Vanguard v twin problem.

[fleehillfarm]

Thanks I will certainly give that a try. Maybe with WD40?

[fleehillfarm]

Thanks I will certainly give that a try. Maybe with WD40?

[fleehillfarm]

After watching a couple of videos on Youtube I see that I was being incredibly stupid. Of course after removing the cylinder head on a Briggs and Stratton you are down to the main body of the engine and crankcase.  I was thinking of the bike engines that I worked on when I was a kid. Taking apart Triumph 500cc Speedtwin and T100 engines where you took off the cylinder head and then the barrel and the crankcase was a separate entity so you could access the piston rings.

Anyway so it has to be engine out or the scrapyard.

[spudulike]

Well, it is wet outside and the grass isn't growing much...crack on👍

[Muddy42]

On 16/12/2025 at 06:10, fleehillfarm said:

After watching a couple of videos on Youtube I see that I was being incredibly stupid. Of course after removing the cylinder head on a Briggs and Stratton you are down to the main body of the engine and crankcase.  I was thinking of the bike engines that I worked on when I was a kid. Taking apart Triumph 500cc Speedtwin and T100 engines where you took off the cylinder head and then the barrel and the crankcase was a separate entity so you could access the piston rings.

Anyway so it has to be engine out or the scrapyard.

 

I am definitely no expert, but I did successfully rebuild my first B&S v twin last summer.  I am a bit unclear about what you have been doing.  You but you can strip down a v twin from two directions:

 

1. underneath the engine you can remove the single crankcase cover.  this accesses a large area of sump, oil and the single camshaft, compression release, timed cogs etc.

 

2. Behind each of the two cylinders.  Taking off the two valve covers accesses the valves and rockers etc.  Then you can again go behind each of these to get to each of the two heads and pistons where the combustion happens.  

 

which route have you taken?

 

 

 

 

[Mick Jones]

If your not too confident on your ability to remove and inspect your pistons/rings but you have the heads off try putting oil in your cylinders and let them stand overnite to see if you have obvious signs of oil bypassing the rings. Not a 100% test but worth a go before you rip into it.

       In the past I have seen worn piston ring grooves that act like an oil pump when the engine is running causing oil to get into the top end and cause smoking.

Worth a go.

[fleehillfarm]

Thanks for the replies from Mick Jones and Muddy42. The route that I have taken is that I have removed the cylinder head and replaced the head gasket of the smoking right hand cylinder  and it made no difference at all. To remove the crankcase I would have to take out the engine which I am reluctant to do, especially as the right hand cylinder which seems top be the one that all the smoke is coming from is still now ( I tested it again this morning) showing  a 100psi compression. The left hand cylinder which I haven't replaced the head gasket is 75psi. Surely a compression of 100psi must rule out piston ring bypass.

I'm wondering whether there is anything I could have done wrong when I cleaned the carbs that could cause such serious smoking. 

If I remove the cylinder head again I'll try the oil test as suggested.

[Muddy42]

40 minutes ago, fleehillfarm said:

Thanks for the replies from Mick Jones and Muddy42. The route that I have taken is that I have removed the cylinder head and replaced the head gasket of the smoking right hand cylinder  and it made no difference at all. To remove the crankcase I would have to take out the engine which I am reluctant to do, especially as the right hand cylinder which seems top be the one that all the smoke is coming from is still now ( I tested it again this morning) showing  a 100psi compression. The left hand cylinder which I haven't replaced the head gasket is 75psi. Surely a compression of 100psi must rule out piston ring bypass.

I'm wondering whether there is anything I could have done wrong when I cleaned the carbs that could cause such serious smoking. 

If I remove the cylinder head again I'll try the oil test as suggested.

 

Yes, there are a few things that could go cause excess fuel when you cleaned out the carb, or reassembled the choke or governor. BUT I would have thought a carb fuel issue would affect both cylinders equally.  I would try soaking the piston.

 

If all else fails, replacing the engine will require removal anyway, so you might aswell give this a go and tackle the crankcase side.  It takes time, but technically is not that difficult. Just remember the order that everything goes in and the timing marks.