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Shock absorber knocking

Posted: Thu May 23, 2019 8:20 am
by camstevens
Hi
Have just run my newly refurbished Mk1 engine, and whilst it runs sweetly there was a horrendous knocking (like a big end), which transpires to be coming from the shock absorber. This phenomenon was suggested by Marcus and others. I am looking to rectify the slop in the spline sleeve, and have a remedy, but am wondering if some of the noise could be coming from the cammed outer sliding member? I was advised these components do not tend to cause problems, but want to make sure I've covered all bases (realistically).

On the bigger picture of things, there is also the possibility the knock is coming from within.....If so, I suspect it may be a new club rod contacting the sleeve...although I did carefully measure these against the specs provided, and all were within tolerances.

Hoping this does transpire to be the shock absorber. It's becoming like a grieving process....DENIAL, BARGAINING, ACCEPTANCE, and so on......

Cam

Re: Shock absorber knocking

Posted: Thu May 23, 2019 10:18 am
by Gui.dorey
Cam,

As a first thought - primary chain tension is checked and correct? Is the shock absorber tight enough? any chance that the big nut loosened?

Then check the obvious - any bolt, nut or screw in the inner primary case come undone? I used an engine endoscope through the primary case inspection hole to explore in there.

I just had to tear my engine apart because of another problem - no knocking but it wouldn't turn - and was checking for anything that might have been stuck somewhere. I would be extremely surprised if your con rods were touching the sleeves. There's a lot of clearance in there. One of my fears was that one of the sleeves had dropped (none had), but the opinion here was that it is extremely unlikely and if that had happened they would be shattered - so probably you would hear a different awful noise and probably only once.

Cheers,
Gui

Re: Shock absorber knocking

Posted: Thu May 23, 2019 10:55 am
by camstevens
Did you find any potential cause for the pick-up?

Cam

Re: Shock absorber knocking

Posted: Thu May 23, 2019 10:57 am
by camstevens
Did you find any potential cause for the lock-up?

Cam

Re: Shock absorber knocking

Posted: Thu May 23, 2019 1:14 pm
by Gui.dorey
Yes, my plain bearing for the front crank seized due to my mistake in setting the end float. You can read the whole horror story here:

viewtopic.php?f=4&t=9348

Re: Shock absorber knocking

Posted: Thu May 23, 2019 3:13 pm
by camstevens
Hi Gui
I read your thread....you must have been frustrated. It helped me keep my chin up :)
I'll spend the weekend on this.....If I can isolate this knock, I am well on the way.....I'll just work through it as you have.

I saw Sime's (I think) comment regarding the large pipe being for the gauge, and small for rocker feed. My feed lines from Draganfly had the fittings around the other way, i.e. the olive fitting for the rocker union is on the larger tube. Would this have a material effect? Would the smaller tube be intended to "throttle" the flow?

Cam

Re: Shock absorber knocking

Posted: Thu May 23, 2019 4:14 pm
by Gui.dorey
Hi Cam,

Exactly. Simes also documented that on his blog.

My lines came from Drags as well, and the larger pipe feeds the rockers, just like yours. Should be the other way around. If you can solder pipe connections, it is quite simple to exchange the fittings one for the other. But, if you don't, the worst that can happen are oil leaks from the rocker boxes or some oil getting into the valves and you puffing some smoke. It's not critical, but when you have a chance, why not? A job I had planned for next winter, but will probably do it now while I'm waiting to get the bottom end sorted out….

Regarding that knocking of yours - if you don't find anything obvious through the primary inspection hole, then you'll have to get that primary cover off (and yes, also the whole clutch has to come out...). Then turn the engine with a socket wrench on one of the drive side crank nuts, and see if the noise is still there. And if so, you'll just have to keep on disassembling part by part until you find where the knocking comes from…

Gui

Re: Shock absorber knocking

Posted: Fri May 24, 2019 10:40 am
by Bob.Murphy
Regarding the knocking . . . Are your coupling gears a tight fit and tight mesh ??

I had to find three pairs of gears (don't mix & match them) before I found a good tight pair that whined slightly when cold - but still knocked when the motor was hot and idling (I used to ride it hard in the early '70s).

Bob.

Re: Shock absorber knocking

Posted: Sat May 25, 2019 10:39 am
by camstevens
Well, I cracked half a smile this morning.....horrible knock has disappeared, so a massive relief. Other than a bit lumpy with fuel the engine runs nicely, but oils up in cycles......If I leave it for 2-3 minutes and start it runs beautifully cleanly, but then starts to oil up, particularly on the left pipe. I hope it's coming from over-oiling up top..
...as per discussion with Gui, my supply tubes are transposed. So, I'll crank up my 300W soldering iron and swap the fittings. Other than rings bedding in, I can't see what else would cause it.

Cheers
Campbell

Re: Shock absorber knocking

Posted: Sun May 26, 2019 11:23 am
by camstevens
Ok.......I changed the tubes (thin to rockers and larger to gauge).....yes, certainly reduced oiling, but oil gauge now shows towards 100psi, so didn't run it for long through fear of some sort of engine damage. Unless I've got the wrong end of the stick, this is telling me thinner tube is having a reduced capillary tube/office effect, and the relief spring is WAY too strong. This is the original spring from the engine when I bought it.....I removed the spring unit, and it was sitting nicely, not jammed over or anything like that. What should the relief be I really set at? My Ariel manual states 23 - 35 psi, so I'm way off that.

Cam