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Old 26-07-2010, 01:48 PM
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venting shovelhead

working toward getting my shovel on the road after some years dormant in the garage due to other committments. summer's nearly over, but still plenty of time for some neat rides and getting involved with the scene. i'm determined to ride this year.

getting very close to mot'able stage. but i was wondering about the crank-case venting and wet-sumping. due to the lie ups it pukes out quite a bit of oil when it's kicked over/started. i know i need to clean/check/re-seat the ball valve and hoepfully it'll improve/stop when/if in use?

my primary feed has been sealed off, still runs a chain. still have the little oilway on the inner primary and the larger hose connection blocked off.

i was thinking of connecting my crank case vent to the inner primary. my logic was any oil dumped gets fed into the primary, that is an oil bath anyway?

primary is vented to atmospheric, a hole up at the rear or the primary case. so pressure shouldn't build up? and as long as it doesn't keep wet sumping filling the primary it should be o.k with an occassional check, no?

i could make an inspection level in the derby cover or somehting?

i've never come across anyone doing this, so i'm assuming it's a not good? but my thoughts tell me why not? can i see the wood for the trees?
cheers, j.
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Old 26-07-2010, 02:10 PM
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Paul P. Paul P. is offline
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Join Date: Mar 2006
Posts: 3,547
Re: venting shovelhead

Sounds like an interesting idea tho' I have to wonder if there is some reason to be cautious however, one thing that is a proven wise move on shovels is to separate the primary from the oil system. The tiny shavings of nylon are not a happy ingredient for the oil but one only needs a mugfull of oil in the separated chaincase, just enough for the bottom of the chain passing round the clutch drum to dip into and splash around. Clutch slip garranteed if you put any more in. I hope to add some last shovel oil improvements to mine - oil seal valve guides the main one and an alteration to the crank case which speeds up scavenging (John Warr was telling me about it, involves a good dealer who knows what they are doing) and a change of oil pipe unions between the heads (might be a drill job if the change is simply larger holes?)(I hope). This all adds up to cleaner, cooler oil and can raise a shovels oil mileage to 500 miles a pint (or more some say) as well as cleaner plugs etc.
Good luck.
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Old 26-07-2010, 05:40 PM
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Re: venting shovelhead

hi, my primary oil feed from the pump is sealed. bike originally ran a belt, but i put it back to a chain, less hassle i thought?

it's due to this retro-fit chain that i had to seal up the oil feed/scavenge ports at the inner primary. one is an oil hose bore size. go me thinking periodically mopping up oil when i started the bike. can i hose my crank breather into the primary?

valve oil seals is soemhting i need to think about too. at present i have none fitted. i had to have a valve guide repair due to a broken guide rattling around in there. i heard seal-less guides get abit more lube and last abit longer?

but it's abit smokey, though in mitigation i've only ever idled it over the past few years. and some of that will be from the oil/grease used when it was in bits for ages. when i've run it proper like, i'll see how smokey it is and maybe fit some then?
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Old 26-07-2010, 05:58 PM
grbrown grbrown is offline
Join Date: Oct 2007
Posts: 5,020
Re: venting shovelhead

As a bit of background, shovels originally had a dry sump primary lubrication system, with a dry clutch. So the oil pump fed oil to the primary chain, but also pumped it back out. If you have a dry clutch you would be wise to avoid feeding oil vapour in there IMHO!

I bought a new shovel many years ago and never modified that side of it, but did my later evo. I bought a small K&N style filter to put on the end of the breather and secured it out of sight under the seat. It was still a bit messy, but not as bad as leaving the breather open.
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Old 26-07-2010, 06:36 PM
Panhead Boris's Avatar
Panhead Boris Panhead Boris is online now
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Posts: 1,289
Re: venting shovelhead

You will only get nice clean oil when the motor is seriously wet-sumped...
the rest of the time you will get mositure and mayonaise like goo when cold - not good for the primary chain.

Also the vent sucks when there is vaccuum beneath the pistons, so all the crap from primary could get drawn into your bottom end.

I use the small pleated K&N type filter on mine, mounted on transmission end cover bolt. Any time I know the motor is heavily wet sumped (after about 6 months of standing idle), I just remove the pipe from the filter and temporarily run it into a drain pan to catch the surplus.

On the subject of valve guide seals, they are fine providing you have valves and seats designed to run like this. Remember the old motors were designed to splash lubricate the valve assembly and heads, and to burn a small amount of oil.
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Old 26-07-2010, 07:55 PM
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Noddy Noddy is offline
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Join Date: Oct 2002
Posts: 523
Re: venting shovelhead

.....don't forget that if your vent pipe is 6 inches or less in lenght, it can and will suck up debris from the road etc and could take it back into the engine , make sure it is a minimum of 8 inches or preferably longer with a filter on the end ..... happy venting....
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Old 27-07-2010, 09:28 AM
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Re: venting shovelhead

thanks for the replies guys.

g, the clutch is wet, so no probs having oil in there. i changed it when i ditched the dry belt.

thanks boris, i now understand, it is not a good idea due to the emulsification and vacuum. thats that sorted. also more reassuring with the guide seals, or lack off infact.

vent pipe is long enough noddy, but i need to filter the end really.

hopefully back on the road over the next fortnight?

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