Author Topic: Engine misses and loses power  (Read 2000 times)

Online BigJim

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Re: Engine misses and loses power
« Reply #15 on: 16.02. 2020 18:33 »
Guess thats that for this eve. I'll be spending money on a valve spring compressor next! *pull hair out* *countdown* *bash*
Jamie,  Supporter of Distinguished Gentleman's Ride

Online chaterlea25

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Re: Engine misses and loses power
« Reply #16 on: 16.02. 2020 19:47 »
Hi Jim
I seldom use a compressor to remove the valve springs
I stuff some rags into the combustion chamber and use a plug socket or similar and whack the top collar smartly *bash*
 *eek* *eek*
Be careful or collets will fly into the darkest recesses  *problem*

Even if using a spring compressor it can take a smack to break the taper seating of the collets

John
1961 Super Rocket
1963 RGS (ongoing)

Online BigJim

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Re: Engine misses and loses power
« Reply #17 on: 16.02. 2020 19:54 »
Like the sound of that. Big hammer work, great way to reduce stress.
 *bash* *computer* *work* *work* *countdown* *bright idea* *beer* *wink2*
Jamie,  Supporter of Distinguished Gentleman's Ride

Online berger

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Re: Engine misses and loses power
« Reply #18 on: 16.02. 2020 22:23 »
hey jim give them a whack as was mentioned the collets will be stuck hence the bend that happened , unless it was useless anyway, if it was throw it in the scrap bin and go to the pub *beer* when the collets are stuck and you use a good tool it always frightens me when they crack off , be careful if you use johns method , cover things with rag so you don't get elf and safety telling you off when your eyes hanging out on your chest *eek* *pull hair out* looking for missing parts *help*

Online BigJim

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Re: Engine misses and loses power
« Reply #19 on: 17.02. 2020 16:32 »
Was thinking lots of rags and safety specks and brandy chasers
 *beer* *beer* *wave* *countdown*
Jamie,  Supporter of Distinguished Gentleman's Ride

Online RDfella

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Re: Engine misses and loses power
« Reply #20 on: 17.02. 2020 17:40 »
Recessed valve springs can be fun and I’ve never found a spring compressor that adequately addresses the issue. That said, any robust compressor that’s not too big will serve the purpose for BSA’s.
I take a piece of steel tube of similar OD to the valve collar, weld a large washer and short bolt to one end (so I can fasten it to the valve spring compressor) and then cut a large hole in the side so I can get to the collets when said spring is compressed. I’ve built up a small collection for various engines over the years. And as John says, you’ll need to give the collar a sharp tap – preferably on one side – to loosen things up first.
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Offline Swarfcut

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Re: Engine misses and loses power
« Reply #21 on: 17.02. 2020 18:02 »
 Jimbo.... How can this job be so difficult? It just needs a nicely fitting valve spring compressor, capable of doing just that, compressing the spring. Yes, with age, heat, etc the collets can stick, so the trick is to set the tool with just a little bit of load on the valve cap and give the fork end of the tool a little smack, as mentioned. This shock will break the adhesive grip between valve cap and collets and the cap will only move a small safe distance, down the valve. No drama, easy. Now  winding on the tool will move the valve cap and spring down the valve stem, exposing the collets which can then be extracted. 

 When reassembling, I smear the collets  with grease, which holds them in place on the valve stem and also helps the valve cap settle back into place.

 In the old days, Sykes-Pickavent were the popular brand, these days the world is your lobster.

 Chaterlea John's is a clever trick, but not for the feint hearted. Also finding a flying collet in among the rest of the stuff turns a simple job into a nightmare, and like magneto armatures, valves don't like big hammers.

RD...I did a similar mod for Ford CVH type engines, allowing use of my usual Sykes tool.

 Swarfy.

Offline stev60

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Re: Engine misses and loses power
« Reply #22 on: 18.02. 2020 07:43 »
I found  an (expensive) valve spring compressor hopeless, and modified a substantial  G clamp which works perfectly with a slight tap as pressure is applied, if a collet hits the ground, its time for a beer and the broom

Offline Beeza

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Re: Engine misses and loses power
« Reply #23 on: 19.02. 2020 06:28 »
I have this same problem on my 57 Flash, and I’ve been over all the previous stuff mentioned. One difference I has was .002 over sized exhaust valve stems, now I had that sorted by reaming new exhaust guides, (there was evidence of binding on the guides). When we reassembled the head we tested the spring tension, and it was LOW, but I still used them——less intermittent but still there. I have discussed this topic with my engine man, but not for this bike, I’m in the process of another fast A10 build. Also I do have new valve springs for the 57Flash but I have not put them in, I wish I could give you my findings but my latest machine is sucking any spare time I have.
In short, if they are original valve springs, PUT NEW ONES IN, not expensive and often an overlooked parts, that do effect performance greatly.
Hope this may help mate.

Cheers Thomas

Online groily

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Re: Engine misses and loses power
« Reply #24 on: 19.02. 2020 08:47 »
Here's one version of an 'RD style' modded compressor that works on just about anything  . . .
Bill

Online BigJim

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Re: Engine misses and loses power
« Reply #25 on: 20.02. 2020 19:29 »
Ok , here's the update. Having withdrawn from the battle for a couple of days i returned to the fray with some vigour today. Was washed out at work and felt able to face up to previous misdemeanors in the garage. So putting the bent arm of the compressor in the vice it was straightened with little effort. On previous occasions when removing valve collets they have hopped out with pressure on the spring. Now i know to give a tap after putting a little pressure on, it's a doddle. Of course this was too late to save the exhaust valves from idiot damage, as was demonstrated when they refused to slide out through the guides. Both bent, through my incompetence! Having resisted the temptation to hammer them through i decided to turn to violence. Those of a nervous or of high engineering skills should look away now. Out with the grinder and off with their heads! Took quite a while to do, that steel is really quite resistant to cutting. Also produces a nice paste of carborundum and hard steel particles, perfect big end grinding material!
Now some thoughts, when assembling and tightening the head bolts the horrid stove enammeling (never again) just kept squishing down! Thought it was done but, when removing, some bolts were loose and there was oil on piston top. Cleaned up and retorqued head. Combustion chamber and exhaust port area was not thoroughly cleaned and more oil got in on the next test run. Is it possible that the excess of oil caused the valve to gum up in its guide?
Jamie,  Supporter of Distinguished Gentleman's Ride

Online berger

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Re: Engine misses and loses power
« Reply #26 on: 20.02. 2020 19:56 »
jim I love the honesty , next time you clout them use a soft bit of brass or hard wood. you would have only bruised the tops and a small hand stone would have got the bruising off as I learnt when I was a young en, I doubt very much you would have bent them.  from looking at your stems they shouldn't be sticking.

Online BigJim

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Re: Engine misses and loses power
« Reply #27 on: 20.02. 2020 20:14 »
Cheers Berger. Those valves did 30 miles tops. all new bits.
Jamie,  Supporter of Distinguished Gentleman's Ride

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Re: Engine misses and loses power
« Reply #28 on: 20.02. 2020 20:22 »
jim go to the pub mate *beer* o dear we live and learn, you won't do that again, your a very naughty boy, stay away from  thor *whistle*

Online berger

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Re: Engine misses and loses power
« Reply #29 on: 20.02. 2020 20:59 »
ok jim we know sticky valves can be a problem but I have seen my valves super carboned and gunked up and never had a problem. there may be problems with nipping up on some engines but I would also be giving the points and the pick ups a coat of looking at, if the NEW *dribble* exhaust valves slide in ok and you can hold the valve head about 2 to 3 mm off the seat and feel a bit of rock [ not seaside rock ] you shouldn't be having problems there. don't go shoving the old ones up and down the guides unless you stone off all the sharp bits *problem* if you do feel the need to try your old valves this way once all sharpies have been removed you  could gorilla glue the tops back on *bright idea* it stuck my old boots so is good stuff.