Ariel Owners Motorcycle Club

Terry,

I have discovered that the oil sludge trap was totally blocked

When you say the sludge trap was totally blocked, was it blocked beyond the end of the sludge trap itself i.e. did you have to poke crud out the crankshaft as well as the sludge trap tube? The big-end oil passage is over an inch beyond the top of the sludge trap, so the build-up has to go a long way beyond the sludge trap to affect the big-end. I have, in the past, blown compressed (mixed with flushing oil and with the sludge trap removed) into the end of the crankshaft to clear out any bits of debris. DO NOT blow into the sludge trap hole as you will drive loosened crud back up into the oil passages. After refitting the sludge trap blow compessed air into the end of the crankshaft again. The only place it can come out now is the big-end feed however...

...has the big-end given any indication of problems? If not, I get the feeling that you are getting diverted down a blind alley (both literally and metaphorically). The fundamental issue is your oil circulation.


With all the kicking and running of the engine, has the oil tank level gone down and, when you removed the sump plate, did much oil come out? If so the oil feed side is working and the problem lies in the oil return side so you need to isolate where this problem resides.

1) Start by disconnecting the lower oil pipe at the back of the cam chest and blow air up the pipe. If the air doesn't come out from the pipe in the oil tank mouth then there is a blockage between these two points (a leak isn't an issue).

2) Check the pump is working as per Paul Jameson's post (wear eye protection).

3) If the pump works, the problem lies with the tube from the sump to the back of the pump which is either blocked or leaking.

Pete

If your using Windows then MSPaint can be used to add arrows, lines and simple text however just a photo of the part you discussing always helps.

There's 2 aspects of the Oil system. Supply and scavenge. It's odd for Both to fail. Add oil to the engine through one of the rocker boxes to make sure it's oiled while you play around with it. About 150 CCs.(Mls) The scavenge flow rate is way above the supply rate to ensure there is no build up of oil in the Sump/crankcase. It pays to replace the little Balls that act as valves in the Pump as they tend to wear oval. Use the Tapered springs preferably as well, and the Proper gasket under the Pump. I wouldn't try to make one. Don't fill the Oil tank above Min while you are playing with it Nev

Pete that,s a good point.
I did not delve any deeper into the sludge trap to see if there was any crud coming out of the crankshaft.
This is what I did today. Removed pump and sump cover. Lots of oil came out of the sump. Then I blew compressed air through every port under the pump area. Everything came out clear eg through the pickup pipe to the pump from the oil feed back to tank feed from the tank to the pump. All let air through. Then I blew air into the crankshaft but of course nothing came out of there. Before fitting the pump back on I injected oil into the crankshaft with a high pressure oil can. Reffited the sump cover and kicked the bike over a few times. Then I started the bike up and let it run for a few minutes but still no oil returning back to the tank.
Does this suggest what Pete stated about a blockage in the cranckshaft or is the pump not working.
Terry

Just to chip in here - if you pump oil into the end of the crankshaft with the sump plate off, you should get oil pouring out of the sump plate. It passes into the crankshaft, through the drillings into the big end, and out of the big end.

If you do the same thing with the sludge trap out it will come pouring out of there too - or should do.

I can tell you that when I built my W/NG the goop in the sludge trap extended all the way up to the big end. I used a large twist drill to remove it.

HI Simon, That,s a good tip I,ll give that a try today.
Did you do the twist drill job with the motor in the bike or stripped down on the bench?
I shall report back if I get any results
T

Terry.C. wrote: Fri May 22, 2026 7:24 am HI Simon, That,s a good tip I,ll give that a try today.
Did you do the twist drill job with the motor in the bike or stripped down on the bench?
I shall report back if I get any results
T

It was in the bike. If I recall correctly, it's a half inch hole, and I just used a regular Wesco-type oil can in the end of the crank.

I have just tried Simons tip and I get oil coming out of the sludge trap but not the crankshaft. I used air first because of the mess oil makes but the result is the same.
It looks as if there is a blockage in the crankshaft am I correct thing this?
Simon what size drill did you use to unblock the oilway?
When I put a wire down the crankshaft it comes to a solid dead end. Is this where the blockage starts?
T

Terry.C. wrote: Fri May 22, 2026 9:36 am When I put a wire down the crankshaft it comes to a solid dead end. Is this where the blockage starts?

Hi

Probably not, the gallery through the shaft runs along it's axis and stops where it meets a drilling coming from the sludge trap, this is probably what you are feeling. Try passing a wire up to the gallery from the sludge trap, this is where it is probably blocked, if it is, clear it out with a series of drills, start at around 1/8", (3mm), and work up through the sizes until you can't put a bigger one in using only finger pressure to turn it. Blow the crud out periodically with an air line from the crankshaft hole, debris should come out of the sludge trap.

Regards Mick

Edited to add: If there is this much sludge in the system it would be prudent to clear out the crank pin galleries, not sure if this is possible without stripping the crank.

Hi Guy's,
Further update. I have blown through every oil connection including the sludge trap, flow and returns. Before doing that I checked the ports into the crankshaft for crud with a drill as suggested but nothing excessive there.
I also checked into the sludge trap area but with the same results.
I then tried Simons suggestion of pumping oil into the crankshaft and oil came out of there and the sludge trap. started the bike up but still no oil returning to the tank or rocker feed. I only ran the bike for a few minutes just in case no oil is getting to the big end.
Whero do I go from here?
Beginning to look like a total strip down again.
T

Just to clarify Terry - when you pump oil into the end of crankshaft, with the sludge trap in, do you get oil coming out of the sump plate?