Vibration/Knocking from primary area

Greetings

Over the last 100-300 miles I noticed a strange knocking/vibration in my left foot (due to a PO's accident it is slightly touching primary case so it has direct contact). This bike being my first motorcycle and still new to me I wasn't sure if I was just starting to notice it because i had gotten use to the rattles and shakes from the rest of the bike or if it was getting worse the more i rode it. The knocking is unregular compared to the rest of the bike's "smoothness", or maybe "squareness" is the better word, with the 360 crank. I could see it fitting right in on a HD v-twin or a big block V-8 with a cam in it...you know what i mean? Kinda un-regularly regular? Maybe? Anyways, I can usually only feel it when it's in neutral and it almost completely goes away when i pull the clutch in. I did just replace the layshaft bearing and after inspecting the old one you could feel it catch and grind a bit when spun by hand and was somewhat erratic so i thought maybe that was it. Nope, not so. I did some reading on this site and it led me to check the primary. It was really tight. I corrected the primary and started it and it still knocked. I did the layshaft bearing with the gearbox in the bike and every gear and bush that i took out looked pretty good to my eyes, nothing seemed to worn or buggered up. I should, and probably will, pull the gearbox out, but before i do; what am i likely to find wrong in there? Am all i am going to need is new mainshaft bearings and new sleeve gear bush? FWIW, the clutch and the shifting seem to be the best i'v felt since replacing the layshaft and shimming to the correct endplay. It's wonderful here in the upper-midwest and i want to ride it so i was thinking about ordering what i need before i take it apart to try and speed up the repair process.

Any input? Thanks!

Take the alternator rotor off and see if the centre will move in relation to the outer including the magnets, look carefully at the magnets and if they are standing proud of the alloy. Replace if it shows any of these issues, you can try a short test drive with it replaced with a dummy spacer.

The engine is rubber mounted on these bikes, the rubber mounting system is called the isolastics.

On mine, these were worn / incorrectly assembled / both and the chain case would touch the end of the swinging arm spindle. Being rubber mounted, this would make a dreadful knocking noise, it sounded like something really horrible!

So, I'd be looking at adjusting your isolastics as a first option, also, the primary chain case needs to be correctly spaced away with the central mounting point, this would be worth checkout out too.

Is your foot or your footrest slightly touching the primary. Is it possible that your primary case is hitting your footrest while the motor is running and this is causing the noise?

The Isolastics are the Veirneir replacements and about two years/700 miles old. I set them to be a bit on the tight side just to keep the handling a little tighter and limit any weirdness as i got use to the bike. There is not excessive vibration any other place on the bike and everything looks good as far as the primary case rubbing anything. Except, yes, the left footpeg is touching...thats how i noticed the strange knock/vibration...the knock/vibration isn't the normal buzzy kind that can be felt in most of the other bike at some rev range or another but a completely different one that i can only feel in the left footpeg when im actually on the bike. I can only feel it when i'm sitting still with the bike in neutral with the clutch lever out, once i pull the clutch in it almost disappears. The knock/vibration is still there even with the footpeg and outer primary case removed. I can snake my hand down in between the inner primary case and tranny and feel it with my hand. I suspect it has something to do with the primary chain being so tight for the last however many miles. Im not sure exactly how many miles it has been that tight for it was just something i noticed recently.

"Over the last 100-300 miles I noticed a strange knocking/vibration in my left foot (due to a PO's accident it is slightly touching primary case so it has direct contact)."


Fix the footrest first.... and the problem will likely be solved. :idea:

Tell us about your skillset... and it'll be easier to guide you in the right direction. Sounds like your footrest forging is bent. Any friends with metal working skills? Bribe them with beer... the part must be removed first, don't just pull on it.

At the moment the footrest isn't even attached to the bike, and i can still feel the knock in question when i shove my hand down there. But yes, i do plan on messing with the footrest eventually as i could see it wearing a hole in the primary cover eventually if i just leave it. But, I'm more concerned with why the knocking is there, not just the fact that i feel it.

As previously stated , pull primary cover and check the alternator rotor..If that thing is loose it can cause a huge mess...

The foot rest is a easy job to fix mount it a vice with soft jaws put a long pipe over the end of the arm, foot peg removed of course and just pull the long pipe on the arm the direction it needs to so it is away from your primary cover, you don't need to bend it much,

Take the primary apart and make sure everything inside is tight, router nut or clutch nut could be lose, chain to tight, inner cove rubbing, you won't know for sure till you open it up and have a look inside.did it have the knocking noise before you replaced the lay shaft or only after you put it back together???

Ashley

theocean said:

At the moment the footrest isn't even attached to the bike, and i can still feel the knock in question when i shove my hand down there. But yes, i do plan on messing with the footrest eventually as i could see it wearing a hole in the primary cover eventually if i just leave it. But, I'm more concerned with why the knocking is there, not just the fact that i feel it.

Click to expand...

As mentioned, open up, have a look. :mrgreen:

Ok, alternator looked good as far as i could tell. Magnets seemed nice and flush. The rotor nut was tight as was the clutch nut. And I don't see any strange marks where something was rubbing on the inner cover. But like i mentioned earlier it did have a tight primary chain and thats what i was thinking is causing this knock. So, a couple of days ago I set the chain properly and the knock is still there. So, what are the usual symptoms of a tight primary chain? What damage does it do that could be the source of this knock? Just the mainshaft bearings? I did the layshaft bearing with the tranny in the bike and every gear and bush i took out looked good to me. It knocked before and after i did the layshaft bearing. It still shifts nice and all, so my assumption is that it's not too out-of-wack yet. But the way it knocks i feel it can only be a matter of time till it does go.

a too tight primary chain could bend the main shaft enough to make the clutch basket wobble

can you take the outer cover off, start it, and observe how true it seems to be spinning?

Test the oil pressure. Before we determine what it IS, first we figure out what it ISN'T :idea:

It seemed to have a bit of a wobble when the chain was tight...after i loosened it to it's correct taught-ness the wobble looked less noticeable if it was still there at all. But the knock was still there.

You've searched all over the engine for incidental contact with frame/other parts :?: :idea:

Ok, I just went to double check and take a close look and the clutch still wobbles enough to notice.

It doesn't look like the engine is hitting anything it's not supposed to. But I can only feel the knock when its in neutral and i have the clutch out, once i pull the clutch in the knock disappears. And i cant feel it going down the road but i think thats because it gets drowned out by the other sensations/vibrations.

I thought maybe you guys could be somewhat sure what was damaged by a tight primary chain and i could order the most likely damaged parts before i actually get the chance to take the transmission and clutch apart to see. But I guess i'll just bite the bullet and take everything apart then wait for parts...that way even if it takes a week or so longer to get it back on the road at least everything that needs replaceing gets replaced.

Take a look at the back (rear) of the inner primary cover to see if there are any witness marks and fretting against the frame. Unless the isolastic rubbers have been replaced recently, they are probably sacked out from old age and may allow the primary inner cover to hit up against the frame.

Get a couple of the clutch location circlips pt number 060752. This may have jumped out of it's slot or partially come out when you reassembled the clutch. The torque reading given for the clutch center nut in the workshop manual is incorrectly stated as 70 ft lbs, it should actually be around 40 ft lbs.

Check if the gearbox is tight in the cradle particularly the bottom through bolt. Mine became loose and I had the same vibration through my foot when I touched the primary cover. There was also some knocking noise.