, I checked the rod and despite my best efforts, I could not detect any up/down movement which would indicate the big end rod bearing was worn. The rod did have slight play in a twisting manner. It would also "lean" over left and right some. But up/down play was undetectable.

When rocking the flywheel back and forth at TDC, it makes an odd sound which makes me think the big end bearing could in fact be faulty.

Here is a video of it:

I checked my 99 600 by doing the same thing and it is a lot smoother and does not make the knocking sound.

I am hoping one of you guys more familiar with these motors could give me your thoughts.
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April 19th, 2017, 11:21 AM   #8
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not good.

are the primary gear and clutch on?

I like to put the piston at TDC and feel for this? it can be the little end.

the other thing is, if your carnk was out of balance, the rod will wear on the first and third third leaving only yhr middle third working all the time. that is why you could rock the rod like a windscreen wiper. OK?

Taffy
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April 19th, 2017, 01:28 PM   #9
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Motor is fully assembled. The piston pin fit properly in the little end of the rod - don't think that is it. I had my doubts about the condition of the big end bearing. I will probably go ahead and split the cases and see what is going on down there.
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April 19th, 2017, 04:55 PM   #10
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Well I disassembled the top end this evening. I believe the main bearings could be the issue. Rather than spinning freely, the crank acts like it hits flat spots that require some effort to move past. Its not rough, but feels like it is building compression or something, then moves past it - if that makes sense. And its the crank making the knocking sound when rocking it back and forth.

Another video:




On a positive note: I am fairly certain my top end experiment with the Ktm piston and shim is going to work. I found a formula for determing the change in cam timing from the increased cylinder height from the shim I am using. It indicates only 1.2 degrees of advance, which doesn't seem like much. Factor in the retarding of the timing from cam chain stretch and I would estimate the timing to be pretty close to normal.

Also, I checked the tensioner while disassembling to inspect the lower end, and it was on the 5th notch with the shim installed.

Last edited by VOR165; April 20th, 2017 at 09:37 AM.
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