Restoration of 1951 Vincent Rapide - Part 19 - Top End 1

[@robfrye4664]

With all of the unfinished business up top, and weird out-of-phase assembly work, I'd be biting the bullet and completely disassembling that motor/transmission assembly in order to be certain the bottom end is properly done. The motor looks very clean and fresh, but who knows what maybe lurking in the interior. Been there on a few 'fresh overhaulss' that were definitely not as advertised!

[@duckysan]

Fabulous, but totally over-engineered design! I find your disassembly videos quite captivating - I never had any idea why Vincent's have such a legendary reputation, but thanks to you I do now. Quite scary to see how many fasteners that were never tightened by the previous owner!

[@vincentl.9469]

the parts look like sculpture..works of art. A lot of things to be sure are tight, as in the rest of the bike..not something to just put away forget

[@vwmountainman9701]

I know this video is a couple years old. But at this point of inspection. I don't think I would trust anything. Complete tear down - it's only time right !! Well - time & $$$$ Nice work - you seem to really know ur way around these vintage bikes !!

[@54macdog]

I feared the worst but the head is excellent. That's a pile of tricky jobs you won't have to deal with. I'm loving this saga - as one of your other subs said below, Journey to the Centre of the Vincent. I hope very much that splitting the cases won't be necessary.

[@charliesharpe5004]

Just watch the length of the 1/4" B.S.F. bolts attaching the rocker feed pipes. They should all be 1/2" long. Too long and they can block the feed.

[@ThePianoCentre]

Very interesting , thanks for posting .

[@TheMightyGarage]

Thanks David, Cheers, Mike

[@rvanderw998]

Your epic journey to the center of the Vincent is great Mike, I'm interested in how you assess crank and big end condition. Keep it coming!

[@bobstevens9040]

I love your videos Mike . Like a good whodunnit TV drama serial! I can't wait for the next cliffhanging installment. The Vincent engine is a work of art and is deserving of the time and effort you're putting in. Greetings from a cold and foggy UK

[@TheMightyGarage]

Thank you very much Bob! I saw how bad the weather was.. and folks had to take a day off work.. heaven forbid ;) Best wishes, Mike

[@deanhoare8789]

difficult to know when to stop with a project like this , imagine if after all that work the bike suffers from vibration due to worn or misaligned crank assembly , if the bike is one you want to keep id be tempted to go the extra mile and split the cases to check big ends and main bearings at this stage, correctly assembled a bottom end could last 100 000 miles according to the factory ,these videos are great ,many thanks

[@elrayox8932]

Enjoyed this! 👍

[@TheMightyGarage]

Thanks very much! Hope all is well, Mike

[@Hiwheelman]

Hi Mike, I've been using this as my guide and now I am waiting on parts (push rod seals) to arrive. I note this was posted four years ago. Did you end up retorquing the heads? I'm getting mixed responses as to the need, given there is no head gasket.

[@TheMightyGarage]

Hi Daniel, sorry for the delay. I have not been feeling very well. No, I did not actually end up retorquing the cylinder head bolts. It’s been one of those things that I have been “meaning to do“ for a couple of years! I think the next time that I take the front end off the bike, I will check the torque settings. Best wishes, Mike

[@jimh.5286]

"I'm pretty confident that everything's fine." Never, ever say that - it angers the Gods of mechanical fate.

[@TheMightyGarage]

Hehe, so true Jim. Best wishes, Mike

[@Mainforce66]

No head gaskets?

[@deepthought3316]

Remember on my Comet the rocker assembly would work its way loose and begin to hammer its way into the rocker tunnel making things even worse. The cure was a 'modified rocker feed bolt' which anchored the entire assembly into the rocker tunnel..

[@TheMightyGarage]

Ah yes, I did consider that mod. Perhaps another time in the future! There are lots of other projects to complete first ;)

[@minibikeaction4266]

What a beautiful engine! looking at the valve rocker I dont see how the valve is pushed down. The rocker clearly gos into the head but there looks to be nothing above the valve stem and springs were the other end of the rocker is normally seen. Even from the diagram I could not see how valve actuation was achieved. It would be interesting to know how this was done by Vincent.

[@romanroad483]

John, the valves are pushed down by a forked rocker that engages with a groove in the valve stem. There are also two valve guides per valve, one above the rocker arm and one below. I guess the idea was to reduce the side thrust on the valve stem, caused by the wiping action of the rocker on the end of the valve stem in a conventional design. Modern ohc designs use bucket cam followers which take all the side thrust. Consequently valve stems can be much smaller diameter, reducing inertia.

[@bigred8438]

Thank you for your 19th installment. From what I could see the Rapide doesn't have head gaskets. Is that because that locating ring at the top of the sleeve has such fine tolerances that it acts as a gasket?

[@TheMightyGarage]

Hi Big Red, yes that's true. There is only a paper gasket on the barrels but no head gasket for the reasons you mention. Cheers, Mike

[@tadpoles10]

End of the day you will have 'peace of mind' Mike, as you said 'having gone this far removing the cylinders had to be done. It's looking to be a nice clean engine with great potential once everything is back in place with the missing parts installed. atvb t ..

[@nickjonesjones]

Hi plan to remove my head as been sat a long time (12 year) and want to check the seats . on inspection of the exhaust port seems a slight weep, so need to check the stem. Hope not to remove barrel. No gasket on the head? only the barrels . Took the head to my machine guy who will go through them and check seats etc..

[@TheMightyGarage]

Hi Nick, good idea to take them off just to check. Yes, that's correct, only a gasket at the base of the barrels. Good luck with your machine work! Best wishes, Mike

[@453421abcdefg12345]

I am sure you have made the right decision to go further with your investigation, looking at some of the "slap it together" moves that have been discovered so far you could never trust what has been done, it looks like the job was started with good intent, but then the decision was made to sell it, and it was just thrown together in one piece, can you imagine what would have happened had you tried to start it up, you will now have a twin that you can trust, having been inside and checked, a very good investment in time I think, there are oil banjo bolts that pull up the rocker bushes and hold then tightly in place, worth looking into at this stage, I don't like the design of those rocker covers, every time you need to undo them you will have to strip half the engine down, an awful design, if the breather part turned on the cap it may be worth having, but they are something you may regret fitting at a later stage. It all looks a lot better now than when you got it .

[@TheMightyGarage]

Thank you Chris for your very thoughtful comments. You have me thinking carefully about that rocker cover breather now ;) Hmm, I might have to re-think as, like you say, I don't want to have to reassemble the whole top end again if, for example, the spigot needs to point in a slightly different direction when I finally get it all back together again! Thanks very much! Cheers, Mike

[@johncone9516]

Having taken out the rocker feed bolts i would of taken the rockers out and fitted the new rocker bush locking nut. This stops the rocker bush from becoming loose in the tunnel, the nut fits through the bush and lines up with the rocker oil feed bolts, when they are tightened it pulls the rocker bush up in the tunnel nice and tight.

[@TheMightyGarage]

Thanks a lot John. I might do that modification in the future. Cheers, Mike

[@johncone9516]

@@TheMightyGarage Hi, I presume you have a copy of Know thy Beast, the article is on page 159. Chow for now.

[@TheMightyGarage]

Hi John, I do have that book and a few of the other common books. I had read about the new feed bolts and have jotted it down as a future job. Best wishes, Mike

[@thakery5720]

Looking at the almost flat top pistons and large volume of the combustion chamber, it must be quite a low compression ratio motor.... probably needed for the poor quality low octane petrol available in those days !

[@thakery5720]

@po18guy 7:1 is low..... I was talking about static compression ratio, anything below 9.5 : ! I consider to be low ! Don't get me wrong - I am not trashing the bike, todays bikes may make more power but the Vincent is what, 70 -80 years old.... so far ahead of it's time.....

[@JohnJones-cp4wh]

@@thakery5720 Rapide is 6.8 Shadow is 7.1, shadow good for over 100MPH.

[@kurtjens]

I'm wondering how the rocker arms engage the valves. It clearly can't push on the top of the valve stem.

[@TheMightyGarage]

Hi Kurt, the rocker arms have a fork at the end of that engages with the valves. Here’s a link to a site with a diagram of the cylinder head assembly including rockers. Hope this helps, cheers, Mike. www.thevincent.com/vincent%20engine.html

[@kurtjens]

@@TheMightyGarage So, the notch in roughly the middle of the valve stem is where the fork in the end of the rocker arm engages? Are there other engines that have used this design? Maybe radial aircraft engines? The Vincent engine has always looked like a couple of cylinders from a radial engine to me. Thanks very much.

[@ollimakkonen6481]

Hi @@TheMightyGarage & Kurt Jensen. Desmodromic valves, same as Ducati engines. The valves are actuated on a shoulder, located part of the way down the stem. That's why the rockers are forked, in order to push equally on both sides of the stem.

[@graemewilliams1308]

Another Brit escaping the UK ?

[@TheMightyGarage]

Graeme Williams hehe. Yes, we came for just a year and that was 21 years ago :-)