High Sump

[ClassicBiker]

Speaking with Doug Sawicki recently the conversation got around to the May 2023 MPH (892) and the Series A review. In the review Peter Barker discusses GLX17, a Series A single in Australia. Peter refers to GLX17 as having a "high sump". Doug asked if I knew the difference between a "high sump" engine and a later engine. Having never heard the term before I was at a loss, Doug said he had heard the term before but didn't know anything in particular that distinguished one from the other. So we started to play spot the difference between the Series A in the review on page 53 and the Series A in the Bohnham's advertisement on page 57. Can anyone educate us on the differences please?
Steven

 

[Simon Dinsdale]

Here is my understanding which may be slightly wrong so cannot guarantee its 100% accurate:

High sump refers to the very early series A singles where the sump was actually at the front of the engine at around 2 to 3 oclock when viewing from the timing side. The idea was that the flywheels would throw the oil up there into a gallery which could then drain down to the oil pump. The bottom of the crankcases was rounded in shape. It was in general a failure which limited oil return and hence the reason only 49 engines using these crankcases were made. The crankcase part numbers were E1 & E2. Some of these crankcases were converted during manufacture and had flywheel scrapers added inside to try and create the 2nd version below.

The 2nd version of A single crankcases had the high sump bulge missing. Instead a close fitting flywheel scraper was added to the inside of the crankcases so oil gathered in the bottom and then was returned to the oild tank via the pump. This was an improvment but as the crankcases were still rounded in shape at the bottom and the sump volume was not very large due to clearance to the flywheels. Approximately 54 engines using these crankcases were made and the case part numbers were E1/1 & E2/1.

The 3rd and final design was what most series A singles used. The sump was still at the bottom of the crankcases but was moved backwards which is the lump cast into the bottom rear of the crankcases. This enlarged the sump and improved oil return and is similar in operation to the later series B & C engines. This changed the shape of the crankcases from rounded to a more flat bottom and required a redesign of the rear engine pates. Crankcase parts numbers are E1/2 & E2/2.

 

[ClassicBiker]

Simon,
Thank you for that explanation. I'll pass that along to Doug.
Steven

 

[Flyinglow]

Steven,
This is one of the E1/E2 type crankcase engines. You can see the distinct bulge on the forward face/side of the engine.

Colin

 

[Marvel]

Here is my understanding which may be slightly wrong so cannot guarantee its 100% accurate:

High sump refers to the very early series A singles where the sump was actually at the front of the engine at around 2 to 3 oclock when viewing from the timing side. The idea was that the flywheels would throw the oil up there into a gallery which could then drain down to the oil pump. The bottom of the crankcases was rounded in shape. It was in general a failure which limited oil return and hence the reason only 49 engines using these crankcases were made. The crankcase part numbers were E1 & E2. Some of these crankcases were converted during manufacture and had flywheel scrapers added inside to try and create the 2nd version below.

The 2nd version of A single crankcases had the high sump bulge missing. Instead a close fitting flywheel scraper was added to the inside of the crankcases so oil gathered in the bottom and then was returned to the oild tank via the pump. This was an improvment but as the crankcases were still rounded in shape at the bottom and the sump volume was not very large due to clearance to the flywheels. Approximately 54 engines using these crankcases were made and the case part numbers were E1/1 & E2/1.

The 3rd and final design was what most series A singles used. The sump was still at the bottom of the crankcases but was moved backwards which is the lump cast into the bottom rear of the crankcases. This enlarged the sump and improved oil return and is similar in operation to the later series B & C engines. This changed the shape of the crankcases from rounded to a more flat bottom and required a redesign of the rear engine pates. Crankcase parts numbers are E1/2 & E2/2.

Would engine number C50 been a high sump type?

 

[ClassicBiker]

Colin,
Thanks for that photo. That helps out quite a bit. It confirmed what I had thought when spotting the difference between the two photos in MPH.
Steven

 

[Simon Dinsdale]

Would engine number C50 been a high sump type?

Most probably yes.