Vince
New Member
Posts: 28
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Post by Vince on Jul 25, 2023 10:52:46 GMT
There seems to be a lack of compression on my Villiers 8e engine on my James Captain. Starts from cold reasonably well but a bugger to start from hot. Can the crankcase seals be replaced with the engine in situ? I presume one removes the flywheel on the one side and the clutch on the other? Anybody have practical experience of doing it?
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d7er
New Member
I'm not that new, I re-joined four years ago. I volunteered for the south Northamptonshire area rep'
Posts: 46
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Post by d7er on Jul 25, 2023 11:13:07 GMT
In my experience with mostly Bantam engines, one failed crank oil seal will generally mean either no or very hard to start engine from cold, let alone hot. I'd look at float level, worn out jets, etc. firstly.
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Post by buttybach1932 on Jul 25, 2023 15:22:54 GMT
Hi Vince Low compression would not be caused by leaking crankcase seals. It would be a piston rings stuck in their grooves, worn piston rings, worn cylinder bore or a leaking cylinder head to barrel joint. Worn crankcase seals reduce the suction on the carburettor so it struggles to lift the fuel into the carburettor venturi. This normally means you have to use the tickler a lot to get fuel into the engine for a cold start. As you need a richer mixture for a cold start, starting from cold is normally more difficult. Once the engine is running there is less time for air to be drawn through the leaky seals and the engine runs fairly OK but the tick-over mixture would be weak. Hot starting problems are normally caused by either the ignition system or fuel vaporisation in the carburettor. Modern lead free fuels have a lower boiling point than the older leaded fuels. If the carburettor gets hot, the fuel boils and starting becomes virtually impossible. This has been a problem on some old cars where the carburettor is mounted above the exhaust manifold. If you sit in a traffic jam with the engine running the engine stalls and you cannot restart until it cools down. On the later D7 to B175 Bantams that have a flange fitted carburettor I fit longer studs and a Paxolin heat spacer to reduce the heat transfer to the carburettor. The Villiers 8E has a stub mounted carburettor so this solution is not possible. The next time you have a hot starting problem check the temperature of the carburettor float bowl with your hand to see how hot it feels. The magneto ignition can also be affected by heat. The ignition capacitor can break down when it is hot so you do not get a proper spark. Also the heat temporarily reduces the magnetism in the flywheel which obviously affects the spark. If the magnetism in the flywheel has reduced over the years, getting it re-magnetised would probably overcome the hot starting problem. It is possible to fit a temporary battery and coil ignition system to see if it overcomes the hot starting problem. Finally we come to the crankcase seals. On the 8E they are rubber gaiter seals and can be accessed without removing the cylinder barrel or splitting the crankcases but it is a fiddly operation. The Magneto, Primary Chain and Engine Sprocket have to be removed to access the seals. They can be removed by drilling three small holes at 120° spacings and screwing self tapping screws into the holes. 'Hopefully' the seals will pull out using a pair of mole grips on the heads of the screws. If they will not pull out it is strip the engine time. The new seals can be pushed in but it can be difficult to keep them square and you really need a tubular tool to tap them home with ( you may get away with using an old tubular spanner but make sure the end is filed square and flat ). Best of luck with your problem. Regards Butty Bach
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Post by buttybach1932 on Jul 26, 2023 11:14:06 GMT
Hi Vince
What I forgot to say in by previous post was that piston rings stuck in their grooves, worn piston rings or a worn cylinder bore will also affect the crankcase suction / compression. So you get a double whammy of problems that affect starting.
Another foible of two stroke engines is that they can suffer from a 'wet' mixture. A wet mixture is when the fuel is in liquid form instead of being atomised in the air. In liquid form the spark plug cannot ignite the fuel. You can also get a problem where the engine appears to run weak but it is throwing unburnt liquid fuel globules out of the exhaust. Both these problems were reduced when lead free fuel became available because it has a lower boiling point and evaporates easier.
The new E10 fuel is likely to cause problems in two stroke engines because the alcohol in the fuel could affect the rubber crankcase seals and it could also cause bearing corrosion problems because alcohol absorbs water. Use E5 fuel if you can.
Regards Butty Bach
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Vince
New Member
Posts: 28
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Post by Vince on Jul 26, 2023 16:50:57 GMT
Thank you Butty Bach,that's a very comprehensive reply and given me plenty to think about. The coil and condenser were replaced when I first did a rebuild about 6 years ago. (Doesn't time fly past, feels like yesterday!) I have also had the head and barrel off to fit new gaskets and bore / ring condition is good. The only major thing I haven't done is have the flywheel re-magnetised so I think perhaps I should get that done to eliminate it from the possibilities. A task for winter perhaps. BTW since E10 was introduced I have always used E5 and it certainly runs better using the high octane fuel.
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Post by nortonjohn on Jul 29, 2023 15:32:01 GMT
There seems to be a lack of compression on my Villiers 8e engine on my James Captain. Starts from cold reasonably well but a bugger to start from hot. Can the crankcase seals be replaced with the engine in situ? I presume one removes the flywheel on the one side and the clutch on the other? Anybody have practical experience of doing it? There is a YouTube video by Mr. Tweed that shows him installing seals on a 9D engine which originally didn't have them. I find all of his videos very interesting.
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Post by buttybach1932 on Jul 30, 2023 10:06:29 GMT
Hi Norton John
I had a look at the 'Tweeds Garage' videos on U Tube and agree they are amusing and interesting. However he did make several cock ups when he rebuilt the Villiers 9D engine. The crankcase seal modification from bronze sealing bushes to rubber gaiter seals was done very professionally but from the other videos that I have watched he is a very competent machinist and has some decent equipment.
The cock ups were the dismantling of the crankshaft where he bored out the old big end pin. This would have pressed out no problem on a decent hydraulic press. I admit that the Villiers bobweight cranks are a bit of a problem to support and making a proper tool can be expensive because of the cost of the steel. But if it is a one off you can get away with making a tool out of a 3 foot length of 4" × 2" channel iron and a couple of M12 hook studs ( like they use on spring compressors ).
The next cock up was not cleaning up the damaged taper on the crankshaft whilst be had the crankshaft in pieces. Plus I would have ground the taper in after cleaning it up.
Finally it was obvious that the clutch was not going to work when he assembled it because the springs were virtually coil bound. I would not have bothered to fit the primary chaincase cover gasket until I knew the clutch lifted square a freed properly. The mystery was, what engine was the clutch pressure plate from. It looked to be Villiers but I could not recognise what engine it was from, so it might have been Albion.
We all make cock ups and I make plenty but I do not put mine on video for people to view.
Regards Butty Bach
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