crankcase sealing

[headdownarseup]

just thinking outside the box a bit here!
with regards to correct sealing of the crankcase with ALL seagulls (except perhaps QB models) has anyone thought about using regular motor oil in with the fuel. e.g 10w40 or similar.
i've read on here somewhere that the "racing boys" sometimes do this.
Is there any benefit in doing this that anybody knows of especially if your motor has seen better days in the crank bushes department.
Its come up quite a lot recently on another thread loosely along the lines of lack of compression with the normal answers being "fit new rings" etc.
Great if everything else checks out ok! but as i say, what if your crank bushes are slightly stuffed or worse. Anybody tried using thicker oil as a short term fix?

Back in the days when we used to rebuild car engines on a regular basis it was common practice to rebore and regrind most if not all the reciprocating parts of an engine.
I'm talking about the 1950's up to late 70's early 80's when we were using multi grade motor oils in our engines.
When seagulls were first designed and built they didn't have semi synthetic oils and high octane fuels etc. but with potentially 60-80 years worth of use, there will be a lot of old gulls out there still managing to run on a wing and a prayer so to speak, and with probably more than the usual amount of end float and play in the crank part of the engine.


any thoughts on this gents

[Keith.P]

The old two stroke oil is a lot different to today's modern stuff, the problem is the oil has to go though the carburettor and a thicker oil will make a leaner fuel mix, the thicker the oil the more running problems you will get, less oil will get burnt, plus spark plugs getting oiled up all the time and lot more carbon build up.
I think you will find two stroke oil is a specific weight oil not a multi grade oil, so It wouldn't help at all.
Crank cases are not usually a problem, crank bushes, yes had problems with them and just replace them, I don't think today's petrol is any better than it used to be, probably worse now with all the additives, can you still get four star.

[JERSEYMAN]

I think you will find that British Seagull initially specified 30W motor oil.

[Keith.P]

I don't know why I bother, using thicker oil will not help a leaking motor.
30W, is there such an oil, like 10W40 oil, W stands for winter, or do you mean SAE30.

[JERSEYMAN]

I meant straight 30 weight or SAE30 (I thought it was obvious), hell, Am I the only one who has read the original seagull handbook

[Stelios_Rjk]

I also remember that about straight SAE30 been mentioned here some time ago!

[croweater]

I will stick with a TCW3 two stroke oil at 10-1.
I would sooner have a motor that starts easily with little smoke if the bearings are crook I will change them.

John

[denchen]

If the old grey cells are working right I think Castrolite was 20 `grade`, Castrol XL 30 and Castrol XXL was 40 ish. We were racing gocarts in the 60s and used Castrol R in with the petrol with a mix of Redex. The engines in the carts were Villiers 9Es. Basic 197cc single cylinder motors. We were grinding crankshafts, reboring cylinder blocks etc of the cars of the time, and even white metaling big ends of some of the older models. The boss would say ``if it wasn`t for Castrol we would be out of a job`` as we didnt rate many of the oils then and you would be lucky to get more than about 40,000 miles before a rebore was needed. Also it was a bit before my time, but I was told that in war years, the octane of the petrol available to the public was at times as low as 78 octane. My bottom line is that modern oils and petrol are far better quality than what the original Seagulls were designed for.

[headdownarseup]

hi all

keith, yes i agree that crankcases are not usually a problem but the bushes being phosphor bronze will be a bit softer than the hardened steel crank itself and so will wear quicker leading to leakage. Sometimes, depending on what model you're running, there tends to be a bit of seepage from the top bush under the base plate.
with regards to modern oils, yes i agree there is far superior lubricating qualities compared to the older stuff! incedentally i tend to use a tcw3 semi synthetic oil which seems ok to me and interestingly, not too much smoke either. I'd almost say smoke levels have been halved chelp to seal thing aompared to mineral oil.
Anybody else use semi synthetic?

Going back to worn bushes though, would a higher oil content help things a bit. my thoughts behind this are that it would "dump" (if thats the right word) more oil around the bush and due to crankcase compression would help to seal things a bit better. a bit more smoke, yes, more likely to foul a plug up a bit quicker, probably. but until a more effective repair could be carried out i.e replace the worn bushes, it couldn't hurt things any more could it?

[Keith.P]

However much oil you use, if the crank seal is leaking, usually the top one, the crank pressure will just force the extra oil out.
If the motor will not run at a low tick over speed, its too far gone, there are plenty of cranks about, especially on this site.

[headdownarseup]

fair comment keith.

just wondering that's all. I've used some really thick gloopy stuff in the past that looks like golden syrup that's supposed to "help" (and i use the word "help" loosely) with oil burning and compression loss in car engines before, but was just wondering if using slightly thicker oil in a 2 stroke would help, but as you've answered everything i need to know i won't bother.



next question then HEEEEEELLLLPPPPP. Can anybody make me up some crank bushes for a 102 please.

[Stelios_Rjk]

I may can help, I 'll send you a PM.

[Charles uk]

Post the engine number, so you can be sure your getting the correct type of main bearing bushes, apart from myself, John is the only person I know who has the corrrect reamer to ensure that both of the main bearings are reamed perfectly in line.

Often it's cheaper to buy a new crankcase, as bearings made from the correct material are expensive!

Talk to John.