Oil circulation g3ls 1955

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Oil circulation g3ls 1955

Postby allanmg9 » Wed May 02, 2018 10:35 pm

Hello , I need advice on a problem with my g3 ,I took it for its first run after years laid up and although there is oil returning to tank the engine casings are massively overheating and the oil is only warm? This was after a 3 mile gentle run . The bike has had an overhaul with engine rebore before I bought it as a non runner . I reground the valves new clutch new carb etc etc. But I have no knowledge of its history before or why it was rebored. It seems to suggest the oil is not getting to the right areas but circulating back to tank anyway, any suggestions please.
Regards Allan

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Re: Oil circulation g3ls 1955

Postby Mick D » Thu May 03, 2018 7:31 am

Hi

First thing I'd do would be to check the oil pump guide pin is installed in the correct orientation and is engaged in the oil pump plunger - if you don't know already, manuals for your bike are available here under 'Books':

http://archives.jampot.dk/

I see your in Banffshire, I'm in the Turriff area - PM me if you want to chat over a call.

Regards Mick

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Re: Oil circulation g3ls 1955

Postby SPRIDDLER » Thu May 03, 2018 7:43 am

allanmg9 wrote:...the engine casings are massively overheating and the oil is only warm? This was after a 3 mile gentle run .

Although the engine is very hot I wouldn't expect the oil to be more than warm after just a 3 mile run but as Mick has said, check that the oil pump guide pin is correctly fitted.

The bike has had an overhaul with engine rebore before I bought it as a non runner .

'Overhauled' and yet a non-runner?? That's an unknown. It depends upon the competence/honesty of whoever did the work.

I reground the valves

Why was that necessary on an overhauled engine?

I suggest you deal first with the two prime causes of overheating (Ignition timing & weak mixture). The ignition timing may be too retarded (it must be set on Full Advance when setting the timing). If you have auto A/R (the 350's changed from manual to auto for '55) the auto A/R mechanism may be stuck.

new clutch new carb

Overheating may be due to a weak mixture so check that you have the right jets, needle position and there are no air leaks between the carb and cyl head.
Which carb is it? Some new carbs have been found to have a blockage/swarf in the Pilot jet.
Has the first foot or so of the exhaust pipe become very discoloured (blue/mauve)?
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Re: Oil circulation g3ls 1955

Postby alanengineer » Thu May 03, 2018 8:42 am

Did you check the oil return by looking in the oil tank and looking for the dribble when the engine is running.
Then its checking the ignition timing like Spriddler says.

Our Bikes dont do 3 miles without oil

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Re: Oil circulation g3ls 1955

Postby Mick D » Thu May 03, 2018 9:28 am

Hi

The OP says the engine cases are very hot - in my opinion after only a three mile run this is unlikely to be the result of a fuelling or timing issue, (the overheating should be limited to the head, exhaust and cylinder)

If the oil pump guide pin is fitted 'upside down' the oil flow is greatly reduced - if it's not engaged the flow is zero.

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Re: Oil circulation g3ls 1955

Postby SPRIDDLER » Thu May 03, 2018 10:52 am

Mick D wrote:The OP says the engine cases are very hot - (the overheating should be limited to the head, exhaust and cylinder)

Agreed; the heat is coming from the combustion area, but there's very little oil cooling of the head or cylinder. Probably 85% of the oil feeds the big end and main bearings which are roller bearings with perhaps just 15% going to the little end and rocker box. The main and big end are roller bearings which are unlikely to overheat to the extent that the 'engine cases' (the crankcase or cylinder??) become 'massively hot'. The cylinder is only splash oiled with crankcase mist.
As so often happens we can only guess as there are various unknowns; what was done at the 'overhaul'? Was it done competently? I'm rather cynical that the bike was 'overhauled' yet still a non-runner and that the valves needed grinding................. I can't imagine anyone overhauling a bike but not get it running... :?
It could well turn out that it's due to global warming. ;)
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Re: Oil circulation g3ls 1955

Postby allanmg9 » Fri May 04, 2018 8:36 am

Thanks for all the replies they are much appreciated . I should clarify the engine work that had been done before I bought the bike was partial and not documented, and yes oil does return but a poorer flow than my g9 . Thanks to all who took time to answer . Investigation starts soon and I will post the results when I have answers ( or more questions ).
Thanks Mick I may need to contact you as we are practicaly neighbours it would make sense.

Regards Allan

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Re: Oil circulation g3ls 1955

Postby SPRIDDLER » Fri May 04, 2018 5:42 pm

allanmg9 wrote:I should clarify the engine work that had been done before I bought the bike was partial and not documented,

O.K. Checking the pump guide pin is quite simple fortunately and a good place to start. Don't rotate the engine when you have removed the pin since if it was correctly fitted and you rotate the engine the plunger will move out of register with the pin position. If the pin wasn't fitted correctly lined up with the annular groove in the plunger you will have to remove the pump rear plate to line it up. It is essential to have the rear plate seal well - a new gasket may be required and it's not a good idea to use sealant on it.
Ensure that you have the correct (the reduced diameter) end of the guide pin in its holder.

....and yes oil does return but a poorer flow than my g9 .

You're probably aware of this but the twins have a gear oil pump which delivers a more or less continuous flow back to the tank. The oscillating plunger type pump in the single engines produces a fairly continuous return for a minute or so and then the oil will return only in an interrupted flow with occasional spurts and bubbles.
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Re: Oil circulation g3ls 1955

Postby allanmg9 » Mon May 07, 2018 9:49 pm

Update ! The pump guide pin is good all seems fine there . The cylinder head has been removed because it has lost compression , caused by the inlet valve guide having dropped it also looks like it may have been out of rotational position . The good news is the piston and cylinder bore are fine. The plan is to fit a new guide and get her running again to see what happens temp wise , as their are still question marks there.
Thanks again for the help
Allan

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Re: Oil circulation g3ls 1955

Postby 1608 » Tue May 08, 2018 6:13 pm

You say the engine has been re-bored. This can cause the engine to run a little on the hot side.

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