Shock absorber knocking

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pauldridge
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Re: Shock absorber knocking

Postby pauldridge » Thu May 30, 2019 5:36 am

My recently rebuilt mk II engine with Morgo pump tops out at 70 PSI and pretty much stays there at cruise rpm even after warm. I believe the Morgo has its own regulator internal. 70 seems to have no adverse effect but 100 PSI seems pretty excessive
Phil Auldridge Austin, Texas - USA
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53 SQ 4 MK II, '72 Norton Commando, '78 BMW R100/7, '79 Honda CBX, 2014 Indian Chief Vintage

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Bob.Murphy
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Re: Shock absorber knocking

Postby Bob.Murphy » Thu May 30, 2019 10:39 am

Gui.dorey wrote: you could always try this - again from the Sq 4 Workshop manual. No idea if works.


Have I got this right, now ?? - The "MkII Valve Guide Modification" is the addition of the sleeve over the inner valve spring.

Which begs the question - Does the modification introduce the cylindrical-topped valve guide as well (why would the shape have changed otherwise, other than to provide the conical oil scraper in the top face)?

Which implies that earlier MkII engines had the same guides as the MkI - but it seems the MkII guides don't work in MkI motors so did the rocker box re-design on the MkII allow more clearance - a happy accident ?

Whatever, it seems that the MkII guides are not a solution for MkI over-oiling issues.

(I used to earn my crust as a Business & Systems Analyst - I like to get to the bottom of issues that don't make sense :roll: ).

Bob.
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john.whiting
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Re: Shock absorber knocking

Postby john.whiting » Thu May 30, 2019 12:47 pm

One simple thing to try is to fill the gap in the collets with silastic.....this does work ,and Ive done it in several engines...not S4 ,tho.

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Re: Shock absorber knocking

Postby camstevens » Sat Jun 01, 2019 4:03 pm

Thanks John
I might just try that....even if it's not a final solution, it will help with process of elimination.

Other than the smoking I had a very successful morning.....the engine is running unbelievably smoothly now that the fuel mixture is closer to right (was way rich) and ignition timing. Ran it for 15 mins.

Pattern for smoking/Oiling is a follows:
- starts nicely and runs cleanly for 2-3 mins, then
- wisps of vapour appear, then
- starts to smoke and will blow smoke with revs.
- stop the engine and let it rest for 2-3 mins and the process starts again, beginning with 2-3 mins of clean running.
- will actually blow some spots of unburnt oil out around exhaust at head

I heard SQ4s have a valve sticking problem, so I really polished the stems (you could shave in them). I didn't remove material, but I wonder if the highly polished surfaces allow oils to flow down stems?

Cam

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Re: Shock absorber knocking

Postby will_curry » Sat Jun 01, 2019 5:29 pm

Sounds like the rocker box is flooding with oil. The oil should drain down through
the tappet blocks and any blockage there is a recipe for smoke.

The stud which connects the rocker and oil gauge pipe to the crankcase has a hole
designed to regulate the amount of oil going 'upstairs'. This means that when the
rocker gear gets some play the gauge is depressingly pessimistic but the rocker
box doesn't flood.

Tim Healey put me right about the stud years ago when they were still in 'Rockhill' and I've
still got Fred my 1951 Mk1 and still showing only about 10psi on the gauge but no longer
followed by a smoke trail. He did warn me not to cut the supply any more or the cam will
suffer.

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Re: Shock absorber knocking

Postby camstevens » Sun Jun 02, 2019 6:44 pm

Hi
I've sealed the collets as per John's suggestion (temporary)...will see effects once it has cured.

Just another thought: I doubt there is much of a vacuum break when the tappet covers are down tight....perhaps this could contribute to slow oil return?

Campbell

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Re: Shock absorber knocking

Postby roger.fellows » Sun Jun 02, 2019 7:13 pm

Have you thought much about crankcase breathing Cam? That might resist oil flow out of the head and help force oil out through the guides.

Somebody shoot this down if it's irrelevant please.

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Re: Shock absorber knocking

Postby camstevens » Sun Jun 02, 2019 7:28 pm

Hi Roger
The external breather (tube bolted to crankvase) is clear, and there is a port (hole) in high in the timing part of the crankcase...should be venting OK?

Cam

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Re: Shock absorber knocking

Postby roger.fellows » Sun Jun 02, 2019 7:39 pm

Sounds okay, have you considered enlarging it?

camstevens
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Re: Shock absorber knocking

Postby camstevens » Sun Jun 02, 2019 7:44 pm

No, but if that turns out to be a common problem, for sure. I will check the tappet venting by removing a sleeve nut and see what happens. If I can get this oiling sorted it's good to go....it really does run like a sewing machine


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