Hitchcocks Forum

I've just read the article in the technical notes section on the Hitchcocks site about the Bullet lubrication and wet sumping. It advices to check that the sump drain plug threads don't obscure the oil passage just up inside the sump hole. I have just drained the oil from all 3 drains in the bottom of the engine. There was about 800cc in the sump - but the bike has been standing un-used for a year. I carefully measured the threads on the drain plug - 8.5mm. From my estimation most of the oil passageway in the sump hole will be obscured when the plug is in place. What will be the effect of this do you think? Reduced oil flow through the scavenge pump? Leading to wet sumping and insufficient oiling of the rockers? Has anyone found the same thing and did you just fit an extra steel washer behind the copper washer to increase the clearance?

Go for the Dowty seals, much thicker to start with and just over hand tight will seal till the next time..

Dont mess about with copper and steel, if it drips its too tempting to just nip it up a bit more and see..

I can tell you exactly what the effect is - horrible clouds of thick white oil smoke on start-up which last for several minutes until the poor scavenge pump finally catches up, and with, as you say, a restriction in the rocker feed (though once everything is running normally it's a mixture of oil and air pumped up as the scavenge pump has a larger capacity than the feed pump).



My Electra-X wet sumps like a good 'un but never smokes, I looked in my spare set of Electra cases to see why, and it may be due to the fact that there's more than enough threaded section for the scavenge-side strainer plug before the drilling from the sump enters the plug chamber. Result, the scavenge pump slurps up all the oil through its nice fat pump gears double quick, and all is well.



My other RE engined bike is a bit of a work in progress at the moment as I have found that its scavenge drain plug DOES block the oilway from the sump to quite an extent. So far I have added a couple of thicker steel washers (no Dowty seals to hand!) in an attempt to move the plug down far enough for the oil to be pumped up without the plug running out of thread. This has achieved a little improvement in the white smoke elimination department, but it still needs more work before I'm happy with it. Not to mention the neighbours.



A.

Just as I thought. What do you think of the idea of grinding off some of the threads (just on the side that is obscuring the oil passageway). I thought that this would help to preserve more of the threaded length of the plug to help hold it tight.

I'm with Gwilly, Dowty washers.

If I could check my sump hole I would be in a Circus.

I've found a source of 14mm dowty washers - £2.76 for 10 inc p+p. Will they do , or must they be 13.5mm as sold by Hitchcocks?. Is it OK to fit 2 together on the sump drain?

The rubber lip inside the washer will probably squash out to some extent, at that price you can afford to experiment. If you're worried about marginal thread being left to hold the plug in place, you could always drill and lock-wire the scavenge plug's hex head, as they would on a race bike.



My extra washer-fitted smoker wasn't too bad on start-up this afternoon, though having discussed it with Bullet Whisperer, there are a couple more things I can try. A.

Potboiler, I wouldn't try the bigger ones. The seal has to be snug on the bolt to work properly.
I don't think you could stack them either but you could use a plain washer on the plug first.
The good news is they seal with little more than finger pressure so there's not danger of stripping threads. In fact, I was worried they might vibrate off so this is what I did

I'm into microlight flying as well as bikes. A lot of the fastenings are lock wired for the obvious safety reasons. If you have a look on e bay you can get very reasonably priced proper locking pliers and the correct stainless locking wire for not much more than about 25/30 quid and be able to lock most fasteners against vibration. With a bit of practice (have a look on you tube) it also looks very neat and professional . Cheap peace of mind on a bike with a tendency to vibrate things loose.