• 4 Stroke Husqvarna Motorcycles Made In Italy - About 1989 to 2014
    TE = 4st Enduro & TC = 4st Cross

  • Hi everyone,

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Sm450 bad vibration and blowby, piston/ cylinder good...?

Roadhazardguy

Husqvarna
B Class
Ok guys so a couple weeks ago after a few minutes into my ride home the bike started vibrating with it increasing in intensity as the revs went up. It felt fine at idle and probably up to 2500 or so but no weird sounds that I can remember. I decided just to ride it home and it did fine and still felt like it had full power but vibrated through my hands and butt like a big bore 2 stroke but worse. It was dark so when I got home I found that it had blown the vent tube off the valve/ cam cover and left nice big oil spot on my pants leg. The bike has 10,700 something miles so I figured the piston and or rings were toast if not the crank too. Compression test showed 80 psi so I finally got time today and tore the top end off of it. The piston and rings looks perfect, the bore looks perfect, there's absolutely no up and down play in the rod or crank bearings. The only thing I found was the nut to hold the impeller was loose and it allowed the impeller to move in and out wearing a tiny bit into the housing and some off the veins, also I didn't check it before I pulled it apart but it "looks" like one of the intake valves could use a shim.

So what do yall think? Could that water pump cause all my vibrations? And what about the low comp and what I think is some pretty excessive blowby. Oil wasn't high, sitting level it was in the middle of the sight glass. Thanks

Tony
 
The low compression is due to the ADC (automatic decompression) device which bleeds most of the 160 lbs down to 80 so the tiny starter can start the bike.

Middle of the sight glass on my 450 means there will be some breather oil in my airbox. The oil level gets itself down to about the lower level line and then it stays there pretty predictably.

Have you checked the motor mounts for the source of the vibrations?
 
Check the main bearing on the clutch side. If its starting to go it will vibrate and make a noise and the seal will go and suck trans. oil.
 
Sounds like typical main bearing symptoms to me, pop the stator cover off and see if there is up and down movement on the flywheel.
 
Ok so that confirms the ADC bleeds compression at idle, (I found out about that last night). Ok I'll check the crank from the stator side, I already pulled the cover and didn't see the flywheel eating into the stator or anything. I didn't check the motor mounts yet either.
 
Alright I checked it again and from the flywheel too but I still can't feel any play at all. I guess I'll pull the clutch cover to see if anything strange happened in there.
 
Ok so that confirms the ADC bleeds compression at idle,

The ADC bleeds off compression at revolutions LESS THAN idle, as in cranking speed. At idle (approx 1600 RPMs and higher) the engine operates at full compression for that particular engine speed and cam profile.
 
Is the clutch basket supposed to have play in it? I can wobble it around a little and that seems kinda odd to me. I didn't pull it all the way apart, just the outer pressure plate and the clutches to get a better look inside then I put it back together. I figured I'd ask first before I tear into it further.
 
I'm no expert on the clutches on these bikes so can't be of much help there but did you check the engine mount bolts for tightness?
 
I pulled the big side cover and can see that the basket is still riveted to the steel drive gear securely and see that the play is only side to side on the shaft so I think I'm good there.

The sprockets look good but I was going to order a new chain anyway. I think I'm going to order a new high flow water pump, new gaskets, filters, chain, then put it back together and give it hell. Hopefully it will be good.
 
If your mount bolts were lose then that is hopefully your source of vibration. I had a Husaberg 650 do the same, these big singles vibrate a lot anyway but with engine bolts slightly lose things can feel a whole lot worse.
 
That's my hope, I guess I'll see what happens. At least I know the crank is good now, the 10k miles was starting to worry me.
 
The guy I bought the bike from cut the hose for the breather right by the airbox then tucked the hose down in between the frame and engine. Should I put it back like that or reconnect it to the airbox?
 
Ok I'll put it back like it should be. All I'm waiting for now is my air filter and rear tire from amazon, and the high flow water pump from halls was on backorder so I'm waiting for that too.

OlderHuskyRider do you ride your TE around Austin much? I was riding with my buddy up there last weekend on his drz & v-muscle and had a blast. I'll be headed back up there in a week or two more than likely.
 
Ok I'll put it back like it should be. All I'm waiting for now is my air filter and rear tire from amazon, and the high flow water pump from halls was on backorder so I'm waiting for that too.

OlderHuskyRider do you ride your TE around Austin much? I was riding with my buddy up there last weekend on his drz & v-muscle and had a blast. I'll be headed back up there in a week or two more than likely.

We ride alot up here, stuff like this tho....

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